Re: [PATCH bpf] libbpf: Fix register in PT_REGS MIPS macros

[Daniel Borkmann <daniel@iogearbox.net>]

On 7/31/20 11:56 AM, Jerry Crunchtime wrote:
> Hi,
> 
>  > Jerry, your patch is missing a Signed-off-by from you.
> 
> Signed-off-by: Jerry Crunchtime <jerry.c.t@web.de>

Thanks! One more comment below:

> On 7/31/20 1:00 AM, Daniel Borkmann wrote:
>> On 7/30/20 1:44 PM, Jerry Crunchtime 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.")
>>
>> Jerry, your patch is missing a Signed-off-by from you. It should be
>> enough if
>> you just reply with one in here that I'll add to the commit message and
>> I'll
>> take it via bpf tree then, thanks.
>>
>>> ---
>>>   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])
>>>   #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])
>>>   #define PT_REGS_SP(x) ((x)->regs[29])
>>>   #define PT_REGS_IP(x) ((x)->cp0_epc)

While in process of applying, I noticed that there is one more thing broken; you
fixed the PT_REGS_RC() but by that logic at the same time we would also need to
fix PT_REGS_RC_CORE() given it still points to regs[1] as well:

   #define PT_REGS_RC_CORE(x) BPF_CORE_READ((x), regs[1])

Please fix up and resubmit.

Thanks,
Daniel