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Diffstat (limited to 'arch/x86/kernel/hw_breakpoint.c')
-rw-r--r--arch/x86/kernel/hw_breakpoint.c514
1 files changed, 514 insertions, 0 deletions
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
new file mode 100644
index 000000000..7114ba220
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+++ b/arch/x86/kernel/hw_breakpoint.c
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+/*
+ * 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
+ * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Authors: Alan Stern <stern@rowland.harvard.edu>
+ * K.Prasad <prasad@linux.vnet.ibm.com>
+ * Frederic Weisbecker <fweisbec@gmail.com>
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ */
+
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/irqflags.h>
+#include <linux/notifier.h>
+#include <linux/kallsyms.h>
+#include <linux/percpu.h>
+#include <linux/kdebug.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+
+#include <asm/hw_breakpoint.h>
+#include <asm/processor.h>
+#include <asm/debugreg.h>
+
+/* Per cpu debug control register value */
+DEFINE_PER_CPU(unsigned long, cpu_dr7);
+EXPORT_PER_CPU_SYMBOL(cpu_dr7);
+
+/* Per cpu debug address registers values */
+static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
+
+/*
+ * Stores the breakpoints currently in use on each breakpoint address
+ * register for each cpus
+ */
+static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
+
+
+static inline 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));
+
+ return bp_info;
+}
+
+/*
+ * Encode the length, type, Exact, and Enable bits for a particular breakpoint
+ * as stored in debug register 7.
+ */
+unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
+{
+ return __encode_dr7(drnum, len, type) | DR_GLOBAL_SLOWDOWN;
+}
+
+/*
+ * Decode the length and type bits for a particular breakpoint as
+ * stored in debug register 7. Return the "enabled" status.
+ */
+int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
+{
+ int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
+
+ *len = (bp_info & 0xc) | 0x40;
+ *type = (bp_info & 0x3) | 0x80;
+
+ return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
+}
+
+/*
+ * Install a perf counter breakpoint.
+ *
+ * We seek a free debug address register and use it for this
+ * breakpoint. Eventually we enable it in the debug control register.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ unsigned long *dr7;
+ int i;
+
+ for (i = 0; i < HBP_NUM; i++) {
+ struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
+
+ if (!*slot) {
+ *slot = bp;
+ break;
+ }
+ }
+
+ if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+ return -EBUSY;
+
+ set_debugreg(info->address, i);
+ __this_cpu_write(cpu_debugreg[i], info->address);
+
+ dr7 = this_cpu_ptr(&cpu_dr7);
+ *dr7 |= encode_dr7(i, info->len, info->type);
+
+ set_debugreg(*dr7, 7);
+ if (info->mask)
+ set_dr_addr_mask(info->mask, i);
+
+ return 0;
+}
+
+/*
+ * Uninstall the breakpoint contained in the given counter.
+ *
+ * First we search the debug address register it uses and then we disable
+ * it.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ unsigned long *dr7;
+ int i;
+
+ for (i = 0; i < HBP_NUM; i++) {
+ struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
+
+ if (*slot == bp) {
+ *slot = NULL;
+ break;
+ }
+ }
+
+ if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+ return;
+
+ dr7 = this_cpu_ptr(&cpu_dr7);
+ *dr7 &= ~__encode_dr7(i, info->len, info->type);
+
+ set_debugreg(*dr7, 7);
+ if (info->mask)
+ set_dr_addr_mask(0, i);
+}
+
+/*
+ * Check for virtual address in kernel space.
