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

From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Dmitry Safonov <dsafonov@virtuozzo.com>,
	Andrew Lutomirski <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"linux-tip-commits@vger.kernel.org" 
	<linux-tip-commits@vger.kernel.org>
Subject: Re: [tip:x86/asm] x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()
Date: Fri, 22 Apr 2016 10:36:41 +0200	[thread overview]
Message-ID: <20160422083641.GA17242@gmail.com> (raw)
In-Reply-To: <CALCETrU=zws=cHjXE6N3jh=9+E4as2-3xciBPF+oV0_K1FMnzw@mail.gmail.com>

* Andy Lutomirski <luto@amacapital.net> wrote:

> On Tue, Apr 19, 2016 at 4:15 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * tip-bot for Dmitry Safonov <tipbot@zytor.com> wrote:
> >
> >> Commit-ID:  abfb9498ee1327f534df92a7ecaea81a85913bae
> >> Gitweb:     http://git.kernel.org/tip/abfb9498ee1327f534df92a7ecaea81a85913bae
> >> Author:     Dmitry Safonov <dsafonov@virtuozzo.com>
> >> AuthorDate: Mon, 18 Apr 2016 16:43:43 +0300
> >> Committer:  Ingo Molnar <mingo@kernel.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.

Ok, so how about:

 - rename CONFIG_IA32_EMULATION => CONFIG_X86_32_COMPAT

 - introduce CONFIG_X86_32_ABI to separate the 'convenience' functionality of 
   CONFIG_IA32_EMULATION from the ABI meaning.

 - rename is_ia32_syscall() -> is_x86_32_syscall()
 - rename is_x32_syscall()  -> is_x86_x32_syscall()

 - is_compat_syscall() remains as-is.

?

In the long run I'd like to get rid of two naming variants:

 - Fix all names that use 'IA32' that refer to 32-bit compat functionality,
   and only name the things 'IA32' that are truly Intel specific.

 - Fix all names that use 'emulation' when they really refer to 32-bit compat. We 
   don't actually emulate anything, we are just calling convention compatible with 
   very little overhead. The CPU is a fully 32-bit/64-bit dual mode hardware, 
   there's nothing that is emulated. Calling it IA32_EMULATION was a misnomer.

Thanks,

	Ingo