This patch introduces two new files hw_breakpoint.[ch] which defines the generic interfaces to use hardware breakpoint infrastructure of the system. Signed-off-by: K.Prasad Signed-off-by: Alan Stern --- arch/Kconfig | 4 include/asm-generic/hw_breakpoint.h | 138 +++++++++++++ kernel/Makefile | 1 kernel/hw_breakpoint.c | 367 ++++++++++++++++++++++++++++++++++++ 4 files changed, 510 insertions(+) Index: linux-2.6-tip/kernel/hw_breakpoint.c =================================================================== --- /dev/null +++ linux-2.6-tip/kernel/hw_breakpoint.c @@ -0,0 +1,367 @@ +/* + * 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 +#include + +/* + * 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 + */ +unsigned int hbp_kernel_pos; + +/* + * 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]; + +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); + last_debugged_task = current; +} + +/* + * Install the debug register values for just the kernel, no thread. + */ +void switch_to_none_hw_breakpoint(void) +{ + arch_install_none(); +} + +/* + * 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_load_debug_registers(); + 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; + } + } + thread->hbp_num_installed = 0; + + /* 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); + return 0; +} + +/* + * Validate the settings in a hw_breakpoint structure. + */ +static int validate_settings(struct hw_breakpoint *bp, struct task_struct *tsk) +{ + int ret; + unsigned int align; + + if (!bp) + return -EINVAL; + + ret = arch_validate_hwbkpt_settings(bp, &align, tsk); + if (ret < 0) + goto err; + + /* + * Check that the low-order bits of the address are appropriate + * for the alignment implied by len. + */ + if (bp->info.address & align) + return -EINVAL; + + /* 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; + thread->hbp_num_installed++; + hbp_user_refcount[pos]++; + + arch_register_user_hw_breakpoint(pos, bp, 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) +{ + int rc; + struct thread_struct *thread = &(tsk->thread); + + if ((pos >= hbp_kernel_pos) || (validate_settings(bp, tsk))) + 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 + */ + rc = arch_modify_user_hw_breakpoint(pos, bp, tsk); + if (rc) + return rc; + + if (tsk == current) + switch_to_thread_hw_breakpoint(tsk); + return 0; +} + +/* + * Actual implementation of unregister_user_hw_breakpoint. + */ +void __unregister_user_hw_breakpoint(int pos, struct task_struct *tsk, + struct hw_breakpoint *bp) +{ + struct thread_struct *thread = &(tsk->thread); + + if (!bp) + return; + + hbp_user_refcount[pos]--; + thread->hbp_num_installed--; + + arch_unregister_user_hw_breakpoint(pos, bp, tsk); + + if (tsk == current) + switch_to_thread_hw_breakpoint(tsk); + kfree(tsk->thread.hbp[pos]); + tsk->thread.hbp[pos] = NULL; +} + +/** + * 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; + arch_register_kernel_hw_breakpoint(hbp_kernel_pos); + 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; + /* + * We'll shift the breakpoints one-level above to compact if + * unregistration creates a hole + */ + if (i > hbp_kernel_pos) + for (j = i; j == hbp_kernel_pos; j--) + hbp_kernel[j] = hbp_kernel[j-1]; + + /* + * Delete the last kernel breakpoint entry after compaction and update + * the pointer to the lowest numbered kernel entry after updating its + * corresponding value in kdr7 + */ + hbp_kernel[hbp_kernel_pos] = 0; + arch_unregister_kernel_hw_breakpoint(); + 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) +{ + int i; + + hbp_kernel_pos = HB_NUM; + for (i = 0; i < HB_NUM; i++) + hbp_user_refcount[i] = 0; + load_debug_registers(); + + return register_die_notifier(&hw_breakpoint_exceptions_nb); +} + +core_initcall(init_hw_breakpoint); Index: linux-2.6-tip/kernel/Makefile =================================================================== --- linux-2.6-tip.orig/kernel/Makefile +++ linux-2.6-tip/kernel/Makefile @@ -95,6 +95,7 @@ obj-$(CONFIG_FUNCTION_TRACER) += trace/ obj-$(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 , the -fno-omit-frame-pointer is Index: linux-2.6-tip/include/asm-generic/hw_breakpoint.h =================================================================== --- /dev/null +++ linux-2.6-tip/include/asm-generic/hw_breakpoint.h @@ -0,0 +1,138 @@ +#ifndef _ASM_GENERIC_HW_BREAKPOINT_H +#define _ASM_GENERIC_HW_BREAKPOINT_H + +#ifndef __ARCH_HW_BREAKPOINT_H +#error "Please don't include this file directly" +#endif + +#ifdef __KERNEL__ +#include +#include +#include + +/** + * struct hw_breakpoint - unified kernel/user-space hardware breakpoint + * @triggered: callback invoked after target address access + * @info: arch-specific breakpoint info (address, length, and type) + * + * %hw_breakpoint structures are the kernel's way of representing + * hardware breakpoints. These are