From: Linus Torvalds <torvalds@linux-foundation.org>
To: Tejun Heo <tj@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] Additional x86 fixes for 2.6.31-rc5
Date: Sun, 2 Aug 2009 18:14:40 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.01.0908021811130.3352@localhost.localdomain> (raw)
In-Reply-To: <4A7636DF.8090201@kernel.org>
On Mon, 3 Aug 2009, Tejun Heo wrote:
>
> Yeap, this part is strange. I can't understand why it was done that
> way. Interestingly, the segment override doesn't trigger any
> exception, it just gets ignored. Is there a way to retrieve %gs value
> without accessing memory? ie. other than %gs:identity_gs?
No. There's a "load segment limit" instruction, but not a base one. It's
intentional - segments are supposed to be "anonymous" in protected mode
(in real more of vm86 mode, the base is normally the segment register
shifted left by four of course, but even that isn't _strictly_ always
true).
You're very much not supposed to look at the base.
Linus
next prev parent reply other threads:[~2009-08-03 1:16 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-31 18:13 [GIT PULL] Additional x86 fixes for 2.6.31-rc5 H. Peter Anvin
2009-07-31 19:45 ` Linus Torvalds
2009-07-31 19:57 ` Ingo Molnar
2009-08-01 19:28 ` Linus Torvalds
2009-08-01 19:38 ` H. Peter Anvin
2009-08-01 22:04 ` Linus Torvalds
2009-08-01 22:35 ` H. Peter Anvin
2009-08-02 1:20 ` Paul Mackerras
2009-08-02 3:52 ` H. Peter Anvin
2009-08-03 1:01 ` Tejun Heo
2009-08-03 1:14 ` Linus Torvalds [this message]
2009-08-03 1:49 ` Tejun Heo
2009-08-03 2:14 ` Linus Torvalds
2009-08-03 5:08 ` [PATCH 1/3] x86: Add 'percpu_read_stable()' interface for cacheable accesses Tejun Heo
2009-08-03 5:13 ` H. Peter Anvin
2009-08-03 5:18 ` Tejun Heo
2009-08-03 6:04 ` Ingo Molnar
2009-08-03 6:08 ` H. Peter Anvin
2009-08-03 6:16 ` Ingo Molnar
2009-08-03 7:00 ` Ingo Molnar
2009-08-03 15:13 ` [PATCH 1/3 UPDATED] x86, percpu: " Tejun Heo
2009-08-03 5:10 ` [PATCH 2/3] x86,percpu: fix DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED() Tejun Heo
2009-08-03 5:12 ` [PATCH 3/3] x86: collect hot percpu variables into one cacheline Tejun Heo
2009-08-05 7:34 ` [GIT PULL] Additional x86 fixes for 2.6.31-rc5 Tan, Wei Chong
2009-08-05 8:06 ` Ingo Molnar
2009-08-10 0:42 ` Tan, Wei Chong
2009-08-10 9:05 ` Ingo Molnar
2009-08-10 15:32 ` Linus Torvalds
2009-08-10 9:06 ` [tip:x86/urgent] x86: Fix serialization in pit_expect_msb() tip-bot for Linus Torvalds
2009-08-10 18:01 ` tip-bot for Linus Torvalds
2009-08-05 23:10 ` [GIT PULL] Additional x86 fixes for 2.6.31-rc5 Tan, Wei Chong
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