Commit 54034beb authored by Jocelyn Falempe's avatar Jocelyn Falempe
Browse files

drm/panic: Add a kmsg panic screen 



Add a kmsg option, which will display the last lines of kmsg,
and should be similar to fbcon.
Add a drm.panic_screen module parameter, so you can choose between
the different panic screens available.
two options currently, but more will be added later:
 * "user": a short message telling the user to reboot the machine.
 * "kmsg": fill the screen with the last lines of kmsg.

You can even change it at runtime by writing to
/sys/module/drm/parameters/panic_screen

v2:
 * Use module parameter instead of Kconfig choice
   (Javier Martinez Canillas)

v3:
 * Add help for module parameter usage in Kconfig
   (Javier Martivez Canillas)
 * Fix use of font->height before checking it isn't null.
   (kernel test robot, Dan Carpenter)

Signed-off-by: default avatarJocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240603095343.39588-4-jfalempe@redhat.com
parent 24d07f11

drivers/gpu/drm/Kconfig

+13 −0
Original line number Diff line number Diff line
@@ -137,6 +137,19 @@ config DRM_PANIC_DEBUG 
	  This is unsafe and should not be enabled on a production build.

	  If in doubt, say "N".



config DRM_PANIC_SCREEN

	string "Panic screen formater"

	default "user"

	depends on DRM_PANIC

	help

	  This option enable to choose what will be displayed when a kernel

	  panic occurs. You can choose between "user", a short message telling

	  the user to reboot the system, or "kmsg" which will display the last

	  lines of kmsg.

	  This can also be overridden by drm.panic_screen=xxxx kernel parameter

	  or by writing to /sys/module/drm/parameters/panic_screen sysfs entry

	  Default is "user"



config DRM_DEBUG_DP_MST_TOPOLOGY_REFS

        bool "Enable refcount backtrace history in the DP MST helpers"

	depends on STACKTRACE_SUPPORT

drivers/gpu/drm/drm_panic.c

+99 −10
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/kmsg_dump.h>

#include <linux/list.h>

#include <linux/module.h>

#include <linux/printk.h>

#include <linux/types.h>



#include <drm/drm_drv.h>
@@ -27,6 +28,12 @@ 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

 *
@@ -437,24 +444,18 @@ static void draw_txt_rectangle(struct drm_scanout_buffer *sb, 
	}

}



/*

 * Draw the panic message at the center of the screen

 */

static void draw_panic_static(struct drm_scanout_buffer *sb)

static void draw_panic_static_user(struct drm_scanout_buffer *sb)

{

	size_t msg_lines = ARRAY_SIZE(panic_msg);

	size_t logo_lines = ARRAY_SIZE(logo);

	u32 fg_color = CONFIG_DRM_PANIC_FOREGROUND_COLOR;

	u32 bg_color = CONFIG_DRM_PANIC_BACKGROUND_COLOR;

	u32 fg_color = convert_from_xrgb8888(CONFIG_DRM_PANIC_FOREGROUND_COLOR, sb->format->format);

	u32 bg_color = convert_from_xrgb8888(CONFIG_DRM_PANIC_BACKGROUND_COLOR, sb->format->format);

	const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);

	struct drm_rect r_screen, r_logo, r_msg;



	if (!font)

		return;



	fg_color = convert_from_xrgb8888(fg_color, sb->format->format);

	bg_color = convert_from_xrgb8888(bg_color, sb->format->format);



	r_screen = DRM_RECT_INIT(0, 0, sb->width, sb->height);



	r_logo = DRM_RECT_INIT(0, 0,
@@ -477,6 +478,85 @@ static void draw_panic_static(struct drm_scanout_buffer *sb) 
	draw_txt_rectangle(sb, font, panic_msg, msg_lines, true, &r_msg, fg_color);

}



/*

 * Draw one line of kmsg, and handle wrapping if it won't fit in the screen width.

 * Return the y-offset of the next line.

 */

static int draw_line_with_wrap(struct drm_scanout_buffer *sb, const struct font_desc *font,

			       struct drm_panic_line *line, int yoffset, u32 fg_color)

{

	int chars_per_row = sb->width / font->width;

	struct drm_rect r_txt = DRM_RECT_INIT(0, yoffset, sb->width, sb->height);

	struct drm_panic_line line_wrap;



	if (line->len > chars_per_row) {

		line_wrap.len = line->len % chars_per_row;

		line_wrap.txt = line->txt + line->len - line_wrap.len;

		draw_txt_rectangle(sb, font, &line_wrap, 1, false, &r_txt, fg_color);

		r_txt.y1 -= font->height;

		if (r_txt.y1 < 0)

			return r_txt.y1;

		while (line_wrap.txt > line->txt) {

			line_wrap.txt -= chars_per_row;

			line_wrap.len = chars_per_row;

			draw_txt_rectangle(sb, font, &line_wrap, 1, false, &r_txt, fg_color);

			r_txt.y1 -= font->height;

			if (r_txt.y1 < 0)

				return r_txt.y1;

		}

	} else {

		draw_txt_rectangle(sb, font, line, 1, false, &r_txt, fg_color);

		r_txt.y1 -= font->height;

	}

	return r_txt.y1;

}



/*

 * Draw the kmsg buffer to the screen, starting from the youngest message at the bottom,

 * and going up until reaching the top of the screen.

 */

static void draw_panic_static_kmsg(struct drm_scanout_buffer *sb)

{

	u32 fg_color = convert_from_xrgb8888(CONFIG_DRM_PANIC_FOREGROUND_COLOR, sb->format->format);

	u32 bg_color = convert_from_xrgb8888(CONFIG_DRM_PANIC_BACKGROUND_COLOR, sb->format->format);

	const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);

	struct drm_rect r_screen = DRM_RECT_INIT(0, 0, sb->width, sb->height);

	struct kmsg_dump_iter iter;

	char kmsg_buf[512];

	size_t kmsg_len;

	struct drm_panic_line line;

	int yoffset;



	if (!font)

		return;



	yoffset = sb->height - font->height - (sb->height % font->height) / 2;



	/* Fill with the background color, and draw text on top */

	drm_panic_fill(sb, &r_screen, bg_color);



	kmsg_dump_rewind(&iter);

	while (kmsg_dump_get_buffer(&iter, false, kmsg_buf, sizeof(kmsg_buf), &kmsg_len)) {

		char *start;

		char *end;



		/* ignore terminating NUL and newline */

		start = kmsg_buf + kmsg_len - 2;

		end = kmsg_buf + kmsg_len - 1;

		while (start > kmsg_buf && yoffset >= 0) {

			while (start > kmsg_buf && *start != '\n')

				start--;

			/* don't count the newline character */

			line.txt = start + (start == kmsg_buf ? 0 : 1);

			line.len = end - line.txt;



			yoffset = draw_line_with_wrap(sb, font, &line, yoffset, fg_color);

			end = start;

			start--;

		}

	}

}



/*

 * drm_panic_is_format_supported()

 * @format: a fourcc color code
@@ -491,6 +571,15 @@ static bool drm_panic_is_format_supported(const struct drm_format_info *format) 
	return convert_from_xrgb8888(0xffffff, format->format) != 0;

}



static void draw_panic_dispatch(struct drm_scanout_buffer *sb)

{

	if (!strcmp(drm_panic_screen, "kmsg")) {

		draw_panic_static_kmsg(sb);

	} else {

		draw_panic_static_user(sb);

	}

}



static void draw_panic_plane(struct drm_plane *plane)

{

	struct drm_scanout_buffer sb;
@@ -503,7 +592,7 @@ static void draw_panic_plane(struct drm_plane *plane) 
	ret = plane->helper_private->get_scanout_buffer(plane, &sb);



	if (!ret && drm_panic_is_format_supported(sb.format)) {

		draw_panic_static(&sb);

		draw_panic_dispatch(&sb);

		if (plane->helper_private->panic_flush)

			plane->helper_private->panic_flush(plane);

	}