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Date: Mon, 10 Dec 2007 10:10:01 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Sam Ravnborg <sam@ravnborg.org>, akpm@linux-foundation.org,
       lkml <linux-kernel@vger.kernel.org>,
       Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
       davem@davemloft.net, hskinnemoen@atmel.com
Subject: Re: [PATCH 1/2] Kprobes: Indicate kretprobe support in
	arch/<arch>/Kconfig - updated
Message-ID: <20071210151001.GD2082@Krystal>
References: <20071210095221.GA19425@in.ibm.com> <20071210101307.GA14359@uranus.ravnborg.org> <20071210113249.GC8437@in.ibm.com>
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* Ananth N Mavinakayanahalli (ananth@in.ibm.com) wrote:
> On Mon, Dec 10, 2007 at 11:13:07AM +0100, Sam Ravnborg wrote:
> > On Mon, Dec 10, 2007 at 03:22:22PM +0530, Ananth N Mavinakayanahalli wrote:
> > > From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> > > 
> > > This patch adds CONFIG_HAVE_KRETPROBES to the arch/<arch>/Kconfig file
> > > for relevant architectures with kprobes support. This facilitates easy
> > > handling of in-kernel modules (like samples/kprobes/kretprobe_example.c)
> > > that depend on kretprobes being present in the kernel.
> > > 
> > > This patch depends on Mathieu Desnoyers' "Instrumentation menu removal"
> > > patchset (http://marc.info/?l=linux-kernel&m=119496432229633&w=2)
> > > 
> > > Updated to apply on 2.6.24-rc4-mm1.
> > > 
> > > Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> > > ---
> > >  arch/avr32/Kconfig            |    5 +++++
> > >  arch/ia64/Kconfig             |    5 +++++
> > >  arch/powerpc/Kconfig          |    5 +++++
> > >  arch/s390/Kconfig             |    5 +++++
> > >  arch/sparc64/Kconfig          |    5 +++++
> > >  arch/x86/Kconfig              |    5 +++++
> > >  include/asm-ia64/kprobes.h    |    1 -
> > >  include/asm-powerpc/kprobes.h |    1 -
> > >  include/asm-s390/kprobes.h    |    1 -
> > >  include/asm-x86/kprobes_32.h  |    1 -
> > >  include/asm-x86/kprobes_64.h  |    1 -
> > >  include/linux/kprobes.h       |    6 +++---
> > >  kernel/kprobes.c              |    8 +++-----
> > >  13 files changed, 36 insertions(+), 13 deletions(-)
> > > 
> > > Index: linux-2.6.24-rc4/arch/avr32/Kconfig
> > > ===================================================================
> > > --- linux-2.6.24-rc4.orig/arch/avr32/Kconfig
> > > +++ linux-2.6.24-rc4/arch/avr32/Kconfig
> > > @@ -66,6 +66,11 @@ config GENERIC_BUG
> > >  	def_bool y
> > >  	depends on BUG
> > >  
> > > +config HAVE_KRETPROBES
> > > +	bool
> > > +	depends on HAVE_KPROBES
> > > +	default n
> > > +
> > 
> > The symbol HAVE_KRETPROBES should be defined in the common file - so
> > the only thing you have to do is a single line:
> >  config AVR32
> > +	select HAVE_KRETPROBES
> > 
> > 
> > Much more dense than defining the symbols once for each arch.
> 
> Agreed. Updated patch below.
> 
> From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> 
> This patch adds CONFIG_HAVE_KRETPROBES to the arch/<arch>/Kconfig file
> for relevant architectures with kprobes support. This facilitates easy
> handling of in-kernel modules (like samples/kprobes/kretprobe_example.c)
> that depend on kretprobes being present in the kernel.
> 
> This patch depends on Mathieu Desnoyers' "Instrumentation menu removal"
> patchset (http://marc.info/?l=linux-kernel&m=119496432229633&w=2)
> 
> Updated to apply on 2.6.24-rc4-mm1. Thanks to Sam Ravnborg for helping
> make the patch more lean.
> 
> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> ---
>  arch/Kconfig                  |    4 ++++
>  arch/ia64/Kconfig             |    1 +
>  arch/powerpc/Kconfig          |    1 +
>  arch/s390/Kconfig             |    1 +
>  arch/x86/Kconfig              |    1 +
>  include/asm-ia64/kprobes.h    |    1 -
>  include/asm-powerpc/kprobes.h |    1 -
>  include/asm-x86/kprobes_32.h  |    1 -
>  include/asm-x86/kprobes_64.h  |    1 -
>  include/linux/kprobes.h       |    6 +++---
>  kernel/kprobes.c              |    8 +++-----
>  11 files changed, 14 insertions(+), 12 deletions(-)
> 
> Index: linux-2.6.24-rc4/arch/Kconfig
> ===================================================================
