[tip: x86/core] x86/ftrace: Remove ftrace_epilogue()

tip-bot2 for Peter Zijlstra
2022-10-17T14:54:23Z

The following commit has been merged into the x86/core branch of tip:

Commit-ID: eac828eaef295cd0cc8b58f55fa5c8401fdc2370
Gitweb: https://git.kernel.org/tip/eac828eaef295cd0cc8b58f55fa5c8401fdc2370
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 15 Sep 2022 13:11:35 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 17 Oct 2022 16:41:18 +02:00

x86/ftrace: Remove ftrace_epilogue()

Remove the weird jumps to RET and simply use RET.

This then promotes ftrace_stub() to a real function; which becomes
important for kcfi.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111148.719080593@infradead.org
---
arch/x86/kernel/ftrace_64.S | 21 ++++++---------------
1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index dfeb227..a90c55a 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -172,20 +172,14 @@ SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
*/
SYM_INNER_LABEL(ftrace_caller_end, SYM_L_GLOBAL)
ANNOTATE_NOENDBR
-
- jmp ftrace_epilogue
+ RET
SYM_FUNC_END(ftrace_caller);
STACK_FRAME_NON_STANDARD_FP(ftrace_caller)

-SYM_FUNC_START(ftrace_epilogue)
-/*
- * This is weak to keep gas from relaxing the jumps.
- */
-SYM_INNER_LABEL_ALIGN(ftrace_stub, SYM_L_WEAK)
+SYM_FUNC_START(ftrace_stub)
UNWIND_HINT_FUNC
- ENDBR
RET
-SYM_FUNC_END(ftrace_epilogue)
+SYM_FUNC_END(ftrace_stub)

SYM_FUNC_START(ftrace_regs_caller)
/* Save the current flags before any operations that can change them */
@@ -262,14 +256,11 @@ SYM_INNER_LABEL(ftrace_regs_caller_jmp, SYM_L_GLOBAL)
popfq

/*
- * As this jmp to ftrace_epilogue can be a short jump
- * it must not be copied into the trampoline.
- * The trampoline will add the code to jump
- * to the return.
+ * The trampoline will add the return.
*/
SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
ANNOTATE_NOENDBR
- jmp ftrace_epilogue
+ RET

/* Swap the flags with orig_rax */
1: movq MCOUNT_REG_SIZE(%rsp), %rdi
@@ -280,7 +271,7 @@ SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
/* Restore flags */
popfq
UNWIND_HINT_FUNC
- jmp ftrace_epilogue
+ RET

SYM_FUNC_END(ftrace_regs_caller)
STACK_FRAME_NON_STANDARD_FP(ftrace_regs_caller)