linux-kernel - [PATCH v2] loongarch/bpf: Skip speculation barrier opcode, which caused ltp testcase bpf

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Message-Id: <20230328071335.2664966-1-guodongtai@kylinos.cn>
Date:   Tue, 28 Mar 2023 15:13:35 +0800
From:   George Guo <guodongtai@...inos.cn>
To:     daniel@...earbox.net
Cc:     ast@...nel.org, bpf@...r.kernel.org, chenhuacai@...nel.org,
        guodongtai@...inos.cn, kernel@...0n.name,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, masahiroy@...nel.org,
        michal.lkml@...kovi.net, ndesaulniers@...gle.com
Subject: [PATCH v2] loongarch/bpf: Skip speculation barrier opcode, which caused ltp testcase bpf_prog02 to fail

Here just skip the opcode(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>

---
Changelog:
v2:
	- place it to build_insn
	- add printing for skipping bpf_jit the opcode
---
 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..d3c6b1c4ccbb 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1022,6 +1022,11 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
 		emit_atomic(insn, ctx);
 		break;
 
+	/* Speculation barrier */
+	case BPF_ST | BPF_NOSPEC:
+		pr_info_once("bpf_jit: skip speculation barrier opcode %0x2x\n", code);
+		break;
+
 	default:
 		pr_err("bpf_jit: unknown opcode %02x\n", code);
 		return -EINVAL;
-- 
2.34.1