This patch introduces the generic Hardware Breakpoint interfaces for both user
and kernel space requests.
Signed-off-by: K.Prasad <[email protected]>
Signed-off-by: Alan Stern <[email protected]>
---
arch/Kconfig | 4
kernel/Makefile | 1
kernel/hw_breakpoint.c | 401 +++++++++++++++++++++++++++++++++++
3 files changed, 406 insertions(+)
Index: arch/Kconfig
===================================================================
--- arch/Kconfig.orig 2009-04-01 20:53:43.000000000 +0530
+++ arch/Kconfig 2009-04-01 20:54:15.000000000 +0530
@@ -109,3 +109,7 @@
config HAVE_DMA_API_DEBUG
bool
+
+config HAVE_HW_BREAKPOINT
+ bool
+
Index: kernel/Makefile
===================================================================
--- kernel/Makefile.orig 2009-04-01 20:53:43.000000000 +0530
+++ kernel/Makefile 2009-04-01 20:54:15.000000000 +0530
@@ -95,6 +95,7 @@
obj-$(CONFIG_TRACING) += trace/
obj-$(CONFIG_SMP) += sched_cpupri.o
obj-$(CONFIG_PERF_COUNTERS) += perf_counter.o
+obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
# According to Alan Modra <[email protected]>, the -fno-omit-frame-pointer is
Index: kernel/hw_breakpoint.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ kernel/hw_breakpoint.c 2009-04-01 20:54:15.000000000 +0530
@@ -0,0 +1,401 @@
+/*
+ * 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 (C) 2007 Alan Stern
+ * Copyright (C) IBM Corporation, 2009
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ *
+ * This file contains the arch-independent routines. It is not meant
+ * to be compiled as a standalone source file; rather it should be
+ * #include'd by the arch-specific implementation.
+ */
+
+#include <linux/irqflags.h>
+#include <linux/kallsyms.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+
+#include <asm/hw_breakpoint.h>
+#include <asm/processor.h>
+#include <asm/debugreg.h>
+
+/*
+ * Mutex that protects all (un)register operations over kernel/user-space
+ * breakpoint requests
+ */
+DEFINE_MUTEX(hw_breakpoint_mutex);
+
+/* Array of kernel-space breakpoint structures */
+struct hw_breakpoint *hbp_kernel[HB_NUM];
+
+/*
+ * Kernel breakpoints grow downwards, starting from HB_NUM
+ * 'hbp_kernel_pos' denotes lowest numbered breakpoint register occupied for
+ * kernel-space request. We will initialise it here and not in an __init
+ * routine because load_debug_registers(), which uses this variable can be
+ * called very early during CPU initialisation.
+ */
+unsigned int hbp_kernel_pos = HB_NUM;
+
+/*
+ * An array containing refcount of threads using a given bkpt register
+ * Accesses are synchronised by acquiring hw_breakpoint_mutex
+ */
+unsigned int hbp_user_refcount[HB_NUM];
+
+DEFINE_PER_CPU(struct task_struct *, last_debugged_task);
+
+/*
+ * Install the debug register values for a new thread.
+ */
+void switch_to_thread_hw_breakpoint(struct task_struct *tsk)
+{
+ /* Set the debug register */
+ arch_install_thread_hw_breakpoint(tsk);
+ per_cpu(last_debugged_task, get_cpu()) = current;
+ put_cpu_no_resched();
+}
+
+/*
+ * Install the debug register values for just the kernel, no thread.
+ */
+void switch_to_none_hw_breakpoint(void)
+{
+ arch_uninstall_thread_hw_breakpoint();
+}
+
+/*
+ * Load the debug registers during startup of a CPU.
+ */
+void load_debug_registers(void)
+{
+ unsigned long flags;
+ struct task_struct *tsk = current;
+
+ mutex_lock(&hw_breakpoint_mutex);
+
+ /* Prevent IPIs for new kernel breakpoint updates */
+ local_irq_save(flags);
+ arch_update_kernel_hw_breakpoints(NULL);
+ local_irq_restore(flags);
+
+ if (test_tsk_thread_flag(tsk, TIF_DEBUG))
+ switch_to_thread_hw_breakpoint(tsk);
+
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+
+/*
+ * Erase all the hardware breakpoint info associated with a thread.
+ *
+ * If tsk != current then tsk must not be usable (for example, a
+ * child being cleaned up from a failed fork).
