tracing/ksym_tracer: support quick clear for ksym_trace_filter -- v2

It's rather boring to clear symbol one by one in ksym_trace_filter
file, so, this patch will let ksym_trace_filter file support quickly
clear all break points. We can write "0" to this file and it will clear
all symbols

for example:
 # cat ksym_trace_filter
 ksym_filter_head:rw-
 global_trace:rw-
 # echo 0 > ksym_trace_filter
 # cat ksym_trace_filter
 #

Changelog v1->v2:
Add other ways to clear all breakpoints by writing NULL or "*:---"
to ksym_trace_filter file base on K.Prasad's suggestion

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
LKML-Reference: <4A67E092.3080202@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index cd5cb656c3d2b54747a83666eefd634a0e7e061a..2fde875ead4cff51ad09fec0d18fc53d0554bcdf 100644 (file)
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -163,8 +163,6 @@ static int parse_ksym_trace_str(char *input_string, char **ksymname,
 {
        int ret;
 
-       strstrip(input_string);
-
        *ksymname = strsep(&input_string, ":");
        *addr = kallsyms_lookup_name(*ksymname);
 
@@ -262,6 +260,25 @@ static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
        return cnt;
 }
 
+static void __ksym_trace_reset(void)
+{
+       struct trace_ksym *entry;
+       struct hlist_node *node, *node1;
+
+       mutex_lock(&ksym_tracer_mutex);
+       hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
+                                                               ksym_hlist) {
+               unregister_kernel_hw_breakpoint(entry->ksym_hbp);
+               ksym_filter_entry_count--;
+               hlist_del_rcu(&(entry->ksym_hlist));
+               synchronize_rcu();
+               kfree(entry->ksym_hbp->info.name);
+               kfree(entry->ksym_hbp);
+               kfree(entry);
+       }
+       mutex_unlock(&ksym_tracer_mutex);
+}
+
 static ssize_t ksym_trace_filter_write(struct file *file,
                                        const char __user *buffer,
                                                size_t count, loff_t *ppos)
@@ -282,6 +299,21 @@ static ssize_t ksym_trace_filter_write(struct file *file,
        }
        input_string[count] = '\0';
 
+       strstrip(input_string);
+
+       /*
+        * Clear all breakpoints if:
+        * 1: echo > ksym_trace_filter
+        * 2: echo 0 > ksym_trace_filter
+        * 3: echo "*:---" > ksym_trace_filter
+        */
+       if (!input_string[0] || !strcmp(input_string, "0") ||
+           !strcmp(input_string, "*:---")) {
+               __ksym_trace_reset();
+               kfree(input_string);
+               return count;
+       }
+
        ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
        if (ret < 0) {
                kfree(input_string);
@@ -341,23 +373,8 @@ static const struct file_operations ksym_tracing_fops = {
 
 static void ksym_trace_reset(struct trace_array *tr)
 {
-       struct trace_ksym *entry;
-       struct hlist_node *node, *node1;
-
        ksym_tracing_enabled = 0;
-
-       mutex_lock(&ksym_tracer_mutex);
-       hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
-                                                               ksym_hlist) {
-               unregister_kernel_hw_breakpoint(entry->ksym_hbp);
-               ksym_filter_entry_count--;
-               hlist_del_rcu(&(entry->ksym_hlist));
-               synchronize_rcu();
-               kfree(entry->ksym_hbp->info.name);
-               kfree(entry->ksym_hbp);
-               kfree(entry);
-       }
-       mutex_unlock(&ksym_tracer_mutex);
+       __ksym_trace_reset();
 }
 
 static int ksym_trace_init(struct trace_array *tr)