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>
This commit is contained in:
K.Prasad
Frederic Weisbecker
parent
62a038d34d
commit
0067f12972
3 changed files with 384 additions and 1 deletions
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@ -46,6 +46,7 @@ config X86
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select HAVE_KERNEL_GZIP
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select HAVE_KERNEL_BZIP2
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select HAVE_KERNEL_LZMA
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select HAVE_HW_BREAKPOINT
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config ARCH_DEFCONFIG
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string
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@ -36,7 +36,7 @@ obj-$(CONFIG_X86_64) += sys_x86_64.o x8664_ksyms_64.o
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obj-$(CONFIG_X86_64) += syscall_64.o vsyscall_64.o
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obj-y += bootflag.o e820.o
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obj-y += pci-dma.o quirks.o i8237.o topology.o kdebugfs.o
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obj-y += alternative.o i8253.o pci-nommu.o
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obj-y += alternative.o i8253.o pci-nommu.o hw_breakpoint.o
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obj-y += tsc.o io_delay.o rtc.o
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obj-$(CONFIG_X86_TRAMPOLINE) += trampoline.o
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382
arch/x86/kernel/hw_breakpoint.c
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382
arch/x86/kernel/hw_breakpoint.c
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@ -0,0 +1,382 @@
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/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) 2007 Alan Stern
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* Copyright (C) 2009 IBM Corporation
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*/
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/*
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* HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
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* using the CPU's debug registers.
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*/
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#include <linux/irqflags.h>
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#include <linux/notifier.h>
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#include <linux/kallsyms.h>
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#include <linux/kprobes.h>
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#include <linux/percpu.h>
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#include <linux/kdebug.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <asm/hw_breakpoint.h>
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#include <asm/processor.h>
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#include <asm/debugreg.h>
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/* Unmasked kernel DR7 value */
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static unsigned long kdr7;
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/*
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* Masks for the bits corresponding to registers DR0 - DR3 in DR7 register.
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* Used to clear and verify the status of bits corresponding to DR0 - DR3
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*/
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static const unsigned long dr7_masks[HBP_NUM] = {
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0x000f0003, /* LEN0, R/W0, G0, L0 */
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0x00f0000c, /* LEN1, R/W1, G1, L1 */
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0x0f000030, /* LEN2, R/W2, G2, L2 */
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0xf00000c0 /* LEN3, R/W3, G3, L3 */
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};
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/*
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* Encode the length, type, Exact, and Enable bits for a particular breakpoint
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* as stored in debug register 7.
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*/
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static unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
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{
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unsigned long bp_info;
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bp_info = (len | type) & 0xf;
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bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
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bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE)) |
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DR_GLOBAL_SLOWDOWN;
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return bp_info;
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}
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void arch_update_kernel_hw_breakpoint(void *unused)
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{
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struct hw_breakpoint *bp;
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int i, cpu = get_cpu();
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unsigned long temp_kdr7 = 0;
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/* Don't allow debug exceptions while we update the registers */
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set_debugreg(0UL, 7);
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for (i = hbp_kernel_pos; i < HBP_NUM; i++) {
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per_cpu(this_hbp_kernel[i], cpu) = bp = hbp_kernel[i];
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if (bp) {
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temp_kdr7 |= encode_dr7(i, bp->info.len, bp->info.type);
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set_debugreg(bp->info.address, i);
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}
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}
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/* No need to set DR6. Update the debug registers with kernel-space
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* breakpoint values from kdr7 and user-space requests from the
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* current process
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*/
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kdr7 = temp_kdr7;
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set_debugreg(kdr7 | current->thread.debugreg7, 7);
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put_cpu_no_resched();
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}
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/*
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* Install the thread breakpoints in their debug registers.
