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6a71770442
The test proves that a syscall can be livepatched. It is interesting
because syscalls are called a tricky way. Also the process gets
livepatched either when sleeping in the userspace or when entering
or leaving the kernel space.
The livepatch is a bit tricky:
1. The syscall function name is architecture specific. Also
ARCH_HAS_SYSCALL_WRAPPER must be taken in account.
2. The syscall must stay working the same way for other processes
on the system. It is solved by decrementing a counter only
for PIDs of the test processes. It means that the test processes
has to call the livepatched syscall at least once.
The test creates one userspace process per online cpu. The processes
are calling getpid in a busy loop. The intention is to create random
locations when the livepatch gets enabled. Nothing is guarantted.
The magic is in the randomness.
Reviewed-by: Joe Lawrence <joe.lawrence@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
54 lines
1.6 KiB
Bash
Executable File
54 lines
1.6 KiB
Bash
Executable File
#!/bin/bash
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# SPDX-License-Identifier: GPL-2.0
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# Copyright (C) 2023 SUSE
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# Author: Marcos Paulo de Souza <mpdesouza@suse.com>
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. $(dirname $0)/functions.sh
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MOD_SYSCALL=test_klp_syscall
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setup_config
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# - Start _NRPROC processes calling getpid and load a livepatch to patch the
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# getpid syscall. Check if all the processes transitioned to the livepatched
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# state.
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start_test "patch getpid syscall while being heavily hammered"
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for i in $(seq 1 $(getconf _NPROCESSORS_ONLN)); do
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./test_klp-call_getpid &
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pids[$i]="$!"
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done
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pid_list=$(echo ${pids[@]} | tr ' ' ',')
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load_lp $MOD_SYSCALL klp_pids=$pid_list
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# wait for all tasks to transition to patched state
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loop_until 'grep -q '^0$' /sys/kernel/test_klp_syscall/npids'
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pending_pids=$(cat /sys/kernel/test_klp_syscall/npids)
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log "$MOD_SYSCALL: Remaining not livepatched processes: $pending_pids"
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for pid in ${pids[@]}; do
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kill $pid || true
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done
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disable_lp $MOD_SYSCALL
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unload_lp $MOD_SYSCALL
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check_result "% insmod test_modules/$MOD_SYSCALL.ko klp_pids=$pid_list
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livepatch: enabling patch '$MOD_SYSCALL'
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livepatch: '$MOD_SYSCALL': initializing patching transition
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livepatch: '$MOD_SYSCALL': starting patching transition
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livepatch: '$MOD_SYSCALL': completing patching transition
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livepatch: '$MOD_SYSCALL': patching complete
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$MOD_SYSCALL: Remaining not livepatched processes: 0
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% echo 0 > /sys/kernel/livepatch/$MOD_SYSCALL/enabled
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livepatch: '$MOD_SYSCALL': initializing unpatching transition
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livepatch: '$MOD_SYSCALL': starting unpatching transition
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livepatch: '$MOD_SYSCALL': completing unpatching transition
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livepatch: '$MOD_SYSCALL': unpatching complete
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% rmmod $MOD_SYSCALL"
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exit 0
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