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selftests/livepatch: update test-ftrace.sh for deprecated ftrace_enabled

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kernel.ftrace_enabled=0 is now refused on kernels that deprecate the
knob, so the old disable/reload flow no longer applies there. Probe
for this with ftrace_disable_supported() and keep the full original
scenario (disable, fail to load a livepatch, re-enable, load, confirm
disable is refused while loaded) on kernels where it still works;
otherwise just confirm the write is refused.

Link: https://patch.msgid.link/20260806153000.4184871-3-andrey.grodzovsky@crowdstrike.com
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Suggested-by: Joe Lawrence <joe.lawrence@redhat.com>
Assisted-by: Claude:claude-sonnet-5
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@crowdstrike.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Andrey Grodzovsky 2026-08-06 11:30:00 -04:00 committed by Steven Rostedt
parent b0c8570491
commit 88b3e7fedc
2 changed files with 42 additions and 17 deletions
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14
tools/testing/selftests/livepatch/functions.sh
View File

@ -126,6 +126,20 @@ function set_ftrace_enabled() {
echo "livepatch: kernel.ftrace_enabled = $result" > /dev/kmsg
}
# ftrace_disable_supported() - probe whether kernel.ftrace_enabled=0
# can still disable ftrace on this kernel. Newer kernels deprecate
# the knob and always refuse the write with -EOPNOTSUPP.
function ftrace_disable_supported() {
local orig result
orig=$(sysctl --values kernel.ftrace_enabled)
sysctl -q kernel.ftrace_enabled=0 &> /dev/null
result=$(sysctl --values kernel.ftrace_enabled)
sysctl -q "kernel.ftrace_enabled=$orig" &> /dev/null
[[ "$result" == "0" ]]
}
function cleanup() {
pop_config
}

45
tools/testing/selftests/livepatch/test-ftrace.sh
View File

@ -12,29 +12,32 @@ setup_config
# - turn ftrace_enabled OFF and verify livepatches can't load
# - turn ftrace_enabled ON and verify livepatch can load
# - verify that ftrace_enabled can't be turned OFF while a livepatch is loaded
# (skipped on kernels where the sysctl is deprecated and always refuses 0)
start_test "livepatch interaction with ftrace_enabled sysctl"
set_ftrace_enabled 0
load_failing_mod $MOD_LIVEPATCH
if ftrace_disable_supported; then
set_ftrace_enabled 1
load_lp $MOD_LIVEPATCH
if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live patched" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
set_ftrace_enabled 0
load_failing_mod $MOD_LIVEPATCH
# Check that ftrace could not get disabled when a livepatch is enabled
set_ftrace_enabled --fail 0
if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live patched" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
disable_lp $MOD_LIVEPATCH
unload_lp $MOD_LIVEPATCH
set_ftrace_enabled 1
load_lp $MOD_LIVEPATCH
if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live patched" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
check_result "livepatch: kernel.ftrace_enabled = 0
# Check that ftrace could not get disabled when a livepatch is enabled
set_ftrace_enabled --fail 0
if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live patched" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
disable_lp $MOD_LIVEPATCH
unload_lp $MOD_LIVEPATCH
check_result "livepatch: kernel.ftrace_enabled = 0
% insmod test_modules/$MOD_LIVEPATCH.ko
livepatch: enabling patch '$MOD_LIVEPATCH'
livepatch: '$MOD_LIVEPATCH': initializing patching transition
@ -60,6 +63,14 @@ livepatch: '$MOD_LIVEPATCH': completing unpatching transition
livepatch: '$MOD_LIVEPATCH': unpatching complete
% rmmod $MOD_LIVEPATCH"
else
set_ftrace_enabled --fail 0
check_result "livepatch: sysctl: setting key \"kernel.ftrace_enabled\": \
Operation not supported"
fi
# - verify livepatch can load
# - check if traces have a patched function