[v4,2/2] kernel/trace: Provide default impelentations defined in trace_probe_tmpl.h

  There are 7 function definitions in trace_probe_tmpl.h, they are:

1, process_fetch_insn
2, fetch_store_strlen
3, fetch_store_string
4, fetch_store_strlen_user
5, fetch_store_string_user
6, probe_mem_read
7, probe_mem_read_user

Every C file which includes trace_probe_tmpl.h has to implement them,
otherwise it gets warnings and errors. However, some of them are identical,
like kprobe and eprobe, as a result, there is a lot redundant code in those
2 files.

This patch would like to provide default behaviors for those functions
which kprobe and eprobe can share by just including trace_probe_kernel.h
with trace_probe_tmpl.h together.

It removes redundant code, increases readability, and more importantly,
makes it easier to introduce a new feature based on trace probe
(it's possible).

Signed-off-by: Song Chen <chensong_2000@189.cn>
Reported-by: kernel test robot <lkp@intel.com>

---
v2:
1, reorganize patchset

v3:
1, mark nokprobe_inline for get_event_field
2, remove warnings reported from kernel test robot
3, fix errors reported from kernel test robot

v4:
1, reset changes in v3(2) and v3(3), they are not reasonable fix.
2, I intended to introduce a new header file to exclude
trace_events_synth.c out of the patch. However, after looking
further, i found the errors in [1] are introduced by this patch,
but the warning in [1] are not. The errors can be fixed by adding
"#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API".

[1]:https://lore.kernel.org/lkml/202211301946.pkLE4PDp-lkp@intel.com/
---
 kernel/trace/trace_eprobe.c       | 144 ------------------------------
 kernel/trace/trace_events_synth.c |   7 +-
 kernel/trace/trace_kprobe.c       | 102 ---------------------
 kernel/trace/trace_probe_kernel.h | 143 +++++++++++++++++++++++++++--
 4 files changed, 141 insertions(+), 255 deletions(-)
  

On Wed, 28 Dec 2022 15:08:25 +0800
Song Chen <chensong_2000@189.cn> wrote:

> There are 7 function definitions in trace_probe_tmpl.h, they are:
> 
> 1, process_fetch_insn

Other functions except for this are OK for me.
But I think this function should have different instance for kprobe
and eprobe, because the passed 'void *rec' is completely different.
For the kprobe's process_fetch_insn() will take a 'pt_regs *', on the
other hand, the eprobe's process_fetch_insn() will take a
'ftrace_event_field *'.
I also, don't want to expose get_event_field() function because
it is only for the eprobes.

What about making a new common function and call it in default case
from both process_fetch_insn()? Your goal is reducing the redundant
code, then it is enough to share only the common code. :)

For example, in trace_probe_kernel.h,

process_common_fetch_insn(struct fetch_insn *code, void *dest, void *base, unsigned long *val)
{
	switch (code->op) {
	case FETCH_OP_IMM:
		*val = code->immediate;
		break;
	case FETCH_OP_COMM:
		*val = (unsigned long)current->comm;
		break;
	case FETCH_OP_DATA:
		*val = (unsigned long)code->data;
		break;
	default:
		return -EILSEQ;
	}
	return 0;
}

For kprobe events:

process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
{
	while (code->op == FETCH_NOP_SYMBOL)
		code++;
	switch (code->op) {
	case FETCH_OP_REG:
		val = regs_get_register(regs, code->param);
		...
	default:
		ret = process_common_fetch_insn(code, dest, base, &val);
		if (ret < 0)
			return ret;
	}
	...
}

For eprobe events:

process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
{
	while (code->op == FETCH_NOP_SYMBOL)
		code++;
	if (code->op == FETCH_OP_TP_ARG) {
		val = get_event_field(code, rec);
	} else {
		ret = process_common_fetch_insn(code, dest, base, &val);
		if (ret < 0)
			return ret;
	}
	...
}

You also don't see the error related to CONFIG_HAVE_REGS_AND_STACK_ACCESS_API. :)

