Hi Boyan,
On 8/31/20 4:34 PM, Boyan Karatotev wrote:
PAuth signs and verifies return addresses on the stack. It does so by inserting a Pointer Authentication code (PAC) into some of the unused top bits of an address. This is achieved by adding paciasp/autiasp instructions at the beginning and end of a function.
This feature is partially backwards compatible with earlier versions of the ARM architecture. To coerce the compiler into emitting fully backwards compatible code the main file is compiled to target an earlier ARM version. This allows the tests to check for the feature and print meaningful error messages instead of crashing.
Add a test to verify that corrupting the return address results in a SIGSEGV on return.
Cc: Shuah Khan shuah@kernel.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will@kernel.org Reviewed-by: Vincenzo Frascino Vincenzo.Frascino@arm.com Reviewed-by: Amit Daniel Kachhap amit.kachhap@arm.com Signed-off-by: Boyan Karatotev boyan.karatotev@arm.com
tools/testing/selftests/arm64/Makefile | 2 +-
[...]
+/* check that a corrupted PAC results in SIGSEGV */ +TEST_SIGNAL(corrupt_pac, SIGSEGV) +{
- ASSERT_PAUTH_ENABLED();
- pac_corruptor();
With 8.6-Pauth extension merged in arm tree [1]. It makes sense to verify PAC corruption for both SIGSEGV and SIGILL signals.
Code something like below handles both the cases.
----------------------------------------------------------------------------------- int exec_sign_all(struct signatures *signed_vals, size_t val) @@ -187,12 +188,29 @@ int exec_sign_all(struct signatures *signed_vals, size_t val) return 0; }
-/* check that a corrupted PAC results in SIGSEGV */ -TEST_SIGNAL(corrupt_pac, SIGSEGV) +sigjmp_buf jmpbuf; +void pac_signal_handler(int signum, siginfo_t *si, void *uc) { - ASSERT_PAUTH_ENABLED(); + if (signum == SIGSEGV || signum == SIGILL) { + siglongjmp(jmpbuf, 1); + } +} + +/* check that a corrupted PAC results in SIGSEGV or SIGILL */ +TEST(corrupt_pac) +{ + struct sigaction sa;
- pac_corruptor(); + ASSERT_PAUTH_ENABLED(); + if (sigsetjmp(jmpbuf, 1) == 0) { + sa.sa_sigaction = pac_signal_handler; + sa.sa_flags = SA_SIGINFO; + sigemptyset(&sa.sa_mask); + sigaction(SIGSEGV, &sa, NULL); + sigaction(SIGILL, &sa, NULL); + pac_corruptor(); + ASSERT_TRUE(0) TH_LOG("SIGSEGV/SIGILL signal did not occur"); + } }
/* @@ -265,7 +283,7 @@ TEST(single_thread_different_keys)
tmp = n_same_single_set(&signed_vals, nkeys); ---------------------------------------------------------------------------------------
Thanks, Amit Daniel
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-n...
Regards, Amit Daniel
+}
+TEST_HARNESS_MAIN
[...]