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().
v6
* Fix sparse warning for panic_msg and logo.
v7
* Add select DRM_KMS_HELPER for the color conversion functions.
v8
* Register directly each plane to the panic notifier (Sima)
* Add raw_spinlock to properly handle concurrency (Sima)
* Register plane instead of device, to avoid looping through plane
list, and simplify code.
* Replace get_scanout_buffer() logic with drm_panic_set_buffer()
(Thomas Zimmermann)
* Removed the draw_pixel_xy() API, will see later if it can be added back.
v9
* Revert to using get_scanout_buffer() (Sima)
* Move get_scanout_buffer() and panic_flush() to the plane helper
functions (Thomas Zimmermann)
* Register all planes with get_scanout_buffer() to the panic notifier
* Use drm_panic_lock() to protect against race (Sima)
Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
---
Documentation/gpu/drm-kms.rst | 12 +
drivers/gpu/drm/Kconfig | 23 ++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm_drv.c | 4 +
drivers/gpu/drm/drm_panic.c | 322 +++++++++++++++++++++++
drivers/gpu/drm/drm_plane.c | 1 +
include/drm/drm_modeset_helper_vtables.h | 37 +++
include/drm/drm_panic.h | 52 ++++
include/drm/drm_plane.h | 5 +
9 files changed, 457 insertions(+)
create mode 100644 drivers/gpu/drm/drm_panic.c
diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst
index 13d3627d8bc0..b64334661aeb 100644
--- a/Documentation/gpu/drm-kms.rst
+++ b/Documentation/gpu/drm-kms.rst
@@ -398,6 +398,18 @@ Plane Damage Tracking Functions Reference
.. kernel-doc:: include/drm/drm_damage_helper.h
:internal:
+Plane Panic Feature
+-------------------
+
+.. kernel-doc:: drivers/gpu/drm/drm_panic.c
+ :doc: overview
+
+Plane Panic Functions Reference
+-------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/drm_panic.c
+ :export:
+
Display Modes Function Reference
================================
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 16029435b750..f07ca38d3f98 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -102,6 +102,29 @@ 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 DRM_KMS_HELPER
+ 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 a73c04d2d7a3..f9ca4f8fa6c5 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -88,6 +88,7 @@ drm-$(CONFIG_DRM_PRIVACY_SCREEN) += \
drm_privacy_screen.o \
drm_privacy_screen_x86.o
drm-$(CONFIG_DRM_ACCEL) += ../../accel/drm_accel.o
+drm-$(CONFIG_DRM_PANIC) += drm_panic.o
obj-$(CONFIG_DRM) += drm.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 c157500b3135..535b624d4c9d 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>
@@ -944,6 +945,7 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
if (ret)
goto err_unload;
}
+ drm_panic_register(dev);
DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
driver->name, driver->major, driver->minor,
@@ -988,6 +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))
diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
new file mode 100644
index 000000000000..2e2a033d1267
--- /dev/null
+++ b/drivers/gpu/drm/drm_panic.c
@@ -0,0 +1,322 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/*
+ * Copyright (c) 2023 Red Hat.
+ * Author: 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/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_framebuffer.h>
+#include <drm/drm_modeset_helper_vtables.h>
+#include <drm/drm_panic.h>
+#include <drm/drm_plane.h>
+#include <drm/drm_print.h>
+
+
+MODULE_AUTHOR("Jocelyn Falempe");
+MODULE_DESCRIPTION("DRM panic handler");
+MODULE_LICENSE("GPL");
+
+/**
+ * DOC: overview
+ *
+ * To enable DRM panic for a driver, the primary plane must implement a
+ * get_scanout_buffer() helper function. It is then automatically registered to
+ * the drm panic handler.
+ * When a panic occurs, the get_scanout_buffer() will be called, and the driver
+ * can provide a framebuffer so the panic handler can draw the panic screen on
+ * it. The buffer provided must be linear, and use a supported color format.
+ * Optionally the driver can also provide a panic_flush() callback, that will
+ * be called after that, to send additional commands to the hardware to make the
+ * scanout buffer visible.
+ */
+
+/*
+ * 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.
+ */
+
+static inline struct drm_plane *to_drm_plane(struct notifier_block *nb)
+{
+ return container_of(nb, struct drm_plane, panic_notifier);
+}
+
+struct drm_panic_line {
+ u32 len;
+ const char *txt;
+};
+
+#define PANIC_LINE(s) {.len = sizeof(s) - 1, .txt = s}
+
+static 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 */
+};
+
+static const struct drm_panic_line logo[] = {
+ PANIC_LINE(" .--. _"),
+ PANIC_LINE(" |o_o | | |"),
+ PANIC_LINE(" |:_/ | | |"),
+ PANIC_LINE(" // \\ \\ |_|"),
+ PANIC_LINE(" (| | ) _"),
+ PANIC_LINE(" /'\\_ _/`\\ (_)"),
+ PANIC_LINE(" \\___)=(___/"),
+};
+
+static void draw_empty_line(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(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 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,
+ 0x80808080, 0x80808080);
+
+ 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);
+}
+
+/*
+ * drm_panic_is_format_supported()
+ * @format: a fourcc color code
+ * Returns: true if supported, false otherwise.
+ *
+ * Check if drm_panic will be able to use this color format.
