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Message-ID: <alpine.LFD.1.10.0804240837120.2779@woody.linux-foundation.org>
Date: Thu, 24 Apr 2008 08:39:37 -0700 (PDT)
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: David Miller <davem@...emloft.net>
cc: akpm@...ux-foundation.org, sparclinux@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [GIT]: Sparc
On Thu, 24 Apr 2008, David Miller wrote:
>
> 2) Make use of an unused field in pt_regs to store both
> a magic number, and the trap number, this allows:
>
> a) Removing the funny passing of the "restart_syscall"
> boolean in the trap return paths to the signal dispatch.
>
> b) Allow more accurate stack backtraces, since we have the
> magic cookie, we can detect trap frames accurately.
>
> c) The UTRACE guys want to be able to detect if a thread
> off the cpu is in a system call, they can do that trivially
> now just like they can on x86.
>
> In fact much of this idea is from Roland McGrath.
Heh. This is what x86 has done since day#1. I wonder why other
architectures wouldn't have copied that part..
That's "orig_eax". It's a strange name, it really has nothing to do with
"eax" except for the fact that the system call number comes from that
register - for traps etc it's a negative value.
Linus
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