linux-kernel - [PATCH nolibc 08/18] selftests/nolibc: exit with poweroff on success when getpid() == 1

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Date:   Wed, 31 Aug 2022 11:21:38 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     gwml@...r.gnuweeb.org, kernel-team@...com, w@....eu,
        Willy Tarreau <w@....eu>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH nolibc 08/18] selftests/nolibc: exit with poweroff on success when getpid() == 1

From: Willy Tarreau <w@....eu>

The idea is to ease automated testing under qemu. If the test succeeds
while running as PID 1, indicating the system was booted with init=/test,
let's just power off so that qemu can exit with a successful code. In
other situations it will exit and provoke a panic, which may be caught
for example with CONFIG_PVPANIC.

Signed-off-by: Willy Tarreau <w@....eu>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 tools/testing/selftests/nolibc/nolibc-test.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index b928f099431f7..291d96bfd7c12 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -626,6 +626,20 @@ int main(int argc, char **argv, char **envp)
 	}
 
 	printf("Total number of errors: %d\n", ret);
+
+	if (getpid() == 1) {
+		/* we're running as init, there's no other process on the
+		 * system, thus likely started from a VM for a quick check.
+		 * Exiting will provoke a kernel panic that may be reported
+		 * as an error by Qemu or the hypervisor, while stopping
+		 * cleanly will often be reported as a success. This allows
+		 * to use the output of this program for bisecting kernels.
+		 */
+		printf("Leaving init with final status: %d\n", !!ret);
+		if (ret == 0)
+			reboot(LINUX_REBOOT_CMD_POWER_OFF);
+	}
+
 	printf("Exiting with status %d\n", !!ret);
 	return !!ret;
 }
-- 
2.31.1.189.g2e36527f23