diff options
author | K.Prasad <prasad@linux.vnet.ibm.com> | 2009-06-01 23:43:57 +0530 |
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committer | Frederic Weisbecker <fweisbec@gmail.com> | 2009-06-02 22:46:58 +0200 |
commit | 0067f1297241ea567f2b22a455519752d70fcca9 (patch) | |
tree | 793c8cde0cc4ed0204cc7df82329d5b18808e696 /arch/x86/kernel/hw_breakpoint.c | |
parent | 62a038d34db26771756cf3689e36de638bedd2c4 (diff) |
hw-breakpoints: x86 architecture implementation of Hardware Breakpoint interfaces
This patch introduces the arch-specific implementation of the generic
hardware breakpoints in kernel/hw_breakpoint.c inside x86 specific directories.
It contains functions which help to validate and serve requests using
Hardware Breakpoint registers on x86 processors.
[ fweisbec@gmail.com: fix conflict against kmemcheck ]
Original-patch-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Diffstat (limited to 'arch/x86/kernel/hw_breakpoint.c')
-rw-r--r-- | arch/x86/kernel/hw_breakpoint.c | 382 |
1 files changed, 382 insertions, 0 deletions
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c new file mode 100644 index 00000000000..4867c9f3b5f --- /dev/null +++ b/arch/x86/kernel/hw_breakpoint.c @@ -0,0 +1,382 @@ +/* + * 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) 2009 IBM Corporation + */ + +/* + * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility, + * using the CPU's debug registers. + */ + +#include <linux/irqflags.h> +#include <linux/notifier.h> +#include <linux/kallsyms.h> +#include <linux/kprobes.h> +#include <linux/percpu.h> +#include <linux/kdebug.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/debugreg.h> + +/* Unmasked kernel DR7 value */ +static unsigned long kdr7; + +/* + * Masks for the bits corresponding to registers DR0 - DR3 in DR7 register. + * Used to clear and verify the status of bits corresponding to DR0 - DR3 + */ +static const unsigned long dr7_masks[HBP_NUM] = { + 0x000f0003, /* LEN0, R/W0, G0, L0 */ + 0x00f0000c, /* LEN1, R/W1, G1, L1 */ + 0x0f000030, /* LEN2, R/W2, G2, L2 */ + 0xf00000c0 /* LEN3, R/W3, G3, L3 */ +}; + + +/* + * Encode the length, type, Exact, and Enable bits for a particular breakpoint + * as stored in debug register 7. + */ +static unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type) +{ + unsigned long bp_info; + + bp_info = (len | type) & 0xf; + bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE); + bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE)) | + DR_GLOBAL_SLOWDOWN; + return bp_info; +} + +void arch_update_kernel_hw_breakpoint(void *unused) +{ + struct hw_breakpoint *bp; + int i, cpu = get_cpu(); + unsigned long temp_kdr7 = 0; + + /* Don't allow debug exceptions while we update the registers */ + set_debugreg(0UL, 7); + + for (i = hbp_kernel_pos; i < HBP_NUM; i++) { + per_cpu(this_hbp_kernel[i], cpu) = bp = hbp_kernel[i]; + if (bp) { + temp_kdr7 |= encode_dr7(i, bp->info.len, bp->info.type); + set_debugreg(bp->info.address, i); + } + } + + /* No need to set DR6. Update the debug registers with kernel-space + * breakpoint values from kdr7 and user-space requests from the + * current process + */ + kdr7 = temp_kdr7; + set_debugreg(kdr7 | current->thread.debugreg7, 7); + put_cpu_no_resched(); +} + +/* + * Install the thread breakpoints in their debug registers. + */ +void arch_install_thread_hw_breakpoint(struct task_struct *tsk) +{ + struct thread_struct *thread = &(tsk->thread); + + switch (hbp_kernel_pos) { + case 4: + set_debugreg(thread->debugreg[3], 3); + case 3: + set_debugreg(thread->debugreg[2], 2); + case 2: + set_debugreg(thread->debugreg[1], 1); + case 1: + set_debugreg(thread->debugreg[0], 0); + default: + break; + } + + /* No need to set DR6 */ + set_debugreg((kdr7 | thread->debugreg7), 7); +} + +/* + * Install the debug register values for just the kernel, no thread. + */ +void arch_uninstall_thread_hw_breakpoint() +{ + /* Clear the user-space portion of debugreg7 by setting only kdr7 */ + set_debugreg(kdr7, 7); + +} + +static int get_hbp_len(u8 hbp_len) +{ + unsigned int len_in_bytes = 0; + + switch (hbp_len) { + case HW_BREAKPOINT_LEN_1: + len_in_bytes = 1; + break; + case HW_BREAKPOINT_LEN_2: + len_in_bytes = 2; + break; + case HW_BREAKPOINT_LEN_4: + len_in_bytes = 4; + break; +#ifdef CONFIG_X86_64 + case HW_BREAKPOINT_LEN_8: + len_in_bytes = 8; + break; +#endif + } + return len_in_bytes; +} + +/* + * Check for virtual address in user space. + */ +int arch_check_va_in_userspace(unsigned long va, u8 hbp_len) +{ + unsigned int len; + + len = get_hbp_len(hbp_len); + + return (va <= TASK_SIZE - len); +} + +/* + * Check for virtual address in kernel space. + */ +int