Date: Fri, 4 Jan 2002 22:18:29 +0100
From: Bernd Walter <ticso@cicely8.cicely.de>
To: Daniel Eischen <eischen@pcnet1.pcnet.com>
Cc: alpha@FreeBSD.ORG
Subject: Re: {get,set,make,swap}context for alpha
Message-ID: <20020104221828.F8703@cicely8.cicely.de>
In-Reply-To: <Pine.SUN.3.91.1020104124905.23748A-100000@pcnet1.pcnet.com>
References: <20020104182107.D8703@cicely8.cicely.de> <Pine.SUN.3.91.1020104124905.23748A-100000@pcnet1.pcnet.com>
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On Fri, Jan 04, 2002 at 12:56:45PM -0500, Daniel Eischen wrote:
> On Fri, 4 Jan 2002, Bernd Walter wrote:
> > --- _ctx_start.S.orig Fri Jan 4 18:15:18 2002
> > +++ _ctx_start.S Fri Jan 4 18:13:26 2002
> > @@ -40,6 +40,7 @@
> > .set noreorder
> > LEAF(_ctx_start,0)
> > LDGP(pv)
> > + mov s0, t12
> > jsr ra, (s0) /* call start routine; args already set */
> > mov s1, a0 /* load A0 (arg 1) with pointer to ucontext */
> > CALL(_ctx_done) /* call context completion routine */
>
> Ahh, this makes a bit of sense.
After rechecking I found it was incomplete:
ticso@cicely9# diff -u _ctx_start.S.orig _ctx_start.S
--- _ctx_start.S.orig Fri Jan 4 18:15:18 2002
+++ _ctx_start.S Fri Jan 4 22:05:42 2002
@@ -39,8 +39,9 @@
*/
.set noreorder
LEAF(_ctx_start,0)
- LDGP(pv)
+ mov s0, t12
jsr ra, (s0) /* call start routine; args already set */
+ LDGP(ra)
mov s1, a0 /* load A0 (arg 1) with pointer to ucontext */
CALL(_ctx_done) /* call context completion routine */
CALL(abort) /* should never return from above call */
The original LDGP was useless, because it t12 wasn't initialised,
but we also don't need it.
After calling a function we need to reinitialise gp, which is
implied by CALL but not by jsr alone.
We need a valid gp to get _ctx_done savely referenced.
--
B.Walter COSMO-Project http://www.cosmo-project.de
ticso@cicely.de Usergroup info@cosmo-project.de
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