+ */
+int arch_check_bp_in_kernelspace(struct perf_event *bp)
+{
+ unsigned int len;
+ unsigned long va;
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+ va = info->address;
+ len = bp->attr.bp_len;
+
+ return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+}
+
+int arch_bp_generic_fields(int x86_len, int x86_type,
+ int *gen_len, int *gen_type)
+{
+ /* Type */
+ switch (x86_type) {
+ case X86_BREAKPOINT_EXECUTE:
+ if (x86_len != X86_BREAKPOINT_LEN_X)
+ return -EINVAL;
+
+ *gen_type = HW_BREAKPOINT_X;
+ *gen_len = sizeof(long);
+ return 0;
+ case X86_BREAKPOINT_WRITE:
+ *gen_type = HW_BREAKPOINT_W;
+ break;
+ case X86_BREAKPOINT_RW:
+ *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* Len */
+ switch (x86_len) {
+ case X86_BREAKPOINT_LEN_1:
+ *gen_len = HW_BREAKPOINT_LEN_1;
+ break;
+ case X86_BREAKPOINT_LEN_2:
+ *gen_len = HW_BREAKPOINT_LEN_2;
+ break;
+ case X86_BREAKPOINT_LEN_4:
+ *gen_len = HW_BREAKPOINT_LEN_4;
+ break;
+#ifdef CONFIG_X86_64
+ case X86_BREAKPOINT_LEN_8:
+ *gen_len = HW_BREAKPOINT_LEN_8;
+ break;
+#endif
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+
+static int arch_build_bp_info(struct perf_event *bp)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+ info->address = bp->attr.bp_addr;
+
+ /* Type */
+ switch (bp->attr.bp_type) {
+ case HW_BREAKPOINT_W:
+ info->type = X86_BREAKPOINT_WRITE;
+ break;
+ case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+ info->type = X86_BREAKPOINT_RW;
+ break;
+ case HW_BREAKPOINT_X:
+ info->type = X86_BREAKPOINT_EXECUTE;
+ /*
+ * x86 inst breakpoints need to have a specific undefined len.
+ * But we still need to check userspace is not trying to setup
+ * an unsupported length, to get a range breakpoint for example.
+ */
+ if (bp->attr.bp_len == sizeof(long)) {
+ info->len = X86_BREAKPOINT_LEN_X;
+ return 0;
+ }
+ default:
+ return -EINVAL;
+ }
+
+ /* Len */
+ info->mask = 0;
+
+ switch (bp->attr.bp_len) {
+ case HW_BREAKPOINT_LEN_1:
+ info->len = X86_BREAKPOINT_LEN_1;
+ break;
+ case HW_BREAKPOINT_LEN_2:
+ info->len = X86_BREAKPOINT_LEN_2;
+ break;
+ case HW_BREAKPOINT_LEN_4:
+ info->len = X86_BREAKPOINT_LEN_4;
+ break;
+#ifdef CONFIG_X86_64
+ case HW_BREAKPOINT_LEN_8:
+ info->len = X86_BREAKPOINT_LEN_8;
+ break;
+#endif
+ default:
+ if (!is_power_of_2(bp->attr.bp_len))
+ return -EINVAL;
+ if (!cpu_has_bpext)
+ return -EOPNOTSUPP;
+ info->mask = bp->attr.bp_len - 1;
+ info->len = X86_BREAKPOINT_LEN_1;
+ }
+
+ return 0;
+}
+
+/*
+ * Validate the arch-specific HW Breakpoint register settings
+ */
+int arch_validate_hwbkpt_settings(struct perf_event *bp)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ unsigned int align;
+ int ret;
+
+
+ ret = arch_build_bp_info(bp);
+ if (ret)
+ return ret;
+
+ switch (info->len) {
+ case X86_BREAKPOINT_LEN_1:
+ align = 0;
+ if (info->mask)
+ align = info->mask;
+ break;
+ case X86_BREAKPOINT_LEN_2:
+ align = 1;
+ break;
+ case X86_BREAKPOINT_LEN_4:
+ align = 3;
+ break;
+#ifdef CONFIG_X86_64
+ case X86_BREAKPOINT_LEN_8:
+ align = 7;
+ break;
+#endif
+ default:
+ WARN_ON_ONCE(1);
+ }
+
+ /*
+ * Check that the low-order bits of the address are appropriate
+ * for the alignment implied by len.
+ */
+ if (info->address & align)
+ return -EINVAL;
+
+ return 0;
+}
+
+/*
+ * Dump the debug register contents to the user.
+ * We can't dump our per cpu values because it
+ * may contain cpu wide breakpoint, something that
+ * doesn't belong to the current task.
