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

Message ID 20221103083254.237646-2-yangjihong1@huawei.com (mailing list archive)
State New, archived
Headers show
Series bpf: Support kernel function call in 32-bit ARM | expand

Commit Message

Yang Jihong Nov. 3, 2022, 8:32 a.m. UTC 
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@huawei.com>
---
 kernel/bpf/verifier.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

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;