data breakpoints + * (also known as "watchpoints", triggered on data access), and the breakpoint's + * target address can be located in either kernel space or user space. + * + * The breakpoint's address, length, and type are highly + * architecture-specific. The values are encoded in the @info field; you + * specify them when registering the breakpoint. To examine the encoded + * values use hw_breakpoint_get_{kaddress,uaddress,len,type}(), declared + * below. + * + * The address is specified as a regular kernel pointer (for kernel-space + * breakponts) or as an %__user pointer (for user-space breakpoints). + * With register_user_hw_breakpoint(), the address must refer to a + * location in user space. The breakpoint will be active only while the + * requested task is running. Conversely with + * register_kernel_hw_breakpoint(), the address must refer to a location + * in kernel space, and the breakpoint will be active on all CPUs + * regardless of the current task. + * + * The length is the breakpoint's extent in bytes, which is subject to + * certain limitations. include/asm/hw_breakpoint.h contains macros + * defining the available lengths for a specific architecture. Note that + * the address's alignment must match the length. The breakpoint will + * catch accesses to any byte in the range from address to address + + * (length - 1). + * + * The breakpoint's type indicates the sort of access that will cause it + * to trigger. Possible values may include: + * + * %HW_BREAKPOINT_RW (triggered on read or write access), + * %HW_BREAKPOINT_WRITE (triggered on write access), and + * %HW_BREAKPOINT_READ (triggered on read access). + * + * Appropriate macros are defined in include/asm/hw_breakpoint.h; not all + * possibilities are available on all architectures. Execute breakpoints + * must have length equal to the special value %HW_BREAKPOINT_LEN_EXECUTE. + * + * When a breakpoint gets hit, the @triggered callback is + * invoked in_interrupt with a pointer to the %hw_breakpoint structure and the + * processor registers. + * Data breakpoints occur after the memory access has taken place. + * Breakpoints are disabled during execution @triggered, to avoid + * recursive traps and allow unhindered access to breakpointed memory. + * + * This sample code sets a breakpoint on pid_max and registers a callback + * function for writes to that variable. Note that it is not portable + * as written, because not all architectures support HW_BREAKPOINT_LEN_4. + * + * ---------------------------------------------------------------------- + * + * #include + * + * struct hw_breakpoint my_bp; + * + * static void my_triggered(struct hw_breakpoint *bp, struct pt_regs *regs) + * { + * printk(KERN_DEBUG "Inside triggered routine of breakpoint exception\n"); + * dump_stack(); + * ............... + * } + * + * static struct hw_breakpoint my_bp; + * + * static int init_module(void) + * { + * ...................... + * my_bp.info.type = HW_BREAKPOINT_WRITE; + * my_bp.info.len = HW_BREAKPOINT_LEN_4; + * + * my_bp.installed = (void *)my_bp_installed; + * + * rc = register_kernel_hw_breakpoint(&my_bp); + * ...................... + * } + * + * static void cleanup_module(void) + * { + * ...................... + * unregister_kernel_hw_breakpoint(&my_bp); + * ...................... + * } + * + * ---------------------------------------------------------------------- + */ +struct hw_breakpoint { + void (*triggered)(struct hw_breakpoint *, struct pt_regs *); + struct arch_hw_breakpoint info; +}; + +/* + * len and type values are defined in include/asm/hw_breakpoint.h. + * Available values vary according to the architecture. On i386 the + * possibilities are: + * + * HW_BREAKPOINT_LEN_1 + * HW_BREAKPOINT_LEN_2 + * HW_BREAKPOINT_LEN_4 + * HW_BREAKPOINT_LEN_EXECUTE + * HW_BREAKPOINT_RW + * HW_BREAKPOINT_READ + * HW_BREAKPOINT_EXECUTE + * + * On other architectures HW_BREAKPOINT_LEN_8 may be available, and the + * 1-, 2-, and 4-byte lengths may be unavailable. There also may be + * HW_BREAKPOINT_WRITE. You can use #ifdef to check at compile time. + */ + +/* + * Kernel breakpoints are not associated with any particular thread. + */ +int register_kernel_hw_breakpoint(struct hw_breakpoint *bp); +void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp); +void switch_to_none_hw_breakpoint(void); + +extern unsigned int hbp_kernel_pos; +extern struct task_struct *last_debugged_task; +extern struct mutex hw_breakpoint_mutex; + +#endif /* __KERNEL__ */ +#endif /* _ASM_GENERIC_HW_BREAKPOINT_H */ Index: linux-2.6-tip/arch/Kconfig =================================================================== --- linux-2.6-tip.orig/arch/Kconfig +++ linux-2.6-tip/arch/Kconfig @@ -109,3 +109,7 @@ config HAVE_CLK config HAVE_DMA_API_DEBUG bool + +config HAVE_HW_BREAKPOINT + bool + -- 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/