[PATCH bpf-next] bpf, arm64: enable kfunc call

[Hou Tao]

Hi,

On 1/25/2022 12:21 AM, Daniel Borkmann wrote:
> On 1/19/22 3:49 PM, Hou Tao wrote:
>> Since commit b2eed9b58811 ("arm64/kernel: kaslr: reduce module
>> randomization range to 2 GB"), for arm64 whether KASLR is enabled
>> or not, the module is placed within 2GB of the kernel region, so
>> s32 in bpf_kfunc_desc is sufficient to represente the offset of
>> module function relative to __bpf_call_base. The only thing needed
>> is to override bpf_jit_supports_kfunc_call().
>>
>> Signed-off-by: Hou Tao <houtao1 at huawei.com>
>
> Lgtm, could we also add a BPF selftest to assert that this assumption
> won't break in future when bpf_jit_supports_kfunc_call() returns true?
>
> E.g. extending lib/test_bpf.ko could be an option, wdyt?
Make sense.  Will figure out how to done that.

Regards,
Tao
>
>> ---
>>   arch/arm64/net/bpf_jit_comp.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
>> index e96d4d87291f..74f9a9b6a053 100644
>> --- a/arch/arm64/net/bpf_jit_comp.c
>> +++ b/arch/arm64/net/bpf_jit_comp.c
>> @@ -1143,6 +1143,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog
>> *prog)
>>       return prog;
>>   }
>>   +bool bpf_jit_supports_kfunc_call(void)
>> +{
>> +    return true;
>> +}
>> +
>>   u64 bpf_jit_alloc_exec_limit(void)
>>   {
>>       return VMALLOC_END - VMALLOC_START;
>>
>
> .