This module displays a user friendly message when a kernel panic
occurs. It currently doesn't contain any debug information,
but that can be added later.
v2
* Use get_scanout_buffer() instead of the drm client API.
(Thomas Zimmermann)
* Add the panic reason to the panic message (Nerdopolis)
* Add an exclamation mark (Nerdopolis)
v3
* Rework the drawing functions, to write the pixels line by line and
to use the drm conversion helper to support other formats.
(Thomas Zimmermann)
v4
* Use drm_fb_r1_to_32bit for fonts (Thomas Zimmermann)
* Remove the default y to DRM_PANIC config option (Thomas Zimmermann)
* Add foreground/background color config option
* Fix the bottom lines not painted if the framebuffer height
is not a multiple of the font height.
* Automatically register the device to drm_panic, if the function
get_scanout_buffer exists. (Thomas Zimmermann)
v5
* Change the drawing API, use drm_fb_blit_from_r1() to draw the font.
* Also add drm_fb_fill() to fill area with background color.
* Add draw_pixel_xy() API for drivers that can't provide a linear buffer.
* Add a flush() callback for drivers that needs to synchronize the buffer.
* Add a void *private field, so drivers can pass private data to
draw_pixel_xy() and flush().
Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
---
drivers/gpu/drm/Kconfig | 22 +++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm_drv.c | 8 +
drivers/gpu/drm/drm_panic.c | 368 ++++++++++++++++++++++++++++++++++++
include/drm/drm_drv.h | 21 ++
include/drm/drm_panic.h | 96 ++++++++++
6 files changed, 516 insertions(+)
create mode 100644 drivers/gpu/drm/drm_panic.c
create mode 100644 include/drm/drm_panic.h
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 3caa020391c7..9f76cc47d0f3 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -102,6 +102,28 @@ config DRM_KMS_HELPER
help
CRTC helpers for KMS drivers.
+config DRM_PANIC
+ bool "Display a user-friendly message when a kernel panic occurs"
+ depends on DRM && !FRAMEBUFFER_CONSOLE
+ select FONT_SUPPORT
+ help
+ Enable a drm panic handler, which will display a user-friendly message
+ when a kernel panic occurs. It's useful when using a user-space
+ console instead of fbcon.
+ It will only work if your graphic driver supports this feature.
+ To support Hi-DPI Display, you can enable bigger fonts like
+ FONT_TER16x32
+
+config DRM_PANIC_FOREGROUND_COLOR
+ hex "Drm panic screen foreground color, in RGB"
+ depends on DRM_PANIC
+ default 0xffffff
+
+config DRM_PANIC_BACKGROUND_COLOR
+ hex "Drm panic screen background color, in RGB"
+ depends on DRM_PANIC
+ default 0x000000
+
config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
bool "Enable refcount backtrace history in the DP MST helpers"
depends on STACKTRACE_SUPPORT
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 215e78e79125..2c793326c893 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -73,6 +73,7 @@ drm-$(CONFIG_DRM_PRIVACY_SCREEN) += \
drm_privacy_screen_x86.o
drm-$(CONFIG_DRM_ACCEL) += ../../accel/drm_accel.o
obj-$(CONFIG_DRM) += drm.o
+drm-$(CONFIG_DRM_PANIC) += drm_panic.o
obj-$(CONFIG_DRM_PANEL_ORIENTATION_QUIRKS) += drm_panel_orientation_quirks.o
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 3eda026ffac6..d4230e5a472b 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -43,6 +43,7 @@
#include <drm/drm_file.h>
#include <drm/drm_managed.h>
#include <drm/drm_mode_object.h>
+#include <drm/drm_panic.h>
#include <drm/drm_print.h>
#include <drm/drm_privacy_screen_machine.h>
@@ -943,6 +944,9 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
if (drm_core_check_feature(dev, DRIVER_MODESET))
drm_modeset_register_all(dev);
+ if (driver->get_scanout_buffer)
+ drm_panic_register(dev);
+
DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
driver->name, driver->major, driver->minor,
driver->patchlevel, driver->date,
@@ -986,6 +990,8 @@ void drm_dev_unregister(struct drm_device *dev)
