linux-kernel - Re: [PATCH v15 04/13] arch/x86: add syscall_get

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Message-ID: <CABqD9hZgnrKFY_Wei-ysU=Dy7Og2iEemnqPvcQ14M0+vL65gHQ@mail.gmail.com>
Date:	Tue, 10 Apr 2012 22:13:52 -0500
From:	Will Drewry <wad@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-doc@...r.kernel.org, kernel-hardening@...ts.openwall.com,
	netdev@...r.kernel.org, x86@...nel.org, arnd@...db.de,
	davem@...emloft.net, mingo@...hat.com, oleg@...hat.com,
	peterz@...radead.org, rdunlap@...otime.net, mcgrathr@...omium.org,
	tglx@...utronix.de, luto@....edu, eparis@...hat.com,
	serge.hallyn@...onical.com, djm@...drot.org, scarybeasts@...il.com,
	indan@....nu, pmoore@...hat.com, akpm@...ux-foundation.org,
	corbet@....net, eric.dumazet@...il.com, markus@...omium.org,
	coreyb@...ux.vnet.ibm.com, keescook@...omium.org
Subject: Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

On Sun, Mar 25, 2012 at 2:34 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 03/14/2012 08:11 PM, Will Drewry wrote:
>>
>> +static inline int syscall_get_arch(struct task_struct *task,
>> +                                struct pt_regs *regs)
>> +{
>> +#ifdef CONFIG_IA32_EMULATION
>> +     /*
>> +      * TS_COMPAT is set for 32-bit syscall entries and then
>> +      * remains set until we return to user mode.
>> +      *
>> +      * TIF_IA32 tasks should always have TS_COMPAT set at
>> +      * system call time.
>> +      */
>> +     if (task_thread_info(task)->status & TS_COMPAT)
>> +             return AUDIT_ARCH_I386;
>> +#endif
>> +     return AUDIT_ARCH_X86_64;
>> +}
>>  #endif       /* CONFIG_X86_32 */
>>
>>  #endif       /* _ASM_X86_SYSCALL_H */
>
> Just one FYI on this: after the x32 changes are upstream this can be
> implemented in terms of is_ia32_task().

Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
(1)  If we're x86_32, it's ia32
(2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
(3)  Otherwise, it's x86_64, including x32

Am I missing something? Should is_ia32_task(void) take a task_struct?
Right now, I don't see any reason to change the code, as posted, but
maybe I am mis-reading?

thanks!
will
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