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

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Message-ID: <4F84F895.4080101@zytor.com>
Date:	Tue, 10 Apr 2012 20:20:53 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Will Drewry <wad@...omium.org>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-doc@...r.kernel.org, kernel-hardening@...ts.openwall.com,
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Subject: Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

On 04/10/2012 08:13 PM, Will Drewry wrote:
> 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?
> 

Sorry, answered the wrong question.  Yes, it is the same as above...
just wandered if we could centralize this test.  It might indeed make
sense to provide general predicates which take a task pointer.

	-hpa

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