dev->registered = false;
+ drm_panic_unregister(dev);
+
drm_client_dev_unregister(dev);
if (drm_core_check_feature(dev, DRIVER_MODESET))
@@ -1067,6 +1073,7 @@ static void drm_core_exit(void)
unregister_chrdev(DRM_MAJOR, "drm");
debugfs_remove(drm_debugfs_root);
drm_sysfs_destroy();
+ drm_panic_exit();
idr_destroy(&drm_minors_idr);
drm_connector_ida_destroy();
}
@@ -1078,6 +1085,7 @@ static int __init drm_core_init(void)
drm_connector_ida_init();
idr_init(&drm_minors_idr);
drm_memcpy_init_early();
+ drm_panic_init();
ret = drm_sysfs_init();
if (ret < 0) {
diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
new file mode 100644
index 000000000000..70afc153065b
--- /dev/null
+++ b/drivers/gpu/drm/drm_panic.c
@@ -0,0 +1,368 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/*
+ * Copyright (c) 2023 Jocelyn Falempe <jfalempe@xxxxxxxxxx>
+ * inspired by the drm_log driver from David Herrmann <dh.herrmann@xxxxxxxxx>
+ * Tux Ascii art taken from cowsay written by Tony Monroe
+ */
+
+#include <linux/font.h>
+#include <linux/iosys-map.h>
+#include <linux/kdebug.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/panic_notifier.h>
+#include <linux/types.h>
+
+#include <drm/drm_drv.h>
+#include <drm/drm_format_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_panic.h>
+#include <drm/drm_print.h>
+
+
+MODULE_AUTHOR("Jocelyn Falempe");
+MODULE_DESCRIPTION("DRM panic handler");
+MODULE_LICENSE("GPL");
+
+/**
+ * DOC: DRM Panic
+ *
+ * This module displays a user friendly message on screen when a kernel panic
+ * occurs. This is conflicting with fbcon, so you can only enable it when fbcon
+ * is disabled.
+ * It's intended for end-user, so have minimal technical/debug information.
+ */
+
+/*
+ * Implementation details:
+ *
+ * It is a panic handler, so it can't take lock, allocate memory, run tasks/irq,
+ * or attempt to sleep. It's a best effort, and it may not be able to display
+ * the message in all situations (like if the panic occurs in the middle of a
+ * modesetting).
+ * It will display only one static frame, so performance optimizations are low
+ * priority as the machine is already in an unusable state.
+ */
+
+/*
+ * List of active drm devices that can render a panic
+ */
+struct drm_panic_device {
+ struct list_head head;
+ struct drm_device *dev;
+};
+
+struct drm_panic_line {
+ u32 len;
+ const char *txt;
+};
+
+#define PANIC_LINE(s) {.len = sizeof(s) - 1, .txt = s}
+
+struct drm_panic_line panic_msg[] = {
+ PANIC_LINE("KERNEL PANIC !"),
+ PANIC_LINE(""),
+ PANIC_LINE("Please reboot your computer."),
+ PANIC_LINE(""),
+ PANIC_LINE(""), /* overwritten with panic reason */
+};
+
+const struct drm_panic_line logo[] = {
+ PANIC_LINE(" .--. _"),
+ PANIC_LINE(" |o_o | | |"),
+ PANIC_LINE(" |:_/ | | |"),
+ PANIC_LINE(" // \\ \\ |_|"),
+ PANIC_LINE(" (| | ) _"),
+ PANIC_LINE(" /'\\_ _/`\\ (_)"),
+ PANIC_LINE(" \\___)=(___/"),
+};
+
+static LIST_HEAD(drm_panic_devices);
+static DEFINE_MUTEX(drm_panic_lock);
+
+static void draw_empty_line_map(struct drm_scanout_buffer *sb, size_t top, size_t height, u32 color)
+{
+ struct iosys_map dst = sb->map;
+
+ iosys_map_incr(&dst, top * sb->pitch);
+ drm_fb_fill(&dst, sb->pitch, height, sb->width, color, sb->format->cpp[0]);
+}
+
+static void draw_txt_line_map(const struct drm_panic_line *msg, size_t left, size_t top,
+ struct drm_scanout_buffer *sb, u32 fg_color, u32 bg_color,
+ const struct font_desc *font)
+{
+ size_t i;
+ const u8 *src;
+ size_t src_stride = DIV_ROUND_UP(font->width, 8);
+ struct iosys_map dst = sb->map;
+ size_t end_text;
+ unsigned int px_width = sb->format->cpp[0];
+
+ iosys_map_incr(&dst, top * sb->pitch);
+ drm_fb_fill(&dst, sb->pitch, font->height, left, bg_color, px_width);
+ iosys_map_incr(&dst, left * px_width);
+ for (i = 0; i < msg->len; i++) {
+ src = font->data + (msg->txt[i] * font->height) * src_stride;
+ drm_fb_blit_from_r1(&dst, sb->pitch, src, src_stride, font->height, font->width,
