[Patch 2/2] PPC64-HWBKPT: Implement hw-breakpoints for PPC64
K.Prasad
prasad at linux.vnet.ibm.com
Wed Apr 14 13:48:27 EST 2010
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 <prasad at linux.vnet.ibm.com>
---
arch/powerpc/Kconfig | 1
arch/powerpc/include/asm/cputable.h | 4
arch/powerpc/include/asm/hw_breakpoint.h | 45 ++++
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 +++++++
arch/powerpc/lib/Makefile | 1
include/linux/hw_breakpoint.h | 1
11 files changed, 475 insertions(+)
Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h
===================================================================
--- /dev/null
+++ linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h
@@ -0,0 +1,45 @@
+#ifndef _PPC_BOOK3S_64_HW_BREAKPOINT_H
+#define _PPC_BOOK3S_64_HW_BREAKPOINT_H
+
+#ifdef __KERNEL__
+#define __ARCH_HW_BREAKPOINT_H
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+
+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);
+}
+
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+#endif /* __KERNEL__ */
+#endif /* _PPC_BOOK3S_64_HW_BREAKPOINT_H */
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c
===================================================================
--- /dev/null
+++ linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c
@@ -0,0 +1,324 @@
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers. Derived from
+ * "arch/x86/kernel/hw_breakpoint.c"
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright 2009 IBM Corporation
+ * Author: K.Prasad <prasad at linux.vnet.ibm.com>
+ *
+ */
+
+#include <linux/hw_breakpoint.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+#include <linux/percpu.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+
+#include <asm/hw_breakpoint.h>
+#include <asm/processor.h>
+#include <asm/sstep.h>
+
+/*
+ * Store the 'bp' that caused the hw-breakpoint exception just before we
+ * single-step. Use it to distinguish a single-step exception (due to a
+ * previous hw-breakpoint exception) from a normal one
+ */
+static DEFINE_PER_CPU(struct perf_event *, last_hit_bp);
+
+/*
+ * Stores the breakpoints currently in use on each breakpoint address
+ * register for every cpu
+ */
+static DEFINE_PER_CPU(struct perf_event *, bp_per_reg);
+
+/*
+ * Install a perf counter breakpoint.
+ *
+ * We seek a free debug address register and use it for this
+ * breakpoint.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ struct perf_event **slot = &__get_cpu_var(bp_per_reg);
+
+ *slot = bp;
+ set_dabr(info->address | info->type | DABR_TRANSLATION);
+ return 0;
+}
+
+/*
+ * Uninstall the breakpoint contained in the given counter.
+ *
+ * First we search the debug address register it uses and then we disable
+ * it.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+ struct perf_event **slot = &__get_cpu_var(bp_per_reg);
+
+ if (*slot != bp) {
+ WARN_ONCE(1, "Can't find the breakpoint");
+ return;
+ }
+
+ *slot = NULL;
+ set_dabr(0);
+}
+
+/*
+ * Validate the arch-specific HW Breakpoint register settings
+ */
+int arch_validate_hwbkpt_settings(struct perf_event *bp,
+ struct task_struct *tsk)
+{
+ bool is_kernel;
+ int ret = -EINVAL;
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+ if (!bp)
+ return ret;
+
+ switch (bp->attr.bp_type) {
+ case HW_BREAKPOINT_R:
+ info->type = DABR_DATA_READ;
+ break;
+ case HW_BREAKPOINT_W:
+ info->type = DABR_DATA_WRITE;
+ break;
+ case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
+ info->type = (DABR_DATA_READ | DABR_DATA_WRITE);
+ break;
+ default:
+ return ret;
+ }
+
+ is_kernel = is_kernel_addr(bp->attr.bp_addr);
+ if ((tsk && is_kernel) || (!tsk && !is_kernel))
+ return -EINVAL;
+
+ info->address = bp->attr.bp_addr;
+ info->len = bp->attr.bp_len;
+
+ /*
+ * Since breakpoint length can be a maximum of HW_BREAKPOINT_LEN(8)
+ * and breakpoint addresses are aligned to nearest double-word
+ * HW_BREAKPOINT_ALIGN by rounding off to the lower address, the
+ * 'symbolsize' should satisfy the check below.
