linux-kernel - Re: [PATCH v2 2/7] tracing/probes: add traceprobe_expand_dentry

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Date: Mon, 22 Jan 2024 11:08:50 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Ye Bin <yebin10@...wei.com>
Cc: <mhiramat@...nel.org>, <mathieu.desnoyers@...icios.com>,
 <linux-trace-kernel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/7] tracing/probes: add
 traceprobe_expand_dentry_args() helper

On Mon, 22 Jan 2024 15:40:10 +0800
Ye Bin <yebin10@...wei.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@...wei.com>
> ---
>  kernel/trace/trace_probe.c | 34 ++++++++++++++++++++++++++++++++++
>  kernel/trace/trace_probe.h |  2 ++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 4dc74d73fc1d..1599c0c3e6b7 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -1565,6 +1565,40 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
>  	return ERR_PTR(ret);
>  }
>  
> +int traceprobe_expand_dentry_args(int argc, const char *argv[], char *buf,
> +				  int bufsize)
> +{
> +	int i, used, ret;

	size_t idx;

> +
> +	used = 0;
> +	for (i = 0; i < argc; i++) {
> +		if (str_has_suffix(argv[i], ":%pd")) {

If we were to update str_has_suffix() as I said in my reply to the previous
patch, then we could do:

		if (str_has_suffix(argv[i], ":%pd", &idx) {

> +			char *tmp = kstrdup(argv[i], GFP_KERNEL);
> +			char *equal;
> +
> +			if (!tmp)
> +				return -ENOMEM;
> +
> +			equal = strchr(tmp, '=');
> +			if (equal)
> +				*equal = '\0';
> +			tmp[strlen(argv[i]) - 4] = '\0';

			tmp[idx] = '\0';

-- Steve

> +			ret = snprintf(buf + 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)
> +				return -ENOMEM;
> +			argv[i] = buf + used;
> +			used += ret + 1;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  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..553371a4e0b1 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -402,6 +402,8 @@ 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,
> +					 int bufsize);
>  
>  extern int traceprobe_update_arg(struct probe_arg *arg);
>  extern void traceprobe_free_probe_arg(struct probe_arg *arg);