+ fg_color, bg_color, px_width);
+ iosys_map_incr(&dst, font->width * px_width);
+ }
+ end_text = (msg->len * font->width) + left;
+ if (sb->width > end_text)
+ drm_fb_fill(&dst, sb->pitch, font->height, sb->width - end_text,
+ bg_color, px_width);
+}
+
+static void draw_empty_line_px(struct drm_scanout_buffer *sb, size_t top, size_t height, u32 color)
+{
+ unsigned int x, y;
+
+ for (y = 0; y < height; y++)
+ for (x = 0; x < sb->width; x++)
+ sb->draw_pixel_xy(x, y + top, color, sb->private);
+}
+
+static void draw_txt_line_px(const struct drm_panic_line *msg, size_t left, size_t top,
+ struct drm_scanout_buffer *sb, u32 fg_color, u32 bg_color,
+ const struct font_desc *font)
+{
+ unsigned int x, y, i;
+ const u8 *src;
+ u32 color;
+ size_t src_stride = DIV_ROUND_UP(font->width, 8);
+ size_t end_text = msg->len * font->width + left;
+ size_t right = sb->width > end_text ? sb->width - end_text : 0;
+
+ for (y = 0; y < font->height; y++) {
+ for (x = 0; x < left; x++)
+ sb->draw_pixel_xy(x, y + top, bg_color, sb->private);
+
+ for (i = 0; i < msg->len; i++) {
+ src = font->data + (msg->txt[i] * font->height + y) * src_stride;
+ for (x = 0; x < font->width; x++) {
+ color = (src[x / 8] & (0x80 >> (x % 8))) ? fg_color : bg_color;
+ sb->draw_pixel_xy(x + left + font->width * i, y + top, color,
+ sb->private);
+ }
+ }
+
+ for (x = 0; x < right; x++)
+ sb->draw_pixel_xy(x + end_text, y + top, bg_color, sb->private);
+ }
+}
+
+static void draw_empty_line(struct drm_scanout_buffer *sb, size_t top, size_t height, u32 color)
+{
+ if (sb->draw_pixel_xy)
+ draw_empty_line_px(sb, top, height, color);
+ else
+ draw_empty_line_map(sb, top, height, color);
+}
+
+static void draw_txt_line(const struct drm_panic_line *msg, size_t left, size_t top,
+ struct drm_scanout_buffer *sb, u32 fg_color, u32 bg_color,
+ const struct font_desc *font)
+{
+ if (sb->draw_pixel_xy)
+ draw_txt_line_px(msg, left, top, sb, fg_color, bg_color, font);
+ else
+ draw_txt_line_map(msg, left, top, sb, fg_color, bg_color, font);
+}
+
+
+static size_t panic_msg_needed_lines(size_t chars_per_line)
+{
+ size_t msg_len = ARRAY_SIZE(panic_msg);
+ size_t lines = 0;
+ size_t i;
+
+ for (i = 0; i < msg_len; i++)
+ lines += panic_msg[i].len ? DIV_ROUND_UP(panic_msg[i].len, chars_per_line) : 1;
+ return lines;
+}
+
+static bool can_draw_logo(size_t chars_per_line, size_t lines, size_t msg_lines)
+{
+ size_t i;
+
+ for (i = 0; i < ARRAY_SIZE(logo); i++) {
+ if (logo[i].len > chars_per_line)
+ return false;
+ }
+ if (lines < msg_lines + ARRAY_SIZE(logo))
+ return false;
+ return true;
+}
+
+static size_t get_start_line(size_t lines, size_t msg_lines, bool draw_logo)
+{
+ size_t remaining;
+ size_t logo_len = ARRAY_SIZE(logo);
+
+ if (lines < msg_lines)
+ return 0;
+ remaining = lines - msg_lines;
+ if (draw_logo && remaining / 2 <= logo_len)
+ return logo_len + (remaining - logo_len) / 4;
+ return remaining / 2;
+}
+
+/*
+ * Draw the panic message at the center of the screen
+ */
+static void draw_panic_static(struct drm_scanout_buffer *sb, const char *msg)
+{
+ size_t lines, msg_lines, l, msg_start_line, remaining, msgi;
+ size_t chars_per_line;
+ bool draw_logo;
+ struct drm_panic_line panic_line;
+ size_t msg_len = ARRAY_SIZE(panic_msg);
+ size_t logo_len = ARRAY_SIZE(logo);
+ u32 fg_color = CONFIG_DRM_PANIC_FOREGROUND_COLOR;
+ u32 bg_color = CONFIG_DRM_PANIC_BACKGROUND_COLOR;
+ const struct font_desc *font = get_default_font(sb->width, sb->height, 0x8080, 0x8080);
+
+ if (!font)
+ return;
+
+ /* Set the panic reason */
+ panic_msg[msg_len - 1].len = strlen(msg);
+ panic_msg[msg_len - 1].txt = msg;
+
+ lines = sb->height / font->height;
+ chars_per_line = sb->width / font->width;
+
+ msg_lines = panic_msg_needed_lines(chars_per_line);
+ draw_logo = can_draw_logo(chars_per_line, lines, msg_lines);
+ msg_start_line = get_start_line(lines, msg_lines, draw_logo);
+
+ fg_color = drm_fb_convert_from_xrgb8888(fg_color, sb->format->format);
+ bg_color = drm_fb_convert_from_xrgb8888(bg_color, sb->format->format);
+
+ msgi = 0;
+ panic_line.len = 0;
+ for (l = 0; l < lines; l++) {
+ if (draw_logo && l < logo_len)
+ draw_txt_line(&logo[l], 0, l * font->height, sb, fg_color, bg_color, font);
+ else if (l >= msg_start_line && msgi < msg_len) {
+ if (!panic_line.len) {
+ panic_line.txt = panic_msg[msgi].txt;
+ panic_line.len = panic_msg[msgi].len;
+ }
+ if (!panic_line.len) {
+ draw_empty_line(sb, l * font->height, font->height, bg_color);
+ msgi++;
+ } else if (panic_line.len > chars_per_line) {
+ remaining = panic_line.len - chars_per_line;
+ panic_line.len = chars_per_line;
+ draw_txt_line(&panic_line, 0, l * font->height, sb, fg_color,
+ bg_color, font);
+ panic_line.txt += chars_per_line;
+ panic_line.len = remaining;
+ } else {
+ draw_txt_line(&panic_line,
+ font->width * (chars_per_line - panic_line.len) / 2,
+ l * font->height, sb, fg_color, bg_color, font);
+ panic_line.len = 0;
+ msgi++;
+ }
+ } else {
+ draw_empty_line(sb, l * font->height, font->height, bg_color);
+ }
+ }
+ /* Fill the bottom of the screen, if sb->height is not a multiple of font->height */
+ if (sb->height % font->height)
+ draw_empty_line(sb, l * font->height, sb->height - l * font->height, bg_color);
+}
+
+static void draw_panic_device(struct drm_device *dev, const char *msg)
+{
+ struct drm_scanout_buffer sb = {0};
+
+ if (dev->driver->get_scanout_buffer(dev, &sb))
+ return;
+ draw_panic_static(&sb, msg);
+ if (sb.flush)
+ sb.flush(sb.private);
+}
+
+static int drm_panic(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ struct drm_panic_device *drm_panic_device;
+
+ list_for_each_entry(drm_panic_device, &drm_panic_devices, head) {
+ draw_panic_device(drm_panic_device->dev, ptr);
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block drm_panic_notifier = {
+ .notifier_call = drm_panic,
+};
+
+/**
+ * drm_panic_register() - Initialize DRM panic for a device
+ * @dev: the DRM device on which the panic screen will be displayed.
+ */
+void drm_panic_register(struct drm_device *dev)
+{
+ struct drm_panic_device *new;
+
+ new = kzalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return;
+
+ new->dev = dev;
+ mutex_lock(&drm_panic_lock);
+ list_add_tail(&new->head, &drm_panic_devices);
+ mutex_unlock(&drm_panic_lock);
+
+ drm_info(dev, "Registered with drm panic\n");
+}
+EXPORT_SYMBOL(drm_panic_register);
+
+/**
+ * drm_panic_unregister()
+ * @dev: the DRM device previously registered.
+ */
+void drm_panic_unregister(struct drm_device *dev)
+{
+ struct drm_panic_device *drm_panic_device;
+ struct drm_panic_device *found = NULL;
+
+ mutex_lock(&drm_panic_lock);
+ list_for_each_entry(drm_panic_device, &drm_panic_devices, head) {
+ if (drm_panic_device->dev == dev)
+ found = drm_panic_device;
+ }
+ if (found) {
+ list_del(&found->head);
+ kfree(found);
+ drm_info(dev, "Unregistered with drm panic\n");
+ }
+ mutex_unlock(&drm_panic_lock);
+}
+EXPORT_SYMBOL(drm_panic_unregister);
+
+/**
+ * drm_panic_init() - Initialize drm-panic subsystem
+ *
+ * register the panic notifier
+ */
+void drm_panic_init(void)
+{
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &drm_panic_notifier);
+}
+
+/**
+ * drm_panic_exit() - Shutdown drm-panic subsystem
+ */
+void drm_panic_exit(void)
+{
+ atomic_notifier_chain_unregister(&panic_notifier_list,
+ &drm_panic_notifier);
+}
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 9813fa759b75..30bacae32715 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -43,6 +43,7 @@ struct dma_buf_attachment;
struct drm_display_mode;
struct drm_mode_create_dumb;
struct drm_printer;
+struct drm_scanout_buffer;
struct sg_table;
/**
@@ -392,6 +393,26 @@ struct drm_driver {
*/
void (*show_fdinfo)(struct drm_printer *p, struct drm_file *f);
+ /**
+ * @get_scanout_buffer:
+ *
+ * Get the current scanout buffer, to display a panic message with drm_panic.
+ * The driver should do the minimum changes to provide a linear buffer, that
+ * can be used to display the panic screen.
+ * It is called from a panic callback, and must follow its restrictions.
+ * (no locks, no memory allocation, no sleep, no thread/workqueue, ...)
+ * It's a best effort mode, so it's expected that in some complex cases the
+ * panic screen won't be displayed.
+ * Some hardware cannot provide a linear buffer, so there is a draw_pixel_xy()
+ * callback in the struct drm_scanout_buffer that can be used in this case.
+ *
+ * Returns:
+ *
+ * Zero on success, negative errno on failure.
+ */
+ int (*get_scanout_buffer)(struct drm_device *dev,
+ struct drm_scanout_buffer *sb);
+
/** @major: driver major number */
int major;
/** @minor: driver minor number */
diff --git a/include/drm/drm_panic.h b/include/drm/drm_panic.h
new file mode 100644
index 000000000000..c977ab77fba8
--- /dev/null
+++ b/include/drm/drm_panic.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 or MIT */
+#ifndef __DRM_PANIC_H__
+#define __DRM_PANIC_H__
+
+/*
+ * Copyright (c) 2023 Jocelyn Falempe <jfalempe@xxxxxxxxxx>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/iosys-map.h>
+
+struct drm_device;
+
+/**
+ * struct drm_scanout_buffer - DRM scanout buffer
+ *
+ * This structure holds the information necessary for drm_panic to draw the
+ * panic screen, and display it.
+ * If the driver can't provide a linear buffer, it must clear @map with
+ * iosys_map_clear() and provide a draw_pixel_xy() function.
+ */
+struct drm_scanout_buffer {
+ /**
+ * @format:
+ *
+ * drm format of the scanout buffer.
+ */
+ const struct drm_format_info *format;
+ /**
+ * @map:
+ *
+ * Virtual address of the scanout buffer, either in memory or iomem.
+ * The scanout buffer should be in linear format, and can be directly
+ * sent to the display hardware. Tearing is not an issue for the panic
+ * screen.
+ */
+ struct iosys_map map;
+ /**
+ * @width: Width of the scanout buffer, in pixels.
+ */
+ unsigned int width;
+ /**
+ * @height: Height of the scanout buffer, in pixels.
+ */
+ unsigned int height;
+ /**
+ * @pitch: Length in bytes between the start of two consecutive lines.
+ */
+ unsigned int pitch;
+ /**
+ * @private:
+ *
+ * In case the driver can't provide a linear buffer, this is a pointer to
+ * some private data, that will be passed when calling @draw_pixel_xy()
+ * and @flush()
+ */
+ void *private;
+ /**
+ * @draw_pixel_xy:
+ *
+ * In case the driver can't provide a linear buffer, this is a function
+ * that drm_panic will call for each pixel to draw.
+ * Color will be converted to the format specified by @format.
+ */
+ void (*draw_pixel_xy)(unsigned int x, unsigned int y, u32 color, void *private);
+ /**
+ * @flush:
+ *
+ * This function is called after the panic screen is drawn, either using
+ * the iosys_map or the draw_pixel_xy path. In this function, the driver
+ * can send additional commands to the hardware, to make the buffer
+ * visible.
+ */
+ void (*flush)(void *private);
+};
+
+#ifdef CONFIG_DRM_PANIC
+
+void drm_panic_init(void);
+void drm_panic_exit(void);
+
+void drm_panic_register(struct drm_device *dev);
+void drm_panic_unregister(struct drm_device *dev);
+
+#else
+
+static inline void drm_panic_init(void) {}
+static inline void drm_panic_exit(void) {}
+
+static inline void drm_panic_register(struct drm_device *dev) {}
+static inline void drm_panic_unregister(struct drm_device *dev) {}
+
+#endif
+
+#endif /* __DRM_LOG_H__ */
--
2.41.0