+ */
+ if (info->len >
+ (HW_BREAKPOINT_LEN - (info->address & HW_BREAKPOINT_ALIGN)))
+ return -EINVAL;
+ return 0;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+int __kprobes hw_breakpoint_handler(struct die_args *args)
+{
+ bool is_kernel, is_ptrace_bp = false;
+ int rc = NOTIFY_STOP;
+ struct perf_event *bp;
+ struct pt_regs *regs = args->regs;
+ unsigned long dar = regs->dar;
+ int cpu, stepped = 1;
+ struct arch_hw_breakpoint *info;
+
+ /* Disable breakpoints during exception handling */
+ set_dabr(0);
+ cpu = smp_processor_id();
+ /*
+ * The counter may be concurrently released but that can only
+ * occur from a call_rcu() path. We can then safely fetch
+ * the breakpoint, use its callback, touch its counter
+ * while we are in an rcu_read_lock() path.
+ */
+ rcu_read_lock();
+
+ bp = per_cpu(bp_per_reg, cpu);
+ if (!bp)
+ goto out;
+ info = counter_arch_bp(bp);
+ is_kernel = is_kernel_addr(bp->attr.bp_addr);
+ is_ptrace_bp = (bp->overflow_handler == ptrace_triggered) ?
+ true : false;
+
+ /*
+ * Verify if dar lies within the address range occupied by the symbol
+ * being watched to filter extraneous exceptions.
+ */
+ if (!((bp->attr.bp_addr <= dar) &&
+ (dar <= (bp->attr.bp_addr + bp->attr.bp_len))) &&
+ (is_ptrace_bp == false))
+ /*
+ * This exception is triggered not because of a memory access on
+ * the monitored variable but in the double-word address range
+ * in which it is contained. We will consume this exception,
+ * considering it as 'noise'.
+ */
+ goto restore_bp;
+
+ /*
+ * Return early after invoking user-callback function without restoring
+ * DABR if the breakpoint is from ptrace which always operates in
+ * one-shot mode
+ */
+ if (is_ptrace_bp == true) {
+ perf_bp_event(bp, regs);
+ rc = NOTIFY_DONE;
+ goto out;
+ }
+
+ /*
+ * Do not emulate user-space instructions from kernel-space,
+ * instead single-step them.
+ */
+ if (is_kernel == false) {
+ current->thread.last_hit_ubp = bp;
+ regs->msr |= MSR_SE;
+ goto out;
+ }
+
+ stepped = emulate_step(regs, regs->nip);
+ /* emulate_step() could not execute it, single-step them */
+ if (stepped == 0) {
+ regs->msr |= MSR_SE;
+ per_cpu(last_hit_bp, cpu) = bp;
+ goto out;
+ }
+ /*
+ * As a policy, the callback is invoked in a 'trigger-after-execute'
+ * fashion
+ */
+ perf_bp_event(bp, regs);
+
+restore_bp:
+ set_dabr(info->address | info->type | DABR_TRANSLATION);
+out:
+ rcu_read_unlock();
+ return rc;
+}
+
+/*
+ * Handle single-step exceptions following a DABR hit.