Thank you,

> 2, fetch_store_strlen
> 3, fetch_store_string
> 4, fetch_store_strlen_user
> 5, fetch_store_string_user
> 6, probe_mem_read
> 7, probe_mem_read_user
> 
> Every C file which includes trace_probe_tmpl.h has to implement them,
> otherwise it gets warnings and errors. However, some of them are identical,
> like kprobe and eprobe, as a result, there is a lot redundant code in those
> 2 files.
> 
> This patch would like to provide default behaviors for those functions
> which kprobe and eprobe can share by just including trace_probe_kernel.h
> with trace_probe_tmpl.h together.
> 
> It removes redundant code, increases readability, and more importantly,
> makes it easier to introduce a new feature based on trace probe
> (it's possible).
> 
> Signed-off-by: Song Chen <chensong_2000@189.cn>
> Reported-by: kernel test robot <lkp@intel.com>
> 
> ---
> v2:
> 1, reorganize patchset
> 
> v3:
> 1, mark nokprobe_inline for get_event_field
> 2, remove warnings reported from kernel test robot
> 3, fix errors reported from kernel test robot
> 
> v4:
> 1, reset changes in v3(2) and v3(3), they are not reasonable fix.
> 2, I intended to introduce a new header file to exclude
> trace_events_synth.c out of the patch. However, after looking
> further, i found the errors in [1] are introduced by this patch,
> but the warning in [1] are not. The errors can be fixed by adding
> "#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API".
> 
> [1]:https://lore.kernel.org/lkml/202211301946.pkLE4PDp-lkp@intel.com/
> ---
>  kernel/trace/trace_eprobe.c       | 144 ------------------------------
>  kernel/trace/trace_events_synth.c |   7 +-
>  kernel/trace/trace_kprobe.c       | 102 ---------------------
>  kernel/trace/trace_probe_kernel.h | 143 +++++++++++++++++++++++++++--
>  4 files changed, 141 insertions(+), 255 deletions(-)
> 
> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> index bdb26eee7a0c..60ced4a7a25d 100644
> --- a/kernel/trace/trace_eprobe.c
> +++ b/kernel/trace/trace_eprobe.c
> @@ -319,64 +319,6 @@ print_eprobe_event(struct trace_iterator *iter, int flags,
>  	return trace_handle_return(s);
>  }
>  
> -static unsigned long get_event_field(struct fetch_insn *code, void *rec)
> -{
> -	struct ftrace_event_field *field = code->data;
> -	unsigned long val;
> -	void *addr;
> -
> -	addr = rec + field->offset;
> -
> -	if (is_string_field(field)) {
> -		switch (field->filter_type) {
> -		case FILTER_DYN_STRING:
> -			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
> -			break;
> -		case FILTER_RDYN_STRING:
> -			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
> -			break;
> -		case FILTER_STATIC_STRING:
> -			val = (unsigned long)addr;
> -			break;
> -		case FILTER_PTR_STRING:
> -			val = (unsigned long)(*(char *)addr);
> -			break;
> -		default:
> -			WARN_ON_ONCE(1);
> -			return 0;
> -		}
> -		return val;
> -	}
> -
> -	switch (field->size) {
> -	case 1:
> -		if (field->is_signed)
> -			val = *(char *)addr;
> -		else
> -			val = *(unsigned char *)addr;
> -		break;
> -	case 2:
> -		if (field->is_signed)
> -			val = *(short *)addr;
> -		else
> -			val = *(unsigned short *)addr;
> -		break;
> -	case 4:
> -		if (field->is_signed)
> -			val = *(int *)addr;
> -		else
> -			val = *(unsigned int *)addr;
> -		break;
> -	default:
> -		if (field->is_signed)
> -			val = *(long *)addr;
> -		else
> -			val = *(unsigned long *)addr;
> -		break;
> -	}
> -	return val;
> -}
> -
>  static int get_eprobe_size(struct trace_probe *tp, void *rec)
>  {
>  	struct fetch_insn *code;
> @@ -419,92 +361,6 @@ static int get_eprobe_size(struct trace_probe *tp, void *rec)
>  	return ret;
>  }
>  
> -/* Kprobe specific fetch functions */
> -
> -/* Note that we don't verify it, since the code does not come from user space */
> -static int
> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> -		   void *base)
> -{
> -	unsigned long val;
> -
> - retry:
> -	switch (code->op) {
> -	case FETCH_OP_TP_ARG:
> -		val = get_event_field(code, rec);
> -		break;
> -	case FETCH_OP_IMM:
> -		val = code->immediate;
> -		break;
> -	case FETCH_OP_COMM:
> -		val = (unsigned long)current->comm;
> -		break;
> -	case FETCH_OP_DATA:
> -		val = (unsigned long)code->data;
> -		break;
> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
> -		code++;
> -		goto retry;
> -	default:
> -		return -EILSEQ;
> -	}
> -	code++;
> -	return process_fetch_insn_bottom(code, val, dest, base);
> -}
> -NOKPROBE_SYMBOL(process_fetch_insn)
> -
> -/* Return the length of string -- including null terminal byte */
> -static nokprobe_inline int
> -fetch_store_strlen_user(unsigned long addr)
> -{
> -	return kern_fetch_store_strlen_user(addr);
> -}
> -
> -/* Return the length of string -- including null terminal byte */
> -static nokprobe_inline int
> -fetch_store_strlen(unsigned long addr)
> -{
> -	return kern_fetch_store_strlen(addr);
> -}
> -
> -/*
> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
> - * with max length and relative data location.
> - */
> -static nokprobe_inline int
> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
> -{
> -	return kern_fetch_store_string_user(addr, dest, base);
> -}
> -
> -/*
> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
> - * length and relative data location.
> - */
> -static nokprobe_inline int
> -fetch_store_string(unsigned long addr, void *dest, void *base)
> -{
> -	return kern_fetch_store_string(addr, dest, base);
> -}
> -
> -static nokprobe_inline int
> -probe_mem_read_user(void *dest, void *src, size_t size)
> -{
> -	const void __user *uaddr =  (__force const void __user *)src;
> -
> -	return copy_from_user_nofault(dest, uaddr, size);
> -}
> -
> -static nokprobe_inline int
> -probe_mem_read(void *dest, void *src, size_t size)
> -{
> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> -	if ((unsigned long)src < TASK_SIZE)
> -		return probe_mem_read_user(dest, src, size);
> -#endif
> -	return copy_from_kernel_nofault(dest, src, size);
> -}
> -
>  /* eprobe handler */
>  static inline void
>  __eprobe_trace_func(struct eprobe_data *edata, void *rec)
> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> index e310052dc83c..7460f18ba973 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -18,6 +18,7 @@
>  #include <linux/trace_events.h>
>  #include <trace/events/mmflags.h>
>  #include "trace_probe.h"
> +#include "trace_probe_tmpl.h"
>  #include "trace_probe_kernel.h"
>  
>  #include "trace_synth.h"
> @@ -420,12 +421,12 @@ static unsigned int trace_string(struct synth_trace_event *entry,
>  		data_offset += event->n_u64 * sizeof(u64);
>  		data_offset += data_size;
>  
> -		len = kern_fetch_store_strlen((unsigned long)str_val);
> +		len = fetch_store_strlen((unsigned long)str_val);
>  
>  		data_offset |= len << 16;
>  		*(u32 *)&entry->fields[*n_u64] = data_offset;
>  
> -		ret = kern_fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
> +		ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>  
>  		(*n_u64)++;
>  	} else {
> @@ -473,7 +474,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
>  		val_idx = var_ref_idx[field_pos];
>  		str_val = (char *)(long)var_ref_vals[val_idx];
>  
> -		len = kern_fetch_store_strlen((unsigned long)str_val);
> +		len = fetch_store_strlen((unsigned long)str_val);
>  
>  		fields_size += len;
>  	}
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index a4ffa864dbb7..c2e0b741ae82 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1218,108 +1218,6 @@ static const struct file_operations kprobe_profile_ops = {
>  	.release        = seq_release,
>  };
>  
> -/* Kprobe specific fetch functions */
> -
> -/* Return the length of string -- including null terminal byte */
> -static nokprobe_inline int
> -fetch_store_strlen_user(unsigned long addr)
> -{
> -	return kern_fetch_store_strlen_user(addr);
> -}
> -
> -/* Return the length of string -- including null terminal byte */
> -static nokprobe_inline int
> -fetch_store_strlen(unsigned long addr)
> -{
> -	return kern_fetch_store_strlen(addr);
> -}
> -
> -/*
> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
> - * with max length and relative data location.
> - */
> -static nokprobe_inline int
> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
> -{
> -	return kern_fetch_store_string_user(addr, dest, base);
> -}
> -
> -/*
> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
> - * length and relative data location.
> - */
> -static nokprobe_inline int
> -fetch_store_string(unsigned long addr, void *dest, void *base)
> -{
> -	return kern_fetch_store_string(addr, dest, base);
> -}
> -
> -static nokprobe_inline int
> -probe_mem_read_user(void *dest, void *src, size_t size)
> -{
> -	const void __user *uaddr =  (__force const void __user *)src;
> -
> -	return copy_from_user_nofault(dest, uaddr, size);
> -}
> -
> -static nokprobe_inline int
> -probe_mem_read(void *dest, void *src, size_t size)
> -{
> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> -	if ((unsigned long)src < TASK_SIZE)
> -		return probe_mem_read_user(dest, src, size);
> -#endif
> -	return copy_from_kernel_nofault(dest, src, size);
> -}
> -
> -/* Note that we don't verify it, since the code does not come from user space */
> -static int
> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> -		   void *base)
> -{
> -	struct pt_regs *regs = rec;
> -	unsigned long val;
> -
> -retry:
> -	/* 1st stage: get value from context */
> -	switch (code->op) {
> -	case FETCH_OP_REG:
> -		val = regs_get_register(regs, code->param);
> -		break;
> -	case FETCH_OP_STACK:
> -		val = regs_get_kernel_stack_nth(regs, code->param);
> -		break;
> -	case FETCH_OP_STACKP:
> -		val = kernel_stack_pointer(regs);
> -		break;
> -	case FETCH_OP_RETVAL:
> -		val = regs_return_value(regs);
> -		break;
> -	case FETCH_OP_IMM:
> -		val = code->immediate;
> -		break;
> -	case FETCH_OP_COMM:
> -		val = (unsigned long)current->comm;
> -		break;
> -	case FETCH_OP_DATA:
> -		val = (unsigned long)code->data;
> -		break;
> -#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> -	case FETCH_OP_ARG:
> -		val = regs_get_kernel_argument(regs, code->param);
> -		break;
> -#endif
> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
> -		code++;
> -		goto retry;
> -	default:
> -		return -EILSEQ;
> -	}
> -	code++;
> -
> -	return process_fetch_insn_bottom(code, val, dest, base);
> -}
> -NOKPROBE_SYMBOL(process_fetch_insn)
>  
>  /* Kprobe handler */
>  static nokprobe_inline void
> diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
> index 77dbd9ff9782..39f44513ec4e 100644
> --- a/kernel/trace/trace_probe_kernel.h
> +++ b/kernel/trace/trace_probe_kernel.h
> @@ -12,7 +12,7 @@
>   */
>  /* Return the length of string -- including null terminal byte */
>  static nokprobe_inline int
> -kern_fetch_store_strlen_user(unsigned long addr)
> +fetch_store_strlen_user(unsigned long addr)
>  {
>  	const void __user *uaddr =  (__force const void __user *)addr;
>  	int ret;
> @@ -29,14 +29,14 @@ kern_fetch_store_strlen_user(unsigned long addr)
>  
>  /* Return the length of string -- including null terminal byte */
>  static nokprobe_inline int
> -kern_fetch_store_strlen(unsigned long addr)
> +fetch_store_strlen(unsigned long addr)
>  {
>  	int ret, len = 0;
>  	u8 c;
>  
>  #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>  	if (addr < TASK_SIZE)
> -		return kern_fetch_store_strlen_user(addr);
> +		return fetch_store_strlen_user(addr);
>  #endif
>  
>  	do {
> @@ -63,7 +63,7 @@ static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void
>   * with max length and relative data location.
>   */
>  static nokprobe_inline int
> -kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
> +fetch_store_string_user(unsigned long addr, void *dest, void *base)
>  {
>  	const void __user *uaddr =  (__force const void __user *)addr;
>  	int maxlen = get_loc_len(*(u32 *)dest);
> @@ -86,7 +86,7 @@ kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
>   * length and relative data location.
>   */
>  static nokprobe_inline int
> -kern_fetch_store_string(unsigned long addr, void *dest, void *base)
> +fetch_store_string(unsigned long addr, void *dest, void *base)
>  {
>  	int maxlen = get_loc_len(*(u32 *)dest);
>  	void *__dest;
> @@ -94,7 +94,7 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>  
>  #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>  	if ((unsigned long)addr < TASK_SIZE)
> -		return kern_fetch_store_string_user(addr, dest, base);
> +		return fetch_store_string_user(addr, dest, base);
>  #endif
>  
>  	if (unlikely(!maxlen))
> @@ -112,4 +112,135 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>  	return ret;
>  }
>  
> +static nokprobe_inline int
> +probe_mem_read_user(void *dest, void *src, size_t size)
> +{
> +	const void __user *uaddr =  (__force const void __user *)src;
> +
> +	return copy_from_user_nofault(dest, uaddr, size);
> +}
> +
> +static nokprobe_inline int
> +probe_mem_read(void *dest, void *src, size_t size)
> +{
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +	if ((unsigned long)src < TASK_SIZE)
> +		return probe_mem_read_user(dest, src, size);
> +#endif
> +	return copy_from_kernel_nofault(dest, src, size);
> +}
> +
> +static nokprobe_inline unsigned long
> +get_event_field(struct fetch_insn *code, void *rec)
> +{
> +	struct ftrace_event_field *field = code->data;
> +	unsigned long val;
> +	void *addr;
> +
> +	addr = rec + field->offset;
> +
> +	if (is_string_field(field)) {
> +		switch (field->filter_type) {
> +		case FILTER_DYN_STRING:
> +			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
> +			break;
> +		case FILTER_RDYN_STRING:
> +			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
> +			break;
> +		case FILTER_STATIC_STRING:
> +			val = (unsigned long)addr;
> +			break;
> +		case FILTER_PTR_STRING:
> +			val = (unsigned long)(*(char *)addr);
> +			break;
> +		default:
> +			WARN_ON_ONCE(1);
> +			return 0;
> +		}
> +		return val;
> +	}
> +
> +	switch (field->size) {
> +	case 1:
> +		if (field->is_signed)
> +			val = *(char *)addr;
> +		else
> +			val = *(unsigned char *)addr;
> +		break;
> +	case 2:
> +		if (field->is_signed)
> +			val = *(short *)addr;
> +		else
> +			val = *(unsigned short *)addr;
> +		break;
> +	case 4:
> +		if (field->is_signed)
> +			val = *(int *)addr;
> +		else
> +			val = *(unsigned int *)addr;
> +		break;
> +	default:
> +		if (field->is_signed)
> +			val = *(long *)addr;
> +		else
> +			val = *(unsigned long *)addr;
> +		break;
> +	}
> +	return val;
> +}
> +
> +/* Note that we don't verify it, since the code does not come from user space */
> +static int
> +process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> +		   void *base)
> +{
> +	struct pt_regs *regs = rec;
> +	unsigned long val;
> +
> +retry:
> +	/* 1st stage: get value from context */
> +	switch (code->op) {
> +#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API
> +	case FETCH_OP_REG:
> +		val = regs_get_register(regs, code->param);
> +		break;
> +	case FETCH_OP_STACK:
> +		val = regs_get_kernel_stack_nth(regs, code->param);
> +		break;
> +	case FETCH_OP_STACKP:
> +		val = kernel_stack_pointer(regs);
> +		break;
> +	case FETCH_OP_RETVAL:
> +		val = regs_return_value(regs);
> +		break;
> +#endif
> +	case FETCH_OP_IMM:
> +		val = code->immediate;
> +		break;
> +	case FETCH_OP_COMM:
> +		val = (unsigned long)current->comm;
> +		break;
> +	case FETCH_OP_DATA:
> +		val = (unsigned long)code->data;
> +		break;
> +#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> +	case FETCH_OP_ARG:
> +		val = regs_get_kernel_argument(regs, code->param);
> +		break;
> +#endif
> +	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
> +		code++;
> +		goto retry;
> +	case FETCH_OP_TP_ARG:
> +		val = get_event_field(code, rec);
> +		break;
> +	default:
> +		return -EILSEQ;
> +	}
> +	code++;
> +
> +	return process_fetch_insn_bottom(code, val, dest, base);
> +}
> +NOKPROBE_SYMBOL(process_fetch_insn)
> +
>  #endif /* __TRACE_PROBE_KERNEL_H_ */
> -- 
> 2.25.1
>
  

Hi,

在 2022/12/29 17:30, Masami Hiramatsu (Google) 写道:
> On Wed, 28 Dec 2022 15:08:25 +0800
> Song Chen <chensong_2000@189.cn> wrote:
> 
>> There are 7 function definitions in trace_probe_tmpl.h, they are:
>>
>> 1, process_fetch_insn
> 
> Other functions except for this are OK for me.
> But I think this function should have different instance for kprobe
> and eprobe, because the passed 'void *rec' is completely different.
> For the kprobe's process_fetch_insn() will take a 'pt_regs *', on the
> other hand, the eprobe's process_fetch_insn() will take a
> 'ftrace_event_field *'.
> I also, don't want to expose get_event_field() function because
> it is only for the eprobes.
> 
> What about making a new common function and call it in default case
> from both process_fetch_insn()? Your goal is reducing the redundant
> code, then it is enough to share only the common code. :)
> 
> For example, in trace_probe_kernel.h,
> 
> process_common_fetch_insn(struct fetch_insn *code, void *dest, void *base, unsigned long *val)
> {
> 	switch (code->op) {
> 	case FETCH_OP_IMM:
> 		*val = code->immediate;
> 		break;
> 	case FETCH_OP_COMM:
> 		*val = (unsigned long)current->comm;
> 		break;
> 	case FETCH_OP_DATA:
> 		*val = (unsigned long)code->data;
> 		break;
> 	default:
> 		return -EILSEQ;
> 	}
> 	return 0;
> }
> 
> For kprobe events:
> 
> process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
> {
> 	while (code->op == FETCH_NOP_SYMBOL)
> 		code++;
> 	switch (code->op) {
> 	case FETCH_OP_REG:
> 		val = regs_get_register(regs, code->param);
> 		...
> 	default:
> 		ret = process_common_fetch_insn(code, dest, base, &val);
> 		if (ret < 0)
> 			return ret;
> 	}
> 	...
> }
> 
> For eprobe events:
> 
> process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
> {
> 	while (code->op == FETCH_NOP_SYMBOL)
> 		code++;
> 	if (code->op == FETCH_OP_TP_ARG) {
> 		val = get_event_field(code, rec);
> 	} else {
> 		ret = process_common_fetch_insn(code, dest, base, &val);
> 		if (ret < 0)
> 			return ret;
> 	}
> 	...
> }
> 
> You also don't see the error related to CONFIG_HAVE_REGS_AND_STACK_ACCESS_API. :)
> 
> Thank you,
> 

Thanks a lot for the good idea and so specific demo code, i accept it 
and will submit a new one based on it.

