netdev - [PATCH bpf-next] libbpf: fix AF_XDP helper program to support kernels without the JMP32 eBPF instruction class

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Message-Id: <20191219201601.7378-1-aforster@cloudflare.com>
Date:   Thu, 19 Dec 2019 14:16:01 -0600
From:   Alex Forster <aforster@...udflare.com>
To:     netdev@...r.kernel.org
Cc:     Alex Forster <aforster@...udflare.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Björn Töpel <bjorn.topel@...el.com>
Subject: [PATCH bpf-next] libbpf: fix AF_XDP helper program to support kernels without the JMP32 eBPF instruction class

Kernel 5.1 introduced support for the JMP32 eBPF instruction class, and commit d7d962a modified the libbpf AF_XDP helper program to use the BPF_JMP32_IMM instruction. For those on earlier kernels, attempting to load the helper program now results in the verifier failing with "unknown opcode 66". This change replaces the usage of BPF_JMP32_IMM with BPF_JMP_IMM for compatibility with pre-5.1 kernels.

Signed-off-by: Alex Forster <aforster@...udflare.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Björn Töpel <bjorn.topel@...el.com>
---
 tools/lib/bpf/xsk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 8e0ffa800a71..761f8485b80e 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -366,7 +366,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 		/* call bpf_redirect_map */
 		BPF_EMIT_CALL(BPF_FUNC_redirect_map),
 		/* if w0 != 0 goto pc+13 */
-		BPF_JMP32_IMM(BPF_JSGT, BPF_REG_0, 0, 13),
+		BPF_JMP_IMM(BPF_JSGT, BPF_REG_0, 0, 13),
 		/* r2 = r10 */
 		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
 		/* r2 += -4 */
-- 
2.23.0