From: Peter Zijlstra <peterz@infradead.org>
To: x86@kernel.org, rostedt@goodmis.org, hpa@zytor.com,
torvalds@linuxfoundation.org
Cc: linux-kernel@vger.kernel.org, linux-toolchains@vger.kernel.org,
jpoimboe@redhat.com, alexei.starovoitov@gmail.com,
mhiramat@kernel.org
Subject: Re: [PATCH 1/2] x86: Remove dynamic NOP selection
Date: Fri, 12 Mar 2021 13:09:15 +0100 [thread overview]
Message-ID: <YEtZ63iAralvR9eC@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210312115749.065275711@infradead.org>
On Fri, Mar 12, 2021 at 12:32:54PM +0100, Peter Zijlstra wrote:
> +#ifndef CONFIG_64BIT
> +
> +/*
> + * Generic 32bit nops from GAS:
> + *
> + * 1: nop
> + * 2: movl %esi,%esi
> + * 3: leal 0x0(%esi),%esi
> + * 4: leal 0x0(%esi,%eiz,1),%esi
> + * 5: leal %ds:0x0(%esi,%eiz,1),%esi
> + * 6: leal 0x0(%esi),%esi
> + * 7: leal 0x0(%esi,%eiz,1),%esi
> + * 8: leal %ds:0x0(%esi,%eiz,1),%esi
> *
> + * Except 5 and 8, which are DS prefixed 4 and 7 resp, where GAS would emit 2
> + * nop instructions.
> */
> +#define BYTES_NOP1 0x90
> +#define BYTES_NOP2 0x89,0xf6
> +#define BYTES_NOP3 0x8d,0x76,0x00
> +#define BYTES_NOP4 0x8d,0x74,0x26,0x00
> +#define BYTES_NOP5 0x3e,BYTES_NOP4
> +#define BYTES_NOP6 0x8d,0xb6,0x00,0x00,0x00,0x00
> +#define BYTES_NOP7 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00
> +#define BYTES_NOP8 0x3e,BYTES_NOP7
> +
> +#else
>
> +/*
> + * Generic 64bit nops from GAS:
> + *
> + * 1: nop
> + * 2: osp nop
> + * 3: nopl (%eax)
> + * 4: nopl 0x00(%eax)
> + * 5: nopl 0x00(%eax,%eax,1)
> + * 6: osp nopl 0x00(%eax,%eax,1)
> + * 7: nopl 0x00000000(%eax)
> + * 8: nopl 0x00000000(%eax,%eax,1)
> + */
> +#define BYTES_NOP1 0x90
> +#define BYTES_NOP2 0x66,BYTES_NOP1
> +#define BYTES_NOP3 0x0f,0x1f,0x00
> +#define BYTES_NOP4 0x0f,0x1f,0x40,0x00
> +#define BYTES_NOP5 0x0f,0x1f,0x44,0x00,0x00
> +#define BYTES_NOP6 0x66,BYTES_NOP5
> +#define BYTES_NOP7 0x0f,0x1f,0x80,0x00,0x00,0x00,0x00
> +#define BYTES_NOP8 0x0f,0x1f,0x84,0x00,0x00,0x00,0x00,0x00
>
> +#endif /* CONFIG_64BIT */
Note that this also made all NOPs single instructions and removed the
special atomic nop.
next prev parent reply other threads:[~2021-03-12 12:10 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 11:32 [PATCH 0/2] x86: Remove ideal_nops[] Peter Zijlstra
2021-03-12 11:32 ` [PATCH 1/2] x86: Remove dynamic NOP selection Peter Zijlstra
2021-03-12 12:09 ` Peter Zijlstra [this message]
2021-03-12 20:36 ` Linus Torvalds
2024-01-20 6:58 ` Thorsten Glaser
2024-01-20 8:22 ` H. Peter Anvin
2024-01-20 16:53 ` Thorsten Glaser
2024-01-21 23:21 ` H. Peter Anvin
2024-01-21 23:58 ` Thorsten Glaser
2024-01-22 0:15 ` H. Peter Anvin
2024-01-22 0:56 ` Steven Rostedt
2024-01-22 1:17 ` Thorsten Glaser
2024-01-22 2:04 ` H. Peter Anvin
2024-01-22 2:15 ` H. Peter Anvin
2024-01-22 2:22 ` Steven Rostedt
2024-01-22 2:31 ` H. Peter Anvin
2024-01-20 17:00 ` Linus Torvalds
2024-01-20 17:19 ` Thorsten Glaser
2024-01-20 18:21 ` disassemblers (was Re: [PATCH 1/2] x86: Remove dynamic NOP selection) Thorsten Glaser
2024-01-21 22:36 ` [PATCH 1/2] x86: Remove dynamic NOP selection David Laight
2024-01-21 23:10 ` H. Peter Anvin
2021-03-12 11:32 ` [PATCH 2/2] objtool,x86: Use asm/nops.h Peter Zijlstra
2021-03-12 14:29 ` [PATCH 0/2] x86: Remove ideal_nops[] Sedat Dilek
2021-03-12 14:47 ` Borislav Petkov
2021-03-12 17:26 ` Steven Rostedt
2021-03-12 17:35 ` Sedat Dilek
2021-03-12 17:46 ` Borislav Petkov
2021-03-12 17:47 ` Steven Rostedt
2021-03-12 18:13 ` Sedat Dilek
2021-03-12 19:03 ` Sedat Dilek
2021-03-12 20:59 ` Borislav Petkov
[not found] ` <CA+icZUWSCS6vAQOXoG6nsW+Dbnogivzf+rmegCTMjz5hjE5cKQ@mail.gmail.com>
2021-03-13 8:49 ` Borislav Petkov
2021-03-13 11:23 ` Borislav Petkov
2021-03-13 12:10 ` Sedat Dilek
2021-03-13 12:15 ` Borislav Petkov
2021-03-13 12:38 ` Sedat Dilek
2021-03-13 12:49 ` Borislav Petkov
2021-03-13 12:58 ` Sedat Dilek
2021-03-13 13:29 ` Borislav Petkov
2021-03-13 13:47 ` Sedat Dilek
2021-03-15 17:04 ` Sedat Dilek
2021-03-15 17:15 ` Borislav Petkov
2021-03-15 17:19 ` Sedat Dilek
2021-03-15 17:23 ` Borislav Petkov
2021-03-15 18:10 ` Peter Zijlstra
2021-03-15 18:23 ` Sedat Dilek
2021-03-15 22:14 ` Peter Zijlstra
2021-03-16 5:56 ` Sedat Dilek
2021-03-27 12:08 ` Sedat Dilek
2021-03-27 20:02 ` Linus Torvalds
2021-03-30 12:31 ` Sedat Dilek
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