* [PATCH] x86/entry/64: Further improve paranoid_entry comments
@ 2018-10-14 18:38 Andy Lutomirski
2018-10-16 6:21 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski
2018-10-18 6:21 ` tip-bot for Andy Lutomirski
0 siblings, 2 replies; 3+ messages in thread
From: Andy Lutomirski @ 2018-10-14 18:38 UTC (permalink / raw)
To: x86; +Cc: LKML, Andy Lutomirski, Dave Hansen, Thomas Gleixner, Borislav Petkov
Commit 16561f27f94e ("x86/entry: Add some paranoid entry/exit CR3
handling comments") added some comments. This improves them a bit:
- When I first read the new comments, it was unclear to me whether
they were referring to the case where paranoid_entry interrupted
other entry code or where paranoid_entry was itself interrupted.
Clarify it.
- Remove the EBX comment. We no longer use EBX as a SWAPGS
indicator.
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.come
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/entry/entry_64.S | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 1d9b4a300c8c..f95dcb209fdf 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1189,15 +1189,13 @@ ENTRY(paranoid_entry)
1:
/*
* Always stash CR3 in %r14. This value will be restored,
- * verbatim, at exit. Needed if kernel is interrupted
- * after switching to the user CR3 value but before
- * returning to userspace.
+ * verbatim, at exit. Needed if paranoid_entry interrupted
+ * another entry that already switched to the user CR3 value
+ * but has not yet returned to userspace.
*
* This is also why CS (stashed in the "iret frame" by the
* hardware at entry) can not be used: this may be a return
- * to kernel code, but with a user CR3 value. The %ebx flag
- * for SWAPGS is also unusable for CR3 because there is a
- * window with a user GS and a kernel CR3.
+ * to kernel code, but with a user CR3 value.
*/
SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg=%rax save_reg=%r14
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* [tip:x86/urgent] x86/entry/64: Further improve paranoid_entry comments
2018-10-14 18:38 [PATCH] x86/entry/64: Further improve paranoid_entry comments Andy Lutomirski
@ 2018-10-16 6:21 ` tip-bot for Andy Lutomirski
2018-10-18 6:21 ` tip-bot for Andy Lutomirski
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Andy Lutomirski @ 2018-10-16 6:21 UTC (permalink / raw)
To: linux-tip-commits
Cc: dave.hansen, luto, mingo, torvalds, linux-kernel, bp, hpa, peterz, tglx
Commit-ID: 0cd6fa95a4a44ff2d649957423946c19eb98e825
Gitweb: https://git.kernel.org/tip/0cd6fa95a4a44ff2d649957423946c19eb98e825
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Sun, 14 Oct 2018 11:38:18 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 16 Oct 2018 08:19:34 +0200
x86/entry/64: Further improve paranoid_entry comments
Commit:
16561f27f94e ("x86/entry: Add some paranoid entry/exit CR3 handling comments")
... added some comments. This improves them a bit:
- When I first read the new comments, it was unclear to me whether
they were referring to the case where paranoid_entry interrupted
other entry code or where paranoid_entry was itself interrupted.
Clarify it.
- Remove the EBX comment. We no longer use EBX as a SWAPGS
indicator.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/c47daa1888dc2298e7e1d3f82bd76b776ea33393.1539542111.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/entry_64.S | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 1d9b4a300c8c..f95dcb209fdf 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1189,15 +1189,13 @@ ENTRY(paranoid_entry)
1:
/*
* Always stash CR3 in %r14. This value will be restored,
- * verbatim, at exit. Needed if kernel is interrupted
- * after switching to the user CR3 value but before
- * returning to userspace.
+ * verbatim, at exit. Needed if paranoid_entry interrupted
+ * another entry that already switched to the user CR3 value
+ * but has not yet returned to userspace.
*
* This is also why CS (stashed in the "iret frame" by the
* hardware at entry) can not be used: this may be a return
- * to kernel code, but with a user CR3 value. The %ebx flag
- * for SWAPGS is also unusable for CR3 because there is a
- * window with a user GS and a kernel CR3.
+ * to kernel code, but with a user CR3 value.
*/
SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg=%rax save_reg=%r14
^ permalink raw reply related [flat|nested] 3+ messages in thread* [tip:x86/urgent] x86/entry/64: Further improve paranoid_entry comments
2018-10-14 18:38 [PATCH] x86/entry/64: Further improve paranoid_entry comments Andy Lutomirski
2018-10-16 6:21 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski
@ 2018-10-18 6:21 ` tip-bot for Andy Lutomirski
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Andy Lutomirski @ 2018-10-18 6:21 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, peterz, mingo, torvalds, luto, tglx, bp, dave.hansen
Commit-ID: ae852495be365f6be433dde6629d3f0316f8efde
Gitweb: https://git.kernel.org/tip/ae852495be365f6be433dde6629d3f0316f8efde
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Sun, 14 Oct 2018 11:38:18 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 17 Oct 2018 12:30:27 +0200
x86/entry/64: Further improve paranoid_entry comments
Commit:
16561f27f94e ("x86/entry: Add some paranoid entry/exit CR3 handling comments")
... added some comments. This improves them a bit:
- When I first read the new comments, it was unclear to me whether
they were referring to the case where paranoid_entry interrupted
other entry code or where paranoid_entry was itself interrupted.
Clarify it.
- Remove the EBX comment. We no longer use EBX as a SWAPGS
indicator.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/c47daa1888dc2298e7e1d3f82bd76b776ea33393.1539542111.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/entry_64.S | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 1d9b4a300c8c..f95dcb209fdf 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1189,15 +1189,13 @@ ENTRY(paranoid_entry)
1:
/*
* Always stash CR3 in %r14. This value will be restored,
- * verbatim, at exit. Needed if kernel is interrupted
- * after switching to the user CR3 value but before
- * returning to userspace.
+ * verbatim, at exit. Needed if paranoid_entry interrupted
+ * another entry that already switched to the user CR3 value
+ * but has not yet returned to userspace.
*
* This is also why CS (stashed in the "iret frame" by the
* hardware at entry) can not be used: this may be a return
- * to kernel code, but with a user CR3 value. The %ebx flag
- * for SWAPGS is also unusable for CR3 because there is a
- * window with a user GS and a kernel CR3.
+ * to kernel code, but with a user CR3 value.
*/
SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg=%rax save_reg=%r14
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-10-18 6:22 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2018-10-14 18:38 [PATCH] x86/entry/64: Further improve paranoid_entry comments Andy Lutomirski
2018-10-16 6:21 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski
2018-10-18 6:21 ` tip-bot for Andy Lutomirski
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