linux-kernel - [PATCH] um: add "noreboot" command line option for PANIC

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Message-Id: <20220713115617.493376-1-Jason@zx2c4.com>
Date:   Wed, 13 Jul 2022 13:56:17 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     johannes@...solutions.net, linux-um@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] um: add "noreboot" command line option for PANIC_TIMEOUT=-1 setups

QEMU has a -no-reboot option, which halts instead of reboots when the
guest asks to reboot. This is invaluable when used with
CONFIG_PANIC_TIMEOUT=-1 (and panic_on_warn), because it allows panics
and warnings to be caught immediately in CI. Implement this in UML too,
by way of a basic setup param.

Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 arch/um/os-Linux/skas/process.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 87d3129e7362..0df2ebcc97c0 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -5,6 +5,7 @@
  */
 
 #include <stdlib.h>
+#include <stdbool.h>
 #include <unistd.h>
 #include <sched.h>
 #include <errno.h>
@@ -707,10 +708,24 @@ void halt_skas(void)
 	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
 }
 
+static bool noreboot;
+
+static int __init noreboot_cmd_param(char *str, int *add)
+{
+	noreboot = true;
+	return 0;
+}
+
+__uml_setup("noreboot", noreboot_cmd_param,
+"noreboot\n"
+"    Rather than rebooting, exit always, akin to QEMU's -no-reboot option.\n"
+"    This is useful if you're using CONFIG_PANIC_TIMEOUT in order to catch\n"
+"    crashes in CI\n");
+
 void reboot_skas(void)
 {
 	block_signals_trace();
-	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
+	UML_LONGJMP(&initial_jmpbuf, noreboot ? INIT_JMP_HALT : INIT_JMP_REBOOT);
 }
 
 void __switch_mm(struct mm_id *mm_idp)
-- 
2.35.1