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*/
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void arch_install_thread_hw_breakpoint(struct task_struct *tsk)
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{
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struct thread_struct *thread = &(tsk->thread);
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switch (hbp_kernel_pos) {
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case 4:
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set_debugreg(thread->debugreg[3], 3);
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case 3:
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set_debugreg(thread->debugreg[2], 2);
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case 2:
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set_debugreg(thread->debugreg[1], 1);
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case 1:
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set_debugreg(thread->debugreg[0], 0);
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default:
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break;
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}
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/* No need to set DR6 */
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set_debugreg((kdr7 | thread->debugreg7), 7);
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}
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/*
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* Install the debug register values for just the kernel, no thread.
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*/
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void arch_uninstall_thread_hw_breakpoint()
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{
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/* Clear the user-space portion of debugreg7 by setting only kdr7 */
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set_debugreg(kdr7, 7);
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}
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static int get_hbp_len(u8 hbp_len)
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{
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unsigned int len_in_bytes = 0;
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switch (hbp_len) {
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case HW_BREAKPOINT_LEN_1:
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len_in_bytes = 1;
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break;
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case HW_BREAKPOINT_LEN_2:
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len_in_bytes = 2;
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break;
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case HW_BREAKPOINT_LEN_4:
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len_in_bytes = 4;
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break;
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#ifdef CONFIG_X86_64
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case HW_BREAKPOINT_LEN_8:
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len_in_bytes = 8;
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break;
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#endif
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}
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return len_in_bytes;
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}
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/*
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* Check for virtual address in user space.
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*/
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int arch_check_va_in_userspace(unsigned long va, u8 hbp_len)
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{
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unsigned int len;
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len = get_hbp_len(hbp_len);
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return (va <= TASK_SIZE - len);
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}
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/*
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* Check for virtual address in kernel space.
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*/
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int arch_check_va_in_kernelspace(unsigned long va, u8 hbp_len)
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{
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unsigned int len;
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len = get_hbp_len(hbp_len);
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return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
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}
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/*
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* Store a breakpoint's encoded address, length, and type.
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*/
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static int arch_store_info(struct hw_breakpoint *bp, struct task_struct *tsk)
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{
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/*
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* User-space requests will always have the address field populated
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* Symbol names from user-space are rejected
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*/
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if (tsk && bp->info.name)
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return -EINVAL;
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/*
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* For kernel-addresses, either the address or symbol name can be
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* specified.
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*/
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if (bp->info.name)
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bp->info.address = (unsigned long)
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kallsyms_lookup_name(bp->info.name);
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if (bp->info.address)
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return 0;
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return -EINVAL;
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}
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/*
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* Validate the arch-specific HW Breakpoint register settings
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*/
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int arch_validate_hwbkpt_settings(struct hw_breakpoint *bp,
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struct task_struct *tsk)
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{
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unsigned int align;
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int ret = -EINVAL;
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switch (bp->info.type) {
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/*
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* Ptrace-refactoring code
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* For now, we'll allow instruction breakpoint only for user-space
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* addresses
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*/
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case HW_BREAKPOINT_EXECUTE:
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if ((!arch_check_va_in_userspace(bp->info.address,
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bp->info.len)) &&
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bp->info.len != HW_BREAKPOINT_LEN_EXECUTE)
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return ret;
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break;
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case HW_BREAKPOINT_WRITE:
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break;
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case HW_BREAKPOINT_RW:
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break;
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default:
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return ret;
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}
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switch (bp->info.len) {
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case HW_BREAKPOINT_LEN_1:
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align = 0;
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break;
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case HW_BREAKPOINT_LEN_2:
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align = 1;
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break;
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case HW_BREAKPOINT_LEN_4:
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align = 3;
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break;
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#ifdef CONFIG_X86_64
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case HW_BREAKPOINT_LEN_8:
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align = 7;
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break;
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#endif
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default:
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return ret;
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}
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if (bp->triggered)
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ret = arch_store_info(bp, tsk);
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if (ret < 0)
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return ret;
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/*
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* Check that the low-order bits of the address are appropriate
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* for the alignment implied by len.
