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| author | Andy Lutomirski <luto@kernel.org> | 2018-10-14 11:38:18 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-10-17 12:30:27 +0200 |
| commit | ae852495be365f6be433dde6629d3f0316f8efde (patch) | |
| tree | 0b7b8e8b15d0948ccf59f24d000831b7354fea28 | |
| parent | 04f4f954b69526d7af8ffb8e5780f08b8a6cda2d (diff) | |
| download | linux-0-day-ae852495be365f6be433dde6629d3f0316f8efde.tar.gz linux-0-day-ae852495be365f6be433dde6629d3f0316f8efde.tar.xz | |
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>
| -rw-r--r-- | arch/x86/entry/entry_64.S | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 1d9b4a300c8ce..f95dcb209fdff 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 |