> --- linux-2.6.24-rc4.orig/arch/Kconfig
> +++ linux-2.6.24-rc4/arch/Kconfig
> @@ -29,3 +29,7 @@ config KPROBES
>  
>  config HAVE_KPROBES
>  	def_bool n
> +
> +config HAVE_KRETPROBES
> +	def_bool n
> +	depends on HAVE_KPROBES
> Index: linux-2.6.24-rc4/arch/ia64/Kconfig
> ===================================================================
> --- linux-2.6.24-rc4.orig/arch/ia64/Kconfig
> +++ linux-2.6.24-rc4/arch/ia64/Kconfig
> @@ -17,6 +17,7 @@ config IA64
>  	select ARCH_SUPPORTS_MSI
>  	select HAVE_OPROFILE
>  	select HAVE_KPROBES
> +	select HAVE_KRETPROBES
>  	default y
>  	help
>  	  The Itanium Processor Family is Intel's 64-bit successor to
> Index: linux-2.6.24-rc4/arch/powerpc/Kconfig
> ===================================================================
> --- linux-2.6.24-rc4.orig/arch/powerpc/Kconfig
> +++ linux-2.6.24-rc4/arch/powerpc/Kconfig
> @@ -81,6 +81,7 @@ config PPC
>  	default y
>  	select HAVE_OPROFILE
>  	select HAVE_KPROBES
> +	select HAVE_KRETPROBES
>  
>  config EARLY_PRINTK
>  	bool
> Index: linux-2.6.24-rc4/arch/s390/Kconfig
> ===================================================================
> --- linux-2.6.24-rc4.orig/arch/s390/Kconfig
> +++ linux-2.6.24-rc4/arch/s390/Kconfig
> @@ -53,6 +53,7 @@ config S390
>  	def_bool y
>  	select HAVE_OPROFILE
>  	select HAVE_KPROBES
> +	select HAVE_KRETPROBES
>  
>  source "init/Kconfig"
>  
> Index: linux-2.6.24-rc4/arch/x86/Kconfig
> ===================================================================
> --- linux-2.6.24-rc4.orig/arch/x86/Kconfig
> +++ linux-2.6.24-rc4/arch/x86/Kconfig
> @@ -20,6 +20,7 @@ config X86
>  	def_bool y
>  	select HAVE_OPROFILE
>  	select HAVE_KPROBES
> +	select HAVE_KRETPROBES
>  
>  config GENERIC_TIME
>  	def_bool y
> Index: linux-2.6.24-rc4/include/asm-ia64/kprobes.h
> ===================================================================
> --- linux-2.6.24-rc4.orig/include/asm-ia64/kprobes.h
> +++ linux-2.6.24-rc4/include/asm-ia64/kprobes.h
> @@ -82,7 +82,6 @@ struct kprobe_ctlblk {
>  	struct prev_kprobe prev_kprobe[ARCH_PREV_KPROBE_SZ];
>  };
>  
> -#define ARCH_SUPPORTS_KRETPROBES
>  #define kretprobe_blacklist_size 0
>  
>  #define SLOT0_OPCODE_SHIFT	(37)
> Index: linux-2.6.24-rc4/include/asm-powerpc/kprobes.h
> ===================================================================
> --- linux-2.6.24-rc4.orig/include/asm-powerpc/kprobes.h
> +++ linux-2.6.24-rc4/include/asm-powerpc/kprobes.h
> @@ -80,7 +80,6 @@ typedef unsigned int kprobe_opcode_t;
>  #define is_trap(instr)	(IS_TW(instr) || IS_TWI(instr))
>  #endif
>  
> -#define ARCH_SUPPORTS_KRETPROBES
>  #define flush_insn_slot(p)	do { } while (0)
>  #define kretprobe_blacklist_size 0
>  
> Index: linux-2.6.24-rc4/include/asm-x86/kprobes_32.h
> ===================================================================
> --- linux-2.6.24-rc4.orig/include/asm-x86/kprobes_32.h
> +++ linux-2.6.24-rc4/include/asm-x86/kprobes_32.h
> @@ -42,7 +42,6 @@ typedef u8 kprobe_opcode_t;
>  	? (MAX_STACK_SIZE) \
>  	: (((unsigned long)current_thread_info()) + THREAD_SIZE - (ADDR)))
>  
> -#define ARCH_SUPPORTS_KRETPROBES
>  #define flush_insn_slot(p)	do { } while (0)
>  
>  extern const int kretprobe_blacklist_size;
> Index: linux-2.6.24-rc4/include/asm-x86/kprobes_64.h
> ===================================================================
> --- linux-2.6.24-rc4.orig/include/asm-x86/kprobes_64.h
> +++ linux-2.6.24-rc4/include/asm-x86/kprobes_64.h
> @@ -41,7 +41,6 @@ typedef u8 kprobe_opcode_t;
>  	? (MAX_STACK_SIZE) \
>  	: (((unsigned long)current_thread_info()) + THREAD_SIZE - (ADDR)))
>  
> -#define ARCH_SUPPORTS_KRETPROBES
>  extern const int kretprobe_blacklist_size;
>  
>  void kretprobe_trampoline(void);
> Index: linux-2.6.24-rc4/include/linux/kprobes.h
> ===================================================================
> --- linux-2.6.24-rc4.orig/include/linux/kprobes.h
> +++ linux-2.6.24-rc4/include/linux/kprobes.h
> @@ -125,11 +125,11 @@ struct jprobe {
>  DECLARE_PER_CPU(struct kprobe *, current_kprobe);
>  DECLARE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
>  
> -#ifdef ARCH_SUPPORTS_KRETPROBES
> +#ifdef CONFIG_HAVE_KRETPROBES

