On 26/01/2026 20:02, Will Deacon wrote:
> On Mon, Dec 22, 2025 at 07:47:26PM +0800, Jinjie Ruan wrote:
>> [...]
>>
>> To make it more reasonable and in preparation for moving arm64 over to
>> the generic entry code, move rseq_syscall() ahead before
>> audit_syscall_exit().
> I've been struggling a bit to see how this helps to align with the
> generic code.
rseq_syscall(), or rather rseq_debug_syscall_return() since eaa9088d568c
("rseq: Use static branch for syscall exit debug when
GENERIC_IRQ_ENTRY=y"), is called first in the generic
syscall_exit_to_user_mode_work(), so the aim of that patch is to align
the order of calls with generic entry.
> I'm also concerned that rseq_debug_update_user_cs()
> operates on instruction_pointer(regs) which is something that can be
> chaned by ptrace.
Isn't that true regardless of where rseq_syscall() is called on the
syscall exit path, though?
> So, I'm not saying this is wrong, but it feels like a user-visible
> change that needs better justification.
This seems to hang on whether the force_sig(SIGSEGV) that rseq_syscall()
might issue interacts in any way with the tracing calls. My feeling is
that it doesn't, but I haven't confirmed it. Worth noting this is only
relevant if rseq debugging is enabled, so any potential user-visible
effect is limited.
- Kevin
