linux-kernel - Re: [PATCH 2/3] x86: Pass in pt_regs pointer for syscalls that need it

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Message-ID: <20090211155926.GA26194@elte.hu>
Date:	Wed, 11 Feb 2009 16:59:26 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tejun Heo <htejun@...il.com>
Cc:	Brian Gerst <brgerst@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86: Pass in pt_regs pointer for syscalls that
	need it


* Tejun Heo <htejun@...il.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.?

	Ingo
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