On Thu, Jul 30, 2020 at 4:45 AM Jerry Cruntime <jerry.c.t@xxxxxx> wrote:
>
> The o32, n32 and n64 calling conventions require the return
> value to be stored in $v0 which maps to $2 register, i.e.,
> the second register.
>
> Fixes: c1932cd ("bpf: Add MIPS support to samples/bpf.")
> ---
> tools/lib/bpf/bpf_tracing.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
> index 58eceb884..ae205dcf8 100644
> --- a/tools/lib/bpf/bpf_tracing.h
> +++ b/tools/lib/bpf/bpf_tracing.h
> @@ -215,7 +215,7 @@ struct pt_regs;
> #define PT_REGS_PARM5(x) ((x)->regs[8])
I've quickly looked up some doc on MIPS calling convention, doesn't
seem like regs[8] is actually used for 5th input argument (the doc I
found documented only the use of $4 through $7 for first 4 args).
Should we drop PT_REGS_PARM5() for MIPS, while at it?
> #define PT_REGS_RET(x) ((x)->regs[31])
> #define PT_REGS_FP(x) ((x)->regs[30]) /* Works only with
> CONFIG_FRAME_POINTER */
> -#define PT_REGS_RC(x) ((x)->regs[1])
> +#define PT_REGS_RC(x) ((x)->regs[2])
This looks good, though.
> #define PT_REGS_SP(x) ((x)->regs[29])
> #define PT_REGS_IP(x) ((x)->cp0_epc)
>
> --
> 2.17.1
