Re: [PATCH RESEND] syscall_user_dispatch: Introduce ARCH_SUPPORTS_SYSCALL_USER_DISPATCH

On Mon, Jul 13, 2026 at 11:54:22AM +0800, Jinjie Ruan wrote:

Currently, only x86 genuinely implements and supports Syscall User
Dispatch (SUD). Multiple architectures provide a stub
arch_syscall_is_vdso_sigreturn() returning 'false' simply to satisfy
GENERIC_ENTRY compilation, which creates a false impression of feature
support.

Introduce ARCH_SUPPORTS_SYSCALL_USER_DISPATCH to decouple this mechanism
from GENERIC_ENTRY. Select it exclusively on x86 and remove the redundant
stub functions from other architectures.

Link: https://lore.kernel.org/linux-arm-kernel/akZgV0Y4YAmB43_g@J2N7QTR9R3.cambridge.arm.com/ (local)
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Ada Couprie Diaz <redacted>
Cc: Thomas Weißschuh <redacted>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jinjie Ruan <redacted>

Reviewed-by: Thomas Weißschuh <redacted>

---
v1 -> RESEND
- Define missing ARCH_SUPPORTS_SYSCALL_USER_DISPATCH.

If code is changed it is not a resend. Instead it should have been v2.

---
 arch/Kconfig                         | 4 ++++
 arch/loongarch/include/asm/syscall.h | 6 ------
 arch/powerpc/include/asm/syscall.h   | 5 -----
 arch/riscv/include/asm/syscall.h     | 5 -----
 arch/s390/include/asm/syscall.h      | 5 -----
 arch/x86/Kconfig                     | 1 +
 6 files changed, 5 insertions(+), 21 deletions(-)

(...)