On Tue, Feb 8, 2022 at 6:18 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote:
>
> On s390, the first syscall argument should be accessed via orig_gpr2
> (see arch/s390/include/asm/syscall.h). Currently gpr[2] is used
> instead, leading to bpf_syscall_macro test failure.
>
> orig_gpr2 cannot be added to user_pt_regs, since its layout is a part
> of the ABI. Therefore provide access to it only through
> PT_REGS_PARM1_CORE_SYSCALL() by using a struct pt_regs flavor.
>
> Reported-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> ---
> tools/lib/bpf/bpf_tracing.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
> index 928f85f7961c..0e0414801457 100644
> --- a/tools/lib/bpf/bpf_tracing.h
> +++ b/tools/lib/bpf/bpf_tracing.h
> @@ -114,9 +114,19 @@
>
> #elif defined(bpf_target_s390)
>
> +struct pt_regs___s390 {
> + unsigned long orig_gpr2;
> +} __attribute__((preserve_access_index));
> +
> /* s390 provides user_pt_regs instead of struct pt_regs to userspace */
> #define __PT_REGS_CAST(x) ((const user_pt_regs *)(x))
> #define __PT_PARM1_REG gprs[2]
> +#define PT_REGS_PARM1_SYSCALL(x) ({ \
> + _Pragma("GCC error \"PT_REGS_PARM1_SYSCALL() is not supported on s390, use PT_REGS_PARM1_CORE_SYSCALL() instead\""); \
> + 0l; \
> +})
> +#define PT_REGS_PARM1_CORE_SYSCALL(x) \
> + BPF_CORE_READ((const struct pt_regs___s390 *)(x), orig_gpr2)
same manipulations as on previous patch
> #define __PT_PARM2_REG gprs[3]
> #define __PT_PARM3_REG gprs[4]
> #define __PT_PARM4_REG gprs[5]
> --
> 2.34.1
>
