hw-breakpoints: x86 architecture implementation of Hardware Breakpoint interfaces (0067f129) · Commits · 戴 / test

arch/x86/Kconfig

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Original line number	Diff line number	Diff line
		@@ -46,6 +46,7 @@ config X86
		select HAVE_KERNEL_GZIP
		select HAVE_KERNEL_BZIP2
		select HAVE_KERNEL_LZMA
		select HAVE_HW_BREAKPOINT

		config ARCH_DEFCONFIG
		string

arch/x86/kernel/Makefile

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Original line number	Diff line number	Diff line
		@@ -36,7 +36,7 @@ obj-$(CONFIG_X86_64) += sys_x86_64.o x8664_ksyms_64.o
		obj-$(CONFIG_X86_64) += syscall_64.o vsyscall_64.o
		obj-y += bootflag.o e820.o
		obj-y += pci-dma.o quirks.o i8237.o topology.o kdebugfs.o
		obj-y += alternative.o i8253.o pci-nommu.o
		obj-y += alternative.o i8253.o pci-nommu.o hw_breakpoint.o
		obj-y += tsc.o io_delay.o rtc.o

		obj-$(CONFIG_X86_TRAMPOLINE) += trampoline.o

arch/x86/kernel/hw_breakpoint.c

0 → 100644

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Original line number	Diff line number	Diff line
		/*
		* 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);
		}

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