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Message-ID: <CABqD9haw2YutkSQHO0Qq19eveqwKCEi=L3fpCYupqvakW3jDMw@mail.gmail.com>
Date: Wed, 11 Apr 2012 10:41:24 -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,
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Subject: Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h
On Tue, Apr 10, 2012 at 10:20 PM, H. Peter Anvin <hpa@...or.com> wrote:
> 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.
Makes sense to me. I'm leaving this specific patch alone at present.
That said, a quick grep shows only a handful of ia32 references:
./arch/x86/include/asm/compat.h: return is_ia32_task() || is_x32_task();
./arch/x86/ia32/ia32_signal.c: bool ia32 = is_ia32_task();
./arch/x86/kernel/ptrace.c: if (!is_ia32_task())
Would it make sense to make a new predicate or just expand the one
added in 3.4 to take a task_struct parameter? I'm not sure if there'd
be much fallout in converting these from directly checking
current_thread_info to task_thread_info.
It's a small patch either way.
cheers!
will
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