From: Tejun Heo <htejun@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Brian Gerst <brgerst@gmail.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] x86: Pass in pt_regs pointer for syscalls that need it
Date: Thu, 12 Feb 2009 10:12:06 +0900 [thread overview]
Message-ID: <49937766.4070102@gmail.com> (raw)
In-Reply-To: <20090211155926.GA26194@elte.hu>
Ingo Molnar wrote:
> * Tejun Heo <htejun@gmail.com> wrote:
>
>> Brian Gerst wrote:
>>> x86-64 doesn't have the tail-call problem because it doesn't use the
>>> pt_regs on stack trick for syscall args. All the args are passed in
>>> registers.
>> Yeah, I was saying that we can do about the same thing on x86_32 by
>> passing in pointer to pt_regs and defining proper syscall wrappers.
>> It will cost a bit of performance by increasing register pressure tho.
>
> Do you mean converting:
>
> ptregscall int sys_execve(struct pt_regs *regs, char __user *u_filename,
> char __user * __user *argv,
> char __user * __user *envp)
>
> to:
>
> ptregscall int sys_execve(struct pt_regs *regs)
> {
> char __user *u_filename = syscall_arg1(regs);
> char __user * __user *argv = syscall_arg2(regs);
> char __user * __user *envp = syscall_arg3(regs);
>
> etc.?
Not exactly. include/linux/syscalls.h already has syscall wrapping
macros defined, with slight modification to allow archs to define its
own __SC_DECL and __SC_LONG (probably should use different name tho),
the outer function can be easily defined to take pt_regs pointer and
pass in the correct argument to the actual implementation function.
The only added overhead would be pt_regs pointer having to be loaded
into %edi and it having to stay somewhere in the callee till the last
parameter access.
Thanks.
--
tejun
next prev parent reply other threads:[~2009-02-12 1:12 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-10 14:51 [PATCH 0/3] x86: Fix pt_regs passed by value Brian Gerst
2009-02-10 14:51 ` [PATCH 1/3] x86: Use pt_regs pointer in do_device_not_available() Brian Gerst
2009-02-11 7:43 ` Tejun Heo
2009-02-11 10:13 ` Ingo Molnar
2009-02-11 14:34 ` Brian Gerst
2009-02-11 14:42 ` Tejun Heo
2009-02-11 14:46 ` Brian Gerst
2009-02-11 14:53 ` Tejun Heo
2009-02-10 14:51 ` [PATCH 2/3] x86: Pass in pt_regs pointer for syscalls that need it Brian Gerst
2009-02-11 7:41 ` Tejun Heo
2009-02-11 10:18 ` Ingo Molnar
2009-02-11 14:14 ` Tejun Heo
2009-02-11 14:31 ` Brian Gerst
2009-02-11 14:41 ` Tejun Heo
2009-02-11 14:43 ` Tejun Heo
2009-02-11 14:48 ` Tejun Heo
2009-02-11 14:58 ` Ingo Molnar
2009-02-11 14:59 ` Brian Gerst
2009-02-11 15:05 ` Tejun Heo
2009-02-11 15:10 ` Brian Gerst
2009-02-11 15:14 ` Tejun Heo
2009-02-11 15:59 ` Ingo Molnar
2009-02-12 1:12 ` Tejun Heo [this message]
2009-02-11 15:01 ` Ingo Molnar
2009-02-11 17:52 ` H. Peter Anvin
2009-02-11 18:27 ` Brian Gerst
2009-02-11 19:50 ` H. Peter Anvin
2009-02-11 19:57 ` Brian Gerst
2009-02-11 20:00 ` H. Peter Anvin
2009-02-11 21:43 ` [PATCH] x86: pass in pt_regs pointer for syscalls that need it (take 2) Brian Gerst
2009-02-11 21:50 ` H. Peter Anvin
2009-02-11 22:06 ` H. Peter Anvin
2009-02-12 11:02 ` Ingo Molnar
2009-02-10 14:51 ` [PATCH 3/3] x86: Drop -fno-stack-protector after pt_regs fixes Brian Gerst
2009-02-11 11:42 ` [PATCH 0/3] x86: Fix pt_regs passed by value Ingo Molnar
2009-02-11 14:15 ` Tejun Heo
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