From owner-freebsd-ppc  Fri Jul 19  1:40:45 2002
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Date: Fri, 19 Jul 2002 18:57:45 +1000
From: Peter Grehan <peterg@ptree32.com.au>
Organization: Ptree32 Pty Ltd
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To: obrien@FreeBSD.ORG
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Subject: Re: success level with peter g's patch..
References: <1027050508.3d378c0c98e84@www.wantpackets.com> <3D37BB53.D5486D0B@ptree32.com.au> <20020719080635.GA70923@dragon.nuxi.com>
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Hi David,

> How do other FreeBSD platforms handle this?  That is more important.

 From a high-level view, it shouldn't matter: there is no non-error return
from execve(), and all arch's handle EJUSTRETURN in syscall() for sigreturn.

 i386 doesn't get a register trash because the startup params are on the
stack. For alpha, it looks like the ps_strings param is overwritten:

machdep.c:setreg()
   tfp->tf_regs[FRAME_A3] = PS_STRINGS;            /* a3 = ps_strings */

trap.c:syscall()
        switch (error) {
        case 0:
                ...
                framep->tf_regs[FRAME_A3] = 0;    <- overwrite PS_STRINGS

 sparc64 already uses the td_retval[] trick, and does anyone really understand
ia64 assembler ? :-)

later,

Peter.

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