[GIT PULL] hw_breakpoints updates

[GIT PULL] hw_breakpoints updates

[Frederic Weisbecker]

Ingo,

Please pull the perf/breakpoint-v2 branch that can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing.git
	perf/breakpoint-v2

This makes the breakpoints config optable and thus let users
be able to build x86 and sh without perf.

In that takes: more acks added and rebase against latest perf/core
and upstream changes.

Thanks,
	Frederic
---

Frederic Weisbecker (6):
      hw_breakpoints: Split hardware breakpoints config
      hw_breakpoints: Migrate breakpoint conditional build under new config
      x86: Allow the user not to build hw_breakpoints
      hw_breakpoints: Breakpoints arch ability don't need perf events
      hw_breakpoints: Only force perf events if breakpoints are selected
      hw_breakpoints: Drop remaining misplaced dependency on perf


 arch/Kconfig                             |    1 -
 arch/arm/Kconfig                         |    2 +-
 arch/arm/include/asm/hw_breakpoint.h     |    4 +-
 arch/arm/include/asm/processor.h         |    2 +-
 arch/arm/kernel/Makefile                 |    2 +-
 arch/arm/kernel/entry-header.S           |    2 +-
 arch/arm/kernel/ptrace.c                 |    4 +-
 arch/powerpc/Kconfig                     |    2 +-
 arch/powerpc/include/asm/cputable.h      |    4 +-
 arch/powerpc/include/asm/hw_breakpoint.h |    6 ++--
 arch/powerpc/include/asm/processor.h     |    4 +-
 arch/powerpc/kernel/Makefile             |    2 +-
 arch/powerpc/kernel/process.c            |   18 ++++++++--------
 arch/powerpc/kernel/ptrace.c             |   13 ++++++-----
 arch/powerpc/lib/Makefile                |    2 +-
 arch/sh/Kconfig                          |    2 +-
 arch/sh/kernel/Makefile                  |    2 +-
 arch/sh/kernel/cpu/sh4a/Makefile         |    2 +-
 arch/x86/Kconfig                         |    3 +-
 arch/x86/include/asm/debugreg.h          |   33 ++++++++++++++++++++++++++++-
 arch/x86/kernel/Makefile                 |    3 +-
 arch/x86/kernel/process.c                |    1 +
 arch/x86/kernel/ptrace.c                 |   17 +++++++++++++++
 include/linux/hw_breakpoint.h            |    6 ++--
 include/linux/perf_event.h               |    4 +-
 include/linux/ptrace.h                   |    6 ++--
 include/linux/sched.h                    |    2 +-
 init/Kconfig                             |   11 ++++++++++
 kernel/events/Makefile                   |    2 +-
 kernel/events/core.c                     |    4 +-
 kernel/ptrace.c                          |    4 +-
 samples/Kconfig                          |    2 +-
 32 files changed, 115 insertions(+), 57 deletions(-)

[PATCH 1/6] hw_breakpoints: Split hardware breakpoints config

[Frederic Weisbecker]

The hardware breakpoint config is only made of an ability. An
arch that support this feature selects HAVE_HW_BREAKPOINT. If so,
the feature is definetly built-in, the user can't decide to turn
it off. As hw_breakpoints depend on perf, it also makes perf
a mandatory feature. The whole is quite a piece of code and
may not be desired on some embedded systems.

In order to prepare to make this optable by the user, split the
config into the more traditional couple (ability, user choice) by
providing a new HW_BREAKPOINT config. It is default on and depends
on CONFIG_EXPERT because breakpoint ptrace requests are part of the
usual user ABI. The user must know what he's doing before turning
that off.

For now, only the archs that already implemented a conditional
HAVE_HW_BREAKPOINT can turn off HW_BREAKPOINT. x86 and sh have it
always selected because they need more background work to support
this new modularity.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
---
 arch/sh/Kconfig  |    1 +
 arch/x86/Kconfig |    1 +
 init/Kconfig     |   10 ++++++++++
 3 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index f03338c..0a59a82 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -44,6 +44,7 @@ config SUPERH32
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_ARCH_KGDB
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select ARCH_HIBERNATION_POSSIBLE if MMU
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index da34972..ef3effd 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -53,6 +53,7 @@ config X86
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_LZO
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI
diff --git a/init/Kconfig b/init/Kconfig
index 412c21b..9eec0df 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -923,6 +923,16 @@ menuconfig EXPERT
           environments which can tolerate a "non-standard" kernel.
           Only use this if you really know what you are doing.
 
