From: jrvalverde@cnb.csic.es (Jose R. Valverde)
Subject: [TUHS] Introduction
Date: Wed, 25 Jun 2008 12:25:05 +0200 [thread overview]
Message-ID: <20080625122505.4e3d9803@veda.cnb.uam.es> (raw)
In-Reply-To: <20080623181101.e862a3a2.lehmann@ans-netz.de>
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Oliver,
BTW, I am thiking more clearly now and realize I initially confused
the uap struct in lock() with u_uap, although what is actually assigned is
uap->linkname to u.u_dirp.
When seeing the type definitions in param.h I also notice that it
defines caddr_t (the type of the u.u_dirp.l side of the saddr_t union) as
typedef char *caddr_t; /* pointer to kernel things */
that leads me to consider that the &0x7F00FFFF may be an additional
security check to ensure that the pointer falls within valid memory
space, in which case it would match the memory map.
I notice that nsseg in mch.s may return %7F00 on some cases and is used
in machdep.c as stseg = nsseg(u_state->s_sp); so it seems the stack uses
segment 0x7F00. Then may be the & is shorthand to make sure the address
pointed by the ANDed pointer falls within the stack. It would probably
imply user programs have a maximum stack size of 65536 bytes as well.
That may explain why some pointers are ANDed and others not. I haven't
had a thorough look, but if the &0x7F00FFFF usage is consistent, then
that's is an explanation that may guide source reconstruction.
Does this look sensible?
j
--
These opinions are mine and only mine. Hey man, I saw them first!
José R. Valverde
De nada sirve la Inteligencia Artificial cuando falta la Natural
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next prev parent reply other threads:[~2008-06-25 10:25 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-04 11:57 Jose R. Valverde
2008-06-04 15:11 ` Oliver Lehmann
2008-06-04 15:16 ` Oliver Lehmann
2008-06-05 15:07 ` Jose R. Valverde
2008-06-05 17:59 ` Oliver Lehmann
2008-06-05 15:17 ` Jose R. Valverde
2008-06-05 17:45 ` Oliver Lehmann
2008-06-23 14:18 ` Jose R. Valverde
2008-06-23 16:11 ` Oliver Lehmann
2008-06-25 9:40 ` Jose R. Valverde
2008-06-25 10:25 ` Jose R. Valverde [this message]
2008-06-26 14:52 ` Oliver Lehmann
2008-06-27 12:24 ` Jose R. Valverde
2008-06-29 8:25 ` Oliver Lehmann
2008-06-30 9:30 ` Jose R. Valverde
2008-06-30 17:34 ` Oliver Lehmann
2008-07-01 14:21 ` Jose R. Valverde
2008-07-01 18:35 ` Oliver Lehmann
2008-07-03 10:12 ` Jose R. Valverde
2008-07-06 16:14 ` Oliver Lehmann
2008-07-07 9:25 ` [TUHS] SysIII/PDP-11 on SIMH (was Re: Introduction) Jose R. Valverde
2008-07-07 9:32 ` [TUHS] Introduction Jose R. Valverde
2008-07-07 14:45 ` Oliver Lehmann
2008-06-06 9:58 ` Jose R. Valverde
-- strict thread matches above, loose matches on Subject: below --
2008-06-03 4:18 Oliver Lehmann
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