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SubjectRe: [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@goodmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@goodmis.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@kernel.org>

for trace_probe part.

Thanks!

>
> Cc: Joe Perches <joe@perches.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.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@kernel.org>

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