+config HW_BREAKPOINT
+	bool "Hardware breakpoints" if EXPERT
+	depends on HAVE_HW_BREAKPOINT
+	default y
+	help
+	  Hardware breakpoints are a feature implemented by most CPUs
+	  to trigger an event when an instruction or data fetch
+	  matches a given pattern. This is typically used by ptrace
+	  and perf events.
+
 config UID16
 	bool "Enable 16-bit UID system calls" if EXPERT
 	depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
-- 
1.7.5.4

[PATCH 2/6] hw_breakpoints: Migrate breakpoint conditional build under new config

[Frederic Weisbecker]

Migrate conditional hw_breakpoint code compilation under
the new config to prepare for letting the user chose whether
or not to build this feature

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Prasad <prasad@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 arch/arm/include/asm/hw_breakpoint.h     |    4 ++--
 arch/arm/include/asm/processor.h         |    2 +-
 arch/arm/kernel/Makefile                 |    2 +-
 arch/arm/kernel/entry-header.S           |    2 +-
 arch/arm/kernel/ptrace.c                 |    4 ++--
 arch/powerpc/include/asm/cputable.h      |    4 ++--
 arch/powerpc/include/asm/hw_breakpoint.h |    6 +++---
 arch/powerpc/include/asm/processor.h     |    4 ++--
 arch/powerpc/kernel/Makefile             |    2 +-
 arch/powerpc/kernel/process.c            |   18 +++++++++---------
 arch/powerpc/kernel/ptrace.c             |   13 +++++++------
 arch/powerpc/lib/Makefile                |    2 +-
 arch/sh/kernel/Makefile                  |    2 +-
 arch/sh/kernel/cpu/sh4a/Makefile         |    2 +-
 include/linux/hw_breakpoint.h            |    6 +++---
 include/linux/perf_event.h               |    4 ++--
 include/linux/ptrace.h                   |    6 +++---
 include/linux/sched.h                    |    2 +-
 kernel/events/Makefile                   |    2 +-
 kernel/events/core.c                     |    4 ++--
 kernel/ptrace.c                          |    4 ++--
 samples/Kconfig                          |    2 +-
 22 files changed, 49 insertions(+), 48 deletions(-)

diff --git a/arch/arm/include/asm/hw_breakpoint.h b/arch/arm/include/asm/hw_breakpoint.h
index f389b27..fc6ba18 100644
--- a/arch/arm/include/asm/hw_breakpoint.h
+++ b/arch/arm/include/asm/hw_breakpoint.h
@@ -5,7 +5,7 @@
 
 struct task_struct;
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 
 struct arch_hw_breakpoint_ctrl {
 		u32 __reserved	: 9,
@@ -128,6 +128,6 @@ int hw_breakpoint_slots(int type);
 #else
 static inline void clear_ptrace_hw_breakpoint(struct task_struct *tsk) {}
 
-#endif	/* CONFIG_HAVE_HW_BREAKPOINT */
+#endif	/* CONFIG_HW_BREAKPOINT */
 #endif	/* __KERNEL__ */
 #endif	/* _ARM_HW_BREAKPOINT_H */
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index b2d9df5..b86d135 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -30,7 +30,7 @@
 #endif
 
 struct debug_info {
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 	struct perf_event	*hbp[ARM_MAX_HBP_SLOTS];
 #endif
 };
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index a5b31af..9aa1cfd 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -48,7 +48,7 @@ obj-$(CONFIG_OF)		+= devtree.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_SWP_EMULATE)	+= swp_emulate.o
 CFLAGS_swp_emulate.o		:= -Wa,-march=armv7-a
-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
+obj-$(CONFIG_HW_BREAKPOINT)	+= hw_breakpoint.o
 
 obj-$(CONFIG_CRUNCH)		+= crunch.o crunch-bits.o
 AFLAGS_crunch-bits.o		:= -Wa,-mcpu=ep9312
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 051166c..fbc7cc9 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -171,7 +171,7 @@
 	@ we can access the debug registers safely.
 	@
 	.macro	debug_entry, fsr
-#if defined(CONFIG_HAVE_HW_BREAKPOINT) && defined(CONFIG_PREEMPT)
+#if defined(CONFIG_HW_BREAKPOINT) && defined(CONFIG_PREEMPT)
 	ldr	r4, =0x40f		@ mask out fsr.fs
 	and	r5, r4, \fsr
 	cmp	r5, #2			@ debug exception
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 5c19961..e3b1fa5 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -367,7 +367,7 @@ static int ptrace_setcrunchregs(struct task_struct *tsk, void __user *ufp)
 }
 #endif
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 /*
  * Convert a virtual register number into an index for a thread_info
  * breakpoint array. Breakpoints are identified using positive numbers
@@ -896,7 +896,7 @@ long arch_ptrace(struct task_struct *child, long request,
 			break;
 #endif
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 		case PTRACE_GETHBPREGS:
 			if (ptrace_get_breakpoints(child) < 0)
 				return -ESRCH;
diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index c0d842c..d99d7c6 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -539,9 +539,9 @@ static inline int cpu_has_feature(unsigned long feature)
 		& feature);
 }
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 #define HBP_NUM 1
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h
index 80fd4d2..5a6c14e 100644
--- a/arch/powerpc/include/asm/hw_breakpoint.h
+++ b/arch/powerpc/include/asm/hw_breakpoint.h
@@ -24,7 +24,7 @@
 #define _PPC_BOOK3S_64_HW_BREAKPOINT_H
 
 #ifdef	__KERNEL__
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 
 struct arch_hw_breakpoint {
 	bool		extraneous_interrupt;
@@ -65,10 +65,10 @@ static inline void hw_breakpoint_disable(void)
 }
 extern void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs);
 
-#else	/* CONFIG_HAVE_HW_BREAKPOINT */
+#else	/* CONFIG_HW_BREAKPOINT */
 static inline void hw_breakpoint_disable(void) { }
 static inline void thread_change_pc(struct task_struct *tsk,
 					struct pt_regs *regs) { }
-#endif	/* CONFIG_HAVE_HW_BREAKPOINT */
+#endif	/* CONFIG_HW_BREAKPOINT */
 #endif	/* __KERNEL__ */
 #endif	/* _PPC_BOOK3S_64_HW_BREAKPOINT_H */
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index d50c2b6..211c2ca 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -207,14 +207,14 @@ struct thread_struct {
 #ifdef CONFIG_PPC64
 	unsigned long	start_tb;	/* Start purr when proc switched in */
 	unsigned long	accum_tb;	/* Total accumilated purr for process */
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 	struct perf_event *ptrace_bps[HBP_NUM];
 	/*
 	 * Helps identify source of single-step exception and subsequent
 	 * hw-breakpoint enablement
 	 */
 	struct perf_event *last_hit_ubp;
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 #endif
 	unsigned long	dabr;		/* Data address breakpoint register */
 #ifdef CONFIG_ALTIVEC
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index e8b9818..2cca854 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -36,7 +36,7 @@ obj-y				:= cputable.o ptrace.o syscalls.o \
 obj-$(CONFIG_PPC64)		+= setup_64.o sys_ppc32.o \
 				   signal_64.o ptrace32.o \
 				   paca.o nvram_64.o firmware.o
-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
+obj-$(CONFIG_HW_BREAKPOINT)	+= hw_breakpoint.o
 obj-$(CONFIG_PPC_BOOK3S_64)	+= cpu_setup_ppc970.o cpu_setup_pa6t.o
 obj-$(CONFIG_PPC_BOOK3S_64)	+= cpu_setup_power7.o
 obj64-$(CONFIG_RELOCATABLE)	+= reloc_64.o
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 91e52df..e63fa89 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -353,7 +353,7 @@ static void switch_booke_debug_regs(struct thread_struct *new_thread)
 			prime_debug_regs(new_thread);
 }
 #else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
-#ifndef CONFIG_HAVE_HW_BREAKPOINT
+#ifndef CONFIG_HW_BREAKPOINT
 static void set_debug_reg_defaults(struct thread_struct *thread)
 {
 	if (thread->dabr) {
@@ -361,7 +361,7 @@ static void set_debug_reg_defaults(struct thread_struct *thread)
 		set_dabr(0);
 	}
 }
-#endif /* !CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* !CONFIG_HW_BREAKPOINT */
 #endif	/* CONFIG_PPC_ADV_DEBUG_REGS */
 
 int set_dabr(unsigned long dabr)
@@ -472,10 +472,10 @@ struct task_struct *__switch_to(struct task_struct *prev,
  * For PPC_BOOK3S_64, we use the hw-breakpoint interfaces that would
  * schedule DABR
  */
-#ifndef CONFIG_HAVE_HW_BREAKPOINT
+#ifndef CONFIG_HW_BREAKPOINT
 	if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr))
 		set_dabr(new->thread.dabr);
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 #endif
 
 
@@ -693,11 +693,11 @@ void flush_thread(void)
 {
 	discard_lazy_cpu_state();
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 	flush_ptrace_hw_breakpoint(current);
-#else /* CONFIG_HAVE_HW_BREAKPOINT */
+#else /* CONFIG_HW_BREAKPOINT */
 	set_debug_reg_defaults(&current->thread);
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 }
 
 void
@@ -715,9 +715,9 @@ void prepare_to_copy(struct task_struct *tsk)
 	flush_altivec_to_thread(current);
 	flush_vsx_to_thread(current);
 	flush_spe_to_thread(current);
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 	flush_ptrace_hw_breakpoint(tsk);
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 }
 
 /*
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 05b7dd2..dc36416 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -881,7 +881,7 @@ void user_disable_single_step(struct task_struct *task)
 	clear_tsk_thread_flag(task, TIF_SINGLESTEP);
 }
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 void ptrace_triggered(struct perf_event *bp,
 		      struct perf_sample_data *data, struct pt_regs *regs)
 {
@@ -897,17 +897,17 @@ void ptrace_triggered(struct perf_event *bp,
 	attr.disabled = true;
 	modify_user_hw_breakpoint(bp, &attr);
 }
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 
 int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
 			       unsigned long data)
 {
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 	int ret;
 	struct thread_struct *thread = &(task->thread);
 	struct perf_event *bp;
 	struct perf_event_attr attr;
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 
 	/* For ppc64 we support one DABR and no IABR's at the moment (ppc64).
 	 *  For embedded processors we support one DAC and no IAC's at the
@@ -936,7 +936,8 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
 	/* Ensure breakpoint translation bit is set */
 	if (data && !(data & DABR_TRANSLATION))
 		return -EIO;
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+
+#ifdef CONFIG_HW_BREAKPOINT
 	if (ptrace_get_breakpoints(task) < 0)
 		return -ESRCH;
 
@@ -982,7 +983,7 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
 
 	ptrace_put_breakpoints(task);
 
