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Subject[PATCH 2/3] [PATCH 2/3] tracing: remove max_tracer_type_len
From: Li Zefan <lizf@cn.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.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4AB32377.9020601@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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;
--
1.6.3.3



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