Merge branch 'mpi-master' into wip-k-fmlpwip-k-fmlp

Conflicts:
	litmus/sched_cedf.c

1 files changed, 978 insertions, 0 deletions

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
new file mode 100644
index 000000000000..87acc25d7a3e
--- /dev/null
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -0,0 +1,978 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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) 2009, 2010 ARM Limited
+ *
+ * Author: Will Deacon <will.deacon@arm.com>
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ */
+#define pr_fmt(fmt) "hw-breakpoint: " fmt
+
+#include <linux/errno.h>
+#include <linux/hardirq.h>
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/smp.h>
+
+#include <asm/cacheflush.h>
+#include <asm/cputype.h>
+#include <asm/current.h>
+#include <asm/hw_breakpoint.h>
+#include <asm/kdebug.h>
+#include <asm/system.h>
+#include <asm/traps.h>
+
+/* Breakpoint currently in use for each BRP. */
+static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
+
+/* Watchpoint currently in use for each WRP. */
+static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
+
+/* Number of BRP/WRP registers on this CPU. */
+static int core_num_brps;
+static int core_num_reserved_brps;
+static int core_num_wrps;
+
+/* Debug architecture version. */
+static u8 debug_arch;
+
+/* Maximum supported watchpoint length. */
+static u8 max_watchpoint_len;
+
+#define READ_WB_REG_CASE(OP2, M, VAL)           \
+        case ((OP2 << 4) + M):                  \
+                ARM_DBG_READ(c ## M, OP2, VAL); \
+                break
+
+#define WRITE_WB_REG_CASE(OP2, M, VAL)          \
+        case ((OP2 << 4) + M):                  \
+                ARM_DBG_WRITE(c ## M, OP2, VAL);\
+                break
+
+#define GEN_READ_WB_REG_CASES(OP2, VAL)         \
+        READ_WB_REG_CASE(OP2, 0, VAL);          \
+        READ_WB_REG_CASE(OP2, 1, VAL);          \
+        READ_WB_REG_CASE(OP2, 2, VAL);          \
+        READ_WB_REG_CASE(OP2, 3, VAL);          \
+        READ_WB_REG_CASE(OP2, 4, VAL);          \
+        READ_WB_REG_CASE(OP2, 5, VAL);          \
+        READ_WB_REG_CASE(OP2, 6, VAL);          \
+        READ_WB_REG_CASE(OP2, 7, VAL);          \
+        READ_WB_REG_CASE(OP2, 8, VAL);          \
+        READ_WB_REG_CASE(OP2, 9, VAL);          \
+        READ_WB_REG_CASE(OP2, 10, VAL);         \
+        READ_WB_REG_CASE(OP2, 11, VAL);         \
+        READ_WB_REG_CASE(OP2, 12, VAL);         \
+        READ_WB_REG_CASE(OP2, 13, VAL);         \
+        READ_WB_REG_CASE(OP2, 14, VAL);         \
+        READ_WB_REG_CASE(OP2, 15, VAL)
+
+#define GEN_WRITE_WB_REG_CASES(OP2, VAL)        \
+        WRITE_WB_REG_CASE(OP2, 0, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 1, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 2, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 3, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 4, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 5, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 6, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 7, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 8, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 9, VAL);         \
+        WRITE_WB_REG_CASE(OP2, 10, VAL);        \
+        WRITE_WB_REG_CASE(OP2, 11, VAL);        \
+        WRITE_WB_REG_CASE(OP2, 12, VAL);        \
+        WRITE_WB_REG_CASE(OP2, 13, VAL);        \
+        WRITE_WB_REG_CASE(OP2, 14, VAL);        \
+        WRITE_WB_REG_CASE(OP2, 15, VAL)
+
+static u32 read_wb_reg(int n)
+{
+        u32 val = 0;
+
+        switch (n) {
+        GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
+        GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
+        GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
+        GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
+        default:
+                pr_warning("attempt to read from unknown breakpoint "
+                                "register %d\n", n);
+        }
+
+        return val;
+}
+
+static void write_wb_reg(int n, u32 val)
+{
+        switch (n) {
+        GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
+        GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
+        GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
+        GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
+        default:
+                pr_warning("attempt to write to unknown breakpoint "
+                                "register %d\n", n);
+        }
+        isb();
+}