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 
 	/* Move contents to the DABR register */
 	task->thread.dabr = data;
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 166a6a0..515d044 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -19,7 +19,7 @@ obj-$(CONFIG_PPC64)	+= copypage_64.o copyuser_64.o \
 			   checksum_wrappers_64.o hweight_64.o
 obj-$(CONFIG_XMON)	+= sstep.o ldstfp.o
 obj-$(CONFIG_KPROBES)	+= sstep.o ldstfp.o
-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= sstep.o ldstfp.o
+obj-$(CONFIG_HW_BREAKPOINT)	+= sstep.o ldstfp.o
 
 ifeq ($(CONFIG_PPC64),y)
 obj-$(CONFIG_SMP)	+= locks.o
diff --git a/arch/sh/kernel/Makefile b/arch/sh/kernel/Makefile
index 77f7ae1..9d5075c 100644
--- a/arch/sh/kernel/Makefile
+++ b/arch/sh/kernel/Makefile
@@ -45,7 +45,7 @@ obj-$(CONFIG_HIBERNATION)	+= swsusp.o
 obj-$(CONFIG_DWARF_UNWINDER)	+= dwarf.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_callchain.o
 
-obj-$(CONFIG_HAVE_HW_BREAKPOINT)		+= hw_breakpoint.o
+obj-$(CONFIG_HW_BREAKPOINT)		+= hw_breakpoint.o
 obj-$(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST)	+= localtimer.o
 
 ccflags-y := -Werror
diff --git a/arch/sh/kernel/cpu/sh4a/Makefile b/arch/sh/kernel/cpu/sh4a/Makefile
index cc122b1..5bec639 100644
--- a/arch/sh/kernel/cpu/sh4a/Makefile
+++ b/arch/sh/kernel/cpu/sh4a/Makefile
@@ -46,4 +46,4 @@ obj-y					+= $(clock-y)
 obj-$(CONFIG_SMP)			+= $(smp-y)
 obj-$(CONFIG_GENERIC_GPIO)		+= $(pinmux-y)
 obj-$(CONFIG_PERF_EVENTS)		+= perf_event.o
-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= ubc.o
+obj-$(CONFIG_HW_BREAKPOINT)	+= ubc.o
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
index 6ae9c63..2b118e0 100644
--- a/include/linux/hw_breakpoint.h
+++ b/include/linux/hw_breakpoint.h
@@ -31,7 +31,7 @@ enum bp_type_idx {
 
 #include <linux/perf_event.h>
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 
 extern int __init init_hw_breakpoint(void);
 
@@ -111,7 +111,7 @@ static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
 	return &bp->hw.info;
 }
 
-#else /* !CONFIG_HAVE_HW_BREAKPOINT */
+#else /* !CONFIG_HW_BREAKPOINT */
 
 static inline int __init init_hw_breakpoint(void) { return 0; }
 
@@ -150,7 +150,7 @@ static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
 	return NULL;
 }
 
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 #endif /* __KERNEL__ */
 
 #endif /* _LINUX_HW_BREAKPOINT_H */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 3f2711c..9e432a9 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -492,7 +492,7 @@ struct perf_guest_info_callbacks {
 	unsigned long			(*get_guest_ip)(void);
 };
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 #include <asm/hw_breakpoint.h>
 #endif
 
@@ -565,7 +565,7 @@ struct hw_perf_event {
 		struct { /* software */
 			struct hrtimer	hrtimer;
 		};
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 		struct { /* breakpoint */
 			struct arch_hw_breakpoint	info;
 			struct list_head		bp_list;
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 9178d5c..9ff2641 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -190,7 +190,7 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
 		__ptrace_link(child, current->parent);
 	}
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 	atomic_set(&child->ptrace_bp_refcnt, 1);
 #endif
 }
@@ -354,12 +354,12 @@ extern int task_current_syscall(struct task_struct *target, long *callno,
 				unsigned long args[6], unsigned int maxargs,
 				unsigned long *sp, unsigned long *pc);
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 extern int ptrace_get_breakpoints(struct task_struct *tsk);
 extern void ptrace_put_breakpoints(struct task_struct *tsk);
 #else
 static inline void ptrace_put_breakpoints(struct task_struct *tsk) { }
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
 
 #endif /* __KERNEL */
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a837b20..3c05d7e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1558,7 +1558,7 @@ struct task_struct {
 		unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
 	} memcg_batch;
 #endif
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 	atomic_t ptrace_bp_refcnt;
 #endif
 };
diff --git a/kernel/events/Makefile b/kernel/events/Makefile
index 89e5e8a..922bd6e 100644
--- a/kernel/events/Makefile
+++ b/kernel/events/Makefile
@@ -3,4 +3,4 @@ CFLAGS_REMOVE_core.o = -pg
 endif
 
 obj-y := core.o ring_buffer.o
-obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
+obj-$(CONFIG_HW_BREAKPOINT) += hw_breakpoint.o
\ No newline at end of file
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0567e32..48b5f8f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5202,7 +5202,7 @@ static void perf_event_free_filter(struct perf_event *event)
 
