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Subject[PATCH v5 02/33] dyndbg: fix module.dyndbg handling
For CONFIG_DYNAMIC_DEBUG=N, the ddebug_dyndbg_module_param_cb()
stub-fn is too permissive:

bash-5.1# modprobe drm JUNKdyndbg
bash-5.1# modprobe drm dyndbgJUNK
[ 42.933220] dyndbg param is supported only in CONFIG_DYNAMIC_DEBUG builds
[ 42.937484] ACPI: bus type drm_connector registered

This caused no ill effects, because unknown parameters are either
ignored by default with an "unknown parameter" warning, or ignored
because dyndbg allows its no-effect use on non-dyndbg builds.

But since the code has an explicit feedback message, it should be
issued accurately. Fix with strcmp for exact param-name match.

Reported-by: Rasmus Villemoes <>
Fixes: b48420c1d301 dynamic_debug: make dynamic-debug work for module initialization
Signed-off-by: Jim Cromie <>
Acked-by: Jason Baron <>
include/linux/dynamic_debug.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index dce631e678dd..f30b01aa9fa4 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -201,7 +201,7 @@ static inline int ddebug_remove_module(const char *mod)
static inline int ddebug_dyndbg_module_param_cb(char *param, char *val,
const char *modname)
- if (strstr(param, "dyndbg")) {
+ if (!strcmp(param, "dyndbg")) {
/* avoid pr_warn(), which wants pr_fmt() fully defined */
printk(KERN_WARNING "dyndbg param is supported only in "
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