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Date: Thu, 29 Nov 2007 12:34:28 -0500
From: Chuck Ebbert <cebbert@redhat.com>
Organization: Red Hat
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To: Roland McGrath <roland@redhat.com>
CC: Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
       Ingo Molnar <mingo@elte.hu>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH x86/mm 6/6] x86-64 ia32 ptrace get/putreg32 current task
References: <20071129003849.428E026F8E7@magilla.localdomain> <20071129004222.E49AD26F8E7@magilla.localdomain>
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On 11/28/2007 07:42 PM, Roland McGrath wrote:
> --- a/arch/x86/ia32/ptrace32.c
> +++ b/arch/x86/ia32/ptrace32.c
> @@ -48,19 +48,27 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 val)
>  		if (val && (val & 3) != 3)
>  			return -EIO;
>  		child->thread.fsindex = val & 0xffff;
> +		if (child == current)
> +			loadsegment(fs, child->thread.fsindex);
>  		break;
>  	case offsetof(struct user32, regs.gs):
>  		if (val && (val & 3) != 3)
>  			return -EIO;
>  		child->thread.gsindex = val & 0xffff;
> +		if (child == current)
> +			load_gs_index(child->thread.gsindex);
>  		break;
>  	case offsetof(struct user32, regs.ds):
>  		if (val && (val & 3) != 3)
>  			return -EIO;
>  		child->thread.ds = val & 0xffff;
> +		if (child == current)
> +			loadsegment(ds, child->thread.ds);
>  		break;
>  	case offsetof(struct user32, regs.es):
>  		child->thread.es = val & 0xffff;
> +		if (child == current)
> +			loadsegment(es, child->thread.ds);

                                        child->thread.es ??

> @@ -129,15 +137,23 @@ static int getreg32(struct task_struct *child, unsigned regno, u32 *val)
>  	switch (regno) {
>  	case offsetof(struct user32, regs.fs):
>  		*val = child->thread.fsindex;
> +		if (child == current)
> +			asm("movl %%fs,%0" : "=r" (*val));
>  		break;
>  	case offsetof(struct user32, regs.gs):
>  		*val = child->thread.gsindex;
> +		if (child == current)
> +			asm("movl %%gs,%0" : "=r" (*val));

Won't this return the kernel's GS instead of the user's?