ftrace: Drop a VLA in module_exists()

Avoid a VLA by using a real constant expression instead of a variable.
The compiler should be able to optimize the original code and avoid using
an actual VLA. Anyway this change is useful because it will avoid a false
positive with -Wvla, it might also help the compiler generating better
code.

Link: http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
Link: http://lkml.kernel.org/r/1522399988-8815-1-git-send-email-s.mesoraca16@gmail.com
Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eac9ce2c57a2ede6d56bda9985e0d06470babd76..16bbf062018fa79af48db2339db8ad1c094b3e85 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3902,14 +3902,13 @@ static bool module_exists(const char *module)
 {
        /* All modules have the symbol __this_module */
        const char this_mod[] = "__this_module";
-       const int modname_size = MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 1;
-       char modname[modname_size + 1];
+       char modname[MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 2];
        unsigned long val;
        int n;
 
-       n = snprintf(modname, modname_size + 1, "%s:%s", module, this_mod);
+       n = snprintf(modname, sizeof(modname), "%s:%s", module, this_mod);
 
-       if (n > modname_size)
+       if (n > sizeof(modname) - 1)
                return false;
 
        val = module_kallsyms_lookup_name(modname);