[PATCH 4/5] x86/asm/entry/64: do not GET_THREAD_INFO() too early

[Denys Vlasenko]

At exit_intr, we GET_THREAD_INFO(%rcx) and then jump to retint_kernel
if saved CS was from kernel. But code at retint_kernel doesn't need %rcx.

Move GET_THREAD_INFO(%rcx) down, after CS check and branch.

While at it, remove "has a correct top of stack" comment.
After recent changes which eliminated FIXUP_TOP_OF_STACK,
we always have correct pt_regs layout.

Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Borislav Petkov <bp@xxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Oleg Nesterov <oleg@xxxxxxxxxx>
CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
CC: Will Drewry <wad@xxxxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: x86@xxxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
---
 arch/x86/kernel/entry_64.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 290ecb3..16bf357 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -654,13 +654,12 @@ ret_from_intr:
 	CFI_ADJUST_CFA_OFFSET	RBP
 
 exit_intr:
-	GET_THREAD_INFO(%rcx)
 	testl $3,CS(%rsp)
 	je retint_kernel
-
 	/* Interrupt came from user space */
+
+	GET_THREAD_INFO(%rcx)
 	/*
-	 * Has a correct top of stack.
 	 * %rcx: thread info. Interrupts off.
 	 */
 retint_with_reschedule:
-- 
1.8.1.4

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