If we think about it further, we can implement process_common_fetch_insn 
in trace_probe_tmpl.h, uprobe can benefit from it as well, what do you 
think? i will include it in the next submit and you can have a look.

Thanks again.

Song

>> 2, fetch_store_strlen
>> 3, fetch_store_string
>> 4, fetch_store_strlen_user
>> 5, fetch_store_string_user
>> 6, probe_mem_read
>> 7, probe_mem_read_user
>>
>> Every C file which includes trace_probe_tmpl.h has to implement them,
>> otherwise it gets warnings and errors. However, some of them are identical,
>> like kprobe and eprobe, as a result, there is a lot redundant code in those
>> 2 files.
>>
>> This patch would like to provide default behaviors for those functions
>> which kprobe and eprobe can share by just including trace_probe_kernel.h
>> with trace_probe_tmpl.h together.
>>
>> It removes redundant code, increases readability, and more importantly,
>> makes it easier to introduce a new feature based on trace probe
>> (it's possible).
>>
>> Signed-off-by: Song Chen <chensong_2000@189.cn>
>> Reported-by: kernel test robot <lkp@intel.com>
>>
>> ---
>> v2:
>> 1, reorganize patchset
>>
>> v3:
>> 1, mark nokprobe_inline for get_event_field
>> 2, remove warnings reported from kernel test robot
>> 3, fix errors reported from kernel test robot
>>
>> v4:
>> 1, reset changes in v3(2) and v3(3), they are not reasonable fix.
>> 2, I intended to introduce a new header file to exclude
>> trace_events_synth.c out of the patch. However, after looking
>> further, i found the errors in [1] are introduced by this patch,
>> but the warning in [1] are not. The errors can be fixed by adding
>> "#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API".
>>
>> [1]:https://lore.kernel.org/lkml/202211301946.pkLE4PDp-lkp@intel.com/
>> ---
>>   kernel/trace/trace_eprobe.c       | 144 ------------------------------
>>   kernel/trace/trace_events_synth.c |   7 +-
>>   kernel/trace/trace_kprobe.c       | 102 ---------------------
>>   kernel/trace/trace_probe_kernel.h | 143 +++++++++++++++++++++++++++--
>>   4 files changed, 141 insertions(+), 255 deletions(-)
>>
>> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
>> index bdb26eee7a0c..60ced4a7a25d 100644
>> --- a/kernel/trace/trace_eprobe.c
>> +++ b/kernel/trace/trace_eprobe.c
>> @@ -319,64 +319,6 @@ print_eprobe_event(struct trace_iterator *iter, int flags,
>>   	return trace_handle_return(s);
>>   }
>>   
>> -static unsigned long get_event_field(struct fetch_insn *code, void *rec)
>> -{
>> -	struct ftrace_event_field *field = code->data;
>> -	unsigned long val;
>> -	void *addr;
>> -
>> -	addr = rec + field->offset;
>> -
>> -	if (is_string_field(field)) {
>> -		switch (field->filter_type) {
>> -		case FILTER_DYN_STRING:
>> -			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
>> -			break;
>> -		case FILTER_RDYN_STRING:
>> -			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
>> -			break;
>> -		case FILTER_STATIC_STRING:
>> -			val = (unsigned long)addr;
>> -			break;
>> -		case FILTER_PTR_STRING:
>> -			val = (unsigned long)(*(char *)addr);
>> -			break;
>> -		default:
>> -			WARN_ON_ONCE(1);
>> -			return 0;
>> -		}
>> -		return val;
>> -	}
>> -
>> -	switch (field->size) {
>> -	case 1:
>> -		if (field->is_signed)
>> -			val = *(char *)addr;
>> -		else
>> -			val = *(unsigned char *)addr;
>> -		break;
>> -	case 2:
>> -		if (field->is_signed)
>> -			val = *(short *)addr;
>> -		else
>> -			val = *(unsigned short *)addr;
>> -		break;
>> -	case 4:
>> -		if (field->is_signed)
>> -			val = *(int *)addr;
>> -		else
>> -			val = *(unsigned int *)addr;
>> -		break;
>> -	default:
>> -		if (field->is_signed)
>> -			val = *(long *)addr;
>> -		else
>> -			val = *(unsigned long *)addr;
>> -		break;
>> -	}
>> -	return val;
>> -}
>> -
>>   static int get_eprobe_size(struct trace_probe *tp, void *rec)
>>   {
>>   	struct fetch_insn *code;
>> @@ -419,92 +361,6 @@ static int get_eprobe_size(struct trace_probe *tp, void *rec)
>>   	return ret;
>>   }
>>   
>> -/* Kprobe specific fetch functions */
>> -
>> -/* Note that we don't verify it, since the code does not come from user space */
>> -static int
>> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>> -		   void *base)
>> -{
>> -	unsigned long val;
>> -
>> - retry:
>> -	switch (code->op) {
>> -	case FETCH_OP_TP_ARG:
>> -		val = get_event_field(code, rec);
>> -		break;
>> -	case FETCH_OP_IMM:
>> -		val = code->immediate;
>> -		break;
>> -	case FETCH_OP_COMM:
>> -		val = (unsigned long)current->comm;
>> -		break;
>> -	case FETCH_OP_DATA:
>> -		val = (unsigned long)code->data;
>> -		break;
>> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>> -		code++;
>> -		goto retry;
>> -	default:
>> -		return -EILSEQ;
>> -	}
>> -	code++;
>> -	return process_fetch_insn_bottom(code, val, dest, base);
>> -}
>> -NOKPROBE_SYMBOL(process_fetch_insn)
>> -
>> -/* Return the length of string -- including null terminal byte */
>> -static nokprobe_inline int
>> -fetch_store_strlen_user(unsigned long addr)
>> -{
>> -	return kern_fetch_store_strlen_user(addr);
>> -}
>> -
>> -/* Return the length of string -- including null terminal byte */
>> -static nokprobe_inline int
>> -fetch_store_strlen(unsigned long addr)
>> -{
>> -	return kern_fetch_store_strlen(addr);
>> -}
>> -
>> -/*
>> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
>> - * with max length and relative data location.
>> - */
>> -static nokprobe_inline int
>> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
>> -{
>> -	return kern_fetch_store_string_user(addr, dest, base);
>> -}
>> -
>> -/*
>> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
>> - * length and relative data location.
>> - */
>> -static nokprobe_inline int
>> -fetch_store_string(unsigned long addr, void *dest, void *base)
>> -{
>> -	return kern_fetch_store_string(addr, dest, base);
>> -}
>> -
>> -static nokprobe_inline int
>> -probe_mem_read_user(void *dest, void *src, size_t size)
>> -{
>> -	const void __user *uaddr =  (__force const void __user *)src;
>> -
>> -	return copy_from_user_nofault(dest, uaddr, size);
>> -}
>> -
>> -static nokprobe_inline int
>> -probe_mem_read(void *dest, void *src, size_t size)
>> -{
>> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>> -	if ((unsigned long)src < TASK_SIZE)
>> -		return probe_mem_read_user(dest, src, size);
>> -#endif
>> -	return copy_from_kernel_nofault(dest, src, size);
>> -}
>> -
>>   /* eprobe handler */
>>   static inline void
>>   __eprobe_trace_func(struct eprobe_data *edata, void *rec)
>> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
>> index e310052dc83c..7460f18ba973 100644
>> --- a/kernel/trace/trace_events_synth.c
>> +++ b/kernel/trace/trace_events_synth.c
>> @@ -18,6 +18,7 @@
>>   #include <linux/trace_events.h>
>>   #include <trace/events/mmflags.h>
>>   #include "trace_probe.h"
>> +#include "trace_probe_tmpl.h"
>>   #include "trace_probe_kernel.h"
>>   
>>   #include "trace_synth.h"
>> @@ -420,12 +421,12 @@ static unsigned int trace_string(struct synth_trace_event *entry,
>>   		data_offset += event->n_u64 * sizeof(u64);
>>   		data_offset += data_size;
>>   
>> -		len = kern_fetch_store_strlen((unsigned long)str_val);
>> +		len = fetch_store_strlen((unsigned long)str_val);
>>   
>>   		data_offset |= len << 16;
>>   		*(u32 *)&entry->fields[*n_u64] = data_offset;
>>   
>> -		ret = kern_fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>> +		ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>>   
>>   		(*n_u64)++;
>>   	} else {
>> @@ -473,7 +474,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
>>   		val_idx = var_ref_idx[field_pos];
>>   		str_val = (char *)(long)var_ref_vals[val_idx];
>>   
>> -		len = kern_fetch_store_strlen((unsigned long)str_val);
>> +		len = fetch_store_strlen((unsigned long)str_val);
>>   
>>   		fields_size += len;
>>   	}
>> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
>> index a4ffa864dbb7..c2e0b741ae82 100644
>> --- a/kernel/trace/trace_kprobe.c
>> +++ b/kernel/trace/trace_kprobe.c
>> @@ -1218,108 +1218,6 @@ static const struct file_operations kprobe_profile_ops = {
>>   	.release        = seq_release,
>>   };
>>   
>> -/* Kprobe specific fetch functions */
>> -
>> -/* Return the length of string -- including null terminal byte */
>> -static nokprobe_inline int
>> -fetch_store_strlen_user(unsigned long addr)
>> -{
>> -	return kern_fetch_store_strlen_user(addr);
>> -}
>> -
>> -/* Return the length of string -- including null terminal byte */
>> -static nokprobe_inline int
>> -fetch_store_strlen(unsigned long addr)
>> -{
>> -	return kern_fetch_store_strlen(addr);
>> -}
>> -
>> -/*
>> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
>> - * with max length and relative data location.
>> - */
>> -static nokprobe_inline int
>> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
>> -{
>> -	return kern_fetch_store_string_user(addr, dest, base);
>> -}
>> -
>> -/*
>> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
>> - * length and relative data location.
>> - */
>> -static nokprobe_inline int
>> -fetch_store_string(unsigned long addr, void *dest, void *base)
>> -{
>> -	return kern_fetch_store_string(addr, dest, base);
>> -}
>> -
>> -static nokprobe_inline int
>> -probe_mem_read_user(void *dest, void *src, size_t size)
>> -{
>> -	const void __user *uaddr =  (__force const void __user *)src;
>> -
>> -	return copy_from_user_nofault(dest, uaddr, size);
>> -}
>> -
>> -static nokprobe_inline int
>> -probe_mem_read(void *dest, void *src, size_t size)
>> -{
>> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>> -	if ((unsigned long)src < TASK_SIZE)
>> -		return probe_mem_read_user(dest, src, size);
>> -#endif
>> -	return copy_from_kernel_nofault(dest, src, size);
>> -}
>> -
>> -/* Note that we don't verify it, since the code does not come from user space */
