Re: komd issues - was [Re: [openMosix-general] openmosix 2.4.26 in 2.4.31?]

We had FS/GS problems several times. The way the threading lib is using
these registers is complex and changes often

We already had an isssue with FS/GS which was solved in 2002. I will check
again

Moshe
 

-----Original Message-----
From: Vincent Hanquez [mailto:tab-mTI/[email protected]] 
Sent: Thursday, September 21, 2006 3:12 PM
To: Matt Dew
Cc: openmosix-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org; [email protected];
[email protected]; moshe-ay74M1d3r6RWk0Htik3J/[email protected]
Subject: Re: [Openmosix-devel] komd issues - was [Re: [openMosix-general]
openmosix 2.4.26 in 2.4.31?]

On Thu, Sep 21, 2006 at 09:40:08AM -0600, Matt Dew wrote:
> Setting LD_ASSUME_KERNEL=2.4.1 fixes the system call segfaults.
> WOOHOO!! Now we know where to look to fix the problem.

TLS screwup, through fs/gs problem. more than likely.

> Unfortunately, I don't really understand LD_ASSUME_KERNEL in great 
> detail.

only details useful, is that is turn OFF the use of VDSO/TLS .. all kind of
fancy stuff..

00000000 <__getpid>:
0:	b8 14 00 00 00       	mov    $0x14,%eax
5:	65 ff 15 10 00 00 00 	call   *%gs:0x10
c:	c3                   	ret    

if %gs is not correct here, it's going to segfault.

> Are we going to have to redo the sys_call_table?  Have each entry call 
> a new om_sys_call_table that calls the appropriate function?

The syscall_table is absolutely constant. only entry point changes.

Note that i386 sysenter type of syscall (intel syscall on p4) have never
been tested. I changed the entry point code there, but never had any
power-sucker-processor to test it.

--
Vincent Hanquez


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