+ */
+void flush_thread_hw_breakpoint(struct task_struct *tsk)
+{
+ int i;
+ struct thread_struct *thread = &(tsk->thread);
+
+ mutex_lock(&hw_breakpoint_mutex);
+
+ /* The thread no longer has any breakpoints associated with it */
+ clear_tsk_thread_flag(tsk, TIF_DEBUG);
+ for (i = 0; i < HB_NUM; i++) {
+ if (thread->hbp[i]) {
+ hbp_user_refcount[i]--;
+ kfree(thread->hbp[i]);
+ thread->hbp[i] = NULL;
+ }
+ }
+
+ arch_flush_thread_hw_breakpoint(tsk);
+
+ /* Actually uninstall the breakpoints if necessary */
+ if (tsk == current)
+ switch_to_none_hw_breakpoint();
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+
+/*
+ * Copy the hardware breakpoint info from a thread to its cloned child.
+ */
+int copy_thread_hw_breakpoint(struct task_struct *tsk,
+ struct task_struct *child, unsigned long clone_flags)
+{
+ /*
+ * We will assume that breakpoint settings are not inherited
+ * and the child starts out with no debug registers set.
+ * But what about CLONE_PTRACE?
+ */
+ clear_tsk_thread_flag(child, TIF_DEBUG);
+
+ /* We will call flush routine since the debugregs are not inherited */
+ arch_flush_thread_hw_breakpoint(child);
+
+ return 0;
+}
+
+/*
+ * Validate the settings in a hw_breakpoint structure.
+ */
+static int validate_settings(struct hw_breakpoint *bp, struct task_struct *tsk)
+{
+ int ret;
+
+ if (!bp)
+ return -EINVAL;
+
+ ret = arch_validate_hwbkpt_settings(bp, tsk);
+ if (ret < 0)
+ goto err;
+
+ /* Check that the virtual address is in the proper range */
+ if (tsk) {
+ if (!arch_check_va_in_userspace(bp->info.address, bp->info.len))
+ return -EFAULT;
+ } else {
+ if (!arch_check_va_in_kernelspace(bp->info.address,
+ bp->info.len))
+ return -EFAULT;
+ }
+ err:
+ return ret;
+}
+
+int __register_user_hw_breakpoint(int pos, struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ struct thread_struct *thread = &(tsk->thread);
+ int rc;
+
+ /* Do not overcommit. Fail if kernel has used the hbp registers */
+ if (pos >= hbp_kernel_pos)
+ return -ENOSPC;
+
+ rc = validate_settings(bp, tsk);
+ if (rc)
+ return rc;
+
+ thread->hbp[pos] = bp;
+ hbp_user_refcount[pos]++;
+
+ arch_update_user_hw_breakpoint(pos, tsk);
+ /*
+ * Does it need to be installed right now?
+ * Otherwise it will get installed the next time tsk runs
+ */
+ if (tsk == current)
+ switch_to_thread_hw_breakpoint(tsk);
+
+ return rc;
+}
+
+/*
+ * Modify the address of a hbp register already in use by the task
+ * Do not invoke this in-lieu of a __unregister_user_hw_breakpoint()
+ */
+int __modify_user_hw_breakpoint(int pos, struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ struct thread_struct *thread = &(tsk->thread);
+
+ if ((pos >= hbp_kernel_pos) || (validate_settings(bp, tsk)))
+ return -EINVAL;
+
+ if (thread->hbp[pos] == NULL)
+ return -EINVAL;
+
+ thread->hbp[pos] = bp;
+ /*
+ * 'pos' must be that of a hbp register already used by 'tsk'
+ * Otherwise arch_modify_user_hw_breakpoint() will fail
+ */
+ arch_update_user_hw_breakpoint(pos, tsk);
+
+ if (tsk == current)
+ switch_to_thread_hw_breakpoint(tsk);
+
+ return 0;
+}
+
+void __unregister_user_hw_breakpoint(int pos, struct task_struct *tsk)
+{
+ hbp_user_refcount[pos]--;
+ tsk->thread.hbp[pos] = NULL;
+
+ arch_update_user_hw_breakpoint(pos, tsk);
+
+ if (tsk == current)
+ switch_to_thread_hw_breakpoint(tsk);
+}
+
+/**
+ * register_user_hw_breakpoint - register a hardware breakpoint for user space
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ * @bp: the breakpoint structure to register
+ *
