[PATCH] x86/entry: Move thunk restore code into thunk functions

[Josh Poimboeuf]

There's no need for both thunk functions to jump to the same shared
thunk restore code which lives outside the thunk function boundaries.
It disrupts i-cache locality and confuses objtool.  Keep it simple by
keeping each thunk's restore code self-contained within the function.

Fixes a bunch of false positive "missing __noreturn" warnings like:

  vmlinux.o: warning: objtool: do_arch_prctl_common+0xf4: preempt_schedule_thunk() is missing a __noreturn annotation

Fixes: fedb724c3db5 ("objtool: Detect missing __noreturn annotations")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202305281037.3PaI3tW4-lkp@xxxxxxxxx/
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 arch/x86/entry/thunk_64.S | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/entry/thunk_64.S b/arch/x86/entry/thunk_64.S
index 5e37f41e5f14..27b5da2111ac 100644
--- a/arch/x86/entry/thunk_64.S
+++ b/arch/x86/entry/thunk_64.S
@@ -26,17 +26,7 @@ SYM_FUNC_START(\name)
 	pushq %r11
 
 	call \func
-	jmp  __thunk_restore
-SYM_FUNC_END(\name)
-	_ASM_NOKPROBE(\name)
-	.endm
 
-	THUNK preempt_schedule_thunk, preempt_schedule
-	THUNK preempt_schedule_notrace_thunk, preempt_schedule_notrace
-	EXPORT_SYMBOL(preempt_schedule_thunk)
-	EXPORT_SYMBOL(preempt_schedule_notrace_thunk)
-
-SYM_CODE_START_LOCAL(__thunk_restore)
 	popq %r11
 	popq %r10
 	popq %r9
@@ -48,5 +38,11 @@ SYM_CODE_START_LOCAL(__thunk_restore)
 	popq %rdi
 	popq %rbp
 	RET
-	_ASM_NOKPROBE(__thunk_restore)
-SYM_CODE_END(__thunk_restore)
+SYM_FUNC_END(\name)
+	_ASM_NOKPROBE(\name)
+	.endm
+
+THUNK preempt_schedule_thunk, preempt_schedule
+THUNK preempt_schedule_notrace_thunk, preempt_schedule_notrace
+EXPORT_SYMBOL(preempt_schedule_thunk)
+EXPORT_SYMBOL(preempt_schedule_notrace_thunk)
-- 
2.40.1