+ */
+static bool drm_panic_is_format_supported(u32 format)
+{
+ return drm_fb_convert_from_xrgb8888(0xffffff, format) != 0;
+}
+
+static void draw_panic_plane(struct drm_plane *plane, const char *msg)
+{
+ struct drm_scanout_buffer sb;
+ int ret;
+
+ if (!drm_panic_trylock(plane->dev))
+ return;
+
+ ret = plane->helper_private->get_scanout_buffer(plane, &sb);
+
+
+ if (!ret && drm_panic_is_format_supported(sb.format->format)) {
+ draw_panic_static(&sb, msg);
+ if (plane->helper_private->panic_flush)
+ plane->helper_private->panic_flush(plane);
+ }
+ drm_panic_unlock(plane->dev);
+}
+
+static int drm_panic(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ struct drm_plane *plane = to_drm_plane(this);
+
+ draw_panic_plane(plane, ptr);
+
+ return NOTIFY_OK;
+}
+
+/**
+ * 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_plane *plane;
+ int registered_plane = 0;
+
+ if (!dev->mode_config.num_total_plane)
+ return;
+
+ drm_for_each_plane(plane, dev) {
+ if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
+ continue;
+ plane->panic_notifier.notifier_call = drm_panic;
+ plane->panic_notifier.priority = -5;
+ if (atomic_notifier_chain_register(&panic_notifier_list,
+ &plane->panic_notifier)) {
+ drm_warn(dev, "Failed to register panic handler\n");
+ } else {
+ registered_plane++;
+ }
+ }
+ if (registered_plane)
+ drm_info(dev, "Registered %d planes with drm panic\n", registered_plane);
+}
+EXPORT_SYMBOL(drm_panic_register);
+
+/**
+ * drm_panic_unregister()
+ * @dev: the drm device previously registered.
+ */
+void drm_panic_unregister(struct drm_device *dev)
+{
+ struct drm_plane *plane;
+
+ if (!dev->mode_config.num_total_plane)
+ return;
+
+ drm_for_each_plane(plane, dev) {
+ if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
+ continue;
+
+ atomic_notifier_chain_unregister(&panic_notifier_list,
+ &plane->panic_notifier);
+ }
+}
+EXPORT_SYMBOL(drm_panic_unregister);
+
diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index 672c655c7a8e..18af71792e58 100644
--- a/drivers/gpu/drm/drm_plane.c
+++ b/drivers/gpu/drm/drm_plane.c
@@ -31,6 +31,7 @@
#include <drm/drm_crtc.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_managed.h>
+#include <drm/drm_panic.h>
#include <drm/drm_vblank.h>
#include "drm_crtc_internal.h"
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 881b03e4dc28..bd4752b1ce3f 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -48,6 +48,7 @@
* To make this clear all the helper vtables are pulled together in this location here.
*/
+struct drm_scanout_buffer;
struct drm_writeback_connector;
struct drm_writeback_job;
@@ -1442,6 +1443,42 @@ struct drm_plane_helper_funcs {
*/
void (*atomic_async_update)(struct drm_plane *plane,
struct drm_atomic_state *state);
+
+ /**
+ * @get_scanout_buffer:
+ *
+ * Get the current scanout buffer, to display a 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.
+ * The device dev->mode_config.panic_lock is taken before calling this
+ * function, so you can safely access the plane->state
+ * 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.
+ * The returned scanout_buffer->map must be valid if no error code is
+ * returned.
+ *
+ * Returns:
+ *
+ * Zero on success, negative errno on failure.
+ */
+ int (*get_scanout_buffer)(struct drm_plane *plane,
+ struct drm_scanout_buffer *sb);
+
+ /**
+ * @panic_flush:
+ *
+ * It is used by drm_panic, and is called after the panic screen is
+ * drawn to the scanout buffer. In this function, the driver
+ * can send additional commands to the hardware, to make the scanout
+ * buffer visible.
+ * The device dev->mode_config.panic_lock is taken before calling this
+ * function, so you can safely access the plane->state
+ * It is called from a panic callback, and must follow its restrictions.
+ * (no locks, no memory allocation, no sleep, no thread/workqueue, ...)
+ */
+ void (*panic_flush)(struct drm_plane *plane);
};
/**
diff --git a/include/drm/drm_panic.h b/include/drm/drm_panic.h
index f2135d03f1eb..e19adbd0a71a 100644
--- a/include/drm/drm_panic.h
+++ b/include/drm/drm_panic.h
@@ -2,11 +2,51 @@
#ifndef __DRM_PANIC_H__
#define __DRM_PANIC_H__
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/iosys-map.h>
+
#include <drm/drm_device.h>
/*
* Copyright (c) 2024 Intel
*/
+/**
+ * struct drm_scanout_buffer - DRM scanout buffer
+ *
+ * This structure holds the information necessary for drm_panic to draw the
+ * panic screen, and display it.
+ */
+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;
+};
+
/**
* drm_panic_trylock - try to enter the panic printing critical section
* @dev: struct drm_device
@@ -96,4 +136,16 @@ static inline void drm_panic_unlock(struct drm_device *dev)
raw_spin_unlock(&dev->mode_config.panic_lock);
}
+#ifdef CONFIG_DRM_PANIC
+
+void drm_panic_register(struct drm_device *dev);
+void drm_panic_unregister(struct drm_device *dev);
+
+#else
+
+static inline void drm_panic_register(struct drm_device *dev) {}
+static inline void drm_panic_unregister(struct drm_device *dev) {}
+
+#endif
+
#endif /* __DRM_PANIC_H__ */
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 641fe298052d..c7119a1c47fe 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -779,6 +779,11 @@ struct drm_plane {
* @hotspot_y_property: property to set mouse hotspot y offset.
*/
struct drm_property *hotspot_y_property;
+
+ /**
+ * @panic_notifier: Used to register a panic notifier for this plane
+ */
+ struct notifier_block panic_notifier;
};
#define obj_to_plane(x) container_of(x, struct drm_plane, base)
--
2.43.2
