Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1166378 > unrolled thread

Re: [tip:x86/asm] x86/asm/entry: (Re-) rename __NR_entry_INT80_compat_max to __NR_syscall_compat_max

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [tip:x86/asm] x86/asm/entry: (Re-) rename __NR_entry_INT80_compat_max  to __NR_syscall_compat_max "H. Peter Anvin" <hpa@zytor.com> - 2015-06-16 22:30 +0200
    Re: [RFC] Rename various 'IA32' uses in arch/x86/ code Ingo Molnar <mingo@kernel.org> - 2015-06-19 09:10 +0200
    Re: [RFC] Rename various 'IA32' uses in arch/x86/ code Ingo Molnar <mingo@kernel.org> - 2015-06-19 09:20 +0200

#1166378 — Re: [tip:x86/asm] x86/asm/entry: (Re-) rename __NR_entry_INT80_compat_max to __NR_syscall_compat_max

On 06/08/2015 03:24 PM, tip-bot for Ingo Molnar wrote:
> Commit-ID:  bace7117d3fb59a6ed7ea1aa6c8994df6a28a72a
> Gitweb:     http://git.kernel.org/tip/bace7117d3fb59a6ed7ea1aa6c8994df6a28a72a
> Author:     Ingo Molnar <mingo@kernel.org>
> AuthorDate: Mon, 8 Jun 2015 21:20:26 +0200
> Committer:  Ingo Molnar <mingo@kernel.org>
> CommitDate: Mon, 8 Jun 2015 23:43:38 +0200
> 
> x86/asm/entry: (Re-)rename __NR_entry_INT80_compat_max to __NR_syscall_compat_max
> 
> Brian Gerst noticed that I did a weird rename in the following commit:
> 
>    b2502b418e63 ("x86/asm/entry: Untangle 'system_call' into two entry points: entry_SYSCALL_64 and entry_INT80_32")
> 
> which renamed __NR_ia32_syscall_max to __NR_entry_INT80_compat_max.
> 
> Now the original name was a misnomer, but the new one is a misnomer as well,
> as all the 32-bit compat syscall entry points (sysenter, syscall) share the
> system call table, not just the INT80 based one.
> 
> Rename it to __NR_syscall_compat_max.
> 

The original one wasn't really a misnomer, as it referred to the ia32
system calls specifically, but this works too.

	-hpa


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [next] | [standalone]

#1168573 — Re: [RFC] Rename various 'IA32' uses in arch/x86/ code

* Brian Gerst <brgerst@gmail.com> wrote:

> > Ok, so your goal is to allow the x32 ABI, but not 32-bit user-space?
> 
> It just seems odd that x32 (which is really a 64-bit ABI with 32-bit pointers) 
> depended on enabling 32-bit support.  Other than both using the core compat 
> code, they are not really related.

Yeah.

> > I suppose that makes some sense, it might be a valid 'attack surface 
> > reduction' technique, while still allowing the x32 ABI.
> >
> > But I'm not sure we should bother and complicate things: 32-bit compat isn't 
> > going away anytime soon, and most of CONFIG_COMPAT is needed for x32.
> 
> Many of the compat syscalls are unused by x32.  It only needs to handle syscalls 
> with pointers embedded in data structures differently than native 64-bit.

Yeah, but in fact those are the 'most interesting' (read: most complex) aspects of 
the generic compat machinery. So most of the 'core compat' functionality is used - 
even though we don't use many of the (trivial) argument-converted syscall 
variants.

> 64-bit integer arguments (ie., loff_t) do not need special handling, since they 
> can be passed in a single register instead of a pair of 32-bit registers.  This 
> won't solve that particular issue yet, but it's something to be aware of for 
> future cleanups.

Yes, and I think 'X32' is a misnomer in that sense: in reality it's a 90% 64-bit 
ABI that just happens to have a handful of additional system calls that can deal 
with data pointers truncated to 32 bits.

So 'C64' would have been a better name: a compacted 64-bit ABI - but that 
particular name has its own problems ;-) Maybe S64 (small 64-bit memory model)?

'S64' would also have been an easier sell to distros: they generally resist adding 
anything that smells old, 32-bit ... but kernel hackers and marketing were always 
somewhat disjunct sets ;-)

I'm wondering whether we'll ever see a 48-bit user-space pointer model ;-) They 
are misaligned by 32 bits, but x86 CPUs generally handle 32-bit misalignment just 
fine. The killer would be to zero-extend from 48 bits to 64 bits I suspect - 
there's no natural instruction for that.

> > So maybe we could introduce CONFIG_X86_32_ABI=y or so, which would cover just 
> > the 32-bit entry code and the signal frame compatibility layer?
> 
> Yes.

Ok, then it sounds good to me!

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [next] | [standalone]

#1168576 — Re: [RFC] Rename various 'IA32' uses in arch/x86/ code

* H. Peter Anvin <hpa@zytor.com> wrote:

> We have generally used i386 as opposed to x86 for that purpose. [...]

So 'i386' is really the original name that stuck.

'x86-32' sounds more appropriate to me - we should not perpetuate the i386 name, 
as we don't run on an original i386 anymore ;-)

Here's what I think sounds pretty natural:

  CONFIG_X86_32_ABI
  CONFIG_X86_64_ABI
  CONFIG_X86_X32_ABI

- CONFIG_X86_X32_ABI and CONFIG_X86_32_ABI selects CONFIG_COMPAT.
- CONFIG_X86_32_ABI enables the 32-bit/32-bit system call ABI.
- CONFIG_X86_X32_ABI enables the extra 64-bit/32-bit system call entries.
- CONFIG_IA32_EMULATION goes away.

> [...] IA32 in MSR names is part of the MSR name and should not be taken out.

Yes, of course.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web