linux-kernel - Re: [PATCH] strange work_notifysig code since 2.6.16

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Date:	Wed, 25 Oct 2006 00:48:07 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Joe Korty <joe.korty@...r.com>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] strange work_notifysig code since 2.6.16

On Tue, Oct 24, 2006 at 07:19:21PM -0400, Joe Korty wrote:
> tree 9b5daef5280800a0006343a17f63072658d91a1d is surely wrong.
> 
> 	[PATCH] Make vm86 support optional
> 	Jan 8, 2006, tree first appears in 2.6.16
> 
> If the branch to work_notifysig_86 is taken and CONFIG_VM86=n,
> then entry.S drops into unrelated assembly code.
>
> The branch to work_notifysig_v86, a few lines above the patch, says:
>     "returning to kernel-space or vm86-space"
> which implies if vm86-space isn't being supported we still need the
> branch & jumped-to code in order to handle the kernel case.
> 
> However, I don't understand this area all that well, so take this patch
> as more of an indication of a possible problem area than as a true fix.
> 
> Signed-off-by: Joe Korty <joe.korty@...r.com>
> 
> Index: 2.6.18.1/arch/i386/kernel/entry.S
> ===================================================================
> --- 2.6.18.1.orig/arch/i386/kernel/entry.S	2006-09-19 23:42:06.000000000 -0400
> +++ 2.6.18.1/arch/i386/kernel/entry.S	2006-10-24 19:08:36.000000000 -0400
> @@ -457,7 +457,6 @@
>  
>  	ALIGN
>  work_notifysig_v86:
> -#ifdef CONFIG_VM86
>  	pushl %ecx			# save ti_flags for do_notify_resume
>  	CFI_ADJUST_CFA_OFFSET 4
>  	call save_v86_state		# %eax contains pt_regs pointer

I suspect this won't link with CONFIG_VM86 disabled because
save_v86_state goes away. I think we just need to move the #endif up a
few lines.

> @@ -467,7 +466,6 @@
>  	xorl %edx, %edx
>  	call do_notify_resume
>  	jmp resume_userspace_sig
> -#endif
>  
>  	# perform syscall exit tracing
>  	ALIGN

-- 
Mathematics is the supreme nostalgia of our time.
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