>> -static int
>> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>> -		   void *base)
>> -{
>> -	struct pt_regs *regs = rec;
>> -	unsigned long val;
>> -
>> -retry:
>> -	/* 1st stage: get value from context */
>> -	switch (code->op) {
>> -	case FETCH_OP_REG:
>> -		val = regs_get_register(regs, code->param);
>> -		break;
>> -	case FETCH_OP_STACK:
>> -		val = regs_get_kernel_stack_nth(regs, code->param);
>> -		break;
>> -	case FETCH_OP_STACKP:
>> -		val = kernel_stack_pointer(regs);
>> -		break;
>> -	case FETCH_OP_RETVAL:
>> -		val = regs_return_value(regs);
>> -		break;
>> -	case FETCH_OP_IMM:
>> -		val = code->immediate;
>> -		break;
>> -	case FETCH_OP_COMM:
>> -		val = (unsigned long)current->comm;
>> -		break;
>> -	case FETCH_OP_DATA:
>> -		val = (unsigned long)code->data;
>> -		break;
>> -#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
>> -	case FETCH_OP_ARG:
>> -		val = regs_get_kernel_argument(regs, code->param);
>> -		break;
>> -#endif
>> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>> -		code++;
>> -		goto retry;
>> -	default:
>> -		return -EILSEQ;
>> -	}
>> -	code++;
>> -
>> -	return process_fetch_insn_bottom(code, val, dest, base);
>> -}
>> -NOKPROBE_SYMBOL(process_fetch_insn)
>>   
>>   /* Kprobe handler */
>>   static nokprobe_inline void
>> diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
>> index 77dbd9ff9782..39f44513ec4e 100644
>> --- a/kernel/trace/trace_probe_kernel.h
>> +++ b/kernel/trace/trace_probe_kernel.h
>> @@ -12,7 +12,7 @@
>>    */
>>   /* Return the length of string -- including null terminal byte */
>>   static nokprobe_inline int
>> -kern_fetch_store_strlen_user(unsigned long addr)
>> +fetch_store_strlen_user(unsigned long addr)
>>   {
>>   	const void __user *uaddr =  (__force const void __user *)addr;
>>   	int ret;
>> @@ -29,14 +29,14 @@ kern_fetch_store_strlen_user(unsigned long addr)
>>   
>>   /* Return the length of string -- including null terminal byte */
>>   static nokprobe_inline int
>> -kern_fetch_store_strlen(unsigned long addr)
>> +fetch_store_strlen(unsigned long addr)
>>   {
>>   	int ret, len = 0;
>>   	u8 c;
>>   
>>   #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>   	if (addr < TASK_SIZE)
>> -		return kern_fetch_store_strlen_user(addr);
>> +		return fetch_store_strlen_user(addr);
>>   #endif
>>   
>>   	do {
>> @@ -63,7 +63,7 @@ static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void
>>    * with max length and relative data location.
>>    */
>>   static nokprobe_inline int
>> -kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
>> +fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>   {
>>   	const void __user *uaddr =  (__force const void __user *)addr;
>>   	int maxlen = get_loc_len(*(u32 *)dest);
>> @@ -86,7 +86,7 @@ kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>    * length and relative data location.
>>    */
>>   static nokprobe_inline int
>> -kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>> +fetch_store_string(unsigned long addr, void *dest, void *base)
>>   {
>>   	int maxlen = get_loc_len(*(u32 *)dest);
>>   	void *__dest;
>> @@ -94,7 +94,7 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>   
>>   #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>   	if ((unsigned long)addr < TASK_SIZE)
>> -		return kern_fetch_store_string_user(addr, dest, base);
>> +		return fetch_store_string_user(addr, dest, base);
>>   #endif
>>   
>>   	if (unlikely(!maxlen))
>> @@ -112,4 +112,135 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>   	return ret;
>>   }
>>   
>> +static nokprobe_inline int
>> +probe_mem_read_user(void *dest, void *src, size_t size)
>> +{
>> +	const void __user *uaddr =  (__force const void __user *)src;
>> +
>> +	return copy_from_user_nofault(dest, uaddr, size);
>> +}
>> +
>> +static nokprobe_inline int
>> +probe_mem_read(void *dest, void *src, size_t size)
>> +{
>> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>> +	if ((unsigned long)src < TASK_SIZE)
>> +		return probe_mem_read_user(dest, src, size);
>> +#endif
>> +	return copy_from_kernel_nofault(dest, src, size);
>> +}
>> +
>> +static nokprobe_inline unsigned long
>> +get_event_field(struct fetch_insn *code, void *rec)
>> +{
>> +	struct ftrace_event_field *field = code->data;
>> +	unsigned long val;
>> +	void *addr;
>> +
>> +	addr = rec + field->offset;
>> +
>> +	if (is_string_field(field)) {
>> +		switch (field->filter_type) {
>> +		case FILTER_DYN_STRING:
>> +			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
>> +			break;
>> +		case FILTER_RDYN_STRING:
>> +			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
>> +			break;
>> +		case FILTER_STATIC_STRING:
>> +			val = (unsigned long)addr;
>> +			break;
>> +		case FILTER_PTR_STRING:
>> +			val = (unsigned long)(*(char *)addr);
>> +			break;
>> +		default:
>> +			WARN_ON_ONCE(1);
>> +			return 0;
>> +		}
>> +		return val;
>> +	}
>> +
>> +	switch (field->size) {
>> +	case 1:
>> +		if (field->is_signed)
>> +			val = *(char *)addr;
>> +		else
>> +			val = *(unsigned char *)addr;
>> +		break;
>> +	case 2:
>> +		if (field->is_signed)
>> +			val = *(short *)addr;
>> +		else
>> +			val = *(unsigned short *)addr;
>> +		break;
>> +	case 4:
>> +		if (field->is_signed)
>> +			val = *(int *)addr;
>> +		else
>> +			val = *(unsigned int *)addr;
>> +		break;
>> +	default:
>> +		if (field->is_signed)
>> +			val = *(long *)addr;
>> +		else
>> +			val = *(unsigned long *)addr;
>> +		break;
>> +	}
>> +	return val;
>> +}
>> +
>> +/* Note that we don't verify it, since the code does not come from user space */
>> +static int
>> +process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>> +		   void *base)
>> +{
>> +	struct pt_regs *regs = rec;
>> +	unsigned long val;
>> +
>> +retry:
>> +	/* 1st stage: get value from context */
>> +	switch (code->op) {
>> +#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API
>> +	case FETCH_OP_REG:
>> +		val = regs_get_register(regs, code->param);
>> +		break;
>> +	case FETCH_OP_STACK:
>> +		val = regs_get_kernel_stack_nth(regs, code->param);
>> +		break;
>> +	case FETCH_OP_STACKP:
>> +		val = kernel_stack_pointer(regs);
>> +		break;
>> +	case FETCH_OP_RETVAL:
>> +		val = regs_return_value(regs);
>> +		break;
>> +#endif
>> +	case FETCH_OP_IMM:
>> +		val = code->immediate;
>> +		break;
>> +	case FETCH_OP_COMM:
>> +		val = (unsigned long)current->comm;
>> +		break;
>> +	case FETCH_OP_DATA:
>> +		val = (unsigned long)code->data;
>> +		break;
>> +#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
>> +	case FETCH_OP_ARG:
>> +		val = regs_get_kernel_argument(regs, code->param);
>> +		break;
>> +#endif
>> +	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>> +		code++;
>> +		goto retry;
>> +	case FETCH_OP_TP_ARG:
>> +		val = get_event_field(code, rec);
>> +		break;
>> +	default:
>> +		return -EILSEQ;
>> +	}
>> +	code++;
>> +
>> +	return process_fetch_insn_bottom(code, val, dest, base);
>> +}
>> +NOKPROBE_SYMBOL(process_fetch_insn)
>> +
>>   #endif /* __TRACE_PROBE_KERNEL_H_ */
>> -- 
>> 2.25.1
>>
> 
>
  

On Fri, 30 Dec 2022 09:59:31 +0800
Song Chen <chensong_2000@189.cn> wrote:

> Hi,
> 
> 在 2022/12/29 17:30, Masami Hiramatsu (Google) 写道:
> > On Wed, 28 Dec 2022 15:08:25 +0800
> > Song Chen <chensong_2000@189.cn> wrote:
> > 
> >> There are 7 function definitions in trace_probe_tmpl.h, they are:
> >>
> >> 1, process_fetch_insn
> > 
> > Other functions except for this are OK for me.
> > But I think this function should have different instance for kprobe
> > and eprobe, because the passed 'void *rec' is completely different.
> > For the kprobe's process_fetch_insn() will take a 'pt_regs *', on the
> > other hand, the eprobe's process_fetch_insn() will take a
> > 'ftrace_event_field *'.
> > I also, don't want to expose get_event_field() function because
> > it is only for the eprobes.
> > 
> > What about making a new common function and call it in default case
> > from both process_fetch_insn()? Your goal is reducing the redundant
> > code, then it is enough to share only the common code. :)
> > 
> > For example, in trace_probe_kernel.h,
> > 
> > process_common_fetch_insn(struct fetch_insn *code, void *dest, void *base, unsigned long *val)
> > {
> > 	switch (code->op) {
> > 	case FETCH_OP_IMM:
> > 		*val = code->immediate;
> > 		break;
> > 	case FETCH_OP_COMM:
> > 		*val = (unsigned long)current->comm;
> > 		break;
> > 	case FETCH_OP_DATA:
> > 		*val = (unsigned long)code->data;
> > 		break;
> > 	default:
> > 		return -EILSEQ;
> > 	}
> > 	return 0;
> > }
> > 
> > For kprobe events:
> > 
> > process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
> > {
> > 	while (code->op == FETCH_NOP_SYMBOL)
> > 		code++;
> > 	switch (code->op) {
> > 	case FETCH_OP_REG:
> > 		val = regs_get_register(regs, code->param);
> > 		...
> > 	default:
> > 		ret = process_common_fetch_insn(code, dest, base, &val);
> > 		if (ret < 0)
> > 			return ret;
> > 	}
> > 	...
> > }
> > 
> > For eprobe events:
> > 
> > process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
> > {
> > 	while (code->op == FETCH_NOP_SYMBOL)
> > 		code++;
> > 	if (code->op == FETCH_OP_TP_ARG) {
> > 		val = get_event_field(code, rec);
> > 	} else {
> > 		ret = process_common_fetch_insn(code, dest, base, &val);
> > 		if (ret < 0)
> > 			return ret;
> > 	}
> > 	...
> > }
> > 
> > You also don't see the error related to CONFIG_HAVE_REGS_AND_STACK_ACCESS_API. :)
> > 
> > Thank you,
> > 
> 
> Thanks a lot for the good idea and so specific demo code, i accept it 
> and will submit a new one based on it.
> 
> If we think about it further, we can implement process_common_fetch_insn 
> in trace_probe_tmpl.h, uprobe can benefit from it as well, what do you 
> think? i will include it in the next submit and you can have a look.