+
+/* Determine debug architecture. */
+static u8 get_debug_arch(void)
+{
+        u32 didr;
+
+        /* Do we implement the extended CPUID interface? */
+        if (WARN_ONCE((((read_cpuid_id() >> 16) & 0xf) != 0xf),
+            "CPUID feature registers not supported. "
+            "Assuming v6 debug is present.\n"))
+                return ARM_DEBUG_ARCH_V6;
+
+        ARM_DBG_READ(c0, 0, didr);
+        return (didr >> 16) & 0xf;
+}
+
+u8 arch_get_debug_arch(void)
+{
+        return debug_arch;
+}
+
+static int debug_arch_supported(void)
+{
+        u8 arch = get_debug_arch();
+        return arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14;
+}
+
+/* Determine number of BRP register available. */
+static int get_num_brp_resources(void)
+{
+        u32 didr;
+        ARM_DBG_READ(c0, 0, didr);
+        return ((didr >> 24) & 0xf) + 1;
+}
+
+/* Does this core support mismatch breakpoints? */
+static int core_has_mismatch_brps(void)
+{
+        return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
+                get_num_brp_resources() > 1);
+}
+
+/* Determine number of usable WRPs available. */
+static int get_num_wrps(void)
+{
+        /*
+         * FIXME: When a watchpoint fires, the only way to work out which
+         * watchpoint it was is by disassembling the faulting instruction
+         * and working out the address of the memory access.
+         *
+         * Furthermore, we can only do this if the watchpoint was precise
+         * since imprecise watchpoints prevent us from calculating register
+         * based addresses.
+         *
+         * Providing we have more than 1 breakpoint register, we only report
+         * a single watchpoint register for the time being. This way, we always
+         * know which watchpoint fired. In the future we can either add a
+         * disassembler and address generation emulator, or we can insert a
+         * check to see if the DFAR is set on watchpoint exception entry
+         * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
+         * that it is set on some implementations].
+         */
+
+#if 0
+        int wrps;
+        u32 didr;
+        ARM_DBG_READ(c0, 0, didr);
+        wrps = ((didr >> 28) & 0xf) + 1;
+#endif
+        int wrps = 1;
+
+        if (core_has_mismatch_brps() && wrps >= get_num_brp_resources())
+                wrps = get_num_brp_resources() - 1;
+
+        return wrps;
+}
+
+/* We reserve one breakpoint for each watchpoint. */
+static int get_num_reserved_brps(void)
+{
+        if (core_has_mismatch_brps())
+                return get_num_wrps();
+        return 0;
+}
+
+/* Determine number of usable BRPs available. */
+static int get_num_brps(void)
+{
+        int brps = get_num_brp_resources();
+        if (core_has_mismatch_brps())
+                brps -= get_num_reserved_brps();
+        return brps;
+}
+
+/*
+ * In order to access the breakpoint/watchpoint control registers,
+ * we must be running in debug monitor mode. Unfortunately, we can
+ * be put into halting debug mode at any time by an external debugger
+ * but there is nothing we can do to prevent that.
+ */
+static int enable_monitor_mode(void)
+{
+        u32 dscr;
+        int ret = 0;
+
+        ARM_DBG_READ(c1, 0, dscr);
+
+        /* Ensure that halting mode is disabled. */
+        if (WARN_ONCE(dscr & ARM_DSCR_HDBGEN,
+                        "halting debug mode enabled. Unable to access hardware resources.\n")) {
+                ret = -EPERM;
+                goto out;
+        }
+
+        /* If monitor mode is already enabled, just return. */
+        if (dscr & ARM_DSCR_MDBGEN)
+                goto out;
+
+        /* Write to the corresponding DSCR. */
+        switch (get_debug_arch()) {
+        case ARM_DEBUG_ARCH_V6:
+        case ARM_DEBUG_ARCH_V6_1:
+                ARM_DBG_WRITE(c1, 0, (dscr | ARM_DSCR_MDBGEN));
+                break;
+        case ARM_DEBUG_ARCH_V7_ECP14:
+                ARM_DBG_WRITE(c2, 2, (dscr | ARM_DSCR_MDBGEN));
+                break;
+        default:
+                ret = -ENODEV;
+                goto out;
+        }
+
+        /* Check that the write made it through. */
+        ARM_DBG_READ(c1, 0, dscr);
+        if (!(dscr & ARM_DSCR_MDBGEN))
+                ret = -EPERM;
+
+out:
+        return ret;
+}
+
+int hw_breakpoint_slots(int type)
+{
+        if (!debug_arch_supported())
+                return 0;
+
+        /*
+         * We can be called early, so don't rely on
+         * our static variables being initialised.
+         */
+        switch (type) {
+        case TYPE_INST:
+                return get_num_brps();
+        case TYPE_DATA:
+                return get_num_wrps();
+        default:
+                pr_warning("unknown slot type: %d\n", type);
+                return 0;
+        }
+}
+
+/*
+ * Check if 8-bit byte-address select is available.
+ * This clobbers WRP 0.
+ */
+static u8 get_max_wp_len(void)
+{
+        u32 ctrl_reg;
+        struct arch_hw_breakpoint_ctrl ctrl;
+        u8 size = 4;
+
+        if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
+                goto out;
+
+        memset(&ctrl, 0, sizeof(ctrl));
+        ctrl.len = ARM_BREAKPOINT_LEN_8;
+        ctrl_reg = encode_ctrl_reg(ctrl);
+
+        write_wb_reg(ARM_BASE_WVR, 0);
+        write_wb_reg(ARM_BASE_WCR, ctrl_reg);
+        if ((read_wb_reg(ARM_BASE_WCR) & ctrl_reg) == ctrl_reg)
+                size = 8;
+
+out:
+        return size;
+}
+
+u8 arch_get_max_wp_len(void)
+{
+        return max_watchpoint_len;
+}
+
+/*
+ * Install a perf counter breakpoint.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+        struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+        struct perf_event **slot, **slots;
+        int i, max_slots, ctrl_base, val_base, ret = 0;
+        u32 addr, ctrl;
+
+        /* Ensure that we are in monitor mode and halting mode is disabled. */
+        ret = enable_monitor_mode();
+        if (ret)
+                goto out;
+
+        addr = info->address;
+        ctrl = encode_ctrl_reg(info->ctrl) | 0x1;
+
+        if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
+                /* Breakpoint */
+                ctrl_base = ARM_BASE_BCR;
+                val_base = ARM_BASE_BVR;
+                slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
+                max_slots = core_num_brps;
+                if (info->step_ctrl.enabled) {
+                        /* Override the breakpoint data with the step data. */
+                        addr = info->trigger & ~0x3;
+                        ctrl = encode_ctrl_reg(info->step_ctrl);
+                }
+        } else {
+                /* Watchpoint */
+                if (info->step_ctrl.enabled) {
+                        /* Install into the reserved breakpoint region. */
+                        ctrl_base = ARM_BASE_BCR + core_num_brps;
+                        val_base = ARM_BASE_BVR + core_num_brps;
+                        /* Override the watchpoint data with the step data. */
+                        addr = info->trigger & ~0x3;
+                        ctrl = encode_ctrl_reg(info->step_ctrl);
+                } else {
+                        ctrl_base = ARM_BASE_WCR;
+                        val_base = ARM_BASE_WVR;
+                }
+                slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
+                max_slots = core_num_wrps;
+        }
+
+        for (i = 0; i < max_slots; ++i) {
+                slot = &slots[i];
+
+                if (!*slot) {
+                        *slot = bp;
+                        break;
+                }
+        }
+
+        if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n")) {
+                ret = -EBUSY;
+                goto out;
+        }
+
+        /* Setup the address register. */
+        write_wb_reg(val_base + i, addr);
+
+        /* Setup the control register. */
+        write_wb_reg(ctrl_base + i, ctrl);
+
+out:
+        return ret;
+}
+
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+        struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+        struct perf_event **slot, **slots;
+        int i, max_slots, base;
+
+        if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
+                /* Breakpoint */
+                base = ARM_BASE_BCR;
+                slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
+                max_slots = core_num_brps;
+        } else {
+                /* Watchpoint */
+                if (info->step_ctrl.enabled)
+                        base = ARM_BASE_BCR + core_num_brps;
+                else
+                        base = ARM_BASE_WCR;
+                slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
