On 7/23/23 12:21 PM, Eduard Zingerman wrote:
On Sun, 2023-07-23 at 21:14 +0200, Jose E. Marchesi wrote:
On Fri, 2023-07-21 at 18:19 +0200, Jose E. Marchesi wrote:
Hi Yonghong.
This is from the v4 instructions proposal:
======== ===== ========================= ============
code value description notes
======== ===== ========================= ============
BPF_JA 0x00 PC += imm BPF_JMP32 only
Is this instruction using source 1 instead of 0? Otherwise, it would
have exactly the same encoding than the V3< JA instruction. Is that
what is intended?
TIA.
Hi Jose,
I think that assumption is that `BPF_JMP32 | BPF_JA` is currently free:
- documentation [1] implies that only `BPF_JMP` should be used for `BPF_JA`
(see "notes" column for the first line)
- BPF verifier rejects `BPF_JMP32 | BPF_JA`
- clang always generates `BPF_JMP | BPF_JA`
Makes sense, thanks for the info.
Do you know the precise pseudo-c assembly syntax to use for this
instruction?
In [1] Yonghong uses the following form:
gotol +0xcd9b
But it seems to be not specified in the documentation for the patch-set v3.
Thanks Eduard, I will add gotol to the documentation.
[1] https://reviews.llvm.org/D144829
Thanks,
Eduard
[1] https://www.kernel.org/doc/html/latest/bpf/instruction-set.html#jump-instructions