Agreed. It sounds good to me. :)

Thank you!

> 
> Thanks again.
> 
> Song
> 
> >> 2, fetch_store_strlen
> >> 3, fetch_store_string
> >> 4, fetch_store_strlen_user
> >> 5, fetch_store_string_user
> >> 6, probe_mem_read
> >> 7, probe_mem_read_user
> >>
> >> Every C file which includes trace_probe_tmpl.h has to implement them,
> >> otherwise it gets warnings and errors. However, some of them are identical,
> >> like kprobe and eprobe, as a result, there is a lot redundant code in those
> >> 2 files.
> >>
> >> This patch would like to provide default behaviors for those functions
> >> which kprobe and eprobe can share by just including trace_probe_kernel.h
> >> with trace_probe_tmpl.h together.
> >>
> >> It removes redundant code, increases readability, and more importantly,
> >> makes it easier to introduce a new feature based on trace probe
> >> (it's possible).
> >>
> >> Signed-off-by: Song Chen <chensong_2000@189.cn>
> >> Reported-by: kernel test robot <lkp@intel.com>
> >>
> >> ---
> >> v2:
> >> 1, reorganize patchset
> >>
> >> v3:
> >> 1, mark nokprobe_inline for get_event_field
> >> 2, remove warnings reported from kernel test robot
> >> 3, fix errors reported from kernel test robot
> >>
> >> v4:
> >> 1, reset changes in v3(2) and v3(3), they are not reasonable fix.
> >> 2, I intended to introduce a new header file to exclude
> >> trace_events_synth.c out of the patch. However, after looking
> >> further, i found the errors in [1] are introduced by this patch,
> >> but the warning in [1] are not. The errors can be fixed by adding
> >> "#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API".
> >>
> >> [1]:https://lore.kernel.org/lkml/202211301946.pkLE4PDp-lkp@intel.com/
> >> ---
> >>   kernel/trace/trace_eprobe.c       | 144 ------------------------------
> >>   kernel/trace/trace_events_synth.c |   7 +-
> >>   kernel/trace/trace_kprobe.c       | 102 ---------------------
> >>   kernel/trace/trace_probe_kernel.h | 143 +++++++++++++++++++++++++++--
> >>   4 files changed, 141 insertions(+), 255 deletions(-)
> >>
> >> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> >> index bdb26eee7a0c..60ced4a7a25d 100644
> >> --- a/kernel/trace/trace_eprobe.c
> >> +++ b/kernel/trace/trace_eprobe.c
> >> @@ -319,64 +319,6 @@ print_eprobe_event(struct trace_iterator *iter, int flags,
> >>   	return trace_handle_return(s);
> >>   }
> >>   
> >> -static unsigned long get_event_field(struct fetch_insn *code, void *rec)
> >> -{
> >> -	struct ftrace_event_field *field = code->data;
> >> -	unsigned long val;
> >> -	void *addr;
> >> -
> >> -	addr = rec + field->offset;
> >> -
> >> -	if (is_string_field(field)) {
> >> -		switch (field->filter_type) {
> >> -		case FILTER_DYN_STRING:
> >> -			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
> >> -			break;
> >> -		case FILTER_RDYN_STRING:
> >> -			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
> >> -			break;
> >> -		case FILTER_STATIC_STRING:
> >> -			val = (unsigned long)addr;
> >> -			break;
> >> -		case FILTER_PTR_STRING:
> >> -			val = (unsigned long)(*(char *)addr);
> >> -			break;
> >> -		default:
> >> -			WARN_ON_ONCE(1);
> >> -			return 0;
> >> -		}
> >> -		return val;
> >> -	}
> >> -
> >> -	switch (field->size) {
> >> -	case 1:
> >> -		if (field->is_signed)
> >> -			val = *(char *)addr;
> >> -		else
> >> -			val = *(unsigned char *)addr;
> >> -		break;
> >> -	case 2:
> >> -		if (field->is_signed)
> >> -			val = *(short *)addr;
> >> -		else
> >> -			val = *(unsigned short *)addr;
> >> -		break;
> >> -	case 4:
> >> -		if (field->is_signed)
> >> -			val = *(int *)addr;
> >> -		else
> >> -			val = *(unsigned int *)addr;
> >> -		break;
> >> -	default:
> >> -		if (field->is_signed)
> >> -			val = *(long *)addr;
> >> -		else
> >> -			val = *(unsigned long *)addr;
> >> -		break;
> >> -	}
> >> -	return val;
> >> -}
> >> -
> >>   static int get_eprobe_size(struct trace_probe *tp, void *rec)
> >>   {
> >>   	struct fetch_insn *code;
> >> @@ -419,92 +361,6 @@ static int get_eprobe_size(struct trace_probe *tp, void *rec)
> >>   	return ret;
> >>   }
> >>   
> >> -/* Kprobe specific fetch functions */
> >> -
> >> -/* Note that we don't verify it, since the code does not come from user space */
> >> -static int
> >> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> >> -		   void *base)
> >> -{
> >> -	unsigned long val;
> >> -
> >> - retry:
> >> -	switch (code->op) {
> >> -	case FETCH_OP_TP_ARG:
> >> -		val = get_event_field(code, rec);
> >> -		break;
> >> -	case FETCH_OP_IMM:
> >> -		val = code->immediate;
> >> -		break;
> >> -	case FETCH_OP_COMM:
> >> -		val = (unsigned long)current->comm;
> >> -		break;
> >> -	case FETCH_OP_DATA:
> >> -		val = (unsigned long)code->data;
> >> -		break;
> >> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
> >> -		code++;
> >> -		goto retry;
> >> -	default:
> >> -		return -EILSEQ;
> >> -	}
> >> -	code++;
> >> -	return process_fetch_insn_bottom(code, val, dest, base);
> >> -}
> >> -NOKPROBE_SYMBOL(process_fetch_insn)
> >> -
> >> -/* Return the length of string -- including null terminal byte */
> >> -static nokprobe_inline int
> >> -fetch_store_strlen_user(unsigned long addr)
> >> -{
> >> -	return kern_fetch_store_strlen_user(addr);
> >> -}
> >> -
> >> -/* Return the length of string -- including null terminal byte */
> >> -static nokprobe_inline int
> >> -fetch_store_strlen(unsigned long addr)
> >> -{
> >> -	return kern_fetch_store_strlen(addr);
> >> -}
> >> -
> >> -/*
> >> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
> >> - * with max length and relative data location.
> >> - */
> >> -static nokprobe_inline int
> >> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
> >> -{
> >> -	return kern_fetch_store_string_user(addr, dest, base);
> >> -}
> >> -
> >> -/*
> >> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
> >> - * length and relative data location.
> >> - */
> >> -static nokprobe_inline int
> >> -fetch_store_string(unsigned long addr, void *dest, void *base)
> >> -{
> >> -	return kern_fetch_store_string(addr, dest, base);
> >> -}
> >> -
> >> -static nokprobe_inline int
> >> -probe_mem_read_user(void *dest, void *src, size_t size)
> >> -{
> >> -	const void __user *uaddr =  (__force const void __user *)src;
> >> -
> >> -	return copy_from_user_nofault(dest, uaddr, size);
> >> -}
> >> -
> >> -static nokprobe_inline int
> >> -probe_mem_read(void *dest, void *src, size_t size)
> >> -{
> >> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> >> -	if ((unsigned long)src < TASK_SIZE)
> >> -		return probe_mem_read_user(dest, src, size);
> >> -#endif
> >> -	return copy_from_kernel_nofault(dest, src, size);
> >> -}
> >> -
> >>   /* eprobe handler */
> >>   static inline void
> >>   __eprobe_trace_func(struct eprobe_data *edata, void *rec)
> >> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> >> index e310052dc83c..7460f18ba973 100644
> >> --- a/kernel/trace/trace_events_synth.c
> >> +++ b/kernel/trace/trace_events_synth.c
> >> @@ -18,6 +18,7 @@
> >>   #include <linux/trace_events.h>
> >>   #include <trace/events/mmflags.h>
> >>   #include "trace_probe.h"
> >> +#include "trace_probe_tmpl.h"
> >>   #include "trace_probe_kernel.h"
> >>   
> >>   #include "trace_synth.h"
> >> @@ -420,12 +421,12 @@ static unsigned int trace_string(struct synth_trace_event *entry,
> >>   		data_offset += event->n_u64 * sizeof(u64);
> >>   		data_offset += data_size;
> >>   
> >> -		len = kern_fetch_store_strlen((unsigned long)str_val);
> >> +		len = fetch_store_strlen((unsigned long)str_val);
> >>   
> >>   		data_offset |= len << 16;
> >>   		*(u32 *)&entry->fields[*n_u64] = data_offset;
> >>   
> >> -		ret = kern_fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
> >> +		ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
> >>   
> >>   		(*n_u64)++;
> >>   	} else {
> >> @@ -473,7 +474,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
> >>   		val_idx = var_ref_idx[field_pos];
> >>   		str_val = (char *)(long)var_ref_vals[val_idx];
> >>   
> >> -		len = kern_fetch_store_strlen((unsigned long)str_val);
> >> +		len = fetch_store_strlen((unsigned long)str_val);
> >>   
> >>   		fields_size += len;
> >>   	}
> >> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> >> index a4ffa864dbb7..c2e0b741ae82 100644
> >> --- a/kernel/trace/trace_kprobe.c
> >> +++ b/kernel/trace/trace_kprobe.c
> >> @@ -1218,108 +1218,6 @@ static const struct file_operations kprobe_profile_ops = {
> >>   	.release        = seq_release,
> >>   };
> >>   
> >> -/* Kprobe specific fetch functions */
> >> -
> >> -/* Return the length of string -- including null terminal byte */
> >> -static nokprobe_inline int
> >> -fetch_store_strlen_user(unsigned long addr)
> >> -{
> >> -	return kern_fetch_store_strlen_user(addr);
> >> -}
> >> -
> >> -/* Return the length of string -- including null terminal byte */
> >> -static nokprobe_inline int
> >> -fetch_store_strlen(unsigned long addr)
