[PATCH 11/13] powerpc64/bpf elfv2: Setup kernel TOC in r2 on entry

[Naveen N. Rao]

Christophe Leroy wrote:
> 
> 
> Le 11/01/2022 à 15:35, Christophe Leroy a écrit :
>> 
>> 
>> Le 11/01/2022 à 11:31, Naveen N. Rao a écrit :
>>> Christophe Leroy wrote:
>>>>
>>>>
>>>> Le 06/01/2022 à 12:45, Naveen N. Rao a écrit :
>>>>> In preparation for using kernel TOC, load the same in r2 on entry. With
>>>>> elfv1, the kernel TOC is already setup by our caller so we just emit a
>>>>> nop. We adjust the number of instructions to skip on a tail call
>>>>> accordingly.
>>>>>
>>>>> Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
>>>>> ---
>>>>>    arch/powerpc/net/bpf_jit_comp64.c | 8 +++++++-
>>>>>    1 file changed, 7 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/arch/powerpc/net/bpf_jit_comp64.c
>>>>> b/arch/powerpc/net/bpf_jit_comp64.c
>>>>> index ce4fc59bbd6a92..e05b577d95bf11 100644
>>>>> --- a/arch/powerpc/net/bpf_jit_comp64.c
>>>>> +++ b/arch/powerpc/net/bpf_jit_comp64.c
>>>>> @@ -73,6 +73,12 @@ void bpf_jit_build_prologue(u32 *image, struct
>>>>> codegen_context *ctx)
>>>>>    {
>>>>>        int i;
>>>>> +#ifdef PPC64_ELF_ABI_v2
>>>>> +    PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc));
>>>>> +#else
>>>>> +    EMIT(PPC_RAW_NOP());
>>>>> +#endif
>>>>
>>>> Can we avoid the #ifdef, using
>>>>
>>>>      if (__is_defined(PPC64_ELF_ABI_v2))
>>>>          PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc));
>>>>      else
>>>>          EMIT(PPC_RAW_NOP());
>>>
>>> Hmm... that doesn't work for me. Is __is_defined() expected to work with
>>> macros other than CONFIG options?
>> 
>> Yes, __is_defined() should work with any item.
>> 
>> It is IS_ENABLED() which is supposed to work only with CONFIG options.

I suppose you are saying that due to the name? Since IS_ENABLED() and 
IS_BUILTIN() seem to work fine too, once I define the macro as 1.

Along those lines, it would have been nice to have IS_DEFINED().

>> 
>> See commit 5c189c523e78 ("powerpc/time: Fix mftb()/get_tb() for use with
>> the compat VDSO")
>> 
>> Or commit ca5999fde0a1 ("mm: introduce include/linux/pgtable.h")
> 
> Ah ... wait.
> 
> It seems it expects a macro set to 1.
> 
> So it would require arch/powerpc/include/asm/types.h to be modified to 
> define PPC64_ELF_ABI_v2 or PPC64_ELF_ABI_v1 as 1

Thanks, that works.


- Naveen