From 2349341e3e641bb87b879d5547fc4c4a6275e713 Mon Sep 17 00:00:00 2001
From: Xi Ruoyao <xry111@xry111.site>
Date: Sun, 1 Dec 2024 17:30:51 +0800
Subject: [PATCH] drm-panic: kernel: Enable DRM_PANIC

Since the previous commit, we've ensured the kernel displaying via DRM
even in the early stage.  Now enable DRM_PANIC so the kernel will
correctly show the last lines of the kernel messages in case a panic
happens.

Tested with an incorrect root= line in 3 configurations:

- A QEMU VM booted via BIOS
- A real machine booted via BIOS
- A real machine booted via UEFI

And in all configurations the panic message is correctly dumped.
In 1024x768 we can get 48 lines (twice of 24 lines in VGA console).
---
 chapter10/kernel/systemd.toml | 2 ++
 chapter10/kernel/systemd.xml  | 7 +++++--
 chapter10/kernel/sysv.toml    | 2 ++
 chapter10/kernel/sysv.xml     | 7 +++++--
 4 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/chapter10/kernel/systemd.toml b/chapter10/kernel/systemd.toml
index 649df88d4..387a74b66 100644
--- a/chapter10/kernel/systemd.toml
+++ b/chapter10/kernel/systemd.toml
@@ -15,6 +15,8 @@ DEVTMPFS='*'
 DEVTMPFS_MOUNT='*'
 SYSFB_SIMPLEFB='*'
 DRM='*'
+DRM_PANIC='*'
+DRM_PANIC_SCREEN='kmsg'
 DRM_FBDEV_EMULATION='*'
 DRM_SIMPLEDRM='*'
 FRAMEBUFFER_CONSOLE='*'
diff --git a/chapter10/kernel/systemd.xml b/chapter10/kernel/systemd.xml
index beff1eb2d..0525fbd0a 100644
--- a/chapter10/kernel/systemd.xml
+++ b/chapter10/kernel/systemd.xml
@@ -46,9 +46,12 @@
   <emphasis role='blue'>G</emphasis>raphics support ---&gt;
     &lt;*&gt; <emphasis role='blue'>D</emphasis>irect Rendering Manager (XFree86 4.1.0 and higher DRI support) ---&gt;
                                                                       ...  [DRM]
-      [*] <emphasis role='blue'>E</emphasis>nable legacy fbdev support for your modesetting driver
+      [*]    <emphasis role='blue'>D</emphasis>isplay a user-friendly message when a kernel panic occurs
+                                                                ...  [DRM_PANIC]
+      (kmsg)   <emphasis role='blue'>P</emphasis>anic screen formatter                         [DRM_PANIC_SCREEN]
+      [*]    <emphasis role='blue'>E</emphasis>nable legacy fbdev support for your modesetting driver
                                                       ...  [DRM_FBDEV_EMULATION]
-      &lt;*&gt; <emphasis role='blue'>S</emphasis>imple framebuffer driver                              [DRM_SIMPLEDRM]
+      &lt;*&gt;    <emphasis role='blue'>S</emphasis>imple framebuffer driver                           [DRM_SIMPLEDRM]
     <emphasis role='blue'>C</emphasis>onsole display driver support ---&gt;
       [*] <emphasis role='blue'>F</emphasis>ramebuffer Console support                      [FRAMEBUFFER_CONSOLE]
 
diff --git a/chapter10/kernel/sysv.toml b/chapter10/kernel/sysv.toml
index 5f6812821..c8267a303 100644
--- a/chapter10/kernel/sysv.toml
+++ b/chapter10/kernel/sysv.toml
@@ -14,6 +14,8 @@ DEVTMPFS='*'
 DEVTMPFS_MOUNT='*'
 SYSFB_SIMPLEFB='*'
 DRM='*'
+DRM_PANIC='*'
+DRM_PANIC_SCREEN='kmsg'
 DRM_FBDEV_EMULATION='*'
 DRM_SIMPLEDRM='*'
 FRAMEBUFFER_CONSOLE='*'
diff --git a/chapter10/kernel/sysv.xml b/chapter10/kernel/sysv.xml
index 0c1d05e5a..f90164d65 100644
--- a/chapter10/kernel/sysv.xml
+++ b/chapter10/kernel/sysv.xml
@@ -33,8 +33,11 @@
   <emphasis role='blue'>G</emphasis>raphics support ---&gt;
     &lt;*&gt; <emphasis role='blue'>D</emphasis>irect Rendering Manager (XFree86 4.1.0 and higher DRI support) ---&gt;
                                                                       ...  [DRM]
-      [*] <emphasis role='blue'>E</emphasis>nable legacy fbdev support for your modesetting driver
+      [*]    <emphasis role='blue'>D</emphasis>isplay a user-friendly message when a kernel panic occurs
+                                                                ...  [DRM_PANIC]
+      (kmsg)   <emphasis role='blue'>P</emphasis>anic screen formatter                         [DRM_PANIC_SCREEN]
+      [*]    <emphasis role='blue'>E</emphasis>nable legacy fbdev support for your modesetting driver
                                                       ...  [DRM_FBDEV_EMULATION]
-      &lt;*&gt; <emphasis role='blue'>S</emphasis>imple framebuffer driver                              [DRM_SIMPLEDRM]
+      &lt;*&gt;    <emphasis role='blue'>S</emphasis>imple framebuffer driver                           [DRM_SIMPLEDRM]
     <emphasis role='blue'>C</emphasis>onsole display driver support ---&gt;
       [*] <emphasis role='blue'>F</emphasis>ramebuffer Console support                      [FRAMEBUFFER_CONSOLE]</screen>