> >> -{
> >> -	return kern_fetch_store_strlen(addr);
> >> -}
> >> -
> >> -/*
> >> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
> >> - * with max length and relative data location.
> >> - */
> >> -static nokprobe_inline int
> >> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
> >> -{
> >> -	return kern_fetch_store_string_user(addr, dest, base);
> >> -}
> >> -
> >> -/*
> >> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
> >> - * length and relative data location.
> >> - */
> >> -static nokprobe_inline int
> >> -fetch_store_string(unsigned long addr, void *dest, void *base)
> >> -{
> >> -	return kern_fetch_store_string(addr, dest, base);
> >> -}
> >> -
> >> -static nokprobe_inline int
> >> -probe_mem_read_user(void *dest, void *src, size_t size)
> >> -{
> >> -	const void __user *uaddr =  (__force const void __user *)src;
> >> -
> >> -	return copy_from_user_nofault(dest, uaddr, size);
> >> -}
> >> -
> >> -static nokprobe_inline int
> >> -probe_mem_read(void *dest, void *src, size_t size)
> >> -{
> >> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> >> -	if ((unsigned long)src < TASK_SIZE)
> >> -		return probe_mem_read_user(dest, src, size);
> >> -#endif
> >> -	return copy_from_kernel_nofault(dest, src, size);
> >> -}
> >> -
> >> -/* Note that we don't verify it, since the code does not come from user space */
> >> -static int
> >> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> >> -		   void *base)
> >> -{
> >> -	struct pt_regs *regs = rec;
> >> -	unsigned long val;
> >> -
> >> -retry:
> >> -	/* 1st stage: get value from context */
> >> -	switch (code->op) {
> >> -	case FETCH_OP_REG:
> >> -		val = regs_get_register(regs, code->param);
> >> -		break;
> >> -	case FETCH_OP_STACK:
> >> -		val = regs_get_kernel_stack_nth(regs, code->param);
> >> -		break;
> >> -	case FETCH_OP_STACKP:
> >> -		val = kernel_stack_pointer(regs);
> >> -		break;
> >> -	case FETCH_OP_RETVAL:
> >> -		val = regs_return_value(regs);
> >> -		break;
> >> -	case FETCH_OP_IMM:
> >> -		val = code->immediate;
> >> -		break;
> >> -	case FETCH_OP_COMM:
> >> -		val = (unsigned long)current->comm;
> >> -		break;
> >> -	case FETCH_OP_DATA:
> >> -		val = (unsigned long)code->data;
> >> -		break;
> >> -#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> >> -	case FETCH_OP_ARG:
> >> -		val = regs_get_kernel_argument(regs, code->param);
> >> -		break;
> >> -#endif
> >> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
> >> -		code++;
> >> -		goto retry;
> >> -	default:
> >> -		return -EILSEQ;
> >> -	}
> >> -	code++;
> >> -
> >> -	return process_fetch_insn_bottom(code, val, dest, base);
> >> -}
> >> -NOKPROBE_SYMBOL(process_fetch_insn)
> >>   
> >>   /* Kprobe handler */
> >>   static nokprobe_inline void
> >> diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
> >> index 77dbd9ff9782..39f44513ec4e 100644
> >> --- a/kernel/trace/trace_probe_kernel.h
> >> +++ b/kernel/trace/trace_probe_kernel.h
> >> @@ -12,7 +12,7 @@
> >>    */
> >>   /* Return the length of string -- including null terminal byte */
> >>   static nokprobe_inline int
> >> -kern_fetch_store_strlen_user(unsigned long addr)
> >> +fetch_store_strlen_user(unsigned long addr)
> >>   {
> >>   	const void __user *uaddr =  (__force const void __user *)addr;
> >>   	int ret;
> >> @@ -29,14 +29,14 @@ kern_fetch_store_strlen_user(unsigned long addr)
> >>   
> >>   /* Return the length of string -- including null terminal byte */
> >>   static nokprobe_inline int
> >> -kern_fetch_store_strlen(unsigned long addr)
> >> +fetch_store_strlen(unsigned long addr)
> >>   {
> >>   	int ret, len = 0;
> >>   	u8 c;
> >>   
> >>   #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> >>   	if (addr < TASK_SIZE)
> >> -		return kern_fetch_store_strlen_user(addr);
> >> +		return fetch_store_strlen_user(addr);
> >>   #endif
> >>   
> >>   	do {
> >> @@ -63,7 +63,7 @@ static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void
> >>    * with max length and relative data location.
> >>    */
> >>   static nokprobe_inline int
> >> -kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
> >> +fetch_store_string_user(unsigned long addr, void *dest, void *base)
> >>   {
> >>   	const void __user *uaddr =  (__force const void __user *)addr;
> >>   	int maxlen = get_loc_len(*(u32 *)dest);
> >> @@ -86,7 +86,7 @@ kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
> >>    * length and relative data location.
> >>    */
> >>   static nokprobe_inline int
> >> -kern_fetch_store_string(unsigned long addr, void *dest, void *base)
> >> +fetch_store_string(unsigned long addr, void *dest, void *base)
> >>   {
> >>   	int maxlen = get_loc_len(*(u32 *)dest);
> >>   	void *__dest;
> >> @@ -94,7 +94,7 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
> >>   
> >>   #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> >>   	if ((unsigned long)addr < TASK_SIZE)
> >> -		return kern_fetch_store_string_user(addr, dest, base);
> >> +		return fetch_store_string_user(addr, dest, base);
> >>   #endif
> >>   
> >>   	if (unlikely(!maxlen))
> >> @@ -112,4 +112,135 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
> >>   	return ret;
> >>   }
> >>   
> >> +static nokprobe_inline int
> >> +probe_mem_read_user(void *dest, void *src, size_t size)
> >> +{
> >> +	const void __user *uaddr =  (__force const void __user *)src;
> >> +
> >> +	return copy_from_user_nofault(dest, uaddr, size);
> >> +}
> >> +
> >> +static nokprobe_inline int
> >> +probe_mem_read(void *dest, void *src, size_t size)
> >> +{
> >> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> >> +	if ((unsigned long)src < TASK_SIZE)
> >> +		return probe_mem_read_user(dest, src, size);
> >> +#endif
> >> +	return copy_from_kernel_nofault(dest, src, size);
> >> +}
> >> +
> >> +static nokprobe_inline unsigned long
> >> +get_event_field(struct fetch_insn *code, void *rec)
> >> +{
> >> +	struct ftrace_event_field *field = code->data;
> >> +	unsigned long val;
> >> +	void *addr;
> >> +
> >> +	addr = rec + field->offset;
> >> +
> >> +	if (is_string_field(field)) {
> >> +		switch (field->filter_type) {
> >> +		case FILTER_DYN_STRING:
> >> +			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
> >> +			break;
> >> +		case FILTER_RDYN_STRING:
> >> +			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
> >> +			break;
> >> +		case FILTER_STATIC_STRING:
> >> +			val = (unsigned long)addr;
> >> +			break;
> >> +		case FILTER_PTR_STRING:
> >> +			val = (unsigned long)(*(char *)addr);
> >> +			break;
> >> +		default:
> >> +			WARN_ON_ONCE(1);
> >> +			return 0;
> >> +		}
> >> +		return val;
> >> +	}
> >> +
> >> +	switch (field->size) {
> >> +	case 1:
> >> +		if (field->is_signed)
> >> +			val = *(char *)addr;
> >> +		else
> >> +			val = *(unsigned char *)addr;
> >> +		break;
> >> +	case 2:
> >> +		if (field->is_signed)
> >> +			val = *(short *)addr;
> >> +		else
> >> +			val = *(unsigned short *)addr;
> >> +		break;
> >> +	case 4:
> >> +		if (field->is_signed)
> >> +			val = *(int *)addr;
> >> +		else
> >> +			val = *(unsigned int *)addr;
> >> +		break;
> >> +	default:
> >> +		if (field->is_signed)
> >> +			val = *(long *)addr;
> >> +		else
> >> +			val = *(unsigned long *)addr;
> >> +		break;
> >> +	}
> >> +	return val;
> >> +}
> >> +
> >> +/* Note that we don't verify it, since the code does not come from user space */
> >> +static int
> >> +process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> >> +		   void *base)
> >> +{
> >> +	struct pt_regs *regs = rec;
> >> +	unsigned long val;
> >> +
> >> +retry:
> >> +	/* 1st stage: get value from context */
> >> +	switch (code->op) {
> >> +#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API
> >> +	case FETCH_OP_REG:
> >> +		val = regs_get_register(regs, code->param);
> >> +		break;
> >> +	case FETCH_OP_STACK:
> >> +		val = regs_get_kernel_stack_nth(regs, code->param);
> >> +		break;
> >> +	case FETCH_OP_STACKP:
> >> +		val = kernel_stack_pointer(regs);
> >> +		break;
> >> +	case FETCH_OP_RETVAL:
> >> +		val = regs_return_value(regs);
> >> +		break;
> >> +#endif
> >> +	case FETCH_OP_IMM:
> >> +		val = code->immediate;
> >> +		break;
> >> +	case FETCH_OP_COMM:
> >> +		val = (unsigned long)current->comm;
> >> +		break;
> >> +	case FETCH_OP_DATA:
> >> +		val = (unsigned long)code->data;
> >> +		break;
> >> +#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> >> +	case FETCH_OP_ARG:
> >> +		val = regs_get_kernel_argument(regs, code->param);
> >> +		break;
> >> +#endif
> >> +	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
> >> +		code++;
> >> +		goto retry;
> >> +	case FETCH_OP_TP_ARG:
> >> +		val = get_event_field(code, rec);
> >> +		break;
> >> +	default:
> >> +		return -EILSEQ;
> >> +	}
> >> +	code++;
> >> +
> >> +	return process_fetch_insn_bottom(code, val, dest, base);
> >> +}
> >> +NOKPROBE_SYMBOL(process_fetch_insn)
> >> +
> >>   #endif /* __TRACE_PROBE_KERNEL_H_ */
> >> -- 
> >> 2.25.1
> >>
> > 
> >
  

