[v5,0/8] support '%pd' and '%pD' for print file name

  During fault locating, the file name needs to be printed based on the
dentry/file address. The offset needs to be calculated each time, which
is troublesome. Similar to printk, kprobe supports printing file names
for dentry/file addresses.

Diff v5 vs v4:
1. Use glob_match() instead of str_has_suffix(), so remove the first patch;
2. Allocate buffer from heap for expand dentry;
3. Support "%pd/%pD" print type for fprobe;
4. Use $arg1 instead of origin register in test case;
5. Add test case for fprobe;

Diff v4 vs v3:
1. Use "argv[i][idx + 3] == 'd'" instead of "argv[i][strlen(argv[i]) - 1] == 'd'"
to judge print format in PATCH[4/7];

Diff v3 vs v2:
1. Return the index of where the suffix was found in str_has_suffix();

Diff v2 vs v1:
1. Use "%pd/%pD" print format instead of "pd/pD" print format;
2. Add "%pd/%pD" in README;
3. Expand "%pd/%pD" argument before parameter parsing;
4. Add more detail information in ftrace documentation;
5. Add test cases for new print format in selftests/ftrace;

Ye Bin (8):
  tracing/probes: add traceprobe_expand_dentry_args() helper
  tracing/probes: support '%pd' type for print struct dentry's name
  tracing/probes: support '%pD' type for print struct file's name
  tracing/probes: support '%pd/%pD' type for fprobe
  tracing: add new type "%pd/%pD" in readme_msg[]
  Documentation: tracing: add new type '%pd' and '%pD' for kprobe
  selftests/ftrace: add kprobe test cases for VFS type "%pd" and "%pD"
  selftests/ftrace: add fprobe test cases for VFS type "%pd" and "%pD"

 Documentation/trace/kprobetrace.rst           |  8 ++-
 kernel/trace/trace.c                          |  2 +-
 kernel/trace/trace_fprobe.c                   |  6 ++
 kernel/trace/trace_kprobe.c                   |  6 ++
 kernel/trace/trace_probe.c                    | 63 +++++++++++++++++++
 kernel/trace/trace_probe.h                    |  2 +
 .../ftrace/test.d/dynevent/fprobe_args_vfs.tc | 40 ++++++++++++
 .../ftrace/test.d/kprobe/kprobe_args_vfs.tc   | 43 +++++++++++++
 8 files changed, 167 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/fprobe_args_vfs.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_vfs.tc
  

Hi Ye,

On Thu, 25 Jan 2024 15:39:16 +0800
Ye Bin <yebin10@huawei.com> wrote:

> Add traceprobe_expand_dentry_args() to expand dentry args. this API is
> prepare to support "%pd" print format for kprobe.
> 
> Signed-off-by: Ye Bin <yebin10@huawei.com>
> ---
>  kernel/trace/trace_probe.c | 50 ++++++++++++++++++++++++++++++++++++++
>  kernel/trace/trace_probe.h |  2 ++
>  2 files changed, 52 insertions(+)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 4dc74d73fc1d..0c1caf0f474a 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -1565,6 +1565,56 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
>  	return ERR_PTR(ret);
>  }
>  
> +/* @buf: *buf must be equal to NULL. Caller must to free *buf */
> +int traceprobe_expand_dentry_args(int argc, const char *argv[], char **buf)
> +{
> +	int i, used, ret;
> +	int bufsize = MAX_DENTRY_ARGS_LEN;

nit: this bufsize is consistent, thus you should use the MAX_DENTRY_ARGS_LEN
     directly. (or add 'const' or maybe you can update bufsize as remaining size)

