linux-kernel - Re: [PATCH v3 4/7] tracing/probes: support '%pD' type for print struct file's name

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Message-ID: <20240122220357.0105e20b@gandalf.local.home>
Date: Mon, 22 Jan 2024 22:03:57 -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 v3 4/7] tracing/probes: support '%pD' type for print
 struct file's name

On Tue, 23 Jan 2024 10:56:05 +0800
Ye Bin <yebin10@...wei.com> wrote:

> Similar to '%pD' for printk, use '%pD' for print struct file's name.
> 
> Signed-off-by: Ye Bin <yebin10@...wei.com>
> ---
>  kernel/trace/trace_probe.c | 41 ++++++++++++++++++++++++--------------
>  1 file changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index cc8bd7ea5341..6215b9573793 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -12,6 +12,7 @@
>  #define pr_fmt(fmt)	"trace_probe: " fmt
>  
>  #include <linux/bpf.h>
> +#include <linux/fs.h>
>  #include "trace_btf.h"
>  
>  #include "trace_probe.h"
> @@ -1574,28 +1575,38 @@ int traceprobe_expand_dentry_args(int argc, const char *argv[], char *buf,
>  	for (i = 0; i < argc; i++) {
>  		size_t idx;
>  
> -		if (str_has_suffix(argv[i], ":%pd", &idx)) {
> -			char *tmp = kstrdup(argv[i], GFP_KERNEL);
> -			char *equal;
> +		if (!str_has_suffix(argv[i], ":%pd", &idx) &&
> +		    !str_has_suffix(argv[i], ":%pD", &idx))
> +			continue;
>  
> -			if (!tmp)
> -				return -ENOMEM;
> +		char *tmp = kstrdup(argv[i], GFP_KERNEL);
> +		char *equal;
> +
> +		if (!tmp)
> +			return -ENOMEM;
>  
> -			equal = strchr(tmp, '=');
> -			if (equal)
> -				*equal = '\0';
> -			tmp[idx] = '\0';
> +		equal = strchr(tmp, '=');
> +		if (equal)
> +			*equal = '\0';
> +		tmp[idx] = '\0';
> +		if (argv[i][strlen(argv[i]) - 1] == 'd')

You can use idx again here:

		if (argv[i][idx + 3] == 'd')

and save from doing the strlen(argv[i]);

idx will point to ':', and + 3 would point to either 'd' or 'D'

-- 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;
> -		}
> +		else
> +			ret = snprintf(buf + used, bufsize - used,
> +				       "%s%s+0x0(+0x%zx(+0x%zx(%s))):string",
> +				       equal ? tmp : "", equal ? "=" : "",
> +				       offsetof(struct dentry, d_name.name),
> +				       offsetof(struct file, f_path.dentry),
> +				       equal ? equal + 1 : tmp);
> +		kfree(tmp);
> +		if (ret >= bufsize - used)
> +			return -ENOMEM;
> +		argv[i] = buf + used;
> +		used += ret + 1;
>  	}
>  
>  	return 0;