+                max_slots = core_num_wrps;
+        }
+
+        /* Remove the breakpoint. */
+        for (i = 0; i < max_slots; ++i) {
+                slot = &slots[i];
+
+                if (*slot == bp) {
+                        *slot = NULL;
+                        break;
+                }
+        }
+
+        if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n"))
+                return;
+
+        /* Reset the control register. */
+        write_wb_reg(base + i, 0);
+}
+
+static int get_hbp_len(u8 hbp_len)
+{
+        unsigned int len_in_bytes = 0;
+
+        switch (hbp_len) {
+        case ARM_BREAKPOINT_LEN_1:
+                len_in_bytes = 1;
+                break;
+        case ARM_BREAKPOINT_LEN_2:
+                len_in_bytes = 2;
+                break;
+        case ARM_BREAKPOINT_LEN_4:
+                len_in_bytes = 4;
+                break;
+        case ARM_BREAKPOINT_LEN_8:
+                len_in_bytes = 8;
+                break;
+        }
+
+        return len_in_bytes;
+}
+
+/*
+ * Check whether bp virtual address is 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 = get_hbp_len(info->ctrl.len);
+
+        return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+}
+
+/*
+ * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
+ * Hopefully this will disappear when ptrace can bypass the conversion
+ * to generic breakpoint descriptions.
+ */
+int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
+                           int *gen_len, int *gen_type)
+{
+        /* Type */
+        switch (ctrl.type) {
+        case ARM_BREAKPOINT_EXECUTE:
+                *gen_type = HW_BREAKPOINT_X;
+                break;
+        case ARM_BREAKPOINT_LOAD:
+                *gen_type = HW_BREAKPOINT_R;
+                break;
+        case ARM_BREAKPOINT_STORE:
+                *gen_type = HW_BREAKPOINT_W;
+                break;
+        case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
+                *gen_type = HW_BREAKPOINT_RW;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        /* Len */
+        switch (ctrl.len) {
+        case ARM_BREAKPOINT_LEN_1:
+                *gen_len = HW_BREAKPOINT_LEN_1;
+                break;
+        case ARM_BREAKPOINT_LEN_2:
+                *gen_len = HW_BREAKPOINT_LEN_2;
+                break;
+        case ARM_BREAKPOINT_LEN_4:
+                *gen_len = HW_BREAKPOINT_LEN_4;
+                break;
+        case ARM_BREAKPOINT_LEN_8:
+                *gen_len = HW_BREAKPOINT_LEN_8;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+/*
+ * Construct an arch_hw_breakpoint from a perf_event.
+ */
+static int arch_build_bp_info(struct perf_event *bp)
+{
+        struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+        /* Type */
+        switch (bp->attr.bp_type) {
+        case HW_BREAKPOINT_X:
+                info->ctrl.type = ARM_BREAKPOINT_EXECUTE;
+                break;
+        case HW_BREAKPOINT_R:
+                info->ctrl.type = ARM_BREAKPOINT_LOAD;
+                break;
+        case HW_BREAKPOINT_W:
+                info->ctrl.type = ARM_BREAKPOINT_STORE;
+                break;
+        case HW_BREAKPOINT_RW:
+                info->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        /* Len */
+        switch (bp->attr.bp_len) {
+        case HW_BREAKPOINT_LEN_1:
+                info->ctrl.len = ARM_BREAKPOINT_LEN_1;
+                break;
+        case HW_BREAKPOINT_LEN_2:
+                info->ctrl.len = ARM_BREAKPOINT_LEN_2;
+                break;
+        case HW_BREAKPOINT_LEN_4:
+                info->ctrl.len = ARM_BREAKPOINT_LEN_4;
+                break;
+        case HW_BREAKPOINT_LEN_8:
+                info->ctrl.len = ARM_BREAKPOINT_LEN_8;
+                if ((info->ctrl.type != ARM_BREAKPOINT_EXECUTE)
+                        && max_watchpoint_len >= 8)
+                        break;
+        default:
+                return -EINVAL;
+        }
+
+        /*
+         * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
+         * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
+         * by the hardware and must be aligned to the appropriate number of
+         * bytes.
