diff mbox series

[v3,2/4] kernel/trace: Provide default impelentations defined in trace_probe_tmpl.h

Message ID 1670228994-4020-1-git-send-email-chensong_2000@189.cn
State New
Headers
Series reorganize trace_peobe_tmpl.h |

Commit Message

Song Chen Dec. 5, 2022, 8:29 a.m. UTC 
  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>

---
v2:
1, mark nokprobe_inline for get_event_field
---
 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 | 141 +++++++++++++++++++++++++++--
 4 files changed, 139 insertions(+), 255 deletions(-)

Comments

Masami Hiramatsu (Google) Dec. 23, 2022, 3:21 p.m. UTC | #1 
Hi Song,

On Mon,  5 Dec 2022 16:29:54 +0800
Song Chen <chensong_2000@189.cn> wrote:

> @@ -112,4 +112,133 @@ 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);
> +}
> +

So, the error which kernel build bot found has been introduced by this patch.
The easiest acceptable change will add

#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API

here, and #endif after process_fetch_insn(). 

Thank you,

> +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) {
> +	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;
> +	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
>
kernel test robot Dec. 27, 2022, 2:17 p.m. UTC | #2 
Hi Song,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on arnd-asm-generic/master]
[also build test ERROR on linus/master v6.2-rc1 next-20221226]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Song-Chen/reorganize-trace_peobe_tmpl-h/20221206-205410
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git master
patch link:    https://lore.kernel.org/r/1670228994-4020-1-git-send-email-chensong_2000%40189.cn
patch subject: [PATCH v3 2/4] kernel/trace: Provide default impelentations defined in trace_probe_tmpl.h
config: openrisc-randconfig-c44-20221225
compiler: or1k-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/baa4b7fb1f2e923d2d022bdc54f4d72f76aae41c
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Song-Chen/reorganize-trace_peobe_tmpl-h/20221206-205410
        git checkout baa4b7fb1f2e923d2d022bdc54f4d72f76aae41c
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=openrisc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=openrisc SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from kernel/trace/trace_events_synth.c:22:
   kernel/trace/trace_probe_kernel.h: In function 'process_fetch_insn':
>> kernel/trace/trace_probe_kernel.h:204:23: error: implicit declaration of function 'regs_get_register'; did you mean 'kset_register'? [-Werror=implicit-function-declaration]
     204 |                 val = regs_get_register(regs, code->param);
         |                       ^~~~~~~~~~~~~~~~~
         |                       kset_register
>> kernel/trace/trace_probe_kernel.h:207:23: error: implicit declaration of function 'regs_get_kernel_stack_nth' [-Werror=implicit-function-declaration]
     207 |                 val = regs_get_kernel_stack_nth(regs, code->param);
         |                       ^~~~~~~~~~~~~~~~~~~~~~~~~
>> kernel/trace/trace_probe_kernel.h:210:23: error: implicit declaration of function 'kernel_stack_pointer'; did you mean 'user_stack_pointer'? [-Werror=implicit-function-declaration]
     210 |                 val = kernel_stack_pointer(regs);
         |                       ^~~~~~~~~~~~~~~~~~~~
         |                       user_stack_pointer
   cc1: some warnings being treated as errors


vim +204 kernel/trace/trace_probe_kernel.h

   191	
   192	/* Note that we don't verify it, since the code does not come from user space */
   193	static int
   194	process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
   195			   void *base)
   196	{
   197		struct pt_regs *regs = rec;
   198		unsigned long val;
   199	
   200	retry:
   201		/* 1st stage: get value from context */
   202		switch (code->op) {
   203		case FETCH_OP_REG:
 > 204			val = regs_get_register(regs, code->param);
   205			break;
   206		case FETCH_OP_STACK:
 > 207			val = regs_get_kernel_stack_nth(regs, code->param);
   208			break;
   209		case FETCH_OP_STACKP:
 > 210			val = kernel_stack_pointer(regs);
   211			break;
   212		case FETCH_OP_RETVAL:
   213			val = regs_return_value(regs);
   214			break;
   215		case FETCH_OP_IMM:
   216			val = code->immediate;
   217			break;
   218		case FETCH_OP_COMM:
   219			val = (unsigned long)current->comm;
   220			break;
   221		case FETCH_OP_DATA:
   222			val = (unsigned long)code->data;
   223			break;
   224	#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
   225		case FETCH_OP_ARG:
   226			val = regs_get_kernel_argument(regs, code->param);
   227			break;
   228	#endif
   229		case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
   230			code++;
   231			goto retry;
   232		case FETCH_OP_TP_ARG:
   233			val = get_event_field(code, rec);
   234			break;
   235		default:
   236			return -EILSEQ;
   237		}
   238		code++;
   239	
   240		return process_fetch_insn_bottom(code, val, dest, base);
   241	}
   242	NOKPROBE_SYMBOL(process_fetch_insn)
   243
diff mbox series

Patch

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..8c42abe0dacf 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 +112,133 @@  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) {
+	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;
+	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_ */