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PPC64-HWBKPT: Disable interrupts for data breakpoint exceptions

PATCH New K.Prasad 1 participant 2 messages Mar 30, 2010 1 message not in the archive

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A message that is not in the archive (sent off-list or not yet received): 20100330095040.565675261@pr

K.Prasad

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#1 lore raw

PATCH 1/2 PPC64-HWBKPT: Disable interrupts for data breakpoint exceptions

Data address breakpoint exceptions are currently handled along with page-faults which require interrupts to remain in enabled state. Since exception handling for data breakpoints aren't pre-empt safe, we handle them separately.

Signed-off-by K.Prasad <[email protected]>
---
 arch/powerpc/kernel/exceptions-64s.S |   13 ++++++++++++-
 arch/powerpc/mm/fault.c              |    5 +++--
 2 files changed, 15 insertions(+), 3 deletions(-)
arch/powerpc/kernel/exceptions-64s.S +12 -1
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S
===================================================================
@@ -735,8 +735,11 @@ _STATIC(do_hash_page)
 	std	r3,_DAR(r1)
 	std	r4,_DSISR(r1)
 
-	andis.	r0,r4,0xa450		/* weird error? */
+	andis.	r0,r4,0xa410		/* weird error? */
 	bne-	handle_page_fault	/* if not, try to insert a HPTE */
+	andis.  r0,r4,DSISR_DABRMATCH@h
+	bne-    handle_dabr_fault
+
 BEGIN_FTR_SECTION
 	andis.	r0,r4,0x0020		/* Is it a segment table fault? */
 	bne-	do_ste_alloc		/* If so handle it */

@@ -823,6 +826,14 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER
 	bl	.raw_local_irq_restore
 	b	11f
 
+/* We have a data breakpoint exception - handle it */
+handle_dabr_fault:
+	ld      r4,_DAR(r1)
+	ld      r5,_DSISR(r1)
+	addi    r3,r1,STACK_FRAME_OVERHEAD
+	bl      .do_dabr
+	b       .ret_from_except_lite
+
 /* Here we have a page fault that hash_page can't handle. */
 handle_page_fault:
 	ENABLE_INTS
arch/powerpc/mm/fault.c +3 -2
Index: linux-2.6.ppc64_test/arch/powerpc/mm/fault.c
===================================================================
@@ -151,13 +151,14 @@ int __kprobes do_page_fault(struct pt_re
 	if (!user_mode(regs) && (address >= TASK_SIZE))
 		return SIGSEGV;
 
-#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
+			     defined(CONFIG_PPC_BOOK3S_64))
   	if (error_code & DSISR_DABRMATCH) {
 		/* DABR match */
 		do_dabr(regs, address, error_code);
 		return 0;
 	}
-#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/
+#endif
 
 	if (in_atomic() || mm == NULL) {
 		if (!user_mode(regs))
author
#2 lore raw

PATCH 2/2 PPC64-HWBKPT: Implement hw-breakpoints for PPC64

In reply to a message not in the archive

Implement perf-events based hw-breakpoint interfaces for PPC64 processors. These interfaces help arbitrate requests from various users and schedules them as appropriate.

Signed-off-by K.Prasad <[email protected]>
---
 arch/powerpc/Kconfig                     |    1 
 arch/powerpc/include/asm/cputable.h      |    4 
 arch/powerpc/include/asm/hw_breakpoint.h |   50 ++++
 arch/powerpc/include/asm/processor.h     |    8 
 arch/powerpc/kernel/Makefile             |    1 
 arch/powerpc/kernel/hw_breakpoint.c      |  324 +++++++++++++++++++++++++++++++
 arch/powerpc/kernel/machine_kexec_64.c   |    3 
 arch/powerpc/kernel/process.c            |    6 
 arch/powerpc/kernel/ptrace.c             |   81 +++++++
 9 files changed, 478 insertions(+)
arch/powerpc/include/asm/hw_breakpoint.h new file +50 -0
Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h
===================================================================
@@ -0,0 +1,50 @@
+#ifndef _PPC_BOOK3S_64_HW_BREAKPOINT_H
+#define _PPC_BOOK3S_64_HW_BREAKPOINT_H
+
+#ifdef	__KERNEL__
+#define	__ARCH_HW_BREAKPOINT_H
+#ifdef CONFIG_PPC_BOOK3S_64
+
+struct arch_hw_breakpoint {
+	u8		len; /* length of the target data symbol */
+	int		type;
+	unsigned long	address;
+};
+
+#include <linux/kdebug.h>
+#include <asm/reg.h>
+#include <asm/system.h>
+
+struct perf_event;
+struct pmu;
+struct perf_sample_data;
+
+#define HW_BREAKPOINT_ALIGN 0x7
+/* Maximum permissible length of any HW Breakpoint */
+#define HW_BREAKPOINT_LEN 0x8
+
+extern int arch_validate_hwbkpt_settings(struct perf_event *bp,
+						struct task_struct *tsk);
+extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
+						unsigned long val, void *data);
+int arch_install_hw_breakpoint(struct perf_event *bp);
+void arch_uninstall_hw_breakpoint(struct perf_event *bp);
+void hw_breakpoint_pmu_read(struct perf_event *bp);
+extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk);
+
+extern struct pmu perf_ops_bp;
+extern void ptrace_triggered(struct perf_event *bp, int nmi,
+			struct perf_sample_data *data, struct pt_regs *regs);
+static inline void hw_breakpoint_disable(void)
+{
+	set_dabr(0);
+}
+
+#else
+static inline void hw_breakpoint_disable(void)
+{
+	/* Function is defined only on PPC_BOOK3S_64 for now */
+}
+#endif	/* CONFIG_PPC_BOOK3S_64 */
+#endif	/* __KERNEL__ */
+#endif	/* _PPC_BOOK3S_64_HW_BREAKPOINT_H */
arch/powerpc/kernel/hw_breakpoint.c new file +324 -0

