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Message-ID: <c62985530909180200w3e560d23kef9571213b143369@mail.gmail.com>
Date: Fri, 18 Sep 2009 11:00:41 +0200
From: Frédéric Weisbecker <fweisbec@...il.com>
To: Li Zefan <lizf@...fujitsu.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3][RESEND] tracing: remove max_tracer_type_len
2009/9/18 Li Zefan <lizf@...fujitsu.com>:
> Limit the length of a tracer's name within 100 chars, and then we
> don't have to play with max_tracer_type_len.
>
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@...il.com>
> ---
> kernel/trace/trace.c | 49 ++++++++++++++++---------------------------------
> 1 files changed, 16 insertions(+), 33 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index fd52a19..8613080 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -125,13 +125,13 @@ int ftrace_dump_on_oops;
>
> static int tracing_set_tracer(const char *buf);
>
> -#define BOOTUP_TRACER_SIZE 100
> -static char bootup_tracer_buf[BOOTUP_TRACER_SIZE] __initdata;
> +#define MAX_TRACER_SIZE 100
> +static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
> static char *default_bootup_tracer;
>
> static int __init set_ftrace(char *str)
> {
> - strncpy(bootup_tracer_buf, str, BOOTUP_TRACER_SIZE);
> + strncpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
> default_bootup_tracer = bootup_tracer_buf;
> /* We are using ftrace early, expand it */
> ring_buffer_expanded = 1;
> @@ -242,13 +242,6 @@ static struct tracer *trace_types __read_mostly;
> static struct tracer *current_trace __read_mostly;
>
> /*
> - * max_tracer_type_len is used to simplify the allocating of
> - * buffers to read userspace tracer names. We keep track of
> - * the longest tracer name registered.
> - */
> -static int max_tracer_type_len;
> -
> -/*
> * trace_types_lock is used to protect the trace_types list.
> * This lock is also used to keep user access serialized.
> * Accesses from userspace will grab this lock while userspace
> @@ -619,7 +612,6 @@ __releases(kernel_lock)
> __acquires(kernel_lock)
> {
> struct tracer *t;
> - int len;
> int ret = 0;
>
> if (!type->name) {
> @@ -627,6 +619,11 @@ __acquires(kernel_lock)
> return -1;
> }
>
> + if (strlen(type->name) > MAX_TRACER_SIZE) {
> + pr_info("Tracer has a name longer than %d\n", MAX_TRACER_SIZE);
> + return -1;
> + }
> +
> /*
> * When this gets called we hold the BKL which means that
> * preemption is disabled. Various trace selftests however
> @@ -641,7 +638,7 @@ __acquires(kernel_lock)
> for (t = trace_types; t; t = t->next) {
> if (strcmp(type->name, t->name) == 0) {
> /* already found */
> - pr_info("Trace %s already registered\n",
> + pr_info("Tracer %s already registered\n",
> type->name);
> ret = -1;
> goto out;
> @@ -692,9 +689,6 @@ __acquires(kernel_lock)
>
> type->next = trace_types;
> trace_types = type;
> - len = strlen(type->name);
> - if (len > max_tracer_type_len)
> - max_tracer_type_len = len;
>
> out:
> tracing_selftest_running = false;
> @@ -703,7 +697,7 @@ __acquires(kernel_lock)
> if (ret || !default_bootup_tracer)
> goto out_unlock;
>
> - if (strncmp(default_bootup_tracer, type->name, BOOTUP_TRACER_SIZE))
> + if (strncmp(default_bootup_tracer, type->name, MAX_TRACER_SIZE))
> goto out_unlock;
>
> printk(KERN_INFO "Starting tracer '%s'\n", type->name);
> @@ -725,14 +719,13 @@ __acquires(kernel_lock)
> void unregister_tracer(struct tracer *type)
> {
> struct tracer **t;
> - int len;
>
> mutex_lock(&trace_types_lock);
> for (t = &trace_types; *t; t = &(*t)->next) {
> if (*t == type)
> goto found;
> }
> - pr_info("Trace %s not registered\n", type->name);
> + pr_info("Tracer %s not registered\n", type->name);
> goto out;
>
> found:
> @@ -745,17 +738,7 @@ void unregister_tracer(struct tracer *type)
> current_trace->stop(&global_trace);
> current_trace = &nop_trace;
> }
> -
> - if (strlen(type->name) != max_tracer_type_len)
> - goto out;
> -
> - max_tracer_type_len = 0;
> - for (t = &trace_types; *t; t = &(*t)->next) {
> - len = strlen((*t)->name);
> - if (len > max_tracer_type_len)
> - max_tracer_type_len = len;
> - }
> - out:
> +out:
> mutex_unlock(&trace_types_lock);
> }
>
> @@ -2604,7 +2587,7 @@ static ssize_t
> tracing_set_trace_read(struct file *filp, char __user *ubuf,
> size_t cnt, loff_t *ppos)
> {
> - char buf[max_tracer_type_len+2];
> + char buf[MAX_TRACER_SIZE+2];
> int r;
>
> mutex_lock(&trace_types_lock);
> @@ -2754,15 +2737,15 @@ static ssize_t
> tracing_set_trace_write(struct file *filp, const char __user *ubuf,
> size_t cnt, loff_t *ppos)
> {
> - char buf[max_tracer_type_len+1];
> + char buf[MAX_TRACER_SIZE+1];
> int i;
> size_t ret;
> int err;
>
> ret = cnt;
>
> - if (cnt > max_tracer_type_len)
> - cnt = max_tracer_type_len;
> + if (cnt > MAX_TRACER_SIZE)
> + cnt = MAX_TRACER_SIZE;
>
> if (copy_from_user(&buf, ubuf, cnt))
> return -EFAULT;
> --
> 1.6.3
>
>
--
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