From 29e3ea8cbd2958cf237b84652ec236803f2c6202 Mon Sep 17 00:00:00 2001 From: Jordan Niethe Date: Mon, 8 Feb 2021 14:29:57 +1100 Subject: [PATCH] selftests/powerpc: Test for spurious kernel memory faults on radix Previously when mapping kernel memory on radix, no ptesync was included which would periodically lead to unhandled spurious faults. Mapping kernel memory is used when code patching with Strict RWX enabled. As suggested by Chris Riedl, turning ftrace on and off does a large amount of code patching so is a convenient way to see this kind of fault. Add a selftest to try and trigger this kind of a spurious fault. It tests for 30 seconds which is usually long enough for the issue to show up. Signed-off-by: Jordan Niethe [mpe: Rename it to better reflect what it does, rather than the symptom] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210208032957.1232102-2-jniethe5@gmail.com --- tools/testing/selftests/powerpc/mm/Makefile | 1 + .../powerpc/mm/stress_code_patching.sh | 49 +++++++++++++++++++ 2 files changed, 50 insertions(+) create mode 100755 tools/testing/selftests/powerpc/mm/stress_code_patching.sh diff --git a/tools/testing/selftests/powerpc/mm/Makefile b/tools/testing/selftests/powerpc/mm/Makefile index defe488d6bf1..40253abc6208 100644 --- a/tools/testing/selftests/powerpc/mm/Makefile +++ b/tools/testing/selftests/powerpc/mm/Makefile @@ -5,6 +5,7 @@ noarg: TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr \ large_vm_fork_separation bad_accesses pkey_exec_prot \ pkey_siginfo stack_expansion_signal stack_expansion_ldst +TEST_PROGS := stress_code_patching.sh TEST_GEN_PROGS_EXTENDED := tlbie_test TEST_GEN_FILES := tempfile diff --git a/tools/testing/selftests/powerpc/mm/stress_code_patching.sh b/tools/testing/selftests/powerpc/mm/stress_code_patching.sh new file mode 100755 index 000000000000..e454509659f6 --- /dev/null +++ b/tools/testing/selftests/powerpc/mm/stress_code_patching.sh @@ -0,0 +1,49 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0-or-later + +TIMEOUT=30 + +DEBUFS_DIR=`cat /proc/mounts | grep debugfs | awk '{print $2}'` +if [ ! -e "$DEBUFS_DIR" ] +then + echo "debugfs not found, skipping" 1>&2 + exit 4 +fi + +if [ ! -e "$DEBUFS_DIR/tracing/current_tracer" ] +then + echo "Tracing files not found, skipping" 1>&2 + exit 4 +fi + + +echo "Testing for spurious faults when mapping kernel memory..." + +if grep -q "FUNCTION TRACING IS CORRUPTED" "$DEBUFS_DIR/tracing/trace" +then + echo "FAILED: Ftrace already dead. Probably due to a spurious fault" 1>&2 + exit 1 +fi + +dmesg -C +START_TIME=`date +%s` +END_TIME=`expr $START_TIME + $TIMEOUT` +while [ `date +%s` -lt $END_TIME ] +do + echo function > $DEBUFS_DIR/tracing/current_tracer + echo nop > $DEBUFS_DIR/tracing/current_tracer + if dmesg | grep -q 'ftrace bug' + then + break + fi +done + +echo nop > $DEBUFS_DIR/tracing/current_tracer +if dmesg | grep -q 'ftrace bug' +then + echo "FAILED: Mapping kernel memory causes spurious faults" 1>&2 + exit 1 +else + echo "OK: Mapping kernel memory does not cause spurious faults" + exit 0 +fi -- 2.20.1