+ */
+int __kprobes single_step_dabr_instruction(struct die_args *args)
+{
+ struct pt_regs *regs = args->regs;
+ int cpu = smp_processor_id();
+ siginfo_t info;
+ struct perf_event *bp = NULL, *kernel_bp, *user_bp;
+ struct arch_hw_breakpoint *bp_info;
+
+ /*
+ * Identify the cause of single-stepping and find the corresponding
+ * breakpoint structure
+ */
+ user_bp = current->thread.last_hit_ubp;
+ kernel_bp = per_cpu(last_hit_bp, cpu);
+ if (user_bp) {
+ bp = user_bp;
+ current->thread.last_hit_ubp = NULL;
+ } else if (kernel_bp) {
+ bp = kernel_bp;
+ per_cpu(last_hit_bp, cpu) = NULL;
+ }
+
+ /*
+ * Check if we are single-stepping as a result of a
+ * previous HW Breakpoint exception
+ */
+ if (!bp)
+ return NOTIFY_DONE;
+
+ bp_info = counter_arch_bp(bp);
+
+ /*
+ * We shall invoke the user-defined callback function in the single
+ * stepping handler to confirm to 'trigger-after-execute' semantics
+ */
+ perf_bp_event(bp, regs);
+
+ /*
+ * Do not disable MSR_SE if the process was already in
+ * single-stepping mode. We cannot reliable detect single-step mode
+ * for kernel-space breakpoints, so this cannot work along with other
+ * debuggers (like KGDB, xmon) which may be single-stepping kernel code.
+ */
+ if (!(user_bp && test_thread_flag(TIF_SINGLESTEP)))
+ regs->msr &= ~MSR_SE;
+
+ /* Deliver signal to user-space */
+ if (user_bp) {
+ info.si_signo = SIGTRAP;
+ info.si_errno = 0;
+ info.si_code = TRAP_HWBKPT;
+ info.si_addr = (void __user *)bp_info->address;
+ force_sig_info(SIGTRAP, &info, current);
+ }
+
+ set_dabr(bp_info->address | bp_info->type | DABR_TRANSLATION);
+ return NOTIFY_STOP;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+int __kprobes hw_breakpoint_exceptions_notify(
+ struct notifier_block *unused, unsigned long val, void *data)
+{
+ int ret = NOTIFY_DONE;
+
+ switch (val) {
+ case DIE_DABR_MATCH:
+ ret = hw_breakpoint_handler(data);
+ break;
+ case DIE_SSTEP:
+ ret = single_step_dabr_instruction(data);
+ break;
+ }
+
+ return ret;
+}
+
+/*
+ * Release the user breakpoints used by ptrace
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+ struct thread_struct *t = &tsk->thread;
+
+ unregister_hw_breakpoint(t->ptrace_bps[0]);
+ t->ptrace_bps[0] = NULL;
+}
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+ /* TODO */
+}
+
Index: linux-2.6.ppc64_test/arch/powerpc/Kconfig
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/Kconfig
+++ 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 PERF_EVENTS && PPC_BOOK3S_64
config EARLY_PRINTK
bool
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/Makefile
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/Makefile
+++ 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_HAVE_HW_BREAKPOINT) += 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
Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/processor.h
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/include/asm/processor.h
+++ 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_HAVE_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
unsigned long dabr; /* Data address breakpoint register */
#ifdef CONFIG_ALTIVEC
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/ptrace.c
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/ptrace.c
+++ linux-2.6.ppc64_test/arch/powerpc/kernel/ptrace.c
@@ -32,6 +32,8 @@
#ifdef CONFIG_PPC32
#include <linux/module.h>
#endif
+#include <linux/hw_breakpoint.h>
+#include <linux/perf_event.h>
#include <asm/uaccess.h>
#include <asm/page.h>
@@ -763,9 +765,34 @@ void user_disable_single_step(struct tas
clear_tsk_thread_flag(task, TIF_SINGLESTEP);
}
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+void ptrace_triggered(struct perf_event *bp, int nmi,
+ struct perf_sample_data *data, struct pt_regs *regs)
+{
+ struct perf_event_attr attr;
+
+ /*
+ * Disable the breakpoint request here since ptrace has defined a
+ * one-shot behaviour for breakpoint exceptions in PPC64.
+ * The SIGTRAP signal is generated automatically for us in do_dabr().
+ * We don't have to do anything about that here
+ */
+ attr = bp->attr;
+ attr.disabled = true;
+ modify_user_hw_breakpoint(bp, &attr);
+}
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+
int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
unsigned long data)
{
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+ int ret;
+ struct thread_struct *thread = &(task->thread);
+ struct perf_event *bp;
+ struct perf_event_attr attr;
+#endif /* CONFIG_HAVE_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
* moment.
