From owner-cvs-all Fri Feb 23 12: 2:47 2001 Delivered-To: cvs-all@freebsd.org Received: from anchor-post-33.mail.demon.net (anchor-post-33.mail.demon.net [194.217.242.91]) by hub.freebsd.org (Postfix) with ESMTP id 20B1637B401; Fri, 23 Feb 2001 12:02:43 -0800 (PST) (envelope-from dfr@nlsystems.com) Received: from [62.49.251.130] (helo=herring.nlsystems.com) by anchor-post-33.mail.demon.net with esmtp (Exim 2.12 #1) id 14WOQH-000B27-0X; Fri, 23 Feb 2001 20:02:38 +0000 Received: from salmon.nlsystems.com (salmon [10.0.0.3]) by herring.nlsystems.com (8.11.2/8.11.2) with ESMTP id f1NK2b108371; Fri, 23 Feb 2001 20:02:37 GMT (envelope-from dfr@nlsystems.com) Date: Fri, 23 Feb 2001 20:02:37 +0000 (GMT) From: Doug Rabson To: John Baldwin Cc: Bruce Evans , cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/alpha/alpha swtch.s In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Fri, 23 Feb 2001, John Baldwin wrote: > > On i386's, it always has the same value (a fixed amount below the top > > of the process's kernel stack). Setting it more than once per process > > is pessimal. Not setting it in ast() usually works because there was > > a previous syscall or trap that set it. Note that there is no bug in > > old versions that multiplexed ast() through() trap(). Interrupt > > handlers were turned into trap handlers before they called ast(), and > > trap() set md_regs. Interrupt handlers still have a slightly different > > frame from trap handlers, so setting md_regs for them doesn't even > > make sense until they become trap handlers and call ast(). > > Well, should he hackishly set it in vm_fork() or cpu_fork() rather than > bothering to set it for traps, syscalls, and ast's? Do you know if the same > would be true (it being a fixed address) on other archs. It would seem that > any arch that used separate stacks for kernel and user would do this.. Not sure about this. Both alpha and ia64 have the kernel-entry trapframe at predictable places FWIW. -- Doug Rabson Mail: dfr@nlsystems.com Phone: +44 20 8348 6160 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message