Re: [PATCH] riscv: return -ENOSYS for syscall -1

Tycho Andersen
2020-12-22T16:22:37Z

On Mon, Dec 21, 2020 at 11:52:00PM +0100, Andreas Schwab wrote:
> Properly return -ENOSYS for syscall -1 instead of leaving the return value
> uninitialized. This fixes the strace teststuite.
>
> Fixes: 5340627e3fe0 ("riscv: add support for SECCOMP and SECCOMP_FILTER")
> Signed-off-by: Andreas Schwab <schwab@suse.de>
> ---
> arch/riscv/kernel/entry.S | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 524d918f3601..d07763001eb0 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -186,14 +186,7 @@ check_syscall_nr:
> * Syscall number held in a7.
> * If syscall number is above allowed value, redirect to ni_syscall.
> */
> - bge a7, t0, 1f
> - /*
> - * Check if syscall is rejected by tracer, i.e., a7 == -1.
> - * If yes, we pretend it was executed.
> - */
> - li t1, -1
> - beq a7, t1, ret_from_syscall_rejected
> - blt a7, t1, 1f
> + bgeu a7, t0, 1f

IIUC, this is all dead code anyway for the path where seccomp actually
rejects the syscall, since it should do the rejection directly in
handle_syscall_trace_enter(), which is called above this hunk. So it
seems good to me.

Reviewed-by: Tycho Andersen <tycho@tycho.pizza>