[PATCH] selftests/mm: Don't needlessly use sudo to obtain root in run_vmtests.sh

[Mark Brown]

When opening yama/ptrace_scope we unconditionally use sudo to ensure we
are running as root, resulting in failures if running in a minimal root
filesystem where sudo is not installed. Since automated test systems will
typically just run all of kselftest as root (and many kselftests rely on
this for full functionality) add a check to see if we're already root and
only invoke sudo if not.

Since I am unclear what the intended effect of the command being run is I
have not added any error handling for the case where we fail to obtain
root.

Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 tools/testing/selftests/mm/run_vmtests.sh | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index fe140a9f4f9d..c8ca830dba93 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -248,6 +248,17 @@ run_test() {
 
 echo "TAP version 13" | tap_output
 
+HAVE_ROOT=0
+if [ "$(id -u)" = "0" ]; then
+	AS_ROOT=
+	HAVE_ROOT=1
+elif [ "$(command -v sudo)" != "" ]; then
+	AS_ROOT=sudo
+	HAVE_ROOT=1
+else
+	echo # WARNING: Unable to run as root
+fi
+
 CATEGORY="hugetlb" run_test ./hugepage-mmap
 
 shmmax=$(cat /proc/sys/kernel/shmmax)
@@ -363,7 +374,8 @@ CATEGORY="hmm" run_test bash ./test_hmm.sh smoke
 # MADV_POPULATE_READ and MADV_POPULATE_WRITE tests
 CATEGORY="madv_populate" run_test ./madv_populate
 
-(echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
+# FIXME: What if we can't get root?
+(echo 0 | ${AS_ROOT} tee /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
 CATEGORY="memfd_secret" run_test ./memfd_secret
 
 # KSM KSM_MERGE_TIME_HUGE_PAGES test with size of 100

---
base-commit: 445a555e0623387fa9b94e68e61681717e70200a
change-id: 20240209-kselftest-mm-check-deps-01a825e5fed4

Best regards,
-- 
Mark Brown <broonie@xxxxxxxxxx>