324 lines not on this page · raw message

arch/powerpc/Kconfig +1 -0
Index: linux-2.6.ppc64_test/arch/powerpc/Kconfig
===================================================================
@@ -140,6 +140,7 @@ config PPC
 	select HAVE_SYSCALL_WRAPPERS if PPC64
 	select GENERIC_ATOMIC64 if PPC32
 	select HAVE_PERF_EVENTS
+	select HAVE_HW_BREAKPOINT if PPC_BOOK3S_64
 
 config EARLY_PRINTK
 	bool
arch/powerpc/kernel/Makefile +1 -0
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/Makefile
===================================================================
@@ -34,6 +34,7 @@ obj-y				+= vdso32/
 obj-$(CONFIG_PPC64)		+= setup_64.o sys_ppc32.o \
 				   signal_64.o ptrace32.o \
 				   paca.o nvram_64.o firmware.o
+obj-$(CONFIG_PPC_BOOK3S_64)	+= hw_breakpoint.o
 obj-$(CONFIG_PPC_BOOK3S_64)	+= cpu_setup_ppc970.o cpu_setup_pa6t.o
 obj64-$(CONFIG_RELOCATABLE)	+= reloc_64.o
 obj-$(CONFIG_PPC_BOOK3E_64)	+= exceptions-64e.o
arch/powerpc/include/asm/processor.h +8 -0
Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/processor.h
===================================================================
@@ -209,6 +209,14 @@ 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_PPC_BOOK3S_64
+	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_PPC_BOOK3S_64 */
 #endif
 	unsigned long	dabr;		/* Data address breakpoint register */
 #ifdef CONFIG_ALTIVEC
arch/powerpc/kernel/ptrace.c +81 -0

102 lines not on this page · raw message

arch/powerpc/kernel/process.c +6 -0
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/process.c
===================================================================
@@ -459,8 +459,14 @@ struct task_struct *__switch_to(struct t
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 	switch_booke_debug_regs(&new->thread);
 #else
+/*
+ * For PPC_BOOK3S_64, we use the hw-breakpoint interfaces that would
+ * schedule DABR
+ */
+#ifndef CONFIG_PPC_BOOK3S_64
 	if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr))
 		set_dabr(new->thread.dabr);
+#endif /* CONFIG_PPC_BOOK3S_64 */
 #endif
arch/powerpc/include/asm/cputable.h +4 -0
Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/cputable.h
===================================================================
@@ -511,6 +511,10 @@ static inline int cpu_has_feature(unsign
 		& feature);
 }
 
+#ifdef CONFIG_PPC_BOOK3S_64
+#define HBP_NUM 1
+#endif /* CONFIG_PPC_BOOK3S_64 */
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __KERNEL__ */
arch/powerpc/kernel/machine_kexec_64.c +3 -0
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/machine_kexec_64.c
===================================================================
@@ -15,6 +15,7 @@
 #include <linux/thread_info.h>
 #include <linux/init_task.h>
 #include <linux/errno.h>
+#include <linux/hw_breakpoint.h>
 
 #include <asm/page.h>
 #include <asm/current.h>

@@ -161,6 +162,7 @@ void kexec_copy_flush(struct kimage *ima
  */
 static void kexec_smp_down(void *arg)
 {
+	hw_breakpoint_disable();
 	if (ppc_md.kexec_cpu_down)
 		ppc_md.kexec_cpu_down(0, 1);
 

@@ -174,6 +176,7 @@ static void kexec_prepare_cpus(void)
 	int my_cpu, i, notified=-1;
 
 	smp_call_function(kexec_smp_down, NULL, /* wait */0);
+	hw_breakpoint_disable();
 	my_cpu = get_cpu();
 
 	/* check the others cpus are now down (via paca hw cpu id == -1) */