Re: [PATCH 12/15] selftests/seccomp: powerpc: Fix seccomp return value testing

[Michael Ellerman]

Kees Cook <keescook@xxxxxxxxxxxx> writes:
> On powerpc, the errno is not inverted, and depends on ccr.so being
> set. Add this to a powerpc definition of SYSCALL_RET_SET().
>
> Co-developed-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
> Link: https://lore.kernel.org/linux-kselftest/20200911181012.171027-1-cascardo@xxxxxxxxxxxxx/
> Fixes: 5d83c2b37d43 ("selftests/seccomp: Add powerpc support")
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)

This looks right to me, and matches what strace does AFAICS.

Reviewed-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>

cheers

> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 623953a53032..bbab2420d708 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -1750,6 +1750,21 @@ TEST_F(TRACE_poke, getpid_runs_normally)
>  # define ARCH_REGS		struct pt_regs
>  # define SYSCALL_NUM(_regs)	(_regs).gpr[0]
>  # define SYSCALL_RET(_regs)	(_regs).gpr[3]
> +# define SYSCALL_RET_SET(_regs, _val)				\
> +	do {							\
> +		typeof(_val) _result = (_val);			\
> +		/*						\
> +		 * A syscall error is signaled by CR0 SO bit	\
> +		 * and the code is stored as a positive value.	\
> +		 */						\
> +		if (_result < 0) {				\
> +			SYSCALL_RET(_regs) = -result;		\
> +			(_regs).ccr |= 0x10000000;		\
> +		} else {					\
> +			SYSCALL_RET(_regs) = result;		\
> +			(_regs).ccr &= ~0x10000000;		\
> +		}						\
> +	} while (0)
>  #elif defined(__s390__)
>  # define ARCH_REGS		s390_regs
>  # define SYSCALL_NUM(_regs)	(_regs).gprs[2]
> -- 
> 2.25.1