linux-kernel - [PATCH v3 11/14] selftests/nolibc: fix up failures when CONFIG_PROC

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Date:   Fri, 30 Jun 2023 22:56:46 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     thomas@...ch.de, w@....eu
Cc:     arnd@...db.de, falcon@...ylab.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v3 11/14] selftests/nolibc: fix up failures when CONFIG_PROC_FS=n

For CONFIG_PROC_FS=n, the /proc is not mountable, but the /proc
directory has been created in the prepare() stage whenever /proc is
there or not.

so, the checking of /proc in the run_syscall() stage will be always true
and at last it will fail all of the procfs dependent test cases, which
deviates from the 'cond' check design of the EXPECT_xx macros, without
procfs, these test cases should be skipped instead of failed.

To solve this issue, one method is checking /proc/self instead of /proc,
another method is removing the /proc directory completely for
CONFIG_PROC_FS=n, we apply the second method to avoid misleading the
users.

Reviewed-by: Thomas Weißschuh <linux@...ssschuh.net>
Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
---
 tools/testing/selftests/nolibc/nolibc-test.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 34a47c512b97..b7ea95dad0fb 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1046,8 +1046,11 @@ int prepare(void)

 	/* try to mount /proc if not mounted. Silently fail otherwise */
 	if (stat("/proc/.", &stat_buf) == 0 || mkdir("/proc", 0755) == 0) {
-		if (stat("/proc/self", &stat_buf) != 0)
-			mount("/proc", "/proc", "proc", 0, 0);
+		if (stat("/proc/self", &stat_buf) != 0) {
+			/* If not mountable, remove /proc completely to avoid misuse */
+			if (mount("none", "/proc", "proc", 0, 0) != 0)
+				rmdir("/proc");
+		}
 	}

 	return 0;
-- 
2.25.1