Re: [PATCH v11 bpf-next 00/12] BPF indirect jumps

[Eduard Zingerman <eddyz87@gmail.com>]

On Wed, 2025-11-05 at 09:03 +0000, Anton Protopopov wrote:
> This patchset implements a new type of map, instruction set, and uses
> it to build support for indirect branches in BPF (on x86). (The same
> map will be later used to provide support for indirect calls and static
> keys.) See [1], [2] for more context.
> 
> Short table of contents:
> 
>   * Patches 1-6 implement the new map of type
>     BPF_MAP_TYPE_INSN_SET and corresponding selftests. This map can
>     be used to track the "original -> xlated -> jitted mapping" for
>     a given program.
> 
>   * Patches 7-12 implement the support for indirect jumps on x86 and add libbpf
>     support for LLVM-compiled programs containing indirect jumps, and selftests.
> 
> The jump table support was merged to LLVM and now can be
> enabled with -mcpu=v4, see [3]. The __BPF_FEATURE_GOTOX
> macros can be used to check if the compiler supports the
> feature or not.
> 
> See individual patches for more details on the implementation details.

I retested this series with upstream clang [1] (includes latest
changes for relocations handling from Yonghong), and all works as
expected.

The series is ready to land from my perspective.
(AI has a few notes on tests, though).

[1] f60e69315e9e ("[llvm] Emit canonical linkage correct function
symbol (#166487)")

> v10 -> v11 (this series):
> 
>   * rearranged patches and split libbpf patch such that first 6 patches
>     implementing instruction arrays can be applied independently

I actually tried applying first 6 patches and then removing patch #3
"libbpf: Recognize insn_array map type", nothing broke: kernel and
selftests compile, relevant selftests passing.
So, not sure if splitting patch #3 as a separate thing is really
necessary.

> 
>   * instruction arrays:
>     * move [fake] aux->used_maps assignment in this patch
> 
>   * indirect jumps:
>     * call clear_insn_aux_data before bpf_remove_insns (AI)
> 
>   * libbpf:
>     * remove the relocations check after the new LLVM is released (Eduard, Yonghong)
>     * libbpf: fix an index printed in pr_warn (AI)
> 
>   * selftests:
>     * protect programs triggered by nanosleep from fake runs (Eduard)
>     * patch verifier_gotox to not emit .rel.jumptables
> 

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