From ca8b86c5ae91b3041790085d296f5b8fbf71570b Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Wed, 15 Jul 2009 12:29:06 +0800 Subject: [PATCH] tracing/function: Fix the return value of ftrace_trace_onoff_callback() commit 04aef32d39cc4ef80087c0ce8ed113c6d64f1a6b upstream. ftrace_trace_onoff_callback() will return an error even if we do the right operation, for example: # echo _spin_*:traceon:10 > set_ftrace_filter -bash: echo: write error: Invalid argument # cat set_ftrace_filter #### all functions enabled #### _spin_trylock_bh:traceon:count=10 _spin_unlock_irq:traceon:count=10 _spin_unlock_bh:traceon:count=10 _spin_lock_irq:traceon:count=10 _spin_unlock:traceon:count=10 _spin_trylock:traceon:count=10 _spin_unlock_irqrestore:traceon:count=10 _spin_lock_irqsave:traceon:count=10 _spin_lock_bh:traceon:count=10 _spin_lock:traceon:count=10 We want to set _spin_*:traceon:10 to set_ftrace_filter, it complains with "Invalid argument", but the operation is successful. This is because ftrace_process_regex() returns the number of functions that matched the pattern. If the number is not 0, this value is returned by ftrace_regex_write() whereas we want to return the number of bytes virtually written. Also the file offset pointer is not updated in this case. If the number of matched functions is lower than the number of bytes written by the user, this results to a reprocessing of the string given by the user with a lower size, leading to a malformed ftrace regex and then a -EINVAL returned. So, this patch fixes it by returning 0 if no error occured. The fix also applies on 2.6.30 Signed-off-by: Xiao Guangrong Reviewed-by: Li Zefan Signed-off-by: Frederic Weisbecker Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_functions.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index 90f13476483..01e5c4335d1 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -364,7 +364,7 @@ ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable) out_reg: ret = register_ftrace_function_probe(glob, ops, count); - return ret; + return ret < 0 ? ret : 0; } static struct ftrace_func_command ftrace_traceon_cmd = { -- 2.11.4.GIT