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

[KP Singh]

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>
---
 tools/lib/bpf/gen_loader.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

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));
 		}
 	}
 }
-- 
2.53.0