linux-kernel - Re: [PATCH] ftrace,kcfi: Separate ftrace_stub() and ftrace_stub

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Message-ID: <Y06d5X39EmKVamLN@hirez.programming.kicks-ass.net>
Date:   Tue, 18 Oct 2022 14:36:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>
Cc:     Kees Cook <keescook@...omium.org>,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: Re: [PATCH] ftrace,kcfi: Separate ftrace_stub() and
 ftrace_stub_graph()

On Tue, Oct 18, 2022 at 02:35:16PM +0200, Peter Zijlstra wrote:
> 
> Different function signatures means they needs to be different
> functions; otherwise CFI gets upset.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
> 
> Notable; this patch depends on eac828eaef29 ("x86/ftrace: Remove
> ftrace_epilogue()") which can be cleanly picked on top of -rc1.
> 
> Since kCFI is upstream this should go into some /urgent tree.

Combined (eac828eaef29 + this patch) generate a conflict against
tip/x86/core. Resolution looks like:

diff --cc arch/x86/kernel/ftrace_64.S
index 2a4be92fd144,6a7e6d666a12..000000000000
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@@ -4,7 -4,7 +4,8 @@@
   */
  
  #include <linux/linkage.h>
 +#include <linux/cfi_types.h>
+ #include <asm/asm-offsets.h>
  #include <asm/ptrace.h>
  #include <asm/ftrace.h>
  #include <asm/export.h>
@@@ -130,14 -130,6 +131,16 @@@
  
  	.endm
  
 +SYM_TYPED_FUNC_START(ftrace_stub)
++	CALL_DEPTH_ACCOUNT
 +	RET
 +SYM_FUNC_END(ftrace_stub)
 +
 +SYM_TYPED_FUNC_START(ftrace_stub_graph)
++	CALL_DEPTH_ACCOUNT
 +	RET
 +SYM_FUNC_END(ftrace_stub_graph)
 +
  #ifdef CONFIG_DYNAMIC_FTRACE
  
  SYM_FUNC_START(__fentry__)
@@@ -284,8 -305,13 +311,10 @@@ STACK_FRAME_NON_STANDARD_FP(ftrace_regs
  #else /* ! CONFIG_DYNAMIC_FTRACE */
  
  SYM_FUNC_START(__fentry__)
+ 	CALL_DEPTH_ACCOUNT
+ 
  	cmpq $ftrace_stub, ftrace_trace_function
  	jnz trace
 -
 -SYM_INNER_LABEL(ftrace_stub, SYM_L_GLOBAL)
 -	ENDBR
  	RET
  
  trace: