[PATCH 5.10 070/299] kselftest/arm64: mte: Fix MTE feature detection

From: Greg Kroah-Hartman
Date: Mon May 10 2021 - 08:50:50 EST


From: Andre Przywara <andre.przywara@xxxxxxx>

[ Upstream commit 592432862cc4019075a7196d9961562c49507d6f ]

To check whether the CPU and kernel support the MTE features we want
to test, we use an (emulated) CPU ID register read. However we only
check against a very particular feature version (0b0010), even though
the ARM ARM promises ID register features to be backwards compatible.

While this could be fixed by using ">=" instead of "==", we should
actually use the explicit HWCAP2_MTE hardware capability, exposed by the
kernel via the ELF auxiliary vectors.

That moves this responsibility to the kernel, and fixes running the
tests on machines with FEAT_MTE3 capability.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Reviewed-by: Mark Brown <broone@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210319165334.29213-7-andre.przywara@xxxxxxx
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
tools/testing/selftests/arm64/mte/mte_common_util.c | 13 ++-----------
1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/arm64/mte/mte_common_util.c b/tools/testing/selftests/arm64/mte/mte_common_util.c
index 39f8908988ea..70665ba88cbb 100644
--- a/tools/testing/selftests/arm64/mte/mte_common_util.c
+++ b/tools/testing/selftests/arm64/mte/mte_common_util.c
@@ -278,22 +278,13 @@ int mte_switch_mode(int mte_option, unsigned long incl_mask)
return 0;
}

-#define ID_AA64PFR1_MTE_SHIFT 8
-#define ID_AA64PFR1_MTE 2
-
int mte_default_setup(void)
{
- unsigned long hwcaps = getauxval(AT_HWCAP);
+ unsigned long hwcaps2 = getauxval(AT_HWCAP2);
unsigned long en = 0;
int ret;

- if (!(hwcaps & HWCAP_CPUID)) {
- ksft_print_msg("FAIL: CPUID registers unavailable\n");
- return KSFT_FAIL;
- }
- /* Read ID_AA64PFR1_EL1 register */
- asm volatile("mrs %0, id_aa64pfr1_el1" : "=r"(hwcaps) : : "memory");
- if (((hwcaps >> ID_AA64PFR1_MTE_SHIFT) & MT_TAG_MASK) != ID_AA64PFR1_MTE) {
+ if (!(hwcaps2 & HWCAP2_MTE)) {
ksft_print_msg("FAIL: MTE features unavailable\n");
return KSFT_SKIP;
}
--
2.30.2