[PATCH v2 1/2] libbpf: fix off-by-one in emit_signature_match jump offset

[bot+bpf-ci at kernel.org]

> commit 4eb2c1ff205ef1d11b97cef9c13092a8b13ba5e1
> Author: KP Singh <kpsingh at kernel.org>
>
>     libbpf: fix off-by-one in emit_signature_match jump offset
>
>     The offset for the cleanup-label jump is computed before the MOV R7
>     instruction is emitted, but the JMP lands after it. Account for the
>     extra insn in the offset calculation (-2 instead of -1). Drop the
>     redundant self-loop in the else branch; gen->error = -ERANGE already
>     marks the generation as failed.
>
>     Fixes: fb2b0e290147 ("libbpf: Update light skeleton for signing")
>     Signed-off-by: KP Singh <kpsingh at kernel.org>

The Fixes: tag points to commit fb2b0e290147 ("libbpf: Update light
skeleton for signing"), which does not exist in this repository. The bug was
actually introduced by commit b3beebbe6154 ("adding ci files"), which added
the gen_loader.c file containing the emit_signature_match function with the
off-by-one error in the jump offset calculation. Should the Fixes: tag be:

  Fixes: b3beebbe6154 ("adding ci files")

> diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
> index cd5c2543f54d..9478b8f78f26 100644
> --- a/tools/lib/bpf/gen_loader.c
> +++ b/tools/lib/bpf/gen_loader.c
> @@ -592,13 +592,12 @@ static void emit_signature_match(struct bpf_gen *gen)
>  		gen->hash_insn_offset[i] = gen->insn_cur - gen->insn_start;
>  		emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_3, 0, 0, 0, 0, 0));
>
> -		off =  -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 1;
> +		off = -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 2;
>  		if (is_simm16(off)) {
>  			emit(gen, BPF_MOV64_IMM(BPF_REG_7, -EINVAL));
>  			emit(gen, BPF_JMP_REG(BPF_JNE, BPF_REG_2, BPF_REG_3, off));
>  		} else {
>  			gen->error = -ERANGE;
> -			emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, -1));
>  		}
>  	}
>  }

---
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CI run summary: https://github.com/kernel-patches/bpf/actions/runs/26236267798