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)
Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
---
drivers/gpu/drm/Kconfig | 11 ++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm_drv.c | 3 +
drivers/gpu/drm/drm_panic.c | 270 ++++++++++++++++++++++++++++++++++++
include/drm/drm_drv.h | 14 ++
include/drm/drm_panic.h | 41 ++++++
6 files changed, 340 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 afb3b2f5f425..98d78f865180 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -99,6 +99,17 @@ 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
+ default y if DRM_SIMPLEDRM
+ 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.
+
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 7a09a89b493b..a525dd9a2751 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -72,6 +72,7 @@ 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 12687dd9e1ac..0e0f1e258845 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -45,6 +45,7 @@
#include <drm/drm_mode_object.h>
#include <drm/drm_print.h>
#include <drm/drm_privacy_screen_machine.h>
+#include <drm/drm_panic.h>
#include "drm_crtc_internal.h"
#include "drm_internal.h"
@@ -1067,6 +1068,7 @@ 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 +1080,7 @@ 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..32697325456f
--- /dev/null
+++ b/drivers/gpu/drm/drm_panic.c
@@ -0,0 +1,270 @@
+// 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_fourcc.h>
+#include <drm/drm_panic.h>
+#include <drm/drm_print.h>
+
+
+MODULE_AUTHOR("Jocelyn Falempe");
+MODULE_DESCRIPTION("DRM PANIC");
+MODULE_LICENSE("GPL");
+
+/**
+ * DOC: DRM Panic
+ *
+ * This module displays a user friendly message on screen when a kernel panic
+ * occurs. It's useful when using a user-space console instead of fbcon.
+ * It's intended for end-user, so have minimal technical/debug information.
+ *
+ * It will display only one frame, so just clear it, and draw white pixels for
+ * the characters. 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 dpanic_drm_device {
+ struct list_head head;
+ struct drm_device *dev;
+};
+
+struct dpanic_line {
+ u32 len;
+ const char *txt;
+};
+
+#define PANIC_LINE(s) {.len = sizeof(s), .txt = s}
+
+const struct dpanic_line panic_msg[] = {
+ PANIC_LINE("KERNEL PANIC !"),
+ PANIC_LINE(""),
+ PANIC_LINE("Please reboot your computer."),
+ PANIC_LINE(""),
+};
+
+const struct dpanic_line logo[] = {
+ PANIC_LINE(" .--. _"),
+ PANIC_LINE(" |o_o | | |"),
+ PANIC_LINE(" |:_/ | | |"),
+ PANIC_LINE(" // \\ \\ |_|"),
+ PANIC_LINE(" (| | ) _"),
+ PANIC_LINE(" /'\\_ _/`\\ (_)"),
+ PANIC_LINE(" \\___)=(___/"),
+};
+
+static LIST_HEAD(dpanic_devices);
+static DEFINE_MUTEX(dpanic_lock);
+
+#define IOSYS_WRITE8(offset, val) iosys_map_wr(screen_base, offset, u8, val)
+/*
+ * Only handle DRM_FORMAT_XRGB8888 for testing
+ */
+static inline void dpanic_draw_px(struct iosys_map *screen_base, size_t offset, u32 pixel_format,
+ u8 r, u8 g, u8 b)
+{
+ switch (pixel_format) {
+ case DRM_FORMAT_XRGB8888:
+ IOSYS_WRITE8(offset++, b);
+ IOSYS_WRITE8(offset++, g);
+ IOSYS_WRITE8(offset++, r);
+ IOSYS_WRITE8(offset++, 0xff);
+ break;
+ default:
+ pr_err("Format not supported\n");
+ break;
+ /* TODO other format */
+ }
+}
+
+/* Draw a single character at given destination */
+static void dpanic_draw_char(char ch, size_t x, size_t y,
+ struct drm_scanout_buffer *sb,
+ const struct font_desc *font)
+{
+ size_t src_width, src_height, src_stride, i, dst_off;
+ const u8 *src;
+
+ src_width = font->width;
+ src_height = font->height;
+ src_stride = DIV_ROUND_UP(src_width, 8);
+
+ dst_off = x * font->width * sb->format->cpp[0] + y * font->height * sb->pitch;
+
+ src = font->data;
+ src += ch * src_height * src_stride;
+