 #endif /* CONFIG_EVENT_TRACING */
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 void perf_bp_event(struct perf_event *bp, void *data)
 {
 	struct perf_sample_data sample;
@@ -5796,7 +5796,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 
 	if (task) {
 		event->attach_state = PERF_ATTACH_TASK;
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 		/*
 		 * hw_breakpoint is a bit difficult here..
 		 */
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 2df1157..e283010 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -925,7 +925,7 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 }
 #endif	/* CONFIG_COMPAT */
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#ifdef CONFIG_HW_BREAKPOINT
 int ptrace_get_breakpoints(struct task_struct *tsk)
 {
 	if (atomic_inc_not_zero(&tsk->ptrace_bp_refcnt))
@@ -939,4 +939,4 @@ void ptrace_put_breakpoints(struct task_struct *tsk)
 	if (atomic_dec_and_test(&tsk->ptrace_bp_refcnt))
 		flush_ptrace_hw_breakpoint(tsk);
 }
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* CONFIG_HW_BREAKPOINT */
diff --git a/samples/Kconfig b/samples/Kconfig
index 96a7572..56b0320 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -40,7 +40,7 @@ config SAMPLE_KRETPROBES
 
 config SAMPLE_HW_BREAKPOINT
 	tristate "Build kernel hardware breakpoint examples -- loadable module only"
-	depends on HAVE_HW_BREAKPOINT && m
+	depends on HW_BREAKPOINT && m
 	help
 	  This builds kernel hardware breakpoint example modules.
 
-- 
1.7.5.4

[PATCH 3/6] x86: Allow the user not to build hw_breakpoints

[Frederic Weisbecker]

So that hw_breakpoints and perf can be not built on
specific embedded systems.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/Kconfig                |    3 +--
 arch/x86/include/asm/debugreg.h |   33 +++++++++++++++++++++++++++++++--
 arch/x86/kernel/Makefile        |    3 ++-
 arch/x86/kernel/process.c       |    1 +
 arch/x86/kernel/ptrace.c        |   17 +++++++++++++++++
 5 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ef3effd..d7a255d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -40,7 +40,7 @@ config X86
 	select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KVM
-	select HAVE_ARCH_KGDB
+	select HAVE_ARCH_KGDB if HW_BREAKPOINT
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_GENERIC_DMA_COHERENT if X86_32
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
@@ -53,7 +53,6 @@ config X86
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_LZO
 	select HAVE_HW_BREAKPOINT
-	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 078ad0c..c40d6d4 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -78,8 +78,6 @@
  */
 #ifdef __KERNEL__
 
-DECLARE_PER_CPU(unsigned long, cpu_dr7);
-
 static inline void hw_breakpoint_disable(void)
 {
 	/* Zero the control register for HW Breakpoint */
@@ -92,6 +90,10 @@ static inline void hw_breakpoint_disable(void)
 	set_debugreg(0UL, 3);
 }
 
+#ifdef CONFIG_HW_BREAKPOINT
+
+DECLARE_PER_CPU(unsigned long, cpu_dr7);
+
 static inline int hw_breakpoint_active(void)
 {
 	return __this_cpu_read(cpu_dr7) & DR_GLOBAL_ENABLE_MASK;
@@ -100,6 +102,33 @@ static inline int hw_breakpoint_active(void)
 extern void aout_dump_debugregs(struct user *dump);
 
 extern void hw_breakpoint_restore(void);
+#else
+static inline int hw_breakpoint_active(void)
+{
+	return 0;
+}
+
+static inline void hw_breakpoint_restore(void)
+{
+	set_debugreg(0UL, 0);
+	set_debugreg(0UL, 1);
+	set_debugreg(0UL, 2);
+	set_debugreg(0UL, 3);
+	set_debugreg(current->thread.debugreg6, 6);
+	set_debugreg(0UL, 7);
+}
+
+static inline void aout_dump_debugregs(struct user *dump)
+{
+	int i;
+
+	for (i = 0; i < 6; i++)
+		dump->u_debugreg[i] = 0;
+
+	dump->u_debugreg[6] = current->thread.debugreg6;
+	dump->u_debugreg[7] = 0;
+}
+#endif /* CONFIG_HW_BREAKPOINT */
 
 #endif	/* __KERNEL__ */
 
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 90b06d4..1134d15 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -46,7 +46,7 @@ obj-$(CONFIG_X86_64)	+= sys_x86_64.o x8664_ksyms_64.o
 obj-$(CONFIG_X86_64)	+= syscall_64.o vsyscall_64.o vread_tsc_64.o
 obj-y			+= bootflag.o e820.o
 obj-y			+= pci-dma.o quirks.o topology.o kdebugfs.o
-obj-y			+= alternative.o i8253.o pci-nommu.o hw_breakpoint.o
+obj-y			+= alternative.o i8253.o pci-nommu.o
 obj-y			+= tsc.o io_delay.o rtc.o
 obj-y			+= pci-iommu_table.o
 obj-y			+= resource.o
@@ -55,6 +55,7 @@ obj-y				+= trampoline.o trampoline_$(BITS).o
 obj-y				+= process.o
 obj-y				+= i387.o xsave.o
 obj-y				+= ptrace.o
+obj-$(CONFIG_HW_BREAKPOINT)	+= hw_breakpoint.o
 obj-$(CONFIG_X86_32)		+= tls.o
 obj-$(CONFIG_IA32_EMULATION)	+= tls.o
 obj-y				+= step.o
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index e1ba8cb..0989a18 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -22,6 +22,7 @@
 #include <asm/uaccess.h>
 #include <asm/i387.h>
 #include <asm/debugreg.h>
+#include <asm/kdebug.h>
 
 struct kmem_cache *task_xstate_cachep;
 EXPORT_SYMBOL_GPL(task_xstate_cachep);
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 8252879..6e619f2 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -528,6 +528,7 @@ static int genregs_set(struct task_struct *target,
 	return ret;
 }
 