+ * @bp.info->name or @bp.info->address, @bp.info->len, @bp.info->type and
+ * @bp->triggered must be set properly before invocation
+ *
+ */
+int register_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ struct thread_struct *thread = &(tsk->thread);
+ int i, rc = -ENOSPC;
+
+ mutex_lock(&hw_breakpoint_mutex);
+
+ for (i = 0; i < hbp_kernel_pos; i++) {
+ if (!thread->hbp[i]) {
+ rc = __register_user_hw_breakpoint(i, tsk, bp);
+ break;
+ }
+ }
+
+ mutex_unlock(&hw_breakpoint_mutex);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
+
+/**
+ * unregister_user_hw_breakpoint - unregister a user-space hardware breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ * @bp: the breakpoint structure to unregister
+ *
+ */
+void unregister_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ struct thread_struct *thread = &(tsk->thread);
+ int i;
+
+ mutex_lock(&hw_breakpoint_mutex);
+ for (i = 0; i < hbp_kernel_pos; i++) {
+ if (bp == thread->hbp[i]) {
+ __unregister_user_hw_breakpoint(i, tsk);
+ break;
+ }
+ }
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+EXPORT_SYMBOL_GPL(unregister_user_hw_breakpoint);
+
+/**
+ * register_kernel_hw_breakpoint - register a hardware breakpoint for kernel space
+ * @bp: the breakpoint structure to register
+ *
+ * @bp.info->name or @bp.info->address, @bp.info->len, @bp.info->type and
+ * @bp->triggered must be set properly before invocation
+ *
+ */
+int register_kernel_hw_breakpoint(struct hw_breakpoint *bp)
+{
+ int rc;
+
+ rc = validate_settings(bp, NULL);
+ if (rc)
+ return rc;
+
+ mutex_lock(&hw_breakpoint_mutex);
+
+ rc = -EINVAL;
+ /* Check if we are over-committing */
+ if ((hbp_kernel_pos > 0) && (!hbp_user_refcount[hbp_kernel_pos-1])) {
+ hbp_kernel_pos--;
+ hbp_kernel[hbp_kernel_pos] = bp;
+ on_each_cpu(arch_update_kernel_hw_breakpoints, NULL, 0);
+ rc = 0;
+ }
+
+ mutex_unlock(&hw_breakpoint_mutex);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(register_kernel_hw_breakpoint);
+
+/**
+ * unregister_kernel_hw_breakpoint - unregister a HW breakpoint for kernel space
+ * @bp: the breakpoint structure to unregister
+ *
+ * Uninstalls and unregisters @bp.
+ */
+void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp)
+{
+ int i, j;
+
+ mutex_lock(&hw_breakpoint_mutex);
+
+ /* Find the 'bp' in our list of breakpoints for kernel */
+ for (i = hbp_kernel_pos; i < HB_NUM; i++)
+ if (bp == hbp_kernel[i])
+ break;
+
+ /* Check if we did not find a match for 'bp'. If so return early */
+ if (i == HB_NUM) {
+ mutex_unlock(&hw_breakpoint_mutex);
+ return;
+ }
+
+ /*
+ * We'll shift the breakpoints one-level above to compact if
+ * unregistration creates a hole
+ */
+ for (j = i; j > hbp_kernel_pos; j--)
+ hbp_kernel[j] = hbp_kernel[j-1];
+
+ hbp_kernel[hbp_kernel_pos] = 0;
+ on_each_cpu(arch_update_kernel_hw_breakpoints, NULL, 0);
+ hbp_kernel_pos++;
+
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+EXPORT_SYMBOL_GPL(unregister_kernel_hw_breakpoint);
+
+/*
+ * Handle debug exception notifications.
+ */
+static int __kprobes hw_breakpoint_exceptions_notify(
+ struct notifier_block *unused, unsigned long val, void *data)
+{
+ if (val != DIE_DEBUG)
+ return NOTIFY_DONE;
+
+ return hw_breakpoint_handler(data);
+}
+
+static struct notifier_block hw_breakpoint_exceptions_nb = {
+ .notifier_call = hw_breakpoint_exceptions_notify,
+ /* we need to be notified first */
+ .priority = 0x7fffffff
+};
+
+static int __init init_hw_breakpoint(void)
+{
+ return register_die_notifier(&hw_breakpoint_exceptions_nb);
+}
+
+core_initcall(init_hw_breakpoint);