[PATCH 1/4] bpf: Adapt 32-bit return value kfunc for 32-bit ARM when zext extension

[Yang Jihong <yangjihong1@xxxxxxxxxx>]

For ARM32 architecture, if data width of kfunc return value is 32 bits,
need to do explicit zero extension for high 32-bit, insn_def_regno should
return dst_reg for BPF_JMP type of BPF_PSEUDO_KFUNC_CALL. Otherwise,
opt_subreg_zext_lo32_rnd_hi32 returns -EFAULT, resulting in BPF failure.

Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
---
 kernel/bpf/verifier.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7f0a9f6cb889..bac37757ffca 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2404,6 +2404,9 @@ static int insn_def_regno(const struct bpf_insn *insn)
 {
 	switch (BPF_CLASS(insn->code)) {
 	case BPF_JMP:
+		if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL)
+			return insn->dst_reg;
+		fallthrough;
 	case BPF_JMP32:
 	case BPF_ST:
 		return -1;
-- 
2.30.GIT