Hi Ananth,

I just want to point out a detail: if someone sets CONFIG_KPROBES to n,
the CONFIG_HAVE_KPROBES is still y, and so is CONFIG_HAVE_KRETPROBES.
However, I doubt that you want to activate this code in this case ?
The code paths are OK because they are nested into CONFIG_KPROBES
ifdefs (or not built due to dependency on CONFIG_KPROBES in the
Makfile), but if one wants to use CONFIG_HAVE_KRETPROBE for something
else (Makefile), then it could become a problem.

Could we add a menu entry CONFIG_KRETPROBES that depends on
CONFIG_HAVE_KRETPROBES and CONFIG_KPROBES, and also remove the
CONFIG_HAVE_KPROBES dependency for the CONFIG_HAVE_KRETPROBE option ?
This way, we would have much more flexibility (like specifiying if we
want CONFIG_KRETPROBES to be default y or default n...)

Mathieu

>  extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
>  				   struct pt_regs *regs);
>  extern int arch_trampoline_kprobe(struct kprobe *p);
> -#else /* ARCH_SUPPORTS_KRETPROBES */
> +#else /* CONFIG_HAVE_KRETPROBES */
>  static inline void arch_prepare_kretprobe(struct kretprobe *rp,
>  					struct pt_regs *regs)
>  {
> @@ -138,7 +138,7 @@ static inline int arch_trampoline_kprobe
>  {
>  	return 0;
>  }
> -#endif /* ARCH_SUPPORTS_KRETPROBES */
> +#endif /* CONFIG_HAVE_KRETPROBES */
>  /*
>   * Function-return probe -
>   * Note:
> Index: linux-2.6.24-rc4/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.24-rc4.orig/kernel/kprobes.c
> +++ linux-2.6.24-rc4/kernel/kprobes.c
> @@ -678,8 +678,7 @@ void __kprobes unregister_jprobe(struct 
>  	unregister_kprobe(&jp->kp);
>  }
>  
> -#ifdef ARCH_SUPPORTS_KRETPROBES
> -
> +#ifdef CONFIG_HAVE_KRETPROBES
>  /*
>   * This kprobe pre_handler is registered with every kretprobe. When probe
>   * hits it will set up the return probe.
> @@ -762,7 +761,7 @@ int __kprobes register_kretprobe(struct 
>  	return ret;
>  }
>  
> -#else /* ARCH_SUPPORTS_KRETPROBES */
> +#else /* CONFIG_HAVE_KRETPROBES */
>  
>  int __kprobes register_kretprobe(struct kretprobe *rp)
>  {
> @@ -774,8 +773,7 @@ static int __kprobes pre_handler_kretpro
>  {
>  	return 0;
>  }
> -
> -#endif /* ARCH_SUPPORTS_KRETPROBES */
> +#endif /* CONFIG_HAVE_KRETPROBES */
>  
>  void __kprobes unregister_kretprobe(struct kretprobe *rp)
>  {

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68