linux-kernel - Re: [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET

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Date:   Tue, 31 Mar 2020 21:58:41 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, x86@...nel.org, mhiramat@...nel.org,
        mbenes@...e.cz
Subject: Re: [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET

On Tue, Mar 31, 2020 at 11:31:36AM -0400, Steven Rostedt wrote:

> Can you send this change as a separate patch as it has nothing to do with
> this current change, and is a clean up patch that stands on its own.

I also found this.. should I write it up?

---
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index 369e61faacfe..0f108096f278 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -23,7 +23,7 @@
 #endif /* CONFIG_FRAME_POINTER */

 /* Size of stack used to save mcount regs in save_mcount_regs */
-#define MCOUNT_REG_SIZE		(SS+8 + MCOUNT_FRAME_SIZE)
+#define MCOUNT_REG_SIZE		(SIZEOF_PTREGS + MCOUNT_FRAME_SIZE)

 /*
  * gcc -pg option adds a call to 'mcount' in most functions.
@@ -77,7 +77,7 @@
 	/*
 	 * We add enough stack to save all regs.
 	 */
-	subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp
+	subq $(SIZEOF_PTREGS), %rsp
 	movq %rax, RAX(%rsp)
 	movq %rcx, RCX(%rsp)
 	movq %rdx, RDX(%rsp)