linux-kernel - Re: [for-next][PATCH 5/5] tracing: Use the return of str_has

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Date:   Sun, 23 Dec 2018 12:23:52 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [for-next][PATCH 5/5] tracing: Use the return of
 str_has_prefix() to remove open coded numbers

On Sat, 22 Dec 2018 11:20:12 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> There are several locations that compare constants to the beginning of
> string variables to determine what commands should be done, then the
> constant length is used to index into the string. This is error prone as the
> hard coded numbers have to match the size of the constants. Instead, use the
> len returned from str_has_prefix() and remove the open coded string length
> sizes.

Looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

for trace_probe part.

Thanks!

> 
> Cc: Joe Perches <joe@...ches.com>
> Cc: Masami  Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  kernel/trace/trace.c       |  8 +++++---
>  kernel/trace/trace_probe.c | 17 +++++++++--------
>  kernel/trace/trace_stack.c |  6 ++++--
>  3 files changed, 18 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index eac2824a18ab..18b86c3974e1 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -4408,13 +4408,15 @@ static int trace_set_options(struct trace_array *tr, char *option)
>  	int neg = 0;
>  	int ret;
>  	size_t orig_len = strlen(option);
> +	int len;
>  
>  	cmp = strstrip(option);
>  
> -	if (str_has_prefix(cmp, "no")) {
> +	len = str_has_prefix(cmp, "no");
> +	if (len)
>  		neg = 1;
> -		cmp += 2;
> -	}
> +
> +	cmp += len;
>  
>  	mutex_lock(&trace_types_lock);
>  
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 541375737403..9962cb5da8ac 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -186,19 +186,20 @@ int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
>  static int parse_probe_vars(char *arg, const struct fetch_type *t,
>  			    struct fetch_insn *code, unsigned int flags)
>  {
> -	int ret = 0;
>  	unsigned long param;
> +	int ret = 0;
> +	int len;
>  
>  	if (strcmp(arg, "retval") == 0) {
>  		if (flags & TPARG_FL_RETURN)
>  			code->op = FETCH_OP_RETVAL;
>  		else
>  			ret = -EINVAL;
> -	} else if (str_has_prefix(arg, "stack")) {
> -		if (arg[5] == '\0') {
> +	} else if ((len = str_has_prefix(arg, "stack"))) {
> +		if (arg[len] == '\0') {
>  			code->op = FETCH_OP_STACKP;
> -		} else if (isdigit(arg[5])) {
> -			ret = kstrtoul(arg + 5, 10, &param);
> +		} else if (isdigit(arg[len])) {
> +			ret = kstrtoul(arg + len, 10, &param);
>  			if (ret || ((flags & TPARG_FL_KERNEL) &&
>  				    param > PARAM_MAX_STACK))
>  				ret = -EINVAL;
> @@ -213,10 +214,10 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
>  #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
>  	} else if (((flags & TPARG_FL_MASK) ==
>  		    (TPARG_FL_KERNEL | TPARG_FL_FENTRY)) &&
> -		   str_has_prefix(arg, "arg")) {
> -		if (!isdigit(arg[3]))
> +		   (len = str_has_prefix(arg, "arg"))) {
> +		if (!isdigit(arg[len]))
>  			return -EINVAL;
> -		ret = kstrtoul(arg + 3, 10, &param);
> +		ret = kstrtoul(arg + len, 10, &param);
>  		if (ret || !param || param > PARAM_MAX_STACK)
>  			return -EINVAL;
>  		code->op = FETCH_OP_ARG;
> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
> index 3641f28c343f..eec648a0d673 100644
> --- a/kernel/trace/trace_stack.c
> +++ b/kernel/trace/trace_stack.c
> @@ -448,8 +448,10 @@ static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
>  
>  static __init int enable_stacktrace(char *str)
>  {
> -	if (str_has_prefix(str, "_filter="))
> -		strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
> +	int len;
> +
> +	if ((len = str_has_prefix(str, "_filter=")))
> +		strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);
>  
>  	stack_tracer_enabled = 1;
>  	last_stack_tracer_enabled = 1;
> -- 
> 2.19.2
> 
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>