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Subject[PATCH] ftrace: drop a VLA in module_exists()
Date
Avoid a VLA[1] 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.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
---
kernel/trace/ftrace.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eac9ce2..adebb92 100644
--- 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) + 1];
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);
--
1.9.1
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