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From: Dave Marchevsky <davemarchevsky@fb.com>
To: Yonghong Song <yhs@fb.com>, 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: Re: [PATCH bpf-next 03/12] libbpf: Fix an error in 64bit relocation value computation
Date: Sun, 8 May 2022 20:56:59 -0400	[thread overview]
Message-ID: <3eaeb884-1c67-6461-e610-1f6a26068730@fb.com> (raw)
In-Reply-To: <8572184e-7ba7-d16e-8823-0fbc4abac627@fb.com>

On 5/8/22 8:55 PM, Dave Marchevsky wrote:   
> On 5/1/22 3:00 PM, Yonghong Song wrote:   
>> 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(-)
>>
> 
> Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
> 

Whoops, meant:

Acked-by: Dave Marchevsky <davemarchevsky@fb.com>

  reply	other threads:[~2022-05-09  1:29 UTC|newest]

Thread overview: 48+ 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 ` [PATCH bpf-next 03/12] libbpf: Fix an error in 64bit relocation value computation Yonghong Song
2022-05-09  0:55   ` Dave Marchevsky
2022-05-09  0:56     ` Dave Marchevsky [this message]
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
2022-05-05 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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