Re: [Qemu-ppc] [Qemu-devel] [PATCH 10/12] linux-user: clock_nanosleep errno Handling on PPC

[Peter Maydell]

On 4 August 2014 17:45, Tom Musta <address@hidden> wrote:
> The clock_nanosleep syscall is unusual in that it returns positive
> numbers in error handling situations, versus returning -1 and setting
> errno, or returning a negative errno value.  On POWER, the kernel will
> set the SO bit of CR0 to indicate failure in a syscall.  QEMU has
> generic handling to do this for syscalls with standard return values.
>
> Add special case code for clock_nanosleep to handle CR0 properly.
>
> Signed-off-by: Tom Musta <address@hidden>
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 95cee0b..5660520 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -8993,6 +8993,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
> arg1,
>          ret = get_errno(clock_nanosleep(arg1, arg2, &ts, arg4 ? &ts : NULL));
>          if (arg4)
>              host_to_target_timespec(arg4, &ts);
> +
> +#if defined(TARGET_PPC) || defined(TARGET_PPC64)
> +        /* clock_nanosleep is odd in that it returns positive errno values.
> +         * On PPC, CR0 bit 3 should be set in such a situation. */
> +        if (ret) {
> +            ((CPUPPCState *)cpu_env)->crf[0] |= 1;
> +        }
> +#endif
>          break;
>      }
>  #endif

New target-specific ifdefs in syscall.c make me sad, but the
alternative would be to upend the do_syscall() calling
convention to pass return value and success/failure separately
or something, which is clearly ludicrous for this corner case. So

Reviewed-by: Peter Maydell <address@hidden>

thanks
-- PMM