Hi,

在 2023/1/3 18:33, Masami Hiramatsu (Google) 写道:
> On Fri, 30 Dec 2022 09:59:31 +0800
> Song Chen <chensong_2000@189.cn> wrote:
> 
>> Hi,
>>
>> 在 2022/12/29 17:30, Masami Hiramatsu (Google) 写道:
>>> On Wed, 28 Dec 2022 15:08:25 +0800
>>> Song Chen <chensong_2000@189.cn> wrote:
>>>
>>>> There are 7 function definitions in trace_probe_tmpl.h, they are:
>>>>
>>>> 1, process_fetch_insn
>>>
>>> Other functions except for this are OK for me.
>>> But I think this function should have different instance for kprobe
>>> and eprobe, because the passed 'void *rec' is completely different.
>>> For the kprobe's process_fetch_insn() will take a 'pt_regs *', on the
>>> other hand, the eprobe's process_fetch_insn() will take a
>>> 'ftrace_event_field *'.
>>> I also, don't want to expose get_event_field() function because
>>> it is only for the eprobes.
>>>
>>> What about making a new common function and call it in default case
>>> from both process_fetch_insn()? Your goal is reducing the redundant
>>> code, then it is enough to share only the common code. :)
>>>
>>> For example, in trace_probe_kernel.h,
>>>
>>> process_common_fetch_insn(struct fetch_insn *code, void *dest, void *base, unsigned long *val)
>>> {
>>> 	switch (code->op) {
>>> 	case FETCH_OP_IMM:
>>> 		*val = code->immediate;
>>> 		break;
>>> 	case FETCH_OP_COMM:
>>> 		*val = (unsigned long)current->comm;
>>> 		break;
>>> 	case FETCH_OP_DATA:
>>> 		*val = (unsigned long)code->data;
>>> 		break;
>>> 	default:
>>> 		return -EILSEQ;
>>> 	}
>>> 	return 0;
>>> }
>>>
>>> For kprobe events:
>>>
>>> process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
>>> {
>>> 	while (code->op == FETCH_NOP_SYMBOL)
>>> 		code++;
>>> 	switch (code->op) {
>>> 	case FETCH_OP_REG:
>>> 		val = regs_get_register(regs, code->param);
>>> 		...
>>> 	default:
>>> 		ret = process_common_fetch_insn(code, dest, base, &val);
>>> 		if (ret < 0)
>>> 			return ret;
>>> 	}
>>> 	...
>>> }
>>>
>>> For eprobe events:
>>>
>>> process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
>>> {
>>> 	while (code->op == FETCH_NOP_SYMBOL)
>>> 		code++;
>>> 	if (code->op == FETCH_OP_TP_ARG) {
>>> 		val = get_event_field(code, rec);
>>> 	} else {
>>> 		ret = process_common_fetch_insn(code, dest, base, &val);
>>> 		if (ret < 0)
>>> 			return ret;
>>> 	}
>>> 	...
>>> }
>>>
>>> You also don't see the error related to CONFIG_HAVE_REGS_AND_STACK_ACCESS_API. :)
>>>
>>> Thank you,
>>>
>>
>> Thanks a lot for the good idea and so specific demo code, i accept it
>> and will submit a new one based on it.
>>
>> If we think about it further, we can implement process_common_fetch_insn
>> in trace_probe_tmpl.h, uprobe can benefit from it as well, what do you
>> think? i will include it in the next submit and you can have a look.
> 
> Agreed. It sounds good to me. :)
> 
> Thank you!
> 

That's so kind, many thanks :)

