linux-kernel - Re: [PATCH v5 1/8] tracing/probes: add traceprobe_expand_dentry

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Date: Wed, 7 Feb 2024 23:29:36 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Ye Bin <yebin10@...wei.com>
Cc: <rostedt@...dmis.org>, <mathieu.desnoyers@...icios.com>,
 <linux-trace-kernel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/8] tracing/probes: add
 traceprobe_expand_dentry_args() helper

Hi Ye,

On Thu, 25 Jan 2024 15:39:16 +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 | 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
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>