Re: [PATCH] selftests/powerpc: Fix exec_prot test failure on Hash MMU

[Chris Chiu]

On Wed, Sep 9, 2026 at 1:09 PM Chris Chiu <chris.chiu@xxxxxxxxxxxxx> wrote:
>
> Hash MMU maps execute-only pages as readable at the PTE level, so reading
> from a PROT_EXEC-only mapping does not fault there. The exec_prot test
> currently treats that as a failure, while the rest of the permission
> checks are still valid.
>
> Use the existing using_hash_mmu() helper and skip only the read-on-
> execute-only subtest on Hash MMU. Keep the rest of the test unchanged so
> the fix stays local to the unsupported execute-only-read expectation.
>
> Signed-off-by: Chris Chiu <chris.chiu@xxxxxxxxxxxxx>
> ---
>  .../testing/selftests/powerpc/mm/exec_prot.c  | 21 ++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/tools/testing/selftests/powerpc/mm/exec_prot.c b/tools/testing/selftests/powerpc/mm/exec_prot.c
> index db75b2225de1..bd44f49d8449 100644
> --- a/tools/testing/selftests/powerpc/mm/exec_prot.c
> +++ b/tools/testing/selftests/powerpc/mm/exec_prot.c
> @@ -108,11 +108,14 @@ static int check_exec_fault(int rights)
>  static int test(void)
>  {
>         struct sigaction segv_act, trap_act;
> +       bool hash_mmu;
>         int i;
>
>         /* Skip the test if the CPU doesn't support Radix */
>         SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_3_00));
>
> +       FAIL_IF(using_hash_mmu(&hash_mmu));
> +
>         /* Check if pkeys are supported */
>         pkeys_supported = pkeys_unsupported() == 0;
>
> @@ -167,13 +170,17 @@ static int test(void)
>          * Read an instruction word from the address when the page
>          * is execute only. This should generate an access fault.
>          */
> -       fault_code = -1;
> -       remaining_faults = 1;
> -       printf("Testing read on --x, should fault...");
> -       FAIL_IF(mprotect(insns, pgsize, PROT_EXEC) != 0);
> -       i = *fault_addr;
> -       FAIL_IF(remaining_faults != 0 || !is_fault_expected(fault_code));
> -       printf("ok!\n");
> +       if (!hash_mmu) {
> +               fault_code = -1;
> +               remaining_faults = 1;
> +               printf("Testing read on --x, should fault...");
> +               FAIL_IF(mprotect(insns, pgsize, PROT_EXEC) != 0);
> +               i = *fault_addr;
> +               FAIL_IF(remaining_faults != 0 || !is_fault_expected(fault_code));
> +               printf("ok!\n");
> +       } else {
> +               printf("Testing read on --x, skipped on Hash MMU\n");
> +       }
>
>         /*
>          * Write an instruction word to the address when the page
> --
> 2.43.0
>

Gentle ping.