Song

>>
>> Thanks again.
>>
>> Song
>>
>>>> 2, fetch_store_strlen
>>>> 3, fetch_store_string
>>>> 4, fetch_store_strlen_user
>>>> 5, fetch_store_string_user
>>>> 6, probe_mem_read
>>>> 7, probe_mem_read_user
>>>>
>>>> Every C file which includes trace_probe_tmpl.h has to implement them,
>>>> otherwise it gets warnings and errors. However, some of them are identical,
>>>> like kprobe and eprobe, as a result, there is a lot redundant code in those
>>>> 2 files.
>>>>
>>>> This patch would like to provide default behaviors for those functions
>>>> which kprobe and eprobe can share by just including trace_probe_kernel.h
>>>> with trace_probe_tmpl.h together.
>>>>
>>>> It removes redundant code, increases readability, and more importantly,
>>>> makes it easier to introduce a new feature based on trace probe
>>>> (it's possible).
>>>>
>>>> Signed-off-by: Song Chen <chensong_2000@189.cn>
>>>> Reported-by: kernel test robot <lkp@intel.com>
>>>>
>>>> ---
>>>> v2:
>>>> 1, reorganize patchset
>>>>
>>>> v3:
>>>> 1, mark nokprobe_inline for get_event_field
>>>> 2, remove warnings reported from kernel test robot
>>>> 3, fix errors reported from kernel test robot
>>>>
>>>> v4:
>>>> 1, reset changes in v3(2) and v3(3), they are not reasonable fix.
>>>> 2, I intended to introduce a new header file to exclude
>>>> trace_events_synth.c out of the patch. However, after looking
>>>> further, i found the errors in [1] are introduced by this patch,
>>>> but the warning in [1] are not. The errors can be fixed by adding
>>>> "#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API".
>>>>
>>>> [1]:https://lore.kernel.org/lkml/202211301946.pkLE4PDp-lkp@intel.com/
>>>> ---
>>>>    kernel/trace/trace_eprobe.c       | 144 ------------------------------
>>>>    kernel/trace/trace_events_synth.c |   7 +-
>>>>    kernel/trace/trace_kprobe.c       | 102 ---------------------
>>>>    kernel/trace/trace_probe_kernel.h | 143 +++++++++++++++++++++++++++--
>>>>    4 files changed, 141 insertions(+), 255 deletions(-)
>>>>
>>>> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
>>>> index bdb26eee7a0c..60ced4a7a25d 100644
>>>> --- a/kernel/trace/trace_eprobe.c
>>>> +++ b/kernel/trace/trace_eprobe.c
>>>> @@ -319,64 +319,6 @@ print_eprobe_event(struct trace_iterator *iter, int flags,
>>>>    	return trace_handle_return(s);
>>>>    }
>>>>    
>>>> -static unsigned long get_event_field(struct fetch_insn *code, void *rec)
>>>> -{
>>>> -	struct ftrace_event_field *field = code->data;
>>>> -	unsigned long val;
>>>> -	void *addr;
>>>> -
>>>> -	addr = rec + field->offset;
>>>> -
>>>> -	if (is_string_field(field)) {
>>>> -		switch (field->filter_type) {
>>>> -		case FILTER_DYN_STRING:
>>>> -			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
>>>> -			break;
>>>> -		case FILTER_RDYN_STRING:
>>>> -			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
>>>> -			break;
>>>> -		case FILTER_STATIC_STRING:
>>>> -			val = (unsigned long)addr;
>>>> -			break;
>>>> -		case FILTER_PTR_STRING:
>>>> -			val = (unsigned long)(*(char *)addr);
>>>> -			break;
>>>> -		default:
>>>> -			WARN_ON_ONCE(1);
>>>> -			return 0;
>>>> -		}
>>>> -		return val;
>>>> -	}
>>>> -
>>>> -	switch (field->size) {
>>>> -	case 1:
>>>> -		if (field->is_signed)
>>>> -			val = *(char *)addr;
>>>> -		else
>>>> -			val = *(unsigned char *)addr;
>>>> -		break;
>>>> -	case 2:
>>>> -		if (field->is_signed)
>>>> -			val = *(short *)addr;
>>>> -		else
>>>> -			val = *(unsigned short *)addr;
>>>> -		break;
>>>> -	case 4:
>>>> -		if (field->is_signed)
>>>> -			val = *(int *)addr;
>>>> -		else
>>>> -			val = *(unsigned int *)addr;
>>>> -		break;
>>>> -	default:
>>>> -		if (field->is_signed)
>>>> -			val = *(long *)addr;
>>>> -		else
>>>> -			val = *(unsigned long *)addr;
>>>> -		break;
>>>> -	}
>>>> -	return val;
>>>> -}
>>>> -
>>>>    static int get_eprobe_size(struct trace_probe *tp, void *rec)
>>>>    {
>>>>    	struct fetch_insn *code;
>>>> @@ -419,92 +361,6 @@ static int get_eprobe_size(struct trace_probe *tp, void *rec)
>>>>    	return ret;
>>>>    }
>>>>    
>>>> -/* Kprobe specific fetch functions */
>>>> -
>>>> -/* Note that we don't verify it, since the code does not come from user space */
>>>> -static int
>>>> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>>>> -		   void *base)
>>>> -{
>>>> -	unsigned long val;
>>>> -
>>>> - retry:
>>>> -	switch (code->op) {
>>>> -	case FETCH_OP_TP_ARG:
>>>> -		val = get_event_field(code, rec);
>>>> -		break;
>>>> -	case FETCH_OP_IMM:
>>>> -		val = code->immediate;
>>>> -		break;
>>>> -	case FETCH_OP_COMM:
>>>> -		val = (unsigned long)current->comm;
>>>> -		break;
>>>> -	case FETCH_OP_DATA:
>>>> -		val = (unsigned long)code->data;
>>>> -		break;
>>>> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>>>> -		code++;
>>>> -		goto retry;
>>>> -	default:
>>>> -		return -EILSEQ;
>>>> -	}
>>>> -	code++;
>>>> -	return process_fetch_insn_bottom(code, val, dest, base);
>>>> -}
>>>> -NOKPROBE_SYMBOL(process_fetch_insn)
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen_user(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen_user(addr);
>>>> -}
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen(addr);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
>>>> - * with max length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string_user(addr, dest, base);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
>>>> - * length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string(addr, dest, base);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read_user(void *dest, void *src, size_t size)
>>>> -{
>>>> -	const void __user *uaddr =  (__force const void __user *)src;
>>>> -
>>>> -	return copy_from_user_nofault(dest, uaddr, size);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read(void *dest, void *src, size_t size)
>>>> -{
>>>> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>> -	if ((unsigned long)src < TASK_SIZE)
>>>> -		return probe_mem_read_user(dest, src, size);
>>>> -#endif
>>>> -	return copy_from_kernel_nofault(dest, src, size);
>>>> -}
>>>> -
>>>>    /* eprobe handler */
>>>>    static inline void
>>>>    __eprobe_trace_func(struct eprobe_data *edata, void *rec)
>>>> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
>>>> index e310052dc83c..7460f18ba973 100644
>>>> --- a/kernel/trace/trace_events_synth.c
>>>> +++ b/kernel/trace/trace_events_synth.c
>>>> @@ -18,6 +18,7 @@
>>>>    #include <linux/trace_events.h>
>>>>    #include <trace/events/mmflags.h>
>>>>    #include "trace_probe.h"
>>>> +#include "trace_probe_tmpl.h"
>>>>    #include "trace_probe_kernel.h"
>>>>    
>>>>    #include "trace_synth.h"
>>>> @@ -420,12 +421,12 @@ static unsigned int trace_string(struct synth_trace_event *entry,
>>>>    		data_offset += event->n_u64 * sizeof(u64);
>>>>    		data_offset += data_size;
>>>>    
>>>> -		len = kern_fetch_store_strlen((unsigned long)str_val);
>>>> +		len = fetch_store_strlen((unsigned long)str_val);
>>>>    
>>>>    		data_offset |= len << 16;
>>>>    		*(u32 *)&entry->fields[*n_u64] = data_offset;
>>>>    
>>>> -		ret = kern_fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>>>> +		ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>>>>    
>>>>    		(*n_u64)++;
>>>>    	} else {
>>>> @@ -473,7 +474,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
>>>>    		val_idx = var_ref_idx[field_pos];
>>>>    		str_val = (char *)(long)var_ref_vals[val_idx];
>>>>    
>>>> -		len = kern_fetch_store_strlen((unsigned long)str_val);
>>>> +		len = fetch_store_strlen((unsigned long)str_val);
>>>>    
>>>>    		fields_size += len;
>>>>    	}
>>>> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
>>>> index a4ffa864dbb7..c2e0b741ae82 100644
>>>> --- a/kernel/trace/trace_kprobe.c
>>>> +++ b/kernel/trace/trace_kprobe.c
>>>> @@ -1218,108 +1218,6 @@ static const struct file_operations kprobe_profile_ops = {
>>>>    	.release        = seq_release,
>>>>    };
>>>>    
>>>> -/* Kprobe specific fetch functions */
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen_user(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen_user(addr);
>>>> -}
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen(addr);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
>>>> - * with max length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string_user(addr, dest, base);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
>>>> - * length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string(addr, dest, base);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read_user(void *dest, void *src, size_t size)
>>>> -{
>>>> -	const void __user *uaddr =  (__force const void __user *)src;
>>>> -
>>>> -	return copy_from_user_nofault(dest, uaddr, size);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read(void *dest, void *src, size_t size)
>>>> -{
>>>> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>> -	if ((unsigned long)src < TASK_SIZE)
>>>> -		return probe_mem_read_user(dest, src, size);
>>>> -#endif
>>>> -	return copy_from_kernel_nofault(dest, src, size);
>>>> -}
>>>> -
>>>> -/* Note that we don't verify it, since the code does not come from user space */
>>>> -static int
>>>> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>>>> -		   void *base)
>>>> -{
>>>> -	struct pt_regs *regs = rec;
>>>> -	unsigned long val;
>>>> -
>>>> -retry:
>>>> -	/* 1st stage: get value from context */
>>>> -	switch (code->op) {
>>>> -	case FETCH_OP_REG:
>>>> -		val = regs_get_register(regs, code->param);
>>>> -		break;
>>>> -	case FETCH_OP_STACK:
>>>> -		val = regs_get_kernel_stack_nth(regs, code->param);
>>>> -		break;
>>>> -	case FETCH_OP_STACKP:
>>>> -		val = kernel_stack_pointer(regs);
>>>> -		break;
>>>> -	case FETCH_OP_RETVAL:
>>>> -		val = regs_return_value(regs);
>>>> -		break;
>>>> -	case FETCH_OP_IMM:
>>>> -		val = code->immediate;
>>>> -		break;
>>>> -	case FETCH_OP_COMM:
>>>> -		val = (unsigned long)current->comm;
>>>> -		break;
>>>> -	case FETCH_OP_DATA:
>>>> -		val = (unsigned long)code->data;
>>>> -		break;
>>>> -#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
>>>> -	case FETCH_OP_ARG:
>>>> -		val = regs_get_kernel_argument(regs, code->param);
>>>> -		break;
>>>> -#endif
>>>> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>>>> -		code++;
>>>> -		goto retry;
>>>> -	default:
>>>> -		return -EILSEQ;
>>>> -	}
>>>> -	code++;
>>>> -
>>>> -	return process_fetch_insn_bottom(code, val, dest, base);
>>>> -}
>>>> -NOKPROBE_SYMBOL(process_fetch_insn)
>>>>    
>>>>    /* Kprobe handler */
>>>>    static nokprobe_inline void
>>>> diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
>>>> index 77dbd9ff9782..39f44513ec4e 100644
>>>> --- a/kernel/trace/trace_probe_kernel.h
>>>> +++ b/kernel/trace/trace_probe_kernel.h
>>>> @@ -12,7 +12,7 @@
>>>>     */
>>>>    /* Return the length of string -- including null terminal byte */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_strlen_user(unsigned long addr)
>>>> +fetch_store_strlen_user(unsigned long addr)
>>>>    {
>>>>    	const void __user *uaddr =  (__force const void __user *)addr;
>>>>    	int ret;
>>>> @@ -29,14 +29,14 @@ kern_fetch_store_strlen_user(unsigned long addr)
>>>>    
>>>>    /* Return the length of string -- including null terminal byte */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_strlen(unsigned long addr)
>>>> +fetch_store_strlen(unsigned long addr)
>>>>    {
>>>>    	int ret, len = 0;
>>>>    	u8 c;
>>>>    
>>>>    #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>>    	if (addr < TASK_SIZE)
>>>> -		return kern_fetch_store_strlen_user(addr);
>>>> +		return fetch_store_strlen_user(addr);
>>>>    #endif
>>>>    
>>>>    	do {
>>>> @@ -63,7 +63,7 @@ static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void
>>>>     * with max length and relative data location.
>>>>     */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>> +fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>>    {
>>>>    	const void __user *uaddr =  (__force const void __user *)addr;
>>>>    	int maxlen = get_loc_len(*(u32 *)dest);
>>>> @@ -86,7 +86,7 @@ kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>>     * length and relative data location.
>>>>     */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>>> +fetch_store_string(unsigned long addr, void *dest, void *base)
>>>>    {
>>>>    	int maxlen = get_loc_len(*(u32 *)dest);
>>>>    	void *__dest;
>>>> @@ -94,7 +94,7 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>>>    
>>>>    #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>>    	if ((unsigned long)addr < TASK_SIZE)
>>>> -		return kern_fetch_store_string_user(addr, dest, base);
>>>> +		return fetch_store_string_user(addr, dest, base);
>>>>    #endif
>>>>    
>>>>    	if (unlikely(!maxlen))
>>>> @@ -112,4 +112,135 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>>>    	return ret;
>>>>    }
>>>>    
>>>> +static nokprobe_inline int
>>>> +probe_mem_read_user(void *dest, void *src, size_t size)
>>>> +{
>>>> +	const void __user *uaddr =  (__force const void __user *)src;
>>>> +
>>>> +	return copy_from_user_nofault(dest, uaddr, size);
>>>> +}
>>>> +
>>>> +static nokprobe_inline int
>>>> +probe_mem_read(void *dest, void *src, size_t size)
>>>> +{
>>>> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>> +	if ((unsigned long)src < TASK_SIZE)
>>>> +		return probe_mem_read_user(dest, src, size);
>>>> +#endif
>>>> +	return copy_from_kernel_nofault(dest, src, size);
>>>> +}
>>>> +
>>>> +static nokprobe_inline unsigned long
>>>> +get_event_field(struct fetch_insn *code, void *rec)
>>>> +{
>>>> +	struct ftrace_event_field *field = code->data;
>>>> +	unsigned long val;
>>>> +	void *addr;
>>>> +
>>>> +	addr = rec + field->offset;
>>>> +
>>>> +	if (is_string_field(field)) {
>>>> +		switch (field->filter_type) {
>>>> +		case FILTER_DYN_STRING:
>>>> +			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
>>>> +			break;
>>>> +		case FILTER_RDYN_STRING:
>>>> +			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
>>>> +			break;
>>>> +		case FILTER_STATIC_STRING:
>>>> +			val = (unsigned long)addr;
>>>> +			break;
>>>> +		case FILTER_PTR_STRING:
>>>> +			val = (unsigned long)(*(char *)addr);
>>>> +			break;
>>>> +		default:
>>>> +			WARN_ON_ONCE(1);
>>>> +			return 0;
>>>> +		}
>>>> +		return val;
>>>> +	}
>>>> +
>>>> +	switch (field->size) {
>>>> +	case 1:
>>>> +		if (field->is_signed)
>>>> +			val = *(char *)addr;
>>>> +		else
>>>> +			val = *(unsigned char *)addr;
>>>> +		break;
>>>> +	case 2:
>>>> +		if (field->is_signed)
>>>> +			val = *(short *)addr;
>>>> +		else
>>>> +			val = *(unsigned short *)addr;
>>>> +		break;
>>>> +	case 4:
>>>> +		if (field->is_signed)
>>>> +			val = *(int *)addr;
>>>> +		else
>>>> +			val = *(unsigned int *)addr;
>>>> +		break;
>>>> +	default:
>>>> +		if (field->is_signed)
>>>> +			val = *(long *)addr;
>>>> +		else
>>>> +			val = *(unsigned long *)addr;
>>>> +		break;
>>>> +	}
>>>> +	return val;
>>>> +}
>>>> +
>>>> +/* Note that we don't verify it, since the code does not come from user space */
>>>> +static int
>>>> +process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>>>> +		   void *base)
>>>> +{
>>>> +	struct pt_regs *regs = rec;
>>>> +	unsigned long val;
>>>> +
>>>> +retry:
>>>> +	/* 1st stage: get value from context */
>>>> +	switch (code->op) {
>>>> +#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API
>>>> +	case FETCH_OP_REG:
>>>> +		val = regs_get_register(regs, code->param);
>>>> +		break;
>>>> +	case FETCH_OP_STACK:
>>>> +		val = regs_get_kernel_stack_nth(regs, code->param);
>>>> +		break;
>>>> +	case FETCH_OP_STACKP:
>>>> +		val = kernel_stack_pointer(regs);
>>>> +		break;
>>>> +	case FETCH_OP_RETVAL:
>>>> +		val = regs_return_value(regs);
>>>> +		break;
>>>> +#endif
>>>> +	case FETCH_OP_IMM:
>>>> +		val = code->immediate;
>>>> +		break;
>>>> +	case FETCH_OP_COMM:
>>>> +		val = (unsigned long)current->comm;
>>>> +		break;
>>>> +	case FETCH_OP_DATA:
>>>> +		val = (unsigned long)code->data;
>>>> +		break;
>>>> +#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
>>>> +	case FETCH_OP_ARG:
>>>> +		val = regs_get_kernel_argument(regs, code->param);
>>>> +		break;
>>>> +#endif
>>>> +	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>>>> +		code++;
>>>> +		goto retry;
>>>> +	case FETCH_OP_TP_ARG:
>>>> +		val = get_event_field(code, rec);
>>>> +		break;
>>>> +	default:
>>>> +		return -EILSEQ;
>>>> +	}
>>>> +	code++;
>>>> +
>>>> +	return process_fetch_insn_bottom(code, val, dest, base);
>>>> +}
>>>> +NOKPROBE_SYMBOL(process_fetch_insn)
>>>> +
>>>>    #endif /* __TRACE_PROBE_KERNEL_H_ */
>>>> -- 
>>>> 2.25.1
>>>>
>>>
>>>
> 
>