arch_check_va_in_kernelspace(unsigned long va, u8 hbp_len) +{ + unsigned int len; + + len = get_hbp_len(hbp_len); + + return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE); +} + +/* + * Store a breakpoint's encoded address, length, and type. + */ +static int arch_store_info(struct hw_breakpoint *bp, struct task_struct *tsk) +{ + /* + * User-space requests will always have the address field populated + * Symbol names from user-space are rejected + */ + if (tsk && bp->info.name) + return -EINVAL; + /* + * For kernel-addresses, either the address or symbol name can be + * specified. + */ + if (bp->info.name) + bp->info.address = (unsigned long) + kallsyms_lookup_name(bp->info.name); + if (bp->info.address) + return 0; + return -EINVAL; +} + +/* + * Validate the arch-specific HW Breakpoint register settings + */ +int arch_validate_hwbkpt_settings(struct hw_breakpoint *bp, + struct task_struct *tsk) +{ + unsigned int align; + int ret = -EINVAL; + + switch (bp->info.type) { + /* + * Ptrace-refactoring code + * For now, we'll allow instruction breakpoint only for user-space + * addresses + */ + case HW_BREAKPOINT_EXECUTE: + if ((!arch_check_va_in_userspace(bp->info.address, + bp->info.len)) && + bp->info.len != HW_BREAKPOINT_LEN_EXECUTE) + return ret; + break; + case HW_BREAKPOINT_WRITE: + break; + case HW_BREAKPOINT_RW: + break; + default: + return ret; + } + + switch (bp->info.len) { + case HW_BREAKPOINT_LEN_1: + align = 0; + break; + case HW_BREAKPOINT_LEN_2: + align = 1; + break; + case HW_BREAKPOINT_LEN_4: + align = 3; + break; +#ifdef CONFIG_X86_64 + case HW_BREAKPOINT_LEN_8: + align = 7; + break; +#endif + default: + return ret; + } + + if (bp->triggered) + ret = arch_store_info(bp, tsk); + + if (ret < 0) + return ret; + /* + * 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; + } + return 0; +} + +void arch_update_user_hw_breakpoint(int pos, struct task_struct *tsk) +{ + struct thread_struct *thread = &(tsk->thread); + struct hw_breakpoint *bp = thread->hbp[pos]; + + thread->debugreg7 &= ~dr7_masks[pos]; + if (bp) { + thread->debugreg[pos] = bp->info.address; + thread->debugreg7 |= encode_dr7(pos, bp->info.len, + bp->info.type); + } else + thread->debugreg[pos] = 0; +} + +void arch_flush_thread_hw_breakpoint(struct task_struct *tsk) +{ + int i; + struct thread_struct *thread = &(tsk->thread); + + thread->debugreg7 = 0; + for (i = 0; i < HBP_NUM; i++) + thread->debugreg[i] = 0; +} + +/* + * Handle debug exception notifications. + * + * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below. + * + * NOTIFY_DONE returned if one of the following conditions is true. + * i) When the causative address is from user-space and the exception + * is a valid one, i.e. not triggered as a result of lazy debug register + * switching + * ii) When there are more bits than trap<n> set in DR6 register (such + * as BD, BS or BT) indicating that more than one debug condition is + * met and requires some more action in do_debug(). + * + * NOTIFY_STOP returned for all other cases + * + */ +int __kprobes hw_breakpoint_handler(struct die_args *args) +{ + int i, cpu, rc = NOTIFY_STOP; + struct hw_breakpoint *bp; + /* The DR6 value is stored in args->err */ + unsigned long dr7, dr6 = args->err; + + /* Do an early return if no trap bits are set in DR6 */ + if ((dr6 & DR_TRAP_BITS) == 0) + return NOTIFY_DONE; + + /* Lazy debug register switching */ + if (!test_tsk_thread_flag(current, TIF_DEBUG)) + arch_uninstall_thread_hw_breakpoint(); + + get_debugreg(dr7, 7); + /* Disable breakpoints during exception handling */ + set_debugreg(0UL, 7); + /* + * Assert that local interrupts are disabled + * Reset the DRn bits in the virtualized register value. + * The ptrace trigger routine will add in whatever is needed. + */ + current->thread.debugreg6 &= ~DR_TRAP_BITS; + cpu = get_cpu(); + + /* Handle all the breakpoints that were triggered */ + for (i = 0; i < HBP_NUM; ++i) { + if (likely(!(dr6 & (DR_TRAP0 << i)))) + continue; + /* + * Find the corresponding hw_breakpoint structure and + * invoke its triggered callback. + */ + if (i >= hbp_kernel_pos) + bp = per_cpu(this_hbp_kernel[i], cpu); + else { + bp = current->thread.hbp[i]; + if (bp) + rc = NOTIFY_DONE; + } + /* + * bp can be NULL due to lazy debug register switching + * or due to the delay between updates of hbp_kernel_pos + * and this_hbp_kernel. + */ + if (!bp) + continue; + + (bp->triggered)(bp, args->regs); + } + if (dr6 & (~DR_TRAP_BITS)) + rc = NOTIFY_DONE; + + set_debugreg(dr7, 7); + put_cpu_no_resched(); + return rc; +} + +/* + * Handle debug exception notifications. + */ +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); +} |