Re: [PATCH bpf-next 15/25] libbpf: define s390x syscall regs spec in bpf_tracing.h

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On Fri, 2023-01-13 at 00:33 -0800, Andrii Nakryiko wrote:
> Define explicit table of registers used for syscall argument passing.
> Note that we need custom overrides for PT_REGS_PARM1_[CORE_]SYSCALL
> macros due to the need to use BPF CO-RE and custom local pt_regs
> definitions to fetch orig_gpr2, storing 1st argument.
> 
> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> ---
>  tools/lib/bpf/bpf_tracing.h | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/lib/bpf/bpf_tracing.h
> b/tools/lib/bpf/bpf_tracing.h
> index 34ac0a2d7885..888beea6565b 100644
> --- a/tools/lib/bpf/bpf_tracing.h
> +++ b/tools/lib/bpf/bpf_tracing.h
> @@ -157,6 +157,10 @@
>  
>  #elif defined(bpf_target_s390)
>  
> +/*
> + *
> https://en.wikipedia.org/wiki/Calling_convention#IBM_System/360_and_successors
> + */
> +

Here is the more official ABI spec:

https://github.com/IBM/s390x-abi/releases/download/v1.6/lzsabi_s390x.pdf

>  struct pt_regs___s390 {
>         unsigned long orig_gpr2;
>  };
> @@ -168,13 +172,22 @@ struct pt_regs___s390 {
>  #define __PT_PARM3_REG gprs[4]
>  #define __PT_PARM4_REG gprs[5]
>  #define __PT_PARM5_REG gprs[6]
> +
> +#define __PT_PARM1_SYSCALL_REG orig_gpr2
> +#define __PT_PARM2_SYSCALL_REG __PT_PARM2_REG
> +#define __PT_PARM3_SYSCALL_REG __PT_PARM3_REG
> +#define __PT_PARM4_SYSCALL_REG __PT_PARM4_REG
> +#define __PT_PARM5_SYSCALL_REG __PT_PARM5_REG
> +#define __PT_PARM6_SYSCALL_REG gprs[7]
> +#define PT_REGS_PARM1_SYSCALL(x) PT_REGS_PARM1_CORE_SYSCALL(x)
> +#define PT_REGS_PARM1_CORE_SYSCALL(x) \
> +       BPF_CORE_READ((const struct pt_regs___s390 *)(x),
> __PT_PARM1_SYSCALL_REG)
> +
>  #define __PT_RET_REG gprs[14]
>  #define __PT_FP_REG gprs[11]   /* Works only with
> CONFIG_FRAME_POINTER */
>  #define __PT_RC_REG gprs[2]
>  #define __PT_SP_REG gprs[15]
>  #define __PT_IP_REG psw.addr
> -#define PT_REGS_PARM1_SYSCALL(x) PT_REGS_PARM1_CORE_SYSCALL(x)
> -#define PT_REGS_PARM1_CORE_SYSCALL(x) BPF_CORE_READ((const struct
> pt_regs___s390 *)(x), orig_gpr2)
>  
>  #elif defined(bpf_target_arm)
>  

Acked-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>




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