[PATCH] tests: fix tst-rseq with Linux 7.0

[Mathieu Desnoyers]

On 2026-02-20 11:01, Michael Jeanson wrote:
> A sub-test of tst-rseq is to validate the return code and errno of the
> rseq syscall when attempting to register the exact same rseq area as was
> done in the dynamic loader.
> 
> This involves finding the rseq area address by adding the
> '__rseq_offset' to the thread pointer and calculating the area size from
> the AT_RSEQ_FEATURE_SIZE auxiliary vector. However the test currently
> calculates the size of the rseq area allocation in the TLS block which
> must be a multiple of AT_RSEQ_ALIGN.
> 
> Up until now that happened to be the same value since the feature size
> and alignment exposed by the kernel were below the minimum ABI size of
> 32. Starting with Linux 7.0 the feature size has reached 33 while the
> alignment is now 64.
> 
> This results in the test trying to re-register the rseq area with a
> different size and thus not getting the expected errno value.
> 
> Signed-off-by: Michael Jeanson <mjeanson@efficios.com>

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

> ---
>   sysdeps/unix/sysv/linux/tst-rseq.c | 7 +++----
>   1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/tst-rseq.c b/sysdeps/unix/sysv/linux/tst-rseq.c
> index 11371dc6c5..ba93d390f4 100644
> --- a/sysdeps/unix/sysv/linux/tst-rseq.c
> +++ b/sysdeps/unix/sysv/linux/tst-rseq.c
> @@ -48,8 +48,7 @@ do_rseq_main_test (void)
>     size_t rseq_align = MAX (getauxval (AT_RSEQ_ALIGN), RSEQ_MIN_ALIGN);
>     size_t rseq_feature_size = MAX (getauxval (AT_RSEQ_FEATURE_SIZE),
>                                     RSEQ_AREA_SIZE_INITIAL_USED);
> -  size_t rseq_alloc_size = roundup (MAX (rseq_feature_size,
> -                                    RSEQ_AREA_SIZE_INITIAL_USED), rseq_align);
> +  size_t rseq_reg_size = MAX (rseq_feature_size, RSEQ_AREA_SIZE_INITIAL);
>     struct rseq *rseq_abi = __thread_pointer () + __rseq_offset;
>   
>     TEST_VERIFY_EXIT (rseq_thread_registered ());
> @@ -89,8 +88,8 @@ do_rseq_main_test (void)
>     /* Test a rseq registration with the same arguments as the internal
>        registration which should fail with errno == EBUSY.  */
>     TEST_VERIFY (((unsigned long) rseq_abi % rseq_align) == 0);
> -  TEST_VERIFY (__rseq_size <= rseq_alloc_size);
> -  int ret = syscall (__NR_rseq, rseq_abi, rseq_alloc_size, 0, RSEQ_SIG);
> +  TEST_VERIFY (__rseq_size <= rseq_reg_size);
> +  int ret = syscall (__NR_rseq, rseq_abi, rseq_reg_size, 0, RSEQ_SIG);
>     TEST_VERIFY (ret != 0);
>     TEST_COMPARE (errno, EBUSY);
>   }


-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com