|author||Andy Lutomirski <firstname.lastname@example.org>||2018-10-14 11:38:18 -0700|
|committer||Ingo Molnar <email@example.com>||2018-10-17 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 <firstname.lastname@example.org> Acked-by: Thomas Gleixner <email@example.com> Cc: Borislav Petkov <firstname.lastname@example.org> Cc: Dave Hansen <email@example.com> Cc: Linus Torvalds <firstname.lastname@example.org> Cc: Peter Zijlstra <email@example.com> Link: http://firstname.lastname@example.org Signed-off-by: Ingo Molnar <email@example.com>
Diffstat (limited to 'arch/x86/entry/entry_64.S')
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
@@ -1189,15 +1189,13 @@ ENTRY(paranoid_entry)
* 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