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From: Yonghong Song <yhs@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: [PATCH bpf-next 03/12] libbpf: Fix an error in 64bit relocation value computation
Date: Sun, 1 May 2022 12:00:17 -0700	[thread overview]
Message-ID: <20220501190017.2577688-1-yhs@fb.com> (raw)
In-Reply-To: <20220501190002.2576452-1-yhs@fb.com>

Currently, the 64bit relocation value in the instruction
is computed as follows:
  __u64 imm = insn[0].imm + ((__u64)insn[1].imm << 32)

Suppose insn[0].imm = -1 (0xffffffff) and insn[1].imm = 1.
With the above computation, insn[0].imm will first sign-extend
to 64bit -1 (0xffffffffFFFFFFFF) and then add 0x1FFFFFFFF,
producing incorrect value 0xFFFFFFFF. The correct value
should be 0x1FFFFFFFF.

Changing insn[0].imm to __u32 first will prevent 64bit sign
extension and fix the issue.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/lib/bpf/relo_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
index 2ed94daabbe5..f25ffd03c3b1 100644
--- a/tools/lib/bpf/relo_core.c
+++ b/tools/lib/bpf/relo_core.c
@@ -1024,7 +1024,7 @@ int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn,
 			return -EINVAL;
 		}
 
-		imm = insn[0].imm + ((__u64)insn[1].imm << 32);
+		imm = (__u32)insn[0].imm + ((__u64)insn[1].imm << 32);
 		if (res->validate && imm != orig_val) {
 			pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %llu -> %llu\n",
 				prog_name, relo_idx,
-- 
2.30.2


  parent reply	other threads:[~2022-05-01 19:00 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-01 19:00 [PATCH bpf-next 00/12] bpf: Add 64bit enum value support Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 01/12] bpf: Add btf enum64 support Yonghong Song
2022-05-09  0:33   ` Dave Marchevsky
2022-05-09 22:29   ` Andrii Nakryiko
2022-05-10 22:06     ` Yonghong Song
2022-05-10 23:18       ` Andrii Nakryiko
2022-05-11  0:17         ` Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 02/12] libbpf: Permit 64bit relocation value Yonghong Song
2022-05-09  1:06   ` Dave Marchevsky
2022-05-10 19:35     ` Yonghong Song
2022-05-09 22:37   ` Andrii Nakryiko
2022-05-10 22:14     ` Yonghong Song
2022-05-10 23:19       ` Andrii Nakryiko
2022-05-01 19:00 ` Yonghong Song [this message]
2022-05-09  0:55   ` [PATCH bpf-next 03/12] libbpf: Fix an error in 64bit relocation value computation Dave Marchevsky
2022-05-09  0:56     ` Dave Marchevsky
2022-05-09 22:37   ` Andrii Nakryiko
2022-05-10 22:11     ` Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 04/12] libbpf: Add btf enum64 support Yonghong Song
2022-05-03 17:22   ` kernel test robot
2022-05-05 22:44     ` Yonghong Song
2022-05-09 23:25   ` Andrii Nakryiko
2022-05-10 22:40     ` Yonghong Song
2022-05-10 23:02       ` Yonghong Song
2022-05-10 23:40         ` Andrii Nakryiko
2022-05-10 23:38       ` Andrii Nakryiko
2022-05-11  0:39         ` Yonghong Song
2022-05-11 17:43           ` Andrii Nakryiko
2022-05-11 18:56             ` Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 05/12] bpftool: " Yonghong Song
2022-05-09 23:31   ` Andrii Nakryiko
2022-05-10 22:43     ` Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 06/12] selftests/bpf: Fix selftests failure Yonghong Song
2022-05-09  2:21   ` Dave Marchevsky
2022-05-10 19:40     ` Yonghong Song
2022-05-09 23:34   ` Andrii Nakryiko
2022-05-10 22:44     ` Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 07/12] selftests/bpf: Test new libbpf enum32/enum64 API functions Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 08/12] selftests/bpf: Add BTF_KIND_ENUM64 unit tests Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 09/12] selftests/bpf: Test BTF_KIND_ENUM64 for deduplication Yonghong Song
2022-05-09 23:37   ` Andrii Nakryiko
2022-05-10 22:44     ` Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 10/12] selftests/bpf: add a test for enum64 value relocation Yonghong Song
2022-05-09 23:38   ` Andrii Nakryiko
2022-05-10 22:45     ` Yonghong Song
2022-05-01 19:00 ` [PATCH bpf-next 11/12] selftests/bpf: Clarify llvm dependency with possible selftest failures Yonghong Song
2022-05-01 19:01 ` [PATCH bpf-next 12/12] docs/bpf: Update documentation for BTF_KIND_ENUM64 support Yonghong Song

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