+#ifdef CONFIG_HW_BREAKPOINT
 static void ptrace_triggered(struct perf_event *bp,
 			     struct perf_sample_data *data,
 			     struct pt_regs *regs)
@@ -778,6 +779,22 @@ ret_path:
 	return rc;
 }
 
+#else /* !CONFIG_HW_BREAKPOINT */
+
+static inline unsigned long
+ptrace_get_debugreg(struct task_struct *tsk, int n)
+{
+	return -ENOSYS;
+}
+
+static inline
+int ptrace_set_debugreg(struct task_struct *tsk, int n, unsigned long val)
+{
+	return -ENOSYS;
+}
+
+#endif /* CONFIG_HW_BREAKPOINT */
+
 /*
  * These access the current or another (stopped) task's io permission
  * bitmap for debugging or core dump.
-- 
1.7.5.4

[PATCH 4/6] hw_breakpoints: Breakpoints arch ability don't need perf events

[Frederic Weisbecker]

The breakpoint support ability in an arch is not related
to the fact perf events is built or not. HAVE_HW_BREAKPOINT
only shows an ability so this dependency makes no sense
anymore. Archs that select HAVE_HW_BREAKPOINT already
ensure that perf event is built.

Remove that dependency.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
---
 arch/Kconfig |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 26b0e23..341ac95 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -146,7 +146,6 @@ config HAVE_DMA_API_DEBUG
 
 config HAVE_HW_BREAKPOINT
 	bool
-	depends on PERF_EVENTS
 
 config HAVE_MIXED_BREAKPOINTS_REGS
 	bool
-- 
1.7.5.4

[PATCH 5/6] hw_breakpoints: Only force perf events if breakpoints are selected

[Frederic Weisbecker]

Previously, arch were forced to always build perf events if they
supported hw_breakpoints.

Now that the user can choose not to build hw_breakpoints, let
only force perf events if hw_breakpoints are selected.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
---
 arch/sh/Kconfig  |    1 -
 arch/x86/Kconfig |    1 -
 init/Kconfig     |    1 +
 3 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 0a59a82..7130d4b 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -46,7 +46,6 @@ config SUPERH32
 	select HAVE_HW_BREAKPOINT
 	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
-	select PERF_EVENTS
 	select ARCH_HIBERNATION_POSSIBLE if MMU
 	select SPARSE_IRQ
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d7a255d..67979f4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,7 +54,6 @@ config X86
 	select HAVE_KERNEL_LZO
 	select HAVE_HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
-	select PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI
 	select ANON_INODES
 	select HAVE_ARCH_KMEMCHECK
diff --git a/init/Kconfig b/init/Kconfig
index 9eec0df..3cf7855 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -926,6 +926,7 @@ menuconfig EXPERT
 config HW_BREAKPOINT
 	bool "Hardware breakpoints" if EXPERT
 	depends on HAVE_HW_BREAKPOINT
+	select PERF_EVENTS
 	default y
 	help
 	  Hardware breakpoints are a feature implemented by most CPUs
-- 
1.7.5.4

[PATCH 6/6] hw_breakpoints: Drop remaining misplaced dependency on perf

[Frederic Weisbecker]

Powerpc and Arm select breakpoint support ability only if
Perf is built. This is not necessary anymore now that we
enable perf once breakpoints support is selected.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
---
 arch/arm/Kconfig     |    2 +-
 arch/powerpc/Kconfig |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9adc278..0739521 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -24,7 +24,7 @@ config ARM
 	select HAVE_PERF_EVENTS
 	select PERF_USE_VMALLOC
 	select HAVE_REGS_AND_STACK_ACCESS_API
-	select HAVE_HW_BREAKPOINT if (PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7))
+	select HAVE_HW_BREAKPOINT if (CPU_V6 || CPU_V6K || CPU_V7)
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_GENERIC_HARDIRQS
 	select HAVE_SPARSE_IRQ
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2729c66..26beb98 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -126,7 +126,7 @@ config PPC
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
 	select HAVE_REGS_AND_STACK_ACCESS_API
-	select HAVE_HW_BREAKPOINT if PERF_EVENTS && PPC_BOOK3S_64
+	select HAVE_HW_BREAKPOINT if PPC_BOOK3S_64
 	select HAVE_GENERIC_HARDIRQS
 	select HAVE_SPARSE_IRQ
 	select IRQ_PER_CPU
-- 
1.7.5.4

Re: [PATCH 3/6] x86: Allow the user not to build hw_breakpoints

[H. Peter Anvin]

On 07/14/2011 08:03 AM, Frederic Weisbecker wrote:
> So that hw_breakpoints and perf can be not built on
> specific embedded systems.

I want to emphasize I am very, very unhappy about this.  It should be
possible to not build perf while still have breakpoints available...
breakpoints are way more important than perf.

	-hpa

Re: [PATCH 3/6] x86: Allow the user not to build hw_breakpoints

[Frederic Weisbecker]

On Thu, Jul 14, 2011 at 02:26:11PM -0700, H. Peter Anvin wrote:
> On 07/14/2011 08:03 AM, Frederic Weisbecker wrote:
> > So that hw_breakpoints and perf can be not built on
> > specific embedded systems.
> 
> I want to emphasize I am very, very unhappy about this.  It should be
> possible to not build perf while still have breakpoints available...
> breakpoints are way more important than perf.