+ while (src_height--) {
+ for (i = 0; i < src_width; ++i) {
+ /* only draw white pixels */
+ if (src[i / 8] & (0x80 >> (i % 8)))
+ dpanic_draw_px(&sb->map, dst_off + i * sb->format->cpp[0],
+ sb->format->format, 0xff, 0xff, 0xff);
+ }
+ src += src_stride;
+ dst_off += sb->pitch;
+ }
+}
+
+static void dpanic_draw_line_centered(const struct dpanic_line *line, size_t y,
+ struct drm_scanout_buffer *sb,
+ const struct font_desc *font)
+{
+ size_t chars_per_line = sb->width / font->width;
+ size_t skip_left, x;
+
+ if (line->len > chars_per_line)
+ return;
+
+ skip_left = (chars_per_line - line->len) / 2;
+
+ for (x = 0; x < line->len; x++)
+ dpanic_draw_char(line->txt[x], skip_left + x, y, sb, font);
+}
+
+/*
+ * Draw the Tux logo at the upper left corner
+ */
+static void dpanic_draw_logo(struct drm_scanout_buffer *sb,
+ const struct font_desc *font)
+{
+ size_t chars_per_line = sb->width / font->width;
+ size_t x, y;
+
+ for (y = 0; y < ARRAY_SIZE(logo); y++)
+ for (x = 0; x < logo[y].len && x < chars_per_line; x++)
+ dpanic_draw_char(logo[y].txt[x], x, y, sb, font);
+}
+
+/*
+ * Draw the panic message at the center of the screen
+ */
+static void dpanic_static_draw(struct drm_scanout_buffer *sb, const char *msg)
+{
+ size_t y, lines;
+ int skip_top;
+ size_t len = ARRAY_SIZE(panic_msg);
+ struct dpanic_line reason;
+ const struct font_desc *font = get_default_font(sb->width, sb->height, 0x8080, 0x8080);
+
+ if (!font)
+ return;
+
+ reason.len = strlen(msg);
+ reason.txt = msg;
+
+ lines = sb->height / font->height;
+ skip_top = (lines - len - 1) / 2;
+ if (skip_top < 0)
+ return;
+
+ /* clear screen */
+ iosys_map_memset(&sb->map, 0, 0, sb->height * sb->pitch);
+
+ for (y = 0; y < len; y++)
+ dpanic_draw_line_centered(&panic_msg[y], y + skip_top, sb, font);
+ dpanic_draw_line_centered(&reason, y + skip_top, sb, font);
+
+ if (skip_top >= ARRAY_SIZE(logo))
+ dpanic_draw_logo(sb, font);
+}
+
+static void drm_panic_device(struct drm_device *dev, const char *msg)
+{
+ struct drm_scanout_buffer sb;
+
+ if (dev->driver->get_scanout_buffer(dev, &sb))
+ return;
+
+ dpanic_static_draw(&sb, msg);
+}
+
+static int drm_panic(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ struct dpanic_drm_device *dpanic_device;
+
+ list_for_each_entry(dpanic_device, &dpanic_devices, head) {
+ drm_panic_device(dpanic_device->dev, ptr);
+ }
+ return NOTIFY_OK;
+}
+
+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 dpanic_drm_device *new;
+
+ new = kzalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return;
+
+ new->dev = dev;
+ list_add_tail(&new->head, &dpanic_devices);
+
+ 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 dpanic_drm_device *dpanic_device;
+ struct dpanic_drm_device *found = NULL;
+
+ list_for_each_entry(dpanic_device, &dpanic_devices, head) {
+ if (dpanic_device->dev == dev)
+ found = dpanic_device;
+ }
+ if (found) {
+ list_del(&found->head);
+ kfree(found);
+ drm_info(dev, "Unregistered with drm panic\n");
+ }
+}
+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_log_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 89e2706cac56..e538c87116d3 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;
/**
@@ -408,6 +409,19 @@ 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.
+ * It is called from a panic callback, and must follow its restrictions.
+ *
+ * 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..db430b8dfbb2
--- /dev/null
+++ b/include/drm/drm_panic.h
@@ -0,0 +1,41 @@
+/* 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 {
+ const struct drm_format_info *format;
+ struct iosys_map map;
+ unsigned int pitch;
+ unsigned int width;
+ unsigned int height;
+};
+
+#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
