linux-kernel - Re: [for-linus][PATCH 1/3] x86/ftrace: Have ftrace trampolines turn read-only at the end of system boot up

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Date:   Mon, 18 May 2020 09:56:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, stable@...r.kernel.org
Subject: Re: [for-linus][PATCH 1/3] x86/ftrace: Have ftrace trampolines turn
 read-only at the end of system boot up

On Thu, May 14, 2020 at 08:58:18AM -0400, Steven Rostedt wrote:
> +			start_offset = (unsigned long)ftrace_caller;
> +			end_offset = (unsigned long)ftrace_epilogue;


---
Subject: x86/ftrace: Fix compile error

When building x86-64 kernels, my compiler is sad about a missing symbol.

Fixes: 59566b0b622e ("x86/ftrace: Have ftrace trampolines turn read-only at the end of system boot up")
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/kernel/ftrace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index f8917a6f25b7..1cf7d69402e2 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -286,6 +286,7 @@ extern void ftrace_regs_caller_ret(void);
 extern void ftrace_caller_end(void);
 extern void ftrace_caller_op_ptr(void);
 extern void ftrace_regs_caller_op_ptr(void);
+extern void ftrace_epilogue(void);
 
 /* movq function_trace_op(%rip), %rdx */
 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */