[SRU][J][PATCH v3 4/4] selftests/powerpc: Detect taint change in mitigation patching test

[Zixing Liu]

From: Michael Ellerman <mpe at ellerman.id.au>

BugLink: https://bugs.launchpad.net/bugs/2141536

Currently the mitigation patching test errors out if the kernel is
tainted prior to the test running.

That causes the test to fail unnecessarily if some other test has caused
the kernel to be tainted, or if a proprietary or force module is loaded
for example.

Instead just warn if the kernel is tainted to begin with, and only
report a change in the taint state as an error in the test.

Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
(cherry picked from commit a8a54a65cac4f8202df36f925b6746328802d05f)
Signed-off-by: Zixing Liu <zixing.liu at canonical.com>
---
 .../selftests/powerpc/security/mitigation-patching.sh     | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/powerpc/security/mitigation-patching.sh b/tools/testing/selftests/powerpc/security/mitigation-patching.sh
index 00197acb7ff1..971793e93ba9 100755
--- a/tools/testing/selftests/powerpc/security/mitigation-patching.sh
+++ b/tools/testing/selftests/powerpc/security/mitigation-patching.sh
@@ -36,8 +36,7 @@ fi
 
 tainted=$(cat /proc/sys/kernel/tainted)
 if [[ "$tainted" -ne 0 ]]; then
-    echo "Error: kernel already tainted!" >&2
-    exit 1
+    echo "Warning: kernel already tainted! ($tainted)" >&2
 fi
 
 mitigations="barrier_nospec stf_barrier count_cache_flush rfi_flush entry_flush uaccess_flush"
@@ -65,9 +64,10 @@ fi
 echo "Waiting for timeout ..."
 wait
 
+orig_tainted=$tainted
 tainted=$(cat /proc/sys/kernel/tainted)
-if [[ "$tainted" -ne 0 ]]; then
-    echo "Error: kernel became tainted!" >&2
+if [[ "$tainted" != "$orig_tainted" ]]; then
+    echo "Error: kernel newly tainted, before ($orig_tainted) after ($tainted)" >&2
     exit 1
 fi
 
-- 
2.53.0