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, see below), or ignored because dyndbg allows its no-effect use on non-dyndbg builds.
That said, the code has an explicit feedback message, which should be issued accurately. Fix with strcmp, for exact param-name match.
Here is fixed behavior:
bash-5.1# modprobe drm dyndbgJUNK [ 20.127473] drm: unknown parameter 'dyndbgJUNK' ignored [ 20.128835] ACPI: bus type drm_connector registered bash-5.1# rmmod drm [ 37.961656] ACPI: bus type drm_connector unregistered bash-5.1# modprobe drm dyndbg [ 42.933220] dyndbg param is supported only in CONFIG_DYNAMIC_DEBUG builds [ 42.937484] ACPI: bus type drm_connector registered
Reported-by: Rasmus Villemoes linux@rasmusvillemoes.dk Signed-off-by: Jim Cromie jim.cromie@gmail.com --- 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 " "CONFIG_DYNAMIC_DEBUG builds\n");