I know and that's a long term goal. I believe Will Deacon is currently working
on breakpoints to avoid archs to translate ptrace user arch input into perf generic
information (which afterward is eventually translated back to arch information).
This is a necessary first step to have a ptrace breakpoint implementation independant of
perf. Once we'll have that and all archs are converted to that new mode, we can work
toward having breakpoints not requiring perf to work.

Until we reach that point, it's still nice to have optable breakpoints. I think
it is a desired feature given the feedbacks I get from Prasad for example.
If that makes it possible to try a kernel without perf in x86, good too.

But this is not intended to be a solution of the breakpoint - perf dependency. That
dependency was a design mistake that needs more to be fixed.
We want to be able to have breakpoints without perf in the end. This just requires
deeper and longer term work that is currently in progress.

Re: [PATCH 3/6] x86: Allow the user not to build hw_breakpoints

[Ingo Molnar]

* H. Peter Anvin <hpa@zytor.com> wrote:

> On 07/14/2011 08:03 AM, Frederic Weisbecker wrote:
> > So that hw_breakpoints and perf can be not built on
> > specific embedded systems.
> 
> I want to emphasize I am very, very unhappy about this.  It should 
> be possible to not build perf while still have breakpoints 
> available... breakpoints are way more important than perf.

What we could indeed do is to separate out a 'core perf' portion that 
is necessary for hw-breakpoints to work fine, thus allowing for 
example the PMU drivers to be disabled.

Otherwise we have expressed hw breakpoint APIs via perf events and 
that model is working well. Making hw-breakpoints a separate 
subsystem again with isolated (and partly duplicated) infrastructure 
would be a step back really.

Thanks,

	Ingo

Re: [PATCH 3/6] x86: Allow the user not to build hw_breakpoints

[Peter Zijlstra]

On Thu, 2011-07-21 at 09:26 +0200, Ingo Molnar wrote:
> Otherwise we have expressed hw breakpoint APIs via perf events and 
> that model is working well. 

Its working, maybe, working well is pushing it. The whole breakpoint
muck is a horrid mess, it side-steps all of the resource scheduling
stuff of perf and does it itself.

Now part of that is because ptrace requires it, but whichever way you
look at it its damn ugly.

Re: [PATCH 3/6] x86: Allow the user not to build hw_breakpoints

[Frederic Weisbecker]

On Thu, Jul 21, 2011 at 09:26:56AM +0200, Ingo Molnar wrote:
> 
> * H. Peter Anvin <hpa@zytor.com> wrote:
> 
> > On 07/14/2011 08:03 AM, Frederic Weisbecker wrote:
> > > So that hw_breakpoints and perf can be not built on
> > > specific embedded systems.
> > 
> > I want to emphasize I am very, very unhappy about this.  It should 
> > be possible to not build perf while still have breakpoints 
> > available... breakpoints are way more important than perf.
> 
> What we could indeed do is to separate out a 'core perf' portion that 
> is necessary for hw-breakpoints to work fine, thus allowing for 
> example the PMU drivers to be disabled.

That would still require a big chunk of perf.

> 
> Otherwise we have expressed hw breakpoint APIs via perf events and 
> that model is working well. Making hw-breakpoints a separate 
> subsystem again with isolated (and partly duplicated) infrastructure 
> would be a step back really.

I actually don't think it's working well. What we have with the current
design is the dependency to perf as a big midlayer that is apparently
convenient but actually induce some nasty things.

Just look how we need those ptrace_get_breakpoints() protection to deal
with perf exit path implementation for example. Or the need for archs
to translate arch ptrace breakpoint info into generic perf attrs.

I think we had to try the current design just to see if that could plug
nicely. But now that we have this for several releases, I can only conclude
that we should revert back to the design Prasad proposed, consisting in
having breakpoints a service used by perf but not the opposite.

For ptrace, all it takes is a generic hook in the preempt notifiers to
activate/deactivate breakpoints. I much prefer that to a big dependency
on a perf core midlayer.

[PATCH 1/6] hw_breakpoints: Split hardware breakpoints config

[Frederic Weisbecker]

The hardware breakpoint config is only made of an ability. An
arch that support this feature selects HAVE_HW_BREAKPOINT. If so,
the feature is definetly built-in, the user can't decide to turn
it off. As hw_breakpoints depend on perf, it also makes perf
a mandatory feature. The whole is quite a piece of code and
may not be desired on some embedded systems.

In order to prepare to make this optable by the user, split the
config into the more traditional couple (ability, user choice) by
providing a new HW_BREAKPOINT config. It is default on and depends
on CONFIG_EXPERT because breakpoint ptrace requests are part of the
usual user ABI. The user must know what he's doing before turning
that off.

