linux-kernel - Re: [PATCH] x86_64 ptrace orig

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Message-ID: <alpine.LFD.1.00.0803071507240.3013@woody.linux-foundation.org>
Date:	Fri, 7 Mar 2008 15:18:41 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Roland McGrath <roland@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86_64 ptrace orig_ax on ia32 task


On Fri, 7 Mar 2008, Roland McGrath wrote:
> 
> This makes 64-bit ptrace calls setting the 64-bit orig_ax field
> for a 32-bit task sign-extend the low 32 bits up to 64.  This
> matches what a 64-bit debugger expects when tracing a 32-bit task.

Hmm. Why make this conditional on CONFIG_IA32_EMULATION and TIF_IA32?

That field is never really 64-bit anyway. The only allowable values are
 - system call number (== small positive value)
 - a small negative number for traps

So I'd suggest just making it entirely unconditionally just do

	case offsetof(struct user_regs_struct, orig_ax):
		value = (long) (s32) value;
		break;

and be done with it. Why have arbitrarily different code on x86 and x86-64 
when there is no real reason for it?

		Linus
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