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authorAndy Lutomirski <luto@kernel.org>2018-10-14 11:38:18 -0700
committerIngo Molnar <mingo@kernel.org>2018-10-17 12:30:27 +0200
commitae852495be365f6be433dde6629d3f0316f8efde (patch)
tree0b7b8e8b15d0948ccf59f24d000831b7354fea28 /arch/x86/entry/entry_64.S
parent04f4f954b69526d7af8ffb8e5780f08b8a6cda2d (diff)
downloadlinux-stericsson-ae852495be365f6be433dde6629d3f0316f8efde.tar.gz
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>
Diffstat (limited to 'arch/x86/entry/entry_64.S')
-rw-r--r--arch/x86/entry/entry_64.S10
1 files 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