For now, only the archs that already implemented a conditional
HAVE_HW_BREAKPOINT can turn off HW_BREAKPOINT. x86 and sh have it
always selected because they need more background work to support
this new modularity.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
---
 arch/sh/Kconfig  |    1 +
 arch/x86/Kconfig |    1 +
 init/Kconfig     |   10 ++++++++++
 3 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 4b89da2..0d4d124 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -44,6 +44,7 @@ config SUPERH32
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_ARCH_KGDB
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select ARCH_HIBERNATION_POSSIBLE if MMU
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cc6c53a..8b49bff 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,6 +54,7 @@ config X86
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_LZO
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI
diff --git a/init/Kconfig b/init/Kconfig
index d886b1e..76ae53e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -924,6 +924,16 @@ menuconfig EXPERT
           environments which can tolerate a "non-standard" kernel.
           Only use this if you really know what you are doing.
 
+config HW_BREAKPOINT
+	bool "Hardware breakpoints" if EXPERT
+	depends on HAVE_HW_BREAKPOINT
+	default y
+	help
+	  Hardware breakpoints are a feature implemented by most CPUs
+	  to trigger an event when an instruction or data fetch
+	  matches a given pattern. This is typically used by ptrace
+	  and perf events.
+
 config UID16
 	bool "Enable 16-bit UID system calls" if EXPERT
 	depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
-- 
1.7.3.2

[PATCH 1/6] hw_breakpoints: Split hardware breakpoints config

[Frederic Weisbecker]

The hardware breakpoint config is only made of an ability. An
arch that support this feature selects HAVE_HW_BREAKPOINT. If so,
the feature is definetly built-in, the user can't decide to turn
it off. As hw_breakpoints depend on perf, it also makes perf
a mandatory feature. The whole is quite a piece of code and
may not be desired on some embedded systems.

In order to prepare to make this optable by the user, split the
config into the more traditional couple (ability, user choice) by
providing a new HW_BREAKPOINT config. It is default on and depends
on CONFIG_EXPERT because breakpoint ptrace requests are part of the
usual user ABI. The user must know what he's doing before turning
that off.

For now, only the archs that already implemented a conditional
HAVE_HW_BREAKPOINT can turn off HW_BREAKPOINT. x86 and sh have it
always selected because they need more background work to support
this new modularity.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
---
 arch/sh/Kconfig  |    1 +
 arch/x86/Kconfig |    1 +
 init/Kconfig     |   10 ++++++++++
 3 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 4b89da2..0d4d124 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -44,6 +44,7 @@ config SUPERH32
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_ARCH_KGDB
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select ARCH_HIBERNATION_POSSIBLE if MMU
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cc6c53a..8b49bff 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,6 +54,7 @@ config X86
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_LZO
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI
diff --git a/init/Kconfig b/init/Kconfig
index d886b1e..76ae53e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -924,6 +924,16 @@ menuconfig EXPERT
           environments which can tolerate a "non-standard" kernel.
           Only use this if you really know what you are doing.
 
+config HW_BREAKPOINT
+	bool "Hardware breakpoints" if EXPERT
+	depends on HAVE_HW_BREAKPOINT
+	default y
+	help
+	  Hardware breakpoints are a feature implemented by most CPUs
+	  to trigger an event when an instruction or data fetch
+	  matches a given pattern. This is typically used by ptrace
+	  and perf events.
+
 config UID16
 	bool "Enable 16-bit UID system calls" if EXPERT
 	depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
-- 
1.7.3.2

[PATCH 1/6] hw_breakpoints: Split hardware breakpoints config

[Frederic Weisbecker]

The hardware breakpoint config is only made of an ability. An
arch that support this feature selects HAVE_HW_BREAKPOINT. If so,
the feature is definetly built-in, the user can't decide to turn
it off. As hw_breakpoints depend on perf, it also makes perf
a mandatory feature. The whole is quite a piece of code and
may not be desired on some embedded systems.

In order to prepare to make this optable by the user, split the
config into the more traditional couple (ability, user choice) by
providing a new HW_BREAKPOINT config. It is default on and depends
on CONFIG_EXPERT because breakpoint ptrace requests are part of the
usual user ABI. The user must know what he's doing before turning
that off.

For now, only the archs that already implemented a conditional
HAVE_HW_BREAKPOINT can turn off HW_BREAKPOINT. x86 and sh have it
always selected because they need more background work to support
this new modularity.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
---
 arch/sh/Kconfig  |    1 +
 arch/x86/Kconfig |    1 +
 init/Kconfig     |   10 ++++++++++
 3 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 4b89da2..0d4d124 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -44,6 +44,7 @@ config SUPERH32
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_ARCH_KGDB
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select ARCH_HIBERNATION_POSSIBLE if MMU
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cc6c53a..8b49bff 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,6 +54,7 @@ config X86
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_LZO
 	select HAVE_HW_BREAKPOINT
+	select HW_BREAKPOINT
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI
diff --git a/init/Kconfig b/init/Kconfig
index 56240e7..51f587f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -924,6 +924,16 @@ menuconfig EXPERT
           environments which can tolerate a "non-standard" kernel.
           Only use this if you really know what you are doing.
 
+config HW_BREAKPOINT
+	bool "Hardware breakpoints" if EXPERT
+	depends on HAVE_HW_BREAKPOINT
+	default y
+	help
+	  Hardware breakpoints are a feature implemented by most CPUs
+	  to trigger an event when an instruction or data fetch
+	  matches a given pattern. This is typically used by ptrace
+	  and perf events.
+
 config EMBEDDED
 	bool "Embedded system"
 	select EXPERT
-- 
1.7.3.2