+ *
+ * TODO: include non-ptrace user breakpoints (perf)
+ */
+void aout_dump_debugregs(struct user *dump)
+{
+ int i;
+ int dr7 = 0;
+ struct perf_event *bp;
+ struct arch_hw_breakpoint *info;
+ struct thread_struct *thread = &current->thread;
+
+ for (i = 0; i < HBP_NUM; i++) {
+ bp = thread->ptrace_bps[i];
+
+ if (bp && !bp->attr.disabled) {
+ dump->u_debugreg[i] = bp->attr.bp_addr;
+ info = counter_arch_bp(bp);
+ dr7 |= encode_dr7(i, info->len, info->type);
+ } else {
+ dump->u_debugreg[i] = 0;
+ }
+ }
+
+ dump->u_debugreg[4] = 0;
+ dump->u_debugreg[5] = 0;
+ dump->u_debugreg[6] = current->thread.debugreg6;
+
+ dump->u_debugreg[7] = dr7;
+}
+EXPORT_SYMBOL_GPL(aout_dump_debugregs);
+
+/*
+ * Release the user breakpoints used by ptrace
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+ int i;
+ struct thread_struct *t = &tsk->thread;
+
+ for (i = 0; i < HBP_NUM; i++) {
+ unregister_hw_breakpoint(t->ptrace_bps[i]);
+ t->ptrace_bps[i] = NULL;
+ }
+
+ t->debugreg6 = 0;
+ t->ptrace_dr7 = 0;
+}
+
+void hw_breakpoint_restore(void)
+{
+ set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
+ set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
+ set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
+ set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
+ set_debugreg(current->thread.debugreg6, 6);
+ set_debugreg(__this_cpu_read(cpu_dr7), 7);
+}
+EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
+
+/*
+ * 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
+ *
+ */
+static int hw_breakpoint_handler(struct die_args *args)
+{
+ int i, cpu, rc = NOTIFY_STOP;
+ struct perf_event *bp;
+ unsigned long dr7, dr6;
+ unsigned long *dr6_p;
+
+ /* The DR6 value is pointed by args->err */
+ dr6_p = (unsigned long *)ERR_PTR(args->err);
+ dr6 = *dr6_p;
+
+ /* If it's a single step, TRAP bits are random */
+ if (dr6 & DR_STEP)
+ return NOTIFY_DONE;
+
+ /* Do an early return if no trap bits are set in DR6 */
+ if ((dr6 & DR_TRAP_BITS) == 0)
+ return NOTIFY_DONE;
+
+ 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;
+
+ /*
+ * The counter may be concurrently released but that can only
+ * occur from a call_rcu() path. We can then safely fetch
+ * the breakpoint, use its callback, touch its counter
+ * while we are in an rcu_read_lock() path.
+ */
+ rcu_read_lock();
+
+ bp = per_cpu(bp_per_reg[i], cpu);
+ /*
+ * Reset the 'i'th TRAP bit in dr6 to denote completion of
+ * exception handling
+ */
+ (*dr6_p) &= ~(DR_TRAP0 << i);
+ /*
+ * bp can be NULL due to lazy debug register switching
+ * or due to concurrent perf counter removing.
+ */
+ if (!bp) {
+ rcu_read_unlock();
+ break;
+ }
+
+ perf_bp_event(bp, args->regs);
+
+ /*
+ * Set up resume flag to avoid breakpoint recursion when
+ * returning back to origin.
+ */
+ if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
+ args->regs->flags |= X86_EFLAGS_RF;
+
+ rcu_read_unlock();
+ }
+ /*
+ * Further processing in do_debug() is needed for a) user-space
+ * breakpoints (to generate signals) and b) when the system has
+ * taken exception due to multiple causes
+ */
+ if ((current->thread.debugreg6 & DR_TRAP_BITS) ||
+ (dr6 & (~DR_TRAP_BITS)))
+ rc = NOTIFY_DONE;
+
+ set_debugreg(dr7, 7);
+ put_cpu();
+
+ return rc;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+int 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);
+}
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+ /* TODO */
+}
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