From: tip-bot for Andy Lutomirski <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org,
luto@amacapital.net, dvlasenk@redhat.com, bp@alien8.de,
oleg@redhat.com, mingo@kernel.org, hpa@zytor.com,
torvalds@linux-foundation.org
Subject: [tip:x86/asm] x86/asm/entry/32: Document our abuse of x86_hw_tss: :ss1 and x86_hw_tss::sp1
Date: Tue, 17 Mar 2015 01:45:38 -0700 [thread overview]
Message-ID: <tip-76e4c4908a4904a61aa67ae5eb0b2a7588c4a546@git.kernel.org> (raw)
In-Reply-To: <b7efc1b7364039824776f68e9ddee9ec1500e894.1426009661.git.luto@amacapital.net>
Commit-ID: 76e4c4908a4904a61aa67ae5eb0b2a7588c4a546
Gitweb: http://git.kernel.org/tip/76e4c4908a4904a61aa67ae5eb0b2a7588c4a546
Author: Andy Lutomirski <luto@amacapital.net>
AuthorDate: Tue, 10 Mar 2015 11:06:00 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 17 Mar 2015 09:25:27 +0100
x86/asm/entry/32: Document our abuse of x86_hw_tss::ss1 and x86_hw_tss::sp1
This has confused me for a while. Now that I figured it out, document it.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/b7efc1b7364039824776f68e9ddee9ec1500e894.1426009661.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/processor.h | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index fc6d8d0..b262089 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -209,9 +209,24 @@ struct x86_hw_tss {
unsigned short back_link, __blh;
unsigned long sp0;
unsigned short ss0, __ss0h;
- unsigned long sp1;
- /* ss1 caches MSR_IA32_SYSENTER_CS: */
- unsigned short ss1, __ss1h;
+
+ /*
+ * We don't use ring 1, so sp1 and ss1 are convenient scratch
+ * spaces in the same cacheline as sp0. We use them to cache
+ * some MSR values to avoid unnecessary wrmsr instructions.
+ *
+ * We use SYSENTER_ESP to find sp0 and for the NMI emergency
+ * stack, but we need to context switch it because we do
+ * horrible things to the kernel stack in vm86 mode.
+ *
+ * We use SYSENTER_CS to disable sysenter in vm86 mode to avoid
+ * corrupting the stack if we went through the sysenter path
+ * from vm86 mode.
+ */
+ unsigned long sp1; /* MSR_IA32_SYSENTER_ESP */
+ unsigned short ss1; /* MSR_IA32_SYSENTER_CS */
+
+ unsigned short __ss1h;
unsigned long sp2;
unsigned short ss2, __ss2h;
unsigned long __cr3;
prev parent reply other threads:[~2015-03-17 8:46 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-10 18:05 [PATCH 0/3] sp0, ss1, and sp1 docs and minor fixes Andy Lutomirski
2015-03-10 18:05 ` [PATCH 1/3] x86: Create and use a TOP_OF_KERNEL_STACK_PADDING macro Andy Lutomirski
2015-03-10 19:22 ` Denys Vlasenko
2015-03-10 19:47 ` Andy Lutomirski
2015-03-13 14:08 ` Denys Vlasenko
2015-03-16 8:56 ` Ingo Molnar
2015-03-16 12:08 ` [tip:x86/asm] x86/asm/entry: Create and use a ' TOP_OF_KERNEL_STACK_PADDING' macro tip-bot for Andy Lutomirski
2015-03-17 8:45 ` tip-bot for Andy Lutomirski
2015-03-10 18:05 ` [PATCH 2/3] x86: Unify and fix init sp0 Andy Lutomirski
2015-03-11 11:21 ` Borislav Petkov
2015-03-16 12:09 ` [tip:x86/asm] x86/asm/entry: Unify and fix initial thread_struct: :sp0 values tip-bot for Andy Lutomirski
2015-03-17 8:45 ` tip-bot for Andy Lutomirski
2015-03-10 18:06 ` [PATCH 3/3] x86_32: Document our abuse of ss1 and sp1 Andy Lutomirski
2015-03-10 19:13 ` Denys Vlasenko
2015-03-10 20:06 ` Andy Lutomirski
2015-03-10 20:52 ` Denys Vlasenko
2015-03-16 12:09 ` [tip:x86/asm] x86/asm/entry/32: Document our abuse of x86_hw_tss: :ss1 and x86_hw_tss::sp1 tip-bot for Andy Lutomirski
2015-03-16 15:36 ` Andy Lutomirski
2015-03-17 8:45 ` tip-bot for Andy Lutomirski [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=tip-76e4c4908a4904a61aa67ae5eb0b2a7588c4a546@git.kernel.org \
--to=tipbot@zytor.com \
--cc=bp@alien8.de \
--cc=dvlasenk@redhat.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.