This patch introduces the generic Hardware Breakpoint interfaces for both user and kernel space requests. Signed-off-by: K.Prasad Signed-off-by: Alan Stern --- arch/Kconfig | 4 kernel/Makefile | 1 kernel/hw_breakpoint.c | 364 +++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 369 insertions(+) Index: arch/Kconfig =================================================================== --- arch/Kconfig.orig +++ arch/Kconfig @@ -112,3 +112,7 @@ config HAVE_DMA_API_DEBUG config HAVE_DEFAULT_NO_SPIN_MUTEXES bool + +config HAVE_HW_BREAKPOINT + bool + Index: kernel/Makefile =================================================================== --- kernel/Makefile.orig +++ kernel/Makefile @@ -97,6 +97,7 @@ obj-$(CONFIG_X86_DS) += trace/ obj-$(CONFIG_SMP) += sched_cpupri.o obj-$(CONFIG_SLOW_WORK) += slow-work.o obj-$(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 , the -fno-omit-frame-pointer is Index: kernel/hw_breakpoint.c =================================================================== --- /dev/null +++ kernel/hw_breakpoint.c @@ -0,0 +1,364 @@ +/* + * 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#ifdef CONFIG_X86 +#include +#endif +/* + * Spinlock that protects all (un)register operations over kernel/user-space + * breakpoint requests + */ +DEFINE_SPINLOCK(hw_breakpoint_lock); + +/* 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_lock + */ +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; + + spin_lock(&hw_breakpoint_lock); + + /* 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); + + spin_unlock(&hw_breakpoint_lock); +} + +/* + * 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); + + spin_lock(&hw_breakpoint_lock); + + /* 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(); + spin_unlock(&hw_breakpoint_lock); +} + +/* + * 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; +} + +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 = arch_validate_hwbkpt_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) || (arch_validate_hwbkpt_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; + + spin_lock(&hw_breakpoint_lock); + + for (i = 0; i < hbp_kernel_pos; i++) { + if (!thread->hbp[i]) { + rc = __register_user_hw_breakpoint(i, tsk, bp); + break; + } + } + + spin_unlock(&hw_breakpoint_lock); + 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; + + spin_lock(&hw_breakpoint_lock); + for (i = 0; i < hbp_kernel_pos; i++) { + if (bp == thread->hbp[i]) { + __unregister_user_hw_breakpoint(i, tsk); + break; + } + } + spin_unlock(&hw_breakpoint_lock); +} +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 = arch_validate_hwbkpt_settings(bp, NULL); + if (rc) + return rc; + + spin_lock(&hw_breakpoint_lock); + + 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; + } + + spin_unlock(&hw_breakpoint_lock); + 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; + + spin_lock(&hw_breakpoint_lock); + + /* 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) { + spin_unlock(&hw_breakpoint_lock); + 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] = NULL; + on_each_cpu(arch_update_kernel_hw_breakpoints, NULL, 0); + hbp_kernel_pos++; + + spin_unlock(&hw_breakpoint_lock); +} +EXPORT_SYMBOL_GPL(unregister_kernel_hw_breakpoint); + +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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/