2 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
3 * using the CPU's debug registers.
5 * Copyright (C) 2012 ARM Limited
6 * Author: Will Deacon <will.deacon@arm.com>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #define pr_fmt(fmt) "hw-breakpoint: " fmt
23 #include <linux/compat.h>
24 #include <linux/cpu_pm.h>
25 #include <linux/errno.h>
26 #include <linux/hw_breakpoint.h>
27 #include <linux/kprobes.h>
28 #include <linux/perf_event.h>
29 #include <linux/ptrace.h>
30 #include <linux/smp.h>
31 #include <linux/uaccess.h>
33 #include <asm/current.h>
34 #include <asm/debug-monitors.h>
35 #include <asm/hw_breakpoint.h>
36 #include <asm/traps.h>
37 #include <asm/cputype.h>
38 #include <asm/system_misc.h>
40 /* Breakpoint currently in use for each BRP. */
41 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
43 /* Watchpoint currently in use for each WRP. */
44 static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
46 /* Currently stepping a per-CPU kernel breakpoint. */
47 static DEFINE_PER_CPU(int, stepping_kernel_bp);
49 /* Number of BRP/WRP registers on this CPU. */
50 static int core_num_brps;
51 static int core_num_wrps;
53 int hw_breakpoint_slots(int type)
56 * We can be called early, so don't rely on
57 * our static variables being initialised.
61 return get_num_brps();
63 return get_num_wrps();
65 pr_warning("unknown slot type: %d\n", type);
70 #define READ_WB_REG_CASE(OFF, N, REG, VAL) \
72 AARCH64_DBG_READ(N, REG, VAL); \
75 #define WRITE_WB_REG_CASE(OFF, N, REG, VAL) \
77 AARCH64_DBG_WRITE(N, REG, VAL); \
80 #define GEN_READ_WB_REG_CASES(OFF, REG, VAL) \
81 READ_WB_REG_CASE(OFF, 0, REG, VAL); \
82 READ_WB_REG_CASE(OFF, 1, REG, VAL); \
83 READ_WB_REG_CASE(OFF, 2, REG, VAL); \
84 READ_WB_REG_CASE(OFF, 3, REG, VAL); \
85 READ_WB_REG_CASE(OFF, 4, REG, VAL); \
86 READ_WB_REG_CASE(OFF, 5, REG, VAL); \
87 READ_WB_REG_CASE(OFF, 6, REG, VAL); \
88 READ_WB_REG_CASE(OFF, 7, REG, VAL); \
89 READ_WB_REG_CASE(OFF, 8, REG, VAL); \
90 READ_WB_REG_CASE(OFF, 9, REG, VAL); \
91 READ_WB_REG_CASE(OFF, 10, REG, VAL); \
92 READ_WB_REG_CASE(OFF, 11, REG, VAL); \
93 READ_WB_REG_CASE(OFF, 12, REG, VAL); \
94 READ_WB_REG_CASE(OFF, 13, REG, VAL); \
95 READ_WB_REG_CASE(OFF, 14, REG, VAL); \
96 READ_WB_REG_CASE(OFF, 15, REG, VAL)
98 #define GEN_WRITE_WB_REG_CASES(OFF, REG, VAL) \
99 WRITE_WB_REG_CASE(OFF, 0, REG, VAL); \
100 WRITE_WB_REG_CASE(OFF, 1, REG, VAL); \
101 WRITE_WB_REG_CASE(OFF, 2, REG, VAL); \
102 WRITE_WB_REG_CASE(OFF, 3, REG, VAL); \
103 WRITE_WB_REG_CASE(OFF, 4, REG, VAL); \
104 WRITE_WB_REG_CASE(OFF, 5, REG, VAL); \
105 WRITE_WB_REG_CASE(OFF, 6, REG, VAL); \
106 WRITE_WB_REG_CASE(OFF, 7, REG, VAL); \
107 WRITE_WB_REG_CASE(OFF, 8, REG, VAL); \
108 WRITE_WB_REG_CASE(OFF, 9, REG, VAL); \
109 WRITE_WB_REG_CASE(OFF, 10, REG, VAL); \
110 WRITE_WB_REG_CASE(OFF, 11, REG, VAL); \
111 WRITE_WB_REG_CASE(OFF, 12, REG, VAL); \
112 WRITE_WB_REG_CASE(OFF, 13, REG, VAL); \
113 WRITE_WB_REG_CASE(OFF, 14, REG, VAL); \
114 WRITE_WB_REG_CASE(OFF, 15, REG, VAL)
116 static u64 read_wb_reg(int reg, int n)
121 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val);
122 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val);
123 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val);
124 GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val);
126 pr_warning("attempt to read from unknown breakpoint register %d\n", n);
131 NOKPROBE_SYMBOL(read_wb_reg);
133 static void write_wb_reg(int reg, int n, u64 val)
136 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val);
137 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val);
138 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val);
139 GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val);
141 pr_warning("attempt to write to unknown breakpoint register %d\n", n);
145 NOKPROBE_SYMBOL(write_wb_reg);
148 * Convert a breakpoint privilege level to the corresponding exception
151 static enum dbg_active_el debug_exception_level(int privilege)
154 case AARCH64_BREAKPOINT_EL0:
155 return DBG_ACTIVE_EL0;
156 case AARCH64_BREAKPOINT_EL1:
157 return DBG_ACTIVE_EL1;
159 pr_warning("invalid breakpoint privilege level %d\n", privilege);
163 NOKPROBE_SYMBOL(debug_exception_level);
165 enum hw_breakpoint_ops {
166 HW_BREAKPOINT_INSTALL,
167 HW_BREAKPOINT_UNINSTALL,
168 HW_BREAKPOINT_RESTORE
171 static int is_compat_bp(struct perf_event *bp)
173 struct task_struct *tsk = bp->hw.target;
176 * tsk can be NULL for per-cpu (non-ptrace) breakpoints.
177 * In this case, use the native interface, since we don't have
178 * the notion of a "compat CPU" and could end up relying on
179 * deprecated behaviour if we use unaligned watchpoints in
182 return tsk && is_compat_thread(task_thread_info(tsk));
186 * hw_breakpoint_slot_setup - Find and setup a perf slot according to
189 * @slots: pointer to array of slots
190 * @max_slots: max number of slots
191 * @bp: perf_event to setup
192 * @ops: operation to be carried out on the slot
195 * slot index on success
196 * -ENOSPC if no slot is available/matches
197 * -EINVAL on wrong operations parameter
199 static int hw_breakpoint_slot_setup(struct perf_event **slots, int max_slots,
200 struct perf_event *bp,
201 enum hw_breakpoint_ops ops)
204 struct perf_event **slot;
206 for (i = 0; i < max_slots; ++i) {
209 case HW_BREAKPOINT_INSTALL:
215 case HW_BREAKPOINT_UNINSTALL:
221 case HW_BREAKPOINT_RESTORE:
226 pr_warn_once("Unhandled hw breakpoint ops %d\n", ops);
233 static int hw_breakpoint_control(struct perf_event *bp,
234 enum hw_breakpoint_ops ops)
236 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
237 struct perf_event **slots;
238 struct debug_info *debug_info = ¤t->thread.debug;
239 int i, max_slots, ctrl_reg, val_reg, reg_enable;
240 enum dbg_active_el dbg_el = debug_exception_level(info->ctrl.privilege);
243 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
245 ctrl_reg = AARCH64_DBG_REG_BCR;
246 val_reg = AARCH64_DBG_REG_BVR;
247 slots = this_cpu_ptr(bp_on_reg);
248 max_slots = core_num_brps;
249 reg_enable = !debug_info->bps_disabled;
252 ctrl_reg = AARCH64_DBG_REG_WCR;
253 val_reg = AARCH64_DBG_REG_WVR;
254 slots = this_cpu_ptr(wp_on_reg);
255 max_slots = core_num_wrps;
256 reg_enable = !debug_info->wps_disabled;
259 i = hw_breakpoint_slot_setup(slots, max_slots, bp, ops);
261 if (WARN_ONCE(i < 0, "Can't find any breakpoint slot"))
265 case HW_BREAKPOINT_INSTALL:
267 * Ensure debug monitors are enabled at the correct exception
270 enable_debug_monitors(dbg_el);
272 case HW_BREAKPOINT_RESTORE:
273 /* Setup the address register. */
274 write_wb_reg(val_reg, i, info->address);
276 /* Setup the control register. */
277 ctrl = encode_ctrl_reg(info->ctrl);
278 write_wb_reg(ctrl_reg, i,
279 reg_enable ? ctrl | 0x1 : ctrl & ~0x1);
281 case HW_BREAKPOINT_UNINSTALL:
282 /* Reset the control register. */
283 write_wb_reg(ctrl_reg, i, 0);
286 * Release the debug monitors for the correct exception
289 disable_debug_monitors(dbg_el);
297 * Install a perf counter breakpoint.
299 int arch_install_hw_breakpoint(struct perf_event *bp)
301 return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL);
304 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
306 hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL);
309 static int get_hbp_len(u8 hbp_len)
311 unsigned int len_in_bytes = 0;
314 case ARM_BREAKPOINT_LEN_1:
317 case ARM_BREAKPOINT_LEN_2:
320 case ARM_BREAKPOINT_LEN_3:
323 case ARM_BREAKPOINT_LEN_4:
326 case ARM_BREAKPOINT_LEN_5:
329 case ARM_BREAKPOINT_LEN_6:
332 case ARM_BREAKPOINT_LEN_7:
335 case ARM_BREAKPOINT_LEN_8:
344 * Check whether bp virtual address is in kernel space.
346 int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
352 len = get_hbp_len(hw->ctrl.len);
354 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
358 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
359 * Hopefully this will disappear when ptrace can bypass the conversion
360 * to generic breakpoint descriptions.
362 int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
363 int *gen_len, int *gen_type, int *offset)
367 case ARM_BREAKPOINT_EXECUTE:
368 *gen_type = HW_BREAKPOINT_X;
370 case ARM_BREAKPOINT_LOAD:
371 *gen_type = HW_BREAKPOINT_R;
373 case ARM_BREAKPOINT_STORE:
374 *gen_type = HW_BREAKPOINT_W;
376 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
377 *gen_type = HW_BREAKPOINT_RW;
385 *offset = __ffs(ctrl.len);
388 switch (ctrl.len >> *offset) {
389 case ARM_BREAKPOINT_LEN_1:
390 *gen_len = HW_BREAKPOINT_LEN_1;
392 case ARM_BREAKPOINT_LEN_2:
393 *gen_len = HW_BREAKPOINT_LEN_2;
395 case ARM_BREAKPOINT_LEN_3:
396 *gen_len = HW_BREAKPOINT_LEN_3;
398 case ARM_BREAKPOINT_LEN_4:
399 *gen_len = HW_BREAKPOINT_LEN_4;
401 case ARM_BREAKPOINT_LEN_5:
402 *gen_len = HW_BREAKPOINT_LEN_5;
404 case ARM_BREAKPOINT_LEN_6:
405 *gen_len = HW_BREAKPOINT_LEN_6;
407 case ARM_BREAKPOINT_LEN_7:
408 *gen_len = HW_BREAKPOINT_LEN_7;
410 case ARM_BREAKPOINT_LEN_8:
411 *gen_len = HW_BREAKPOINT_LEN_8;
421 * Construct an arch_hw_breakpoint from a perf_event.
423 static int arch_build_bp_info(struct perf_event *bp)
425 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
428 switch (bp->attr.bp_type) {
429 case HW_BREAKPOINT_X:
430 info->ctrl.type = ARM_BREAKPOINT_EXECUTE;
432 case HW_BREAKPOINT_R:
433 info->ctrl.type = ARM_BREAKPOINT_LOAD;
435 case HW_BREAKPOINT_W:
436 info->ctrl.type = ARM_BREAKPOINT_STORE;
438 case HW_BREAKPOINT_RW:
439 info->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
446 switch (bp->attr.bp_len) {
447 case HW_BREAKPOINT_LEN_1:
448 info->ctrl.len = ARM_BREAKPOINT_LEN_1;
450 case HW_BREAKPOINT_LEN_2:
451 info->ctrl.len = ARM_BREAKPOINT_LEN_2;
453 case HW_BREAKPOINT_LEN_3:
454 info->ctrl.len = ARM_BREAKPOINT_LEN_3;
456 case HW_BREAKPOINT_LEN_4:
457 info->ctrl.len = ARM_BREAKPOINT_LEN_4;
459 case HW_BREAKPOINT_LEN_5:
460 info->ctrl.len = ARM_BREAKPOINT_LEN_5;
462 case HW_BREAKPOINT_LEN_6:
463 info->ctrl.len = ARM_BREAKPOINT_LEN_6;
465 case HW_BREAKPOINT_LEN_7:
466 info->ctrl.len = ARM_BREAKPOINT_LEN_7;
468 case HW_BREAKPOINT_LEN_8:
469 info->ctrl.len = ARM_BREAKPOINT_LEN_8;
476 * On AArch64, we only permit breakpoints of length 4, whereas
477 * AArch32 also requires breakpoints of length 2 for Thumb.
478 * Watchpoints can be of length 1, 2, 4 or 8 bytes.
480 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
481 if (is_compat_bp(bp)) {
482 if (info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
483 info->ctrl.len != ARM_BREAKPOINT_LEN_4)
485 } else if (info->ctrl.len != ARM_BREAKPOINT_LEN_4) {
487 * FIXME: Some tools (I'm looking at you perf) assume
488 * that breakpoints should be sizeof(long). This
489 * is nonsense. For now, we fix up the parameter
490 * but we should probably return -EINVAL instead.
492 info->ctrl.len = ARM_BREAKPOINT_LEN_4;
497 info->address = bp->attr.bp_addr;
501 * Note that we disallow combined EL0/EL1 breakpoints because
502 * that would complicate the stepping code.
504 if (arch_check_bp_in_kernelspace(info))
505 info->ctrl.privilege = AARCH64_BREAKPOINT_EL1;
507 info->ctrl.privilege = AARCH64_BREAKPOINT_EL0;
510 info->ctrl.enabled = !bp->attr.disabled;
516 * Validate the arch-specific HW Breakpoint register settings.
518 int arch_validate_hwbkpