Date: Tue, 10 Dec 2002 08:18:20 -0800 From: Chuck Tuffli <chuck_tuffli@agilent.com> To: phk@FreeBSD.ORG Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: registers not saved Message-ID: <20021210161813.GA681@thegrail.rose.agilent.com> In-Reply-To: <99179.1039535914@critter.freebsd.dk> References: <20021210154635.GC605@thegrail.rose.agilent.com> <99179.1039535914@critter.freebsd.dk>
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On Tue, Dec 10, 2002 at 04:58:34PM +0100, phk@FreeBSD.ORG wrote:
> In message <20021210154635.GC605@thegrail.rose.agilent.com>, Chuck Tuffli write
> s:
> >I've been chasing down some weird panics in my CAM driver and have
> >noticed that functions don't seem to save all register values before
> >they modify them.
> >
> >For example, function A uses register ecx to hold the value of a
> >pointer. Part way through, function A calls function B which uses
> >ecx as a loop index. The bad part is function B never
> >saves/restores the value of ecx and function A starts dereferencing
> >garbage.
> >
> >An informal sampling of my driver seems to indicate that ebx gets
> >pushed/poped at entry/exit but ecx and edx don't. Does any of this
> >sound familiar? Thanks!
>
> There are strict rules for which registers should be saved and which not.
The registers I see being saved are ebp, edi, esi, and ebx
> You can modify these rules somewhat using weird compiler options, but
> it should be consistent for all the code generated with the same
> settings.
These are the cc options I get when building the module (-I's removed)
cc -O -pipe -I... -Werror -ggdb -DDBG -D_KERNEL -Wall
-Wredundant-decls -Wnested-externs -Wstrict-prototypes
-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual
-fformat-extensions -ansi -DKLD_MODULE -nostdinc -I- -I...
-mpreferred-stack-boundary=2 -Wall -Wredundant-decls -Wnested-externs
-Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Winline
-Wcast-qual -fformat-extensions -ansi -c
/usr/home/ctuffli/dev/tsdk/samples/bsd/tach/tach_pci.c
> Which FreeBSD version (uname -a) and which compiler version (cc -v)
> is this ?
[522] cc -v
Using builtin specs.
gcc version 2.95.4 20020320 [FreeBSD]
llama# uname -a
FreeBSD llama.rose.agilent.com 4.7-STABLE FreeBSD 4.7-STABLE #3:
Tue Dec 3 14:59:35 PST 2002
ctuffli@thegrail:/home/ctuffli/dev/bsd/sys/compile/THEGRAIL i386
This is 4.7-RELEASE GENERIC compiled with -g, using DDB and all the
CAM debug options. The INET6 and XSERVER options are commented out as
well as the cpu I{3,4,5}86_CPU definitions (i.e. only I686_CPU is
used).
--
Chuck Tuffli <chuck_tuffli AT NO_SPAM agilent DOT com>
Agilent Technologies, Storage and Networking
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