linux-kernel - Re: [tip:x86/asm] x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}

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Message-ID: <CALCETrU=zws=cHjXE6N3jh=9+E4as2-3xciBPF+oV0_K1FMnzw@mail.gmail.com>
Date:	Tue, 19 Apr 2016 09:04:32 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Dmitry Safonov <dsafonov@...tuozzo.com>,
	Andrew Lutomirski <luto@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/asm] x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()

On Tue, Apr 19, 2016 at 4:15 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * tip-bot for Dmitry Safonov <tipbot@...or.com> wrote:
>
>> Commit-ID:  abfb9498ee1327f534df92a7ecaea81a85913bae
>> Gitweb:     http://git.kernel.org/tip/abfb9498ee1327f534df92a7ecaea81a85913bae
>> Author:     Dmitry Safonov <dsafonov@...tuozzo.com>
>> AuthorDate: Mon, 18 Apr 2016 16:43:43 +0300
>> Committer:  Ingo Molnar <mingo@...nel.org>
>> CommitDate: Tue, 19 Apr 2016 10:44:52 +0200
>>
>> x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()
>
> Btw., I'm not _entirely_ happy about the 'IA32' name, but went with this name for
> lack of a better alternative.
>
> So we have 4 system call modes:
>
>  - 64-bit native
>  - 32-bit addresses with 64-bit arguments (x32)
>  - 32-bit compat syscall (x86-32 compatibility on x86-64)
>  - 32-bit native
>
> and we have 2 bits of data that are per system call properties:
>
>  - TS_COMPAT in thread_info->status is set/cleared dynamically by the compat
>    syscall entry code
>
>  - a high bit in pt_regs->orig_ax tells us whether it's an x32 system call.
>
> So I'd suggest the following renames to harmonize these concepts:
>
>  - CONFIG_IA32_EMULATION   => CONFIG_X86_32_ABI
>    this lines up nicely with: CONFIG_X86_X32_ABI

I think I'd prefer a different interpretation: CONFIG_X86_32_ABI is
set if CONFIG_IA32_EMULATION is set *or* CONFIG_X86_32 is set.  There
is a lot of code that manually looks for that, because what it
actually cares about is "do we support 32-bit syscalls".  Also, with
the syscall cleanups I've been doing, a lot of the code is shared
between native 32-bit and 32-on-64 compat, so the distinction between
those two modes is slowly shrinking.

in_ia32_syscall() is consistent with that idea: it returns true on
native 32-bit kernels.

--Andy