+         */
+        if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
+            info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
+            info->ctrl.len != ARM_BREAKPOINT_LEN_4)
+                return -EINVAL;
+
+        /* Address */
+        info->address = bp->attr.bp_addr;
+
+        /* Privilege */
+        info->ctrl.privilege = ARM_BREAKPOINT_USER;
+        if (arch_check_bp_in_kernelspace(bp))
+                info->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
+
+        /* Enabled? */
+        info->ctrl.enabled = !bp->attr.disabled;
+
+        /* Mismatch */
+        info->ctrl.mismatch = 0;
+
+        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);
+        int ret = 0;
+        u32 offset, alignment_mask = 0x3;
+
+        /* Build the arch_hw_breakpoint. */
+        ret = arch_build_bp_info(bp);
+        if (ret)
+                goto out;
+
+        /* Check address alignment. */
+        if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
+                alignment_mask = 0x7;
+        offset = info->address & alignment_mask;
+        switch (offset) {
+        case 0:
+                /* Aligned */
+                break;
+        case 1:
+                /* Allow single byte watchpoint. */
+                if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
+                        break;
+        case 2:
+                /* Allow halfword watchpoints and breakpoints. */
+                if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
+                        break;
+        default:
+                ret = -EINVAL;
+                goto out;
+        }
+
+        info->address &= ~alignment_mask;
+        info->ctrl.len <<= offset;
+
+        /*
+         * Currently we rely on an overflow handler to take
+         * care of single-stepping the breakpoint when it fires.
+         * In the case of userspace breakpoints on a core with V7 debug,
+         * we can use the mismatch feature as a poor-man's hardware
+         * single-step, but this only works for per-task breakpoints.
+         */
+        if (WARN_ONCE(!bp->overflow_handler &&
+                (arch_check_bp_in_kernelspace(bp) || !core_has_mismatch_brps()
+                 || !bp->hw.bp_target),
+                        "overflow handler required but none found\n")) {
+                ret = -EINVAL;
+        }
+out:
+        return ret;
+}
+
+/*
+ * Enable/disable single-stepping over the breakpoint bp at address addr.
+ */
+static void enable_single_step(struct perf_event *bp, u32 addr)
+{
+        struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+        arch_uninstall_hw_breakpoint(bp);
+        info->step_ctrl.mismatch  = 1;
+        info->step_ctrl.len       = ARM_BREAKPOINT_LEN_4;
+        info->step_ctrl.type      = ARM_BREAKPOINT_EXECUTE;
+        info->step_ctrl.privilege = info->ctrl.privilege;
+        info->step_ctrl.enabled   = 1;
+        info->trigger             = addr;
+        arch_install_hw_breakpoint(bp);
+}
+
+static void disable_single_step(struct perf_event *bp)
+{
+        arch_uninstall_hw_breakpoint(bp);
+        counter_arch_bp(bp)->step_ctrl.enabled = 0;
+        arch_install_hw_breakpoint(bp);
+}
+
+static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs)
+{
+        int i;
+        struct perf_event *wp, **slots;
+        struct arch_hw_breakpoint *info;
+
+        slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
+
+        /* Without a disassembler, we can only handle 1 watchpoint. */
+        BUG_ON(core_num_wrps > 1);
+
+        for (i = 0; i < core_num_wrps; ++i) {
+                rcu_read_lock();
+
+                wp = slots[i];
+
+                if (wp == NULL) {
+                        rcu_read_unlock();
+                        continue;
+                }
+
+                /*
+                 * The DFAR is an unknown value. Since we only allow a
+                 * single watchpoint, we can set the trigger to the lowest
+                 * possible faulting address.
+                 */
+                info = counter_arch_bp(wp);
+                info->trigger = wp->attr.bp_addr;
+                pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
+                perf_bp_event(wp, regs);
+
+                /*
+                 * If no overflow handler is present, insert a temporary
+                 * mismatch breakpoint so we can single-step over the
+                 * watchpoint trigger.
+                 */
+                if (!wp->overflow_handler)
+                        enable_single_step(wp, instruction_pointer(regs));
+
+                rcu_read_unlock();
+        }
+}
+
+static void watchpoint_single_step_handler(unsigned long pc)
+{
+        int i;
+        struct perf_event *wp, **slots;
+        struct arch_hw_breakpoint *info;
+
+        slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
+
+        for (i = 0; i < core_num_reserved_brps; ++i) {
+                rcu_read_lock();
+
+                wp = slots[i];
+
+                if (wp == NULL)
+                        goto unlock;
+
+                info = counter_arch_bp(wp);
+                if (!info->step_ctrl.enabled)
+                        goto unlock;
+
+                /*
+                 * Restore the original watchpoint if we've completed the
+                 * single-step.
+                 */
+                if (info->trigger != pc)
+                        disable_single_step(wp);
+
+unlock:
+                rcu_read_unlock();
+        }
+}
+
+static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
+{
+        int i;
+        u32 ctrl_reg, val, addr;
+        struct perf_event *bp, **slots;
+        struct arch_hw_breakpoint *info;
+        struct arch_hw_breakpoint_ctrl ctrl;
+
+        slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
+
+        /* The exception entry code places the amended lr in the PC. */
+        addr = regs->ARM_pc;
+
+        /* Check the currently installed breakpoints first. */
+        for (i = 0; i < core_num_brps; ++i) {
+                rcu_read_lock();
+
+                bp = slots[i];
+
+                if (bp == NULL)
+                        goto unlock;
+
+                info = counter_arch_bp(bp);
+
+                /* Check if the breakpoint value matches. */
+                val = read_wb_reg(ARM_BASE_BVR + i);
+                if (val != (addr & ~0x3))
+                        goto mismatch;
+
+                /* Possible match, check the byte address select to confirm. */
+                ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
+                decode_ctrl_reg(ctrl_reg, &ctrl);
+                if ((1 << (addr & 0x3)) & ctrl.len) {
+                        info->trigger = addr;
+                        pr_debug("breakpoint fired: address = 0x%x\n", addr);
+                        perf_bp_event(bp, regs);
+                        if (!bp->overflow_handler)
+                                enable_single_step(bp, addr);
+                        goto unlock;
+                }
+
+mismatch:
+                /* If we're stepping a breakpoint, it can now be restored. */
+                if (info->step_ctrl.enabled)
+                        disable_single_step(bp);
+unlock:
+                rcu_read_unlock();
+        }
+
+        /* Handle any pending watchpoint single-step breakpoints. */
+        watchpoint_single_step_handler(addr);
+}
+
+/*
+ * Called from either the Data Abort Handler [watchpoint] or the
+ * Prefetch Abort Handler [breakpoint] with preemption disabled.
+ */
+static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
+                                 struct pt_regs *regs)
+{
+        int ret = 0;
+        u32 dscr;
+
+        /* We must be called with preemption disabled. */
+        WARN_ON(preemptible());
+
+        /* We only handle watchpoints and hardware breakpoints. */
+        ARM_DBG_READ(c1, 0, dscr);
+
+        /* Perform perf callbacks. */
+        switch (ARM_DSCR_MOE(dscr)) {
+        case ARM_ENTRY_BREAKPOINT:
+                breakpoint_handler(addr, regs);
+                break;
+        case ARM_ENTRY_ASYNC_WATCHPOINT:
+                WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
+        case ARM_ENTRY_SYNC_WATCHPOINT:
+                watchpoint_handler(addr, regs);
+                break;
+        default:
+                ret = 1; /* Unhandled fault. */
+        }
+
+        /*
+         * Re-enable preemption after it was disabled in the
+         * low-level exception handling code.
+         */
+        preempt_enable();
+
+        return ret;
+}
+
+/*
+ * One-time initialisation.
+ */
+static void reset_ctrl_regs(void *info)
+{
+        int i, cpu = smp_processor_id();
+        u32 dbg_power;
+        cpumask_t *cpumask = info;
+
+        /*
+         * v7 debug contains save and restore registers so that debug state
+         * can be maintained across low-power modes without leaving the debug
+         * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
+         * the debug registers out of reset, so we must unlock the OS Lock
+         * Access Register to avoid taking undefined instruction exceptions
+         * later on.
+         */
+        if (debug_arch >= ARM_DEBUG_ARCH_V7_ECP14) {
+                /*
+                 * Ensure sticky power-down is clear (i.e. debug logic is
+                 * powered up).
+                 */
+                asm volatile("mrc p14, 0, %0, c1, c5, 4" : "=r" (dbg_power));
+                if ((dbg_power & 0x1) == 0) {
+                        pr_warning("CPU %d debug is powered down!\n", cpu);
+                        cpumask_or(cpumask, cpumask, cpumask_of(cpu));
+                        return;
+                }
+
+                /*
+                 * Unconditionally clear the lock by writing a value
+                 * other than 0xC5ACCE55 to the access register.
+                 */
+                asm volatile("mcr p14, 0, %0, c1, c0, 4" : : "r" (0));
+                isb();
+
+                /*
+                 * Clear any configured vector-catch events before
+                 * enabling monitor mode.
+                 */
+                asm volatile("mcr p14, 0, %0, c0, c7, 0" : : "r" (0));
+                isb();
+        }
+
+        if (enable_monitor_mode())
+                return;
+
+        /* We must also reset any reserved registers. */
+        for (i = 0; i < core_num_brps + core_num_reserved_brps; ++i) {
+                write_wb_reg(ARM_BASE_BCR + i, 0UL);
+                write_wb_reg(ARM_BASE_BVR + i, 0UL);
+        }
+
+        for (i = 0; i < core_num_wrps; ++i) {
+                write_wb_reg(ARM_BASE_WCR + i, 0UL);
+                write_wb_reg(ARM_BASE_WVR + i, 0UL);
+        }
+}
+
+static int __cpuinit dbg_reset_notify(struct notifier_block *self,
+                                      unsigned long action, void *cpu)
+{
+        if (action == CPU_ONLINE)
+                smp_call_function_single((int)cpu, reset_ctrl_regs, NULL, 1);
+        return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata dbg_reset_nb = {
+        .notifier_call = dbg_reset_notify,
+};
+
+static int __init arch_hw_breakpoint_init(void)
+{
+        u32 dscr;
+        cpumask_t cpumask = { CPU_BITS_NONE };
+
+        debug_arch = get_debug_arch();
+
+        if (!debug_arch_supported()) {
+                pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
+                return 0;
+        }
+
+        /* Determine how many BRPs/WRPs are available. */
+        core_num_brps = get_num_brps();
+        core_num_reserved_brps = get_num_reserved_brps();
+        core_num_wrps = get_num_wrps();
+
+        pr_info("found %d breakpoint and %d watchpoint registers.\n",
+                core_num_brps + core_num_reserved_brps, core_num_wrps);
+
+        if (core_num_reserved_brps)
+                pr_info("%d breakpoint(s) reserved for watchpoint "
+                                "single-step.\n", core_num_reserved_brps);
+
+        /*
+         * Reset the breakpoint resources. We assume that a halting
+         * debugger will leave the world in a nice state for us.
+         */
+        on_each_cpu(reset_ctrl_regs, &cpumask, 1);
+        if (!cpumask_empty(&cpumask)) {
+                core_num_brps = 0;
+                core_num_reserved_brps = 0;
+                core_num_wrps = 0;
+                return 0;
+        }
+
+        ARM_DBG_READ(c1, 0, dscr);
+        if (dscr & ARM_DSCR_HDBGEN) {
+                max_watchpoint_len = 4;
+                pr_warning("halting debug mode enabled. Assuming maximum watchpoint size of %u bytes.\n",
+                           max_watchpoint_len);
+        } else {
+                /* Work out the maximum supported watchpoint length. */
+                max_watchpoint_len = get_max_wp_len();
+                pr_info("maximum watchpoint size is %u bytes.\n",
+                                max_watchpoint_len);
+        }
+
+        /* Register debug fault handler. */
+        hook_fault_code(2, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT,
+                        "watchpoint debug exception");
+        hook_ifault_code(2, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT,
+                        "breakpoint debug exception");
+
+        /* Register hotplug notifier. */
+        register_cpu_notifier(&dbg_reset_nb);
+        return 0;
+}
+arch_initcall(arch_hw_breakpoint_init);
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+}
+
+/*
+ * Dummy function to register with die_notifier.
+ */
+int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
+                                        unsigned long val, void *data)
+{
+        return NOTIFY_DONE;
+}