Re: ebpf: BPF_ALU32 | BPF_ARSH on BE arches

Yauheni Kaliuta
2019-06-25T10:41:38Z

Hi, Jiong!

>>>>> On Tue, 25 Jun 2019 11:20:07 +0100, Jiong Wang wrote:

> Yauheni Kaliuta writes:

>> Hi!
>>
>> Looks like the code:
>>
>> ALU_ARSH_X:
>> DST = (u64) (u32) ((*(s32 *) &DST) >> SRC);
>> CONT;
>> ALU_ARSH_K:
>> DST = (u64) (u32) ((*(s32 *) &DST) >> IMM);
>> CONT;
>>
>> works incorrectly on BE arches since it must operate on lower
>> parts of 64bit registers.
>>
>> See failure of test_verifier test 'arsh32 on imm 2' (#23 on
>> 5.2-rc6).

> Ah, thanks for reporting this.

> Should not taken the address directly, does the following fix resolved the
> failure?

> ALU_ARSH_X:
> DST = (u64) (u32) ((s32) DST) >> SRC);
> CONT;
> ALU_ARSH_K:
> DST = (u64) (u32) ((s32) DST) >> IMM);
> CONT;

Yes, thanks (just add the missing braces).

--
WBR,
Yauheni Kaliuta