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

Michael Ellerman
2020-09-14T03:38:53Z

Kees Cook <keescook@chromium.org> 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@canonical.com>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
> Link: https://lore.kernel.org/linux-kselftest/20200911181012.171027-1-cascardo@canonical.com/
> Fixes: 5d83c2b37d43 ("selftests/seccomp: Add powerpc support")
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> 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@ellerman.id.au>

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