From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by oss.sgi.com (8.11.2/8.11.3) id g0LK12Y10216 for linux-mips-outgoing; Mon, 21 Jan 2002 12:01:02 -0800 Received: from nevyn.them.org (mail@NEVYN.RES.CMU.EDU [128.2.145.6]) by oss.sgi.com (8.11.2/8.11.3) with SMTP id g0LK0wP10202 for ; Mon, 21 Jan 2002 12:00:59 -0800 Received: from drow by nevyn.them.org with local (Exim 3.33 #1 (Debian)) id 16Sjew-0006z3-00; Mon, 21 Jan 2002 13:59:10 -0500 Date: Mon, 21 Jan 2002 13:59:10 -0500 From: Daniel Jacobowitz To: "H . J . Lu" Cc: Ulrich Drepper , "Maciej W. Rozycki" , "Kevin D. Kissell" , Machida Hiroyuki , GNU C Library , linux-mips@oss.sgi.com Subject: Re: thread-ready ABIs Message-ID: <20020121135910.A26790@nevyn.them.org> Mail-Followup-To: "H . J . Lu" , Ulrich Drepper , "Maciej W. Rozycki" , "Kevin D. Kissell" , Machida Hiroyuki , GNU C Library , linux-mips@oss.sgi.com References: <003701c1a25f$8abfc120$0deca8c0@Ulysses> <20020121102455.A27606@lucon.org> <20020121105253.B28087@lucon.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020121105253.B28087@lucon.org> User-Agent: Mutt/1.3.23i Sender: owner-linux-mips@oss.sgi.com Precedence: bulk On Mon, Jan 21, 2002 at 10:52:53AM -0800, H . J . Lu wrote: > On Mon, Jan 21, 2002 at 10:36:26AM -0800, Ulrich Drepper wrote: > > "H . J . Lu" writes: > > > > > Ulrich, should applciations have access to thread register directly? > > > > It doesn't matter. The value isn't changed in the lifetime of a > > thread. So the overhead of a syscall wouldn't be too much. And > > protection against programs overwriting the register isn't necessary. > > It's the program's fault if that happens. > > Thq question is if we should reserve $23 outside of glibc. $23 is > a saved register in the MIPS ABI. It doesn't change across function > calls. If applications outside of glibc don't need to access the > thread register directly, that means $23 can be used as a saved > register. We don't have to change anything when compiling applications. > We only need to compile glibc with $23 reserved as the thread register. That's not right. If it is call-saved in the application, that means the application can use it. Main may have to restore it before it returns to __libc_start_main, but that doesn't do you any good. It doesn't change across function calls, but it does change inside function calls. -- Daniel Jacobowitz Carnegie Mellon University MontaVista Software Debian GNU/Linux Developer