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From: Blaisorblade <blaisorblade@yahoo.it>
To: user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [uml-devel] [PATCH 8/10] UML - Maintain own LDT entries
Date: Wed, 2 Nov 2005 20:51:22 +0100
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Cc: Jeff Dike <jdike@addtoit.com>, linux-kernel@vger.kernel.org,
       bstroesser@fujitsu-siemens.com, Allan Graves <allan.graves@oracle.com>
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On Monday 31 October 2005 05:39, Jeff Dike wrote:
> From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
>
> Patch imlements full LDT handling in SKAS:
>  * UML holds it's own LDT table, used to deliver data on
>    modify_ldt(READ)
>  * UML disables the default_ldt, inherited from the host (SKAS3)
>    or resets LDT entries, set by host's clib and inherited in
>    SKAS0
>  * A new global variable skas_needs_stub is inserted, that
>    can be used to decide, whether stub-pages must be supported
>    or not.
>  * Uses the syscall-stub to replace missing PTRACE_LDT (therefore,
>    write_ldt_entry needs to be modified)
Two complaints against this patch (to be fixed afterwards, so I'm not CC'ing 
akpm):

*) It reverts my cleanup and consolidation of ldt.c wrt. SKAS vs TT.

Or at least so I think (I must still give a proper look afterwards, and I'll 
post patches). Actually it seems that this is done on purpose, but I don't 
agree too much on this. I will see.

*) Doesn't compile on old GCC's - it uses anonymous unions:
(it's asm-um/ldt-i386.h).
> +
> +struct ldt_entry {
> +	__u32 a;
> +	__u32 b;
> +};

> +typedef struct uml_ldt {
> +	int entry_count;
> +	struct semaphore semaphore;
> +	union {
> +		struct ldt_entry * pages[LDT_PAGES_MAX];
> +		struct ldt_entry entries[LDT_DIRECT_ENTRIES];
> +	};
> +} uml_ldt_t;

Suggestions for almost free replacement of anonymous union: 
> Index: 2.6.14-akpm/include/asm-um/ldt.h
> ===================================================================
> --- 2.6.14-akpm.orig/include/asm-um/ldt.h	2005-08-28 19:41:01.000000000
> -0400 +++ 2.6.14-akpm/include/asm-um/ldt.h	2005-10-28 17:31:07.000000000
AAAAAAAAAAAARGH!!!!!!!!!!!!!! This is supposed to be a  _SYMLINK_!

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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