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-rw-r--r--arch/arm64/kernel/hw_breakpoint.c1031
1 files changed, 1031 insertions, 0 deletions
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
new file mode 100644
index 000000000..e5a0c38f1
--- /dev/null
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -0,0 +1,1031 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ *
+ * Copyright (C) 2012 ARM Limited
+ * Author: Will Deacon <will.deacon@arm.com>
+ */
+
+#define pr_fmt(fmt) "hw-breakpoint: " fmt
+
+#include <linux/compat.h>
+#include <linux/cpu_pm.h>
+#include <linux/errno.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/kprobes.h>
+#include <linux/perf_event.h>
+#include <linux/ptrace.h>
+#include <linux/smp.h>
+#include <linux/uaccess.h>
+
+#include <asm/current.h>
+#include <asm/debug-monitors.h>
+#include <asm/hw_breakpoint.h>
+#include <asm/traps.h>
+#include <asm/cputype.h>
+#include <asm/system_misc.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]);
+
+/* Currently stepping a per-CPU kernel breakpoint. */
+static DEFINE_PER_CPU(int, stepping_kernel_bp);
+
+/* Number of BRP/WRP registers on this CPU. */
+static int core_num_brps;
+static int core_num_wrps;
+
+int hw_breakpoint_slots(int type)
+{
+ /*
+ * 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_warn("unknown slot type: %d\n", type);
+ return 0;
+ }
+}
+
+#define READ_WB_REG_CASE(OFF, N, REG, VAL) \
+ case (OFF + N): \
+ AARCH64_DBG_READ(N, REG, VAL); \
+ break
+
+#define WRITE_WB_REG_CASE(OFF, N, REG, VAL) \
+ case (OFF + N): \
+ AARCH64_DBG_WRITE(N, REG, VAL); \
+ break
+
+#define GEN_READ_WB_REG_CASES(OFF, REG, VAL) \
+ READ_WB_REG_CASE(OFF, 0, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 1, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 2, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 3, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 4, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 5, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 6, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 7, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 8, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 9, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 10, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 11, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 12, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 13, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 14, REG, VAL); \
+ READ_WB_REG_CASE(OFF, 15, REG, VAL)
+
+#define GEN_WRITE_WB_REG_CASES(OFF, REG, VAL) \
+ WRITE_WB_REG_CASE(OFF, 0, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 1, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 2, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 3, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 4, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 5, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 6, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 7, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 8, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 9, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 10, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 11, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 12, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 13, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 14, REG, VAL); \
+ WRITE_WB_REG_CASE(OFF, 15, REG, VAL)
+
+static u64 read_wb_reg(int reg, int n)
+{
+ u64 val = 0;
+
+ switch (reg + n) {
+ GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val);
+ GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val);
+ GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val);
+ GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val);
+ default:
+ pr_warn("attempt to read from unknown breakpoint register %d\n", n);
+ }
+
+ return val;
+}
+NOKPROBE_SYMBOL(read_wb_reg);
+
+static void write_wb_reg(int reg, int n, u64 val)
+{
+ switch (reg + n) {
+ GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val);
+ GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val);
+ GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val);
+ GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val);
+ default:
+ pr_warn("attempt to write to unknown breakpoint register %d\n", n);
+ }
+ isb();
+}
+NOKPROBE_SYMBOL(write_wb_reg);
+
+/*
+ * Convert a breakpoint privilege level to the corresponding exception
+ * level.
+ */
+static enum dbg_active_el debug_exception_level(int privilege)
+{
+ switch (privilege) {
+ case AARCH64_BREAKPOINT_EL0:
+ return DBG_ACTIVE_EL0;
+ case AARCH64_BREAKPOINT_EL1:
+ return DBG_ACTIVE_EL1;
+ default:
+ pr_warn("invalid breakpoint privilege level %d\n", privilege);
+ return -EINVAL;
+ }
+}
+NOKPROBE_SYMBOL(debug_exception_level);
+
+enum hw_breakpoint_ops {
+ HW_BREAKPOINT_INSTALL,
+ HW_BREAKPOINT_UNINSTALL,
+ HW_BREAKPOINT_RESTORE
+};
+
+static int is_compat_bp(struct perf_event *bp)
+{
+ struct task_struct *tsk = bp->hw.target;
+
+ /*
+ * tsk can be NULL for per-cpu (non-ptrace) breakpoints.
+ * In this case, use the native interface, since we don't have
+ * the notion of a "compat CPU" and could end up relying on
+ * deprecated behaviour if we use unaligned watchpoints in
+ * AArch64 state.
+ */
+ return tsk && is_compat_thread(task_thread_info(tsk));
+}
+
+/**
+ * hw_breakpoint_slot_setup - Find and setup a perf slot according to
+ * operations
+ *
+ * @slots: pointer to array of slots
+ * @max_slots: max number of slots
+ * @bp: perf_event to setup
+ * @ops: operation to be carried out on the slot
+ *
+ * Return:
+ * slot index on success
+ * -ENOSPC if no slot is available/matches
+ * -EINVAL on wrong operations parameter
+ */
+static int hw_breakpoint_slot_setup(struct perf_event **slots, int max_slots,
+ struct perf_event *bp,
+ enum hw_breakpoint_ops ops)
+{
+ int i;
+ struct perf_event **slot;
+
+ for (i = 0; i < max_slots; ++i) {
+ slot = &slots[i];
+ switch (ops) {
+ case HW_BREAKPOINT_INSTALL:
+ if (!*slot) {
+ *slot = bp;
+ return i;
+ }
+ break;
+ case HW_BREAKPOINT_UNINSTALL:
+ if (*slot == bp) {
+ *slot = NULL;
+ return i;
+ }
+ break;
+ case HW_BREAKPOINT_RESTORE:
+ if (*slot == bp)
+ return i;
+ break;
+ default:
+ pr_warn_once("Unhandled hw breakpoint ops %d\n", ops);
+ return -EINVAL;
+ }
+ }
+ return -ENOSPC;
+}
+
+static int hw_breakpoint_control(struct perf_event *bp,
+ enum hw_breakpoint_ops ops)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ struct perf_event **slots;
+ struct debug_info *debug_info = &current->thread.debug;
+ int i, max_slots, ctrl_reg, val_reg, reg_enable;
+ enum dbg_active_el dbg_el = debug_exception_level(info->ctrl.privilege);
+ u32 ctrl;
+
+ if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
+ /* Breakpoint */
+ ctrl_reg = AARCH64_DBG_REG_BCR;
+ val_reg = AARCH64_DBG_REG_BVR;
+ slots = this_cpu_ptr(bp_on_reg);
+ max_slots = core_num_brps;
+ reg_enable = !debug_info->bps_disabled;
+ } else {
+ /* Watchpoint */
+ ctrl_reg = AARCH64_DBG_REG_WCR;
+ val_reg = AARCH64_DBG_REG_WVR;
+ slots = this_cpu_ptr(wp_on_reg);
+ max_slots = core_num_wrps;
+ reg_enable = !debug_info->wps_disabled;
+ }
+
+ i = hw_breakpoint_slot_setup(slots, max_slots, bp, ops);
+
+ if (WARN_ONCE(i < 0, "Can't find any breakpoint slot"))
+ return i;
+
+ switch (ops) {
+ case HW_BREAKPOINT_INSTALL:
+ /*
+ * Ensure debug monitors are enabled at the correct exception
+ * level.
+ */
+ enable_debug_monitors(dbg_el);
+ fallthrough;
+ case HW_BREAKPOINT_RESTORE:
+ /* Setup the address register. */
+ write_wb_reg(val_reg, i, info->address);
+
+ /* Setup the control register. */
+ ctrl = encode_ctrl_reg(info->ctrl);
+ write_wb_reg(ctrl_reg, i,
+ reg_enable ? ctrl | 0x1 : ctrl & ~0x1);
+ break;
+ case HW_BREAKPOINT_UNINSTALL:
+ /* Reset the control register. */
+ write_wb_reg(ctrl_reg, i, 0);
+
+ /*
+ * Release the debug monitors for the correct exception
+ * level.
+ */
+ disable_debug_monitors(dbg_el);
+ break;
+ }
+
+ return 0;
+}
+
+/*
+ * Install a perf counter breakpoint.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+ return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL);
+}
+
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+ hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL);
+}
+
+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_3:
+ len_in_bytes = 3;
+ break;
+ case ARM_BREAKPOINT_LEN_4:
+ len_in_bytes = 4;
+ break;
+ case ARM_BREAKPOINT_LEN_5:
+ len_in_bytes = 5;
+ break;
+ case ARM_BREAKPOINT_LEN_6:
+ len_in_bytes = 6;
+ break;
+ case ARM_BREAKPOINT_LEN_7:
+ len_in_bytes = 7;
+ 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 arch_hw_breakpoint *hw)
+{
+ unsigned int len;
+ unsigned long va;
+
+ va = hw->address;
+ len = get_hbp_len(hw->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, int *offset)
+{
+ /* 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;
+ }
+
+ if (!ctrl.len)
+ return -EINVAL;
+ *offset = __ffs(ctrl.len);
+
+ /* Len */
+ switch (ctrl.len >> *offset) {
+ 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_3:
+ *gen_len = HW_BREAKPOINT_LEN_3;
+ break;
+ case ARM_BREAKPOINT_LEN_4:
+ *gen_len = HW_BREAKPOINT_LEN_4;
+ break;
+ case ARM_BREAKPOINT_LEN_5:
+ *gen_len = HW_BREAKPOINT_LEN_5;
+ break;
+ case ARM_BREAKPOINT_LEN_6:
+ *gen_len = HW_BREAKPOINT_LEN_6;
+ break;
+ case ARM_BREAKPOINT_LEN_7:
+ *gen_len = HW_BREAKPOINT_LEN_7;
+ 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,
+ const struct perf_event_attr *attr,
+ struct arch_hw_breakpoint *hw)
+{
+ /* Type */
+ switch (attr->bp_type) {
+ case HW_BREAKPOINT_X:
+ hw->ctrl.type = ARM_BREAKPOINT_EXECUTE;
+ break;
+ case HW_BREAKPOINT_R:
+ hw->ctrl.type = ARM_BREAKPOINT_LOAD;
+ break;
+ case HW_BREAKPOINT_W:
+ hw->ctrl.type = ARM_BREAKPOINT_STORE;
+ break;
+ case HW_BREAKPOINT_RW:
+ hw->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* Len */
+ switch (attr->bp_len) {
+ case HW_BREAKPOINT_LEN_1:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_1;
+ break;
+ case HW_BREAKPOINT_LEN_2:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_2;
+ break;
+ case HW_BREAKPOINT_LEN_3:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_3;
+ break;
+ case HW_BREAKPOINT_LEN_4:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_4;
+ break;
+ case HW_BREAKPOINT_LEN_5:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_5;
+ break;
+ case HW_BREAKPOINT_LEN_6:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_6;
+ break;
+ case HW_BREAKPOINT_LEN_7:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_7;
+ break;
+ case HW_BREAKPOINT_LEN_8:
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_8;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /*
+ * On AArch64, we only permit breakpoints of length 4, whereas
+ * AArch32 also requires breakpoints of length 2 for Thumb.
+ * Watchpoints can be of length 1, 2, 4 or 8 bytes.
+ */
+ if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
+ if (is_compat_bp(bp)) {
+ if (hw->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
+ hw->ctrl.len != ARM_BREAKPOINT_LEN_4)
+ return -EINVAL;
+ } else if (hw->ctrl.len != ARM_BREAKPOINT_LEN_4) {
+ /*
+ * FIXME: Some tools (I'm looking at you perf) assume
+ * that breakpoints should be sizeof(long). This
+ * is nonsense. For now, we fix up the parameter
+ * but we should probably return -EINVAL instead.
+ */
+ hw->ctrl.len = ARM_BREAKPOINT_LEN_4;
+ }
+ }
+
+ /* Address */
+ hw->address = attr->bp_addr;
+
+ /*
+ * Privilege
+ * Note that we disallow combined EL0/EL1 breakpoints because
+ * that would complicate the stepping code.
+ */
+ if (arch_check_bp_in_kernelspace(hw))
+ hw->ctrl.privilege = AARCH64_BREAKPOINT_EL1;
+ else
+ hw->ctrl.privilege = AARCH64_BREAKPOINT_EL0;
+
+ /* Enabled? */
+ hw->ctrl.enabled = !attr->disabled;
+
+ return 0;
+}
+
+/*
+ * Validate the arch-specific HW Breakpoint register settings.
+ */
+int hw_breakpoint_arch_parse(struct perf_event *bp,
+ const struct perf_event_attr *attr,
+ struct arch_hw_breakpoint *hw)
+{
+ int ret;
+ u64 alignment_mask, offset;
+
+ /* Build the arch_hw_breakpoint. */
+ ret = arch_build_bp_info(bp, attr, hw);
+ if (ret)
+ return ret;
+
+ /*
+ * Check address alignment.
+ * We don't do any clever alignment correction for watchpoints
+ * because using 64-bit unaligned addresses is deprecated for
+ * AArch64.
+ *
+ * AArch32 tasks expect some simple alignment fixups, so emulate
+ * that here.
+ */
+ if (is_compat_bp(bp)) {
+ if (hw->ctrl.len == ARM_BREAKPOINT_LEN_8)
+ alignment_mask = 0x7;
+ else
+ alignment_mask = 0x3;
+ offset = hw->address & alignment_mask;
+ switch (offset) {
+ case 0:
+ /* Aligned */
+ break;
+ case 1:
+ case 2:
+ /* Allow halfword watchpoints and breakpoints. */
+ if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
+ break;
+
+ fallthrough;
+ case 3:
+ /* Allow single byte watchpoint. */
+ if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
+ break;
+
+ fallthrough;
+ default:
+ return -EINVAL;
+ }
+ } else {
+ if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE)
+ alignment_mask = 0x3;
+ else
+ alignment_mask = 0x7;
+ offset = hw->address & alignment_mask;
+ }
+
+ hw->address &= ~alignment_mask;
+ hw->ctrl.len <<= offset;
+
+ /*
+ * Disallow per-task kernel breakpoints since these would
+ * complicate the stepping code.
+ */
+ if (hw->ctrl.privilege == AARCH64_BREAKPOINT_EL1 && bp->hw.target)
+ return -EINVAL;
+
+ return 0;
+}
+
+/*
+ * Enable/disable all of the breakpoints active at the specified
+ * exception level at the register level.
+ * This is used when single-stepping after a breakpoint exception.
+ */
+static void toggle_bp_registers(int reg, enum dbg_active_el el, int enable)
+{
+ int i, max_slots, privilege;
+ u32 ctrl;
+ struct perf_event **slots;
+
+ switch (reg) {
+ case AARCH64_DBG_REG_BCR:
+ slots = this_cpu_ptr(bp_on_reg);
+ max_slots = core_num_brps;
+ break;
+ case AARCH64_DBG_REG_WCR:
+ slots = this_cpu_ptr(wp_on_reg);
+ max_slots = core_num_wrps;
+ break;
+ default:
+ return;
+ }
+
+ for (i = 0; i < max_slots; ++i) {
+ if (!slots[i])
+ continue;
+
+ privilege = counter_arch_bp(slots[i])->ctrl.privilege;
+ if (debug_exception_level(privilege) != el)
+ continue;
+
+ ctrl = read_wb_reg(reg, i);
+ if (enable)
+ ctrl |= 0x1;
+ else
+ ctrl &= ~0x1;
+ write_wb_reg(reg, i, ctrl);
+ }
+}
+NOKPROBE_SYMBOL(toggle_bp_registers);
+
+/*
+ * Debug exception handlers.
+ */
+static int breakpoint_handler(unsigned long unused, unsigned int esr,
+ struct pt_regs *regs)
+{
+ int i, step = 0, *kernel_step;
+ u32 ctrl_reg;
+ u64 addr, val;
+ struct perf_event *bp, **slots;
+ struct debug_info *debug_info;
+ struct arch_hw_breakpoint_ctrl ctrl;
+
+ slots = this_cpu_ptr(bp_on_reg);
+ addr = instruction_pointer(regs);
+ debug_info = &current->thread.debug;
+
+ for (i = 0; i < core_num_brps; ++i) {
+ rcu_read_lock();
+
+ bp = slots[i];
+
+ if (bp == NULL)
+ goto unlock;
+
+ /* Check if the breakpoint value matches. */
+ val = read_wb_reg(AARCH64_DBG_REG_BVR, i);
+ if (val != (addr & ~0x3))
+ goto unlock;
+
+ /* Possible match, check the byte address select to confirm. */
+ ctrl_reg = read_wb_reg(AARCH64_DBG_REG_BCR, i);
+ decode_ctrl_reg(ctrl_reg, &ctrl);
+ if (!((1 << (addr & 0x3)) & ctrl.len))
+ goto unlock;
+
+ counter_arch_bp(bp)->trigger = addr;
+ perf_bp_event(bp, regs);
+
+ /* Do we need to handle the stepping? */
+ if (uses_default_overflow_handler(bp))
+ step = 1;
+unlock:
+ rcu_read_unlock();
+ }
+
+ if (!step)
+ return 0;
+
+ if (user_mode(regs)) {
+ debug_info->bps_disabled = 1;
+ toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 0);
+
+ /* If we're already stepping a watchpoint, just return. */
+ if (debug_info->wps_disabled)
+ return 0;
+
+ if (test_thread_flag(TIF_SINGLESTEP))
+ debug_info->suspended_step = 1;
+ else
+ user_enable_single_step(current);
+ } else {
+ toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 0);
+ kernel_step = this_cpu_ptr(&stepping_kernel_bp);
+
+ if (*kernel_step != ARM_KERNEL_STEP_NONE)
+ return 0;
+
+ if (kernel_active_single_step()) {
+ *kernel_step = ARM_KERNEL_STEP_SUSPEND;
+ } else {
+ *kernel_step = ARM_KERNEL_STEP_ACTIVE;
+ kernel_enable_single_step(regs);
+ }
+ }
+
+ return 0;
+}
+NOKPROBE_SYMBOL(breakpoint_handler);
+
+/*
+ * Arm64 hardware does not always report a watchpoint hit address that matches
+ * one of the watchpoints set. It can also report an address "near" the
+ * watchpoint if a single instruction access both watched and unwatched
+ * addresses. There is no straight-forward way, short of disassembling the
+ * offending instruction, to map that address back to the watchpoint. This
+ * function computes the distance of the memory access from the watchpoint as a
+ * heuristic for the likelyhood that a given access triggered the watchpoint.
+ *
+ * See Section D2.10.5 "Determining the memory location that caused a Watchpoint
+ * exception" of ARMv8 Architecture Reference Manual for details.
+ *
+ * The function returns the distance of the address from the bytes watched by
+ * the watchpoint. In case of an exact match, it returns 0.
+ */
+static u64 get_distance_from_watchpoint(unsigned long addr, u64 val,
+ struct arch_hw_breakpoint_ctrl *ctrl)
+{
+ u64 wp_low, wp_high;
+ u32 lens, lene;
+
+ addr = untagged_addr(addr);
+
+ lens = __ffs(ctrl->len);
+ lene = __fls(ctrl->len);
+
+ wp_low = val + lens;
+ wp_high = val + lene;
+ if (addr < wp_low)
+ return wp_low - addr;
+ else if (addr > wp_high)
+ return addr - wp_high;
+ else
+ return 0;
+}
+
+static int watchpoint_report(struct perf_event *wp, unsigned long addr,
+ struct pt_regs *regs)
+{
+ int step = uses_default_overflow_handler(wp);
+ struct arch_hw_breakpoint *info = counter_arch_bp(wp);
+
+ info->trigger = addr;
+
+ /*
+ * If we triggered a user watchpoint from a uaccess routine, then
+ * handle the stepping ourselves since userspace really can't help
+ * us with this.
+ */
+ if (!user_mode(regs) && info->ctrl.privilege == AARCH64_BREAKPOINT_EL0)
+ step = 1;
+ else
+ perf_bp_event(wp, regs);
+
+ return step;
+}
+
+static int watchpoint_handler(unsigned long addr, unsigned int esr,
+ struct pt_regs *regs)
+{
+ int i, step = 0, *kernel_step, access, closest_match = 0;
+ u64 min_dist = -1, dist;
+ u32 ctrl_reg;
+ u64 val;
+ struct perf_event *wp, **slots;
+ struct debug_info *debug_info;
+ struct arch_hw_breakpoint_ctrl ctrl;
+
+ slots = this_cpu_ptr(wp_on_reg);
+ debug_info = &current->thread.debug;
+
+ /*
+ * Find all watchpoints that match the reported address. If no exact
+ * match is found. Attribute the hit to the closest watchpoint.
+ */
+ rcu_read_lock();
+ for (i = 0; i < core_num_wrps; ++i) {
+ wp = slots[i];
+ if (wp == NULL)
+ continue;
+
+ /*
+ * Check that the access type matches.
+ * 0 => load, otherwise => store
+ */
+ access = (esr & AARCH64_ESR_ACCESS_MASK) ? HW_BREAKPOINT_W :
+ HW_BREAKPOINT_R;
+ if (!(access & hw_breakpoint_type(wp)))
+ continue;
+
+ /* Check if the watchpoint value and byte select match. */
+ val = read_wb_reg(AARCH64_DBG_REG_WVR, i);
+ ctrl_reg = read_wb_reg(AARCH64_DBG_REG_WCR, i);
+ decode_ctrl_reg(ctrl_reg, &ctrl);
+ dist = get_distance_from_watchpoint(addr, val, &ctrl);
+ if (dist < min_dist) {
+ min_dist = dist;
+ closest_match = i;
+ }
+ /* Is this an exact match? */
+ if (dist != 0)
+ continue;
+
+ step = watchpoint_report(wp, addr, regs);
+ }
+
+ /* No exact match found? */
+ if (min_dist > 0 && min_dist != -1)
+ step = watchpoint_report(slots[closest_match], addr, regs);
+
+ rcu_read_unlock();
+
+ if (!step)
+ return 0;
+
+ /*
+ * We always disable EL0 watchpoints because the kernel can
+ * cause these to fire via an unprivileged access.
+ */
+ toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 0);
+
+ if (user_mode(regs)) {
+ debug_info->wps_disabled = 1;
+
+ /* If we're already stepping a breakpoint, just return. */
+ if (debug_info->bps_disabled)
+ return 0;
+
+ if (test_thread_flag(TIF_SINGLESTEP))
+ debug_info->suspended_step = 1;
+ else
+ user_enable_single_step(current);
+ } else {
+ toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 0);
+ kernel_step = this_cpu_ptr(&stepping_kernel_bp);
+
+ if (*kernel_step != ARM_KERNEL_STEP_NONE)
+ return 0;
+
+ if (kernel_active_single_step()) {
+ *kernel_step = ARM_KERNEL_STEP_SUSPEND;
+ } else {
+ *kernel_step = ARM_KERNEL_STEP_ACTIVE;
+ kernel_enable_single_step(regs);
+ }
+ }
+
+ return 0;
+}
+NOKPROBE_SYMBOL(watchpoint_handler);
+
+/*
+ * Handle single-step exception.
+ */
+int reinstall_suspended_bps(struct pt_regs *regs)
+{
+ struct debug_info *debug_info = &current->thread.debug;
+ int handled_exception = 0, *kernel_step;
+
+ kernel_step = this_cpu_ptr(&stepping_kernel_bp);
+
+ /*
+ * Called from single-step exception handler.
+ * Return 0 if execution can resume, 1 if a SIGTRAP should be
+ * reported.
+ */
+ if (user_mode(regs)) {
+ if (debug_info->bps_disabled) {
+ debug_info->bps_disabled = 0;
+ toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 1);
+ handled_exception = 1;
+ }
+
+ if (debug_info->wps_disabled) {
+ debug_info->wps_disabled = 0;
+ toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1);
+ handled_exception = 1;
+ }
+
+ if (handled_exception) {
+ if (debug_info->suspended_step) {
+ debug_info->suspended_step = 0;
+ /* Allow exception handling to fall-through. */
+ handled_exception = 0;
+ } else {
+ user_disable_single_step(current);
+ }
+ }
+ } else if (*kernel_step != ARM_KERNEL_STEP_NONE) {
+ toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 1);
+ toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 1);
+
+ if (!debug_info->wps_disabled)
+ toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1);
+
+ if (*kernel_step != ARM_KERNEL_STEP_SUSPEND) {
+ kernel_disable_single_step();
+ handled_exception = 1;
+ } else {
+ handled_exception = 0;
+ }
+
+ *kernel_step = ARM_KERNEL_STEP_NONE;
+ }
+
+ return !handled_exception;
+}
+NOKPROBE_SYMBOL(reinstall_suspended_bps);
+
+/*
+ * Context-switcher for restoring suspended breakpoints.
+ */
+void hw_breakpoint_thread_switch(struct task_struct *next)
+{
+ /*
+ * current next
+ * disabled: 0 0 => The usual case, NOTIFY_DONE
+ * 0 1 => Disable the registers
+ * 1 0 => Enable the registers
+ * 1 1 => NOTIFY_DONE. per-task bps will
+ * get taken care of by perf.
+ */
+
+ struct debug_info *current_debug_info, *next_debug_info;
+
+ current_debug_info = &current->thread.debug;
+ next_debug_info = &next->thread.debug;
+
+ /* Update breakpoints. */
+ if (current_debug_info->bps_disabled != next_debug_info->bps_disabled)
+ toggle_bp_registers(AARCH64_DBG_REG_BCR,
+ DBG_ACTIVE_EL0,
+ !next_debug_info->bps_disabled);
+
+ /* Update watchpoints. */
+ if (current_debug_info->wps_disabled != next_debug_info->wps_disabled)
+ toggle_bp_registers(AARCH64_DBG_REG_WCR,
+ DBG_ACTIVE_EL0,
+ !next_debug_info->wps_disabled);
+}
+
+/*
+ * CPU initialisation.
+ */
+static int hw_breakpoint_reset(unsigned int cpu)
+{
+ int i;
+ struct perf_event **slots;
+ /*
+ * When a CPU goes through cold-boot, it does not have any installed
+ * slot, so it is safe to share the same function for restoring and
+ * resetting breakpoints; when a CPU is hotplugged in, it goes
+ * through the slots, which are all empty, hence it just resets control
+ * and value for debug registers.
+ * When this function is triggered on warm-boot through a CPU PM
+ * notifier some slots might be initialized; if so they are
+ * reprogrammed according to the debug slots content.
+ */
+ for (slots = this_cpu_ptr(bp_on_reg), i = 0; i < core_num_brps; ++i) {
+ if (slots[i]) {
+ hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE);
+ } else {
+ write_wb_reg(AARCH64_DBG_REG_BCR, i, 0UL);
+ write_wb_reg(AARCH64_DBG_REG_BVR, i, 0UL);
+ }
+ }
+
+ for (slots = this_cpu_ptr(wp_on_reg), i = 0; i < core_num_wrps; ++i) {
+ if (slots[i]) {
+ hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE);
+ } else {
+ write_wb_reg(AARCH64_DBG_REG_WCR, i, 0UL);
+ write_wb_reg(AARCH64_DBG_REG_WVR, i, 0UL);
+ }
+ }
+
+ return 0;
+}
+
+#ifdef CONFIG_CPU_PM
+extern void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int));
+#else
+static inline void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
+{
+}
+#endif
+
+/*
+ * One-time initialisation.
+ */
+static int __init arch_hw_breakpoint_init(void)
+{
+ int ret;
+
+ core_num_brps = get_num_brps();
+ core_num_wrps = get_num_wrps();
+
+ pr_info("found %d breakpoint and %d watchpoint registers.\n",
+ core_num_brps, core_num_wrps);
+
+ /* Register debug fault handlers. */
+ hook_debug_fault_code(DBG_ESR_EVT_HWBP, breakpoint_handler, SIGTRAP,
+ TRAP_HWBKPT, "hw-breakpoint handler");
+ hook_debug_fault_code(DBG_ESR_EVT_HWWP, watchpoint_handler, SIGTRAP,
+ TRAP_HWBKPT, "hw-watchpoint handler");
+
+ /*
+ * Reset the breakpoint resources. We assume that a halting
+ * debugger will leave the world in a nice state for us.
+ */
+ ret = cpuhp_setup_state(CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING,
+ "perf/arm64/hw_breakpoint:starting",
+ hw_breakpoint_reset, NULL);
+ if (ret)
+ pr_err("failed to register CPU hotplug notifier: %d\n", ret);
+
+ /* Register cpu_suspend hw breakpoint restore hook */
+ cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);
+
+ return ret;
+}
+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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-26 20:18:31 +0000