linux-kernel - [tip: x86/urgent] x86/ftrace: Remove ftrace

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Message-ID: <166627907851.401.17695370739230342384.tip-bot2@tip-bot2>
Date:   Thu, 20 Oct 2022 15:17:58 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/ftrace: Remove ftrace_epilogue()

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

Commit-ID:     b5f1fc3184405ab955db1b86d41d8b744d07c12d
Gitweb:        https://git.kernel.org/tip/b5f1fc3184405ab955db1b86d41d8b744d07c12d
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 15 Sep 2022 13:11:35 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 20 Oct 2022 17:10:27 +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@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20220915111148.719080593@infradead.org
Signed-off-by: Peter Zijlstra <peterz@...radead.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)