From: dthaler1968@googlemail.com
To: <bpf@ietf.org>, <bpf@vger.kernel.org>
Subject: Sign extension ISA question
Date: Tue, 16 Jan 2024 12:55:44 -0800 [thread overview]
Message-ID: <08ab01da48be$603541a0$209fc4e0$@gmail.com> (raw)
In-Reply-To: <085f01da48bb$fe0c3cb0$fa24b610$@gmail.com>
(Resending since a spam filter seems to have blocked the first attempt.)
Is there any semantic difference between the following two instructions?
{.opcode = BPF_ALU64 | BPF_MOV | BPF_K, .offset = 0, .imm = -1}
{.opcode = BPF_ALU64 | BPF_MOVSX | BPF_K, .offset = 32, .imm = -1}
From my reading both of them treat imm as a signed 32-bit number and
sign-extend it to 64 bits.
Dave
WARNING: multiple messages have this Message-ID (diff)
From: dthaler1968=40googlemail.com@dmarc.ietf.org
To: <bpf@ietf.org>, <bpf@vger.kernel.org>
Subject: [Bpf] Sign extension ISA question
Date: Tue, 16 Jan 2024 12:55:44 -0800 [thread overview]
Message-ID: <08ab01da48be$603541a0$209fc4e0$@gmail.com> (raw)
Message-ID: <20240116205544.03JzkeE5sjM8QjpAVBeLA2Y8fAQE8fc5JVPthlhznHY@z> (raw)
In-Reply-To: <085f01da48bb$fe0c3cb0$fa24b610$@gmail.com>
(Resending since a spam filter seems to have blocked the first attempt.)
Is there any semantic difference between the following two instructions?
{.opcode = BPF_ALU64 | BPF_MOV | BPF_K, .offset = 0, .imm = -1}
{.opcode = BPF_ALU64 | BPF_MOVSX | BPF_K, .offset = 32, .imm = -1}
>From my reading both of them treat imm as a signed 32-bit number and
sign-extend it to 64 bits.
Dave
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next prev parent reply other threads:[~2024-01-16 20:55 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-16 20:38 [Bpf] Sign extension ISA question dthaler1968=40googlemail.com
2024-01-16 20:55 ` dthaler1968 [this message]
2024-01-16 20:55 ` dthaler1968=40googlemail.com
2024-01-16 22:34 ` Yonghong Song
2024-01-16 22:34 ` [Bpf] " Yonghong Song
2024-01-17 1:56 ` dthaler1968
2024-01-17 1:56 ` [Bpf] " dthaler1968=40googlemail.com
2024-01-17 3:48 ` Yonghong Song
2024-01-17 3:48 ` [Bpf] " Yonghong Song
2024-01-24 2:07 ` Jump instructions clarification dthaler1968
2024-01-24 2:07 ` [Bpf] " dthaler1968=40googlemail.com
2024-01-24 19:33 ` Yonghong Song
2024-01-24 19:33 ` [Bpf] " Yonghong Song
2024-01-26 1:12 ` 64-bit immediate " dthaler1968
2024-01-26 1:12 ` [Bpf] " dthaler1968=40googlemail.com
2024-01-26 5:34 ` Yonghong Song
2024-01-26 5:34 ` [Bpf] " Yonghong Song
2024-01-26 22:27 ` dthaler1968
2024-01-26 22:27 ` [Bpf] " dthaler1968=40googlemail.com
2024-01-27 3:41 ` Yonghong Song
2024-01-27 3:41 ` [Bpf] " Yonghong Song
2024-01-27 6:56 ` dthaler1968
2024-01-27 6:56 ` [Bpf] " dthaler1968=40googlemail.com
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