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*/
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if (bp->info.address & align)
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return -EINVAL;
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/* Check that the virtual address is in the proper range */
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if (tsk) {
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if (!arch_check_va_in_userspace(bp->info.address, bp->info.len))
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return -EFAULT;
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} else {
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if (!arch_check_va_in_kernelspace(bp->info.address,
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bp->info.len))
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return -EFAULT;
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}
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return 0;
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}
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void arch_update_user_hw_breakpoint(int pos, struct task_struct *tsk)
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{
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struct thread_struct *thread = &(tsk->thread);
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struct hw_breakpoint *bp = thread->hbp[pos];
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thread->debugreg7 &= ~dr7_masks[pos];
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if (bp) {
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thread->debugreg[pos] = bp->info.address;
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thread->debugreg7 |= encode_dr7(pos, bp->info.len,
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bp->info.type);
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} else
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thread->debugreg[pos] = 0;
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}
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void arch_flush_thread_hw_breakpoint(struct task_struct *tsk)
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{
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int i;
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struct thread_struct *thread = &(tsk->thread);
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thread->debugreg7 = 0;
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for (i = 0; i < HBP_NUM; i++)
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thread->debugreg[i] = 0;
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}
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/*
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* Handle debug exception notifications.
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*
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* Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
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*
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* NOTIFY_DONE returned if one of the following conditions is true.
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* i) When the causative address is from user-space and the exception
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* is a valid one, i.e. not triggered as a result of lazy debug register
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* switching
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* ii) When there are more bits than trap<n> set in DR6 register (such
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* as BD, BS or BT) indicating that more than one debug condition is
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* met and requires some more action in do_debug().
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*
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* NOTIFY_STOP returned for all other cases
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*
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*/
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int __kprobes hw_breakpoint_handler(struct die_args *args)
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{
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int i, cpu, rc = NOTIFY_STOP;
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struct hw_breakpoint *bp;
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/* The DR6 value is stored in args->err */
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unsigned long dr7, dr6 = args->err;
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/* Do an early return if no trap bits are set in DR6 */
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if ((dr6 & DR_TRAP_BITS) == 0)
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return NOTIFY_DONE;
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/* Lazy debug register switching */
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if (!test_tsk_thread_flag(current, TIF_DEBUG))
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arch_uninstall_thread_hw_breakpoint();
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get_debugreg(dr7, 7);
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/* Disable breakpoints during exception handling */
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set_debugreg(0UL, 7);
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/*
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* Assert that local interrupts are disabled
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* Reset the DRn bits in the virtualized register value.
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* The ptrace trigger routine will add in whatever is needed.
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*/
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current->thread.debugreg6 &= ~DR_TRAP_BITS;
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cpu = get_cpu();
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/* Handle all the breakpoints that were triggered */
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for (i = 0; i < HBP_NUM; ++i) {
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if (likely(!(dr6 & (DR_TRAP0 << i))))
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continue;
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/*
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* Find the corresponding hw_breakpoint structure and
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* invoke its triggered callback.
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*/
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if (i >= hbp_kernel_pos)
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bp = per_cpu(this_hbp_kernel[i], cpu);
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else {
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bp = current->thread.hbp[i];
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if (bp)
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rc = NOTIFY_DONE;
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}
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/*
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* bp can be NULL due to lazy debug register switching
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* or due to the delay between updates of hbp_kernel_pos
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* and this_hbp_kernel.
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*/
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if (!bp)
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continue;
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(bp->triggered)(bp, args->regs);
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}
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if (dr6 & (~DR_TRAP_BITS))
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rc = NOTIFY_DONE;
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set_debugreg(dr7, 7);
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put_cpu_no_resched();
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return rc;
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}
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/*
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* Handle debug exception notifications.
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*/
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int __kprobes hw_breakpoint_exceptions_notify(
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struct notifier_block *unused, unsigned long val, void *data)
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{
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if (val != DIE_DEBUG)
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return NOTIFY_DONE;
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return hw_breakpoint_handler(data);
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}
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