linux-kernel - [PATCH] loongarch/bpf: Fix bpf load failed with CONFIG_BPF_JIT_ALWAYS_ON, caused by jit (BPF_ST

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Message-Id: <20230326044019.2139628-1-guodongtai@kylinos.cn>
Date:   Sun, 26 Mar 2023 12:40:19 +0800
From:   George Guo <guodongtai@...inos.cn>
To:     chenhuacai@...nel.org, masahiroy@...nel.org,
        michal.lkml@...kovi.net
Cc:     kernel@...0n.name, ndesaulniers@...gle.com, daniel@...earbox.net,
        ast@...nel.org, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH] loongarch/bpf: Fix bpf load failed with CONFIG_BPF_JIT_ALWAYS_ON, caused by jit (BPF_ST | BPF_NOSPEC) code

Here just skip the code(BPF_ST | BPF_NOSPEC) that has no couterpart to the loongarch.

To verify, use ltp testcase:

Without this patch:
$ ./bpf_prog02
... ...
bpf_common.c:123: TBROK: Failed verification: ??? (524)

Summary:
passed   0
failed   0
broken   1
skipped  0
warnings 0

With this patch:
$ ./bpf_prog02
... ...
Summary:
passed   0
failed   0
broken   0
skipped  0
warnings 0

Signed-off-by: George Guo <guodongtai@...inos.cn>
---
 arch/loongarch/net/bpf_jit.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 288003a9f0ca..745d344385ed 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1046,6 +1046,11 @@ static int build_body(struct jit_ctx *ctx, bool extra_pass)
 		if (ctx->image == NULL)
 			ctx->offset[i] = ctx->idx;
 
+		/* skip the code that has no couterpart to the host arch */
+		if(insn->code == (BPF_ST | BPF_NOSPEC)) {
+			continue;
+		}
+
 		ret = build_insn(insn, ctx, extra_pass);
 		if (ret > 0) {
 			i++;
-- 
2.34.1