[PATCH v2 1/7] powerpc: properly negate error in syscall_set_return_value()

[Alexey Gladkov]

On Mon, Jan 13, 2025 at 07:10:54PM +0200, Dmitry V. Levin wrote:
> Bring syscall_set_return_value() in sync with syscall_get_error(),
> and let upcoming ptrace/set_syscall_info selftest pass on powerpc.
> 
> This reverts commit 1b1a3702a65c ("powerpc: Don't negate error in
> syscall_set_return_value()").
> 
> Signed-off-by: Dmitry V. Levin <ldv at strace.io>
> ---
>  arch/powerpc/include/asm/syscall.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index 3dd36c5e334a..422d7735ace6 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -82,7 +82,11 @@ static inline void syscall_set_return_value(struct task_struct *task,
>  		 */
>  		if (error) {
>  			regs->ccr |= 0x10000000L;
> -			regs->gpr[3] = error;
> +			/*
> +			 * In case of an error regs->gpr[3] contains
> +			 * a positive ERRORCODE.
> +			 */
> +			regs->gpr[3] = -error;

After this change the syscall_get_error() will return positive value if
the system call failed. Since syscall_get_error() still believes
regs->gpr[3] is still positive in case !trap_is_scv().

Or am I missing something?

It looks like the selftest you mentioned in the commit message doesn't
check the !trap_is_scv() branch.

>  		} else {
>  			regs->ccr &= ~0x10000000L;
>  			regs->gpr[3] = val;
> -- 
> ldv

-- 
Rgrds, legion