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drm/panic: Report invalid or unsupported panic modes

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Currently the user can write anything into the drm.panic_screen modparam,
either at runtime via sysfs, or as a kernel boot time argument. Invalid
strings will be silently accepted and ignored at use time by defaulting to
the 'user' panic mode.

Let instead add some validation in order to have immediate feedback when
something has been mistyped, or not compiled in.

For example during kernel boot:

 Booting kernel: `bsod' invalid for parameter `drm.panic_screen'

Or at runtime:

 # echo -n bsod > /sys/module/drm/parameters/panic_screen
 -bash: echo: write error: Invalid argument

Change of behavior is that when invalid mode is attempted to be
configured, currently the code will default to the 'user' mode, while with
this change the code will ignore it, and default to the mode set at kernel
build time via CONFIG_DRM_PANIC_SCREEN.

While at it lets also fix the module parameter description to include all
compiled in modes.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://lore.kernel.org/r/20251127090349.92717-1-tvrtko.ursulin@igalia.com
This commit is contained in:
Tvrtko Ursulin 2025-11-27 09:03:49 +00:00 • committed by Tvrtko Ursulin
parent 36c5dff41f
commit e85e9ccf3f
1 changed files with 63 additions and 14 deletions
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77
drivers/gpu/drm/drm_panic.c
View file

@ -39,12 +39,6 @@ MODULE_AUTHOR("Jocelyn Falempe");
MODULE_DESCRIPTION("DRM panic handler");
MODULE_LICENSE("GPL");
static char drm_panic_screen[16] = CONFIG_DRM_PANIC_SCREEN;
module_param_string(panic_screen, drm_panic_screen, sizeof(drm_panic_screen), 0644);
MODULE_PARM_DESC(panic_screen,
"Choose what will be displayed by drm_panic, 'user' or 'kmsg' [default="
CONFIG_DRM_PANIC_SCREEN "]");
/**
* DOC: overview
*
@ -765,15 +759,60 @@ static void draw_panic_static_qr_code(struct drm_scanout_buffer *sb)
draw_panic_static_user(sb);
}
#else
static void draw_panic_static_qr_code(struct drm_scanout_buffer *sb)
{
draw_panic_static_user(sb);
}
static void drm_panic_qr_init(void) {};
static void drm_panic_qr_exit(void) {};
#endif
enum drm_panic_type {
DRM_PANIC_TYPE_KMSG,
DRM_PANIC_TYPE_USER,
DRM_PANIC_TYPE_QR,
};
static enum drm_panic_type drm_panic_type = -1;
static const char *drm_panic_type_map[] = {
[DRM_PANIC_TYPE_KMSG] = "kmsg",
[DRM_PANIC_TYPE_USER] = "user",
#if IS_ENABLED(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
[DRM_PANIC_TYPE_QR] = "qr",
#endif
};
static int drm_panic_type_set(const char *val, const struct kernel_param *kp)
{
unsigned int i;
for (i = 0; i < ARRAY_SIZE(drm_panic_type_map); i++) {
if (!strcmp(val, drm_panic_type_map[i])) {
drm_panic_type = i;
return 0;
}
}
return -EINVAL;
}
static int drm_panic_type_get(char *buffer, const struct kernel_param *kp)
{
return scnprintf(buffer, PAGE_SIZE, "%s\n",
drm_panic_type_map[drm_panic_type]);
}
static const struct kernel_param_ops drm_panic_ops = {
.set = drm_panic_type_set,
.get = drm_panic_type_get,
};
module_param_cb(panic_screen, &drm_panic_ops, NULL, 0644);
MODULE_PARM_DESC(panic_screen,
#if IS_ENABLED(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
"Choose what will be displayed by drm_panic, 'user', 'kmsg' or 'qr' [default="
#else
"Choose what will be displayed by drm_panic, 'user' or 'kmsg' [default="
#endif
CONFIG_DRM_PANIC_SCREEN "]");
/*
* drm_panic_is_format_supported()
* @format: a fourcc color code
@ -790,11 +829,19 @@ static bool drm_panic_is_format_supported(const struct drm_format_info *format)
static void draw_panic_dispatch(struct drm_scanout_buffer *sb)
{
if (!strcmp(drm_panic_screen, "kmsg")) {
switch (drm_panic_type) {
case DRM_PANIC_TYPE_KMSG:
draw_panic_static_kmsg(sb);
} else if (!strcmp(drm_panic_screen, "qr_code")) {
break;
#if IS_ENABLED(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
case DRM_PANIC_TYPE_QR:
draw_panic_static_qr_code(sb);
} else {
break;
#endif
case DRM_PANIC_TYPE_USER:
default:
draw_panic_static_user(sb);
}
}
@ -977,6 +1024,8 @@ void drm_panic_unregister(struct drm_device *dev)
*/
void __init drm_panic_init(void)
{
if (drm_panic_type == -1)
drm_panic_type_set(CONFIG_DRM_PANIC_SCREEN, NULL);
drm_panic_qr_init();
}