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From:   "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
To:     linux-kernel@vger.kernel.org
Cc:     Andi Kleen <ak@linux.intel.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        bpf@vger.kernel.org, Martin Liska <mliska@suse.cz>,
        Jiri Slaby <jslaby@suse.cz>
Subject: [PATCH 24/46] bpf, lto: mark interpreter jump table as __noreorder
Date:   Mon, 14 Nov 2022 12:43:22 +0100
Message-Id: <20221114114344.18650-25-jirislaby@kernel.org>
In-Reply-To: <20221114114344.18650-1-jirislaby@kernel.org>
References: <20221114114344.18650-1-jirislaby@kernel.org>
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From: Andi Kleen <ak@linux.intel.com>

gcc LTO has a problem that can cause static variables containing &&
labels to be put into a different LTO partition and then fail the build.
This can happen with the jump table in the BPF interprer.

Mark the interpreter function and the jump table as __noreorder, this
guarantees they both end up in the first partition.

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: bpf@vger.kernel.org
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Martin Liska <mliska@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 kernel/bpf/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 25a54e04560e..d40ce00622f6 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1640,7 +1640,7 @@ u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
  *
  * Return: whatever value is in %BPF_R0 at program exit
  */
-static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
+static u64 __noreorder ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 {
 #define BPF_INSN_2_LBL(x, y)    [BPF_##x | BPF_##y] = &&x##_##y
 #define BPF_INSN_3_LBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = &&x##_##y##_##z
-- 
2.38.1