@@ -793,6 +820,60 @@ int ptrace_set_debugreg(struct task_stru
/* Ensure breakpoint translation bit is set */
if (data && !(data & DABR_TRANSLATION))
return -EIO;
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+ bp = thread->ptrace_bps[0];
+ if (data == 0) {
+ if (bp) {
+ unregister_hw_breakpoint(bp);
+ thread->ptrace_bps[0] = NULL;
+ }
+ return 0;
+ }
+ if (bp) {
+ attr = bp->attr;
+ attr.bp_addr = data & ~HW_BREAKPOINT_ALIGN;
+
+ switch (data & (DABR_DATA_WRITE | DABR_DATA_READ)) {
+ case DABR_DATA_READ:
+ attr.bp_type = HW_BREAKPOINT_R;
+ break;
+ case DABR_DATA_WRITE:
+ attr.bp_type = HW_BREAKPOINT_W;
+ break;
+ case (DABR_DATA_WRITE | DABR_DATA_READ):
+ attr.bp_type = HW_BREAKPOINT_R | HW_BREAKPOINT_W;
+ break;
+ }
+ ret = modify_user_hw_breakpoint(bp, &attr);
+ if (ret)
+ return ret;
+ thread->ptrace_bps[0] = bp;
+ thread->dabr = data;
+ return 0;
+ }
+
+ /* Create a new breakpoint request if one doesn't exist already */
+ hw_breakpoint_init(&attr);
+ attr.bp_addr = data & ~HW_BREAKPOINT_ALIGN;
+ switch (data & (DABR_DATA_WRITE | DABR_DATA_READ)) {
+ case DABR_DATA_READ:
+ attr.bp_type = HW_BREAKPOINT_R;
+ break;
+ case DABR_DATA_WRITE:
+ attr.bp_type = HW_BREAKPOINT_W;
+ break;
+ case (DABR_DATA_WRITE | DABR_DATA_READ):
+ attr.bp_type = HW_BREAKPOINT_R | HW_BREAKPOINT_W;
+ break;
+ }
+ thread->ptrace_bps[0] = bp = register_user_hw_breakpoint(&attr,
+ ptrace_triggered, task);
+ if (IS_ERR(bp)) {
+ thread->ptrace_bps[0] = NULL;
+ return PTR_ERR(bp);
+ }
+
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */
/* Move contents to the DABR register */
task->thread.dabr = data;
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/process.c
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/process.c
+++ 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_HAVE_HW_BREAKPOINT
if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr))
set_dabr(new->thread.dabr);
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif
Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/cputable.h
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/include/asm/cputable.h
+++ 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_HAVE_HW_BREAKPOINT
+#define HBP_NUM 1
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/machine_kexec_64.c
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/machine_kexec_64.c
+++ 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) */
Index: linux-2.6.ppc64_test/arch/powerpc/lib/Makefile
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/lib/Makefile
+++ linux-2.6.ppc64_test/arch/powerpc/lib/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_PPC64) += copypage_64.o cop
memcpy_64.o usercopy_64.o mem_64.o string.o
obj-$(CONFIG_XMON) += sstep.o
obj-$(CONFIG_KPROBES) += sstep.o
+obj-$(CONFIG_HAVE_HW_BREAKPOINT) += sstep.o
ifeq ($(CONFIG_PPC64),y)
obj-$(CONFIG_SMP) += locks.o
Index: linux-2.6.ppc64_test/include/linux/hw_breakpoint.h
===================================================================
--- linux-2.6.ppc64_test.orig/include/linux/hw_breakpoint.h
+++ linux-2.6.ppc64_test/include/linux/hw_breakpoint.h
@@ -120,6 +120,7 @@ static inline struct arch_hw_breakpoint
{
return NULL;
}
+static inline void hw_breakpoint_disable(void) { }
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif /* __KERNEL__ */
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