linux-kernel - Re: x86_64: tss_struct layout does not match comments !?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 3 Jul 2008 13:39:25 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Richard Kennedy <richard@....demon.co.uk>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: x86_64: tss_struct layout does not match comments  !?


* Richard Kennedy <richard@....demon.co.uk> wrote:

> Hi Ingo,
> 
> the comments in the definition of tss_struct suggests is should be
> cacheline aligned ( or 256 byte aligned ? ) :- 
> 
> |struct tss_struct {
> |....
> |	/*
> |	 * Pad the TSS to be cacheline-aligned (size is 0x100):
> |	 */
> |	unsigned long		__cacheline_filler[35];
> |	/*
> |	 * .. and then another 0x100 bytes for the emergency kernel stack:
> |	 */
> |	unsigned long		stack[64];
> |
> |} __attribute__((packed));
> 
> However on a 64 bit build the size of tss_struct is 9136,
> cacheline_filler is 280 and stack size is 512 at offset 8624.
> None of which are cacheline aligned.
> 
> I'm guessing this isn't what was intended.
> 
> do you know what the original intention was ?
> 
> 1. struct tss_struct{...} __cacheline_aligned;
> or just
> 2. struct tss_struct {
> ...
> long stack[64] __cacheline_aligned;
> }

#1 is the intent - because each CPU has a separate TSS. init_tss.stack 
is really just an emergency static stack we have in place for very early 
exceptions.

i think the __cacheline_filler could be removed safely. Mind sending a 
patch for that?

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/