Thanks,

> +	char *tmpbuf = NULL;
> +
> +	if (*buf)
> +		return -EINVAL;
> +
> +	used = 0;
> +	for (i = 0; i < argc; i++) {
> +		if (glob_match("*:%pd", argv[i])) {
> +			char *tmp;
> +			char *equal;
> +
> +			if (!tmpbuf) {
> +				tmpbuf = kmalloc(bufsize, GFP_KERNEL);
> +				if (!tmpbuf)
> +					return -ENOMEM;
> +			}
> +
> +			tmp = kstrdup(argv[i], GFP_KERNEL);
> +			if (!tmp)
> +				goto nomem;
> +
> +			equal = strchr(tmp, '=');
> +			if (equal)
> +				*equal = '\0';
> +			tmp[strlen(argv[i]) - 4] = '\0';
> +			ret = snprintf(tmpbuf + used, bufsize - used,
> +				       "%s%s+0x0(+0x%zx(%s)):string",
> +				       equal ? tmp : "", equal ? "=" : "",
> +				       offsetof(struct dentry, d_name.name),
> +				       equal ? equal + 1 : tmp);
> +			kfree(tmp);
> +			if (ret >= bufsize - used)
> +				goto nomem;
> +			argv[i] = tmpbuf + used;
> +			used += ret + 1;
> +		}
> +	}
> +
> +	*buf = tmpbuf;
> +	return 0;
> +nomem:
> +	kfree(tmpbuf);
> +	return -ENOMEM;
> +}
> +
>  void traceprobe_finish_parse(struct traceprobe_parse_context *ctx)
>  {
>  	clear_btf_context(ctx);
> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> index 850d9ecb6765..5800513439f3 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -34,6 +34,7 @@
>  #define MAX_ARRAY_LEN		64
>  #define MAX_ARG_NAME_LEN	32
>  #define MAX_BTF_ARGS_LEN	128
> +#define MAX_DENTRY_ARGS_LEN	256
>  #define MAX_STRING_SIZE		PATH_MAX
>  #define MAX_ARG_BUF_LEN		(MAX_TRACE_ARGS * MAX_ARG_NAME_LEN)
>  
> @@ -402,6 +403,7 @@ extern int traceprobe_parse_probe_arg(struct trace_probe *tp, int i,
>  const char **traceprobe_expand_meta_args(int argc, const char *argv[],
>  					 int *new_argc, char *buf, int bufsize,
>  					 struct traceprobe_parse_context *ctx);
> +extern int traceprobe_expand_dentry_args(int argc, const char *argv[], char **buf);
>  
>  extern int traceprobe_update_arg(struct probe_arg *arg);
>  extern void traceprobe_free_probe_arg(struct probe_arg *arg);
> -- 
> 2.31.1
>
  

On Thu, 25 Jan 2024 15:39:19 +0800
Ye Bin <yebin10@huawei.com> wrote:

> Support print type '%pd/%pD' for print dentry's or file's name.
> 

nit: Looks good to me. but the patch ordering seems a bit strange.
This should be next to [2/8].

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thank you,

> Signed-off-by: Ye Bin <yebin10@huawei.com>
> ---
>  kernel/trace/trace_fprobe.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
> index 7d2ddbcfa377..988d68e906ad 100644
> --- a/kernel/trace/trace_fprobe.c
> +++ b/kernel/trace/trace_fprobe.c
> @@ -976,6 +976,7 @@ static int __trace_fprobe_create(int argc, const char *argv[])
>  	char gbuf[MAX_EVENT_NAME_LEN];
>  	char sbuf[KSYM_NAME_LEN];
>  	char abuf[MAX_BTF_ARGS_LEN];
> +	char *dbuf = NULL;
>  	bool is_tracepoint = false;
>  	struct tracepoint *tpoint = NULL;
>  	struct traceprobe_parse_context ctx = {
> @@ -1086,6 +1087,10 @@ static int __trace_fprobe_create(int argc, const char *argv[])
>  		argv = new_argv;
>  	}
>  
> +	ret = traceprobe_expand_dentry_args(argc, argv, &dbuf);
> +	if (ret)
> +		goto out;
> +
>  	/* setup a probe */
>  	tf = alloc_trace_fprobe(group, event, symbol, tpoint, maxactive,
>  				argc, is_return);
> @@ -1131,6 +1136,7 @@ static int __trace_fprobe_create(int argc, const char *argv[])
>  	trace_probe_log_clear();
>  	kfree(new_argv);
>  	kfree(symbol);
> +	kfree(dbuf);
>  	return ret;
>  
>  parse_error:
> -- 
> 2.31.1
>