Re: ebpf: BPF_ALU32 | BPF_ARSH on BE arches

Jiong Wang
2019-06-25T10:20:16Z

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;

Regards,
Jiong