Re: [PATCH bpf-next 0/4] bpf: arm64: Indirect jumps

[Puranjay Mohan <puranjay@kernel.org>]

Anton Protopopov <a.s.protopopov@gmail.com> writes:

> On 25/11/17 12:46AM, Puranjay Mohan wrote:
>> This set adds the support of indirect jumps to the arm64 JIT. It
>> involves calling bpf_prog_update_insn_ptrs() to support instructions
>> array map. The second piece is supporting BPF_JMP|BPF_X|BPF_JA, SRC=0,
>> DST=Rx, off=0, imm=0 instruction that is trivial to implement on arm64.
>>
>> When running the selftests after doing the above changes, I found that
>> on arm64 builds of llvm, a relocation section was being generated for
>> .jumptables sections and it was making libbpf fail like:
>> 
>> libbpf: relocation against STT_SECTION in non-exec section is not supported!
>> Error: failed to link 'tools/testing/selftests/bpf/cpuv4/bpf_gotox.bpf.o': Invalid argument (22)
>> 
>> Which is due to:
>> 
>> Relocation section '.rel.jumptables' at offset 0x5b50 contains 263 entries:
>>     Offset             Info             Type               Symbol's Value  Symbol's Name
>> 0000000000000000  0000000300000002 R_BPF_64_ABS64         0000000000000000 syscall
>> 0000000000000008  0000000300000002 R_BPF_64_ABS64         0000000000000000 syscall
>> 0000000000000010  0000000300000002 R_BPF_64_ABS64         0000000000000000 syscall
>> 
>> This rel section is not generated by x86 builds of LLVM. The third patch
>> of this set makes libbpf ignore relocation sections for .jumptables.
>
> I added Yonghong to this thread. He had fixed this problem in
> https://github.com/llvm/llvm-project/pull/166301 changes doesn't seem to be
> x86-specific...

My arm64 build didn't have this change, that is why it was failing.
After pulling the latest changes and building again, it works without
the libbpf patch.

So, I will send v2 and drop the libbpf patch.

Thanks,
Puranjay