On Çrş, Sep 17 2025 at 09:55:35 +08:00:00, Jinjie Ruan 
[off-list ref] wrote:

Thank you! I will try to implement arch_syscall_is_vdso_sigreturn() as
this and test it. By the way, is this for supporting arm64 in wine?

No, I don't even know if arm64 windows binaries do direct
syscalls. This is meant for some other project.

quoted

 2 - This trick shouldn't be done if the syscall will be catched by 
SUD:
 if (scno == NO_SYSCALL)
 	syscall_set_return_value(current, regs, -ENOSYS, 0);
 As the ABI could be anything.

This requires discussion with Catalin and Will, which may alter the
original intent.

Sorry, I didnt read the code carefully, syscall_user_dispatch()
already calls syscall_rollback() which should restore x0 from
orig_x0.

You can test SUD using the selftest, but you need to add these
lines at the end of handle_sigsys() in sud_test.c:

#ifdef __aarch64__
	((ucontext_t *)ucontext)->uc_mcontext.regs[0] = (unsigned int)
			((ucontext_t *)ucontext)->uc_mcontext.regs[8];
#endif

and you should define TEST_BLOCKED_RETURN in sud_benchmark.c
to make sure arch_syscall_is_vdso_sigreturn works properly

-kemal

quoted