linux-kernel - Re: [PATCH 1/1] fentry: x86, cleanup function

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Date:	Tue, 20 Oct 2015 15:02:26 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 1/1] fentry: x86, cleanup function_hook uses

On Tue,  6 Oct 2015 14:40:21 +0200
Jiri Slaby <jslaby@...e.cz> wrote:

> Let's define fentry_hook depending on CC_USING_FENTRY and use that
> macro all over. This saves some #ifdef's here and there.
> 
> We do not use the old macro function_hook since it is too generic.
> Hence we introduce fentry_hook which corresponds to what it is.

Actually, I think I like function_hook better that fentry_hook, because
mcount is not an fentry.

What else do you think could be used as "function_hook"?

-- Steve


> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: <x86@...nel.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> ---
>  arch/x86/include/asm/fentry.h    | 14 ++++++++++++++
>  arch/x86/include/asm/ftrace.h    | 11 ++++-------
>  arch/x86/kernel/mcount_64.S      | 15 +++++----------
>  arch/x86/kernel/x8664_ksyms_64.c |  8 ++------
>  4 files changed, 25 insertions(+), 23 deletions(-)
>  create mode 100644 arch/x86/include/asm/fentry.h
> 
> diff --git a/arch/x86/include/asm/fentry.h b/arch/x86/include/asm/fentry.h
> new file mode 100644
> index 000000000000..febe8d272f0f
> --- /dev/null
> +++ b/arch/x86/include/asm/fentry.h
> @@ -0,0 +1,14 @@
> +#ifndef ASM_FENTRY_H
> +#define ASM_FENTRY_H
> +
> +#ifdef CC_USING_FENTRY
> +# define fentry_hook	__fentry__
> +#else
> +# define fentry_hook	mcount
> +#endif
> +
> +#ifndef __ASSEMBLY__
> +extern void fentry_hook(void);
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* ASM_FENTRY_H */
> diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
> index 24938852db30..dc235b3659da 100644
> --- a/arch/x86/include/asm/ftrace.h
> +++ b/arch/x86/include/asm/ftrace.h
> @@ -2,11 +2,10 @@
>  #define _ASM_X86_FTRACE_H
>  
>  #ifdef CONFIG_FUNCTION_TRACER
> -#ifdef CC_USING_FENTRY
> -# define MCOUNT_ADDR		((unsigned long)(__fentry__))
> -#else
> -# define MCOUNT_ADDR		((unsigned long)(mcount))
> -#endif
> +
> +#include <asm/fentry.h>
> +
> +#define MCOUNT_ADDR		((unsigned long)(fentry_hook))
>  #define MCOUNT_INSN_SIZE	5 /* sizeof mcount call */
>  
>  #ifdef CONFIG_DYNAMIC_FTRACE
> @@ -14,9 +13,7 @@
>  #endif
>  
>  #ifndef __ASSEMBLY__
> -extern void mcount(void);
>  extern atomic_t modifying_ftrace_code;
> -extern void __fentry__(void);
>  
>  static inline unsigned long ftrace_call_adjust(unsigned long addr)
>  {
> diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S
> index 94ea120fa21f..ac8d5296d6ec 100644
> --- a/arch/x86/kernel/mcount_64.S
> +++ b/arch/x86/kernel/mcount_64.S
> @@ -6,6 +6,7 @@
>  
>  #include <linux/linkage.h>
>  #include <asm/ptrace.h>
> +#include <asm/fentry.h>
>  #include <asm/ftrace.h>
>  
>  
> @@ -15,12 +16,6 @@
>  
>  #ifdef CONFIG_FUNCTION_TRACER
>  
> -#ifdef CC_USING_FENTRY
> -# define function_hook	__fentry__
> -#else
> -# define function_hook	mcount
> -#endif
> -
>  /* All cases save the original rbp (8 bytes) */
>  #ifdef CONFIG_FRAME_POINTER
>  # ifdef CC_USING_FENTRY
> @@ -147,9 +142,9 @@
>  
>  #ifdef CONFIG_DYNAMIC_FTRACE
>  
> -ENTRY(function_hook)
> +ENTRY(fentry_hook)
>  	retq
> -END(function_hook)
> +END(fentry_hook)
>  
>  ENTRY(ftrace_caller)
>  	/* save_mcount_regs fills in first two parameters */
> @@ -258,7 +253,7 @@ END(ftrace_regs_caller)
>  
>  #else /* ! CONFIG_DYNAMIC_FTRACE */
>  
> -ENTRY(function_hook)
> +ENTRY(fentry_hook)
>  	cmpq $ftrace_stub, ftrace_trace_function
>  	jnz trace
>  
> @@ -283,7 +278,7 @@ trace:
>  	restore_mcount_regs
>  
>  	jmp fgraph_trace
> -END(function_hook)
> +END(fentry_hook)
>  #endif /* CONFIG_DYNAMIC_FTRACE */
>  #endif /* CONFIG_FUNCTION_TRACER */
>  
> diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
> index a0695be19864..5607abc110c7 100644
> --- a/arch/x86/kernel/x8664_ksyms_64.c
> +++ b/arch/x86/kernel/x8664_ksyms_64.c
> @@ -10,15 +10,11 @@
>  #include <asm/pgtable.h>
>  #include <asm/uaccess.h>
>  #include <asm/desc.h>
> -#include <asm/ftrace.h>
> +#include <asm/fentry.h>
>  
>  #ifdef CONFIG_FUNCTION_TRACER
>  /* mcount and __fentry__ are defined in assembly */
> -#ifdef CC_USING_FENTRY
> -EXPORT_SYMBOL(__fentry__);
> -#else
> -EXPORT_SYMBOL(mcount);
> -#endif
> +EXPORT_SYMBOL(fentry_hook);
>  #endif
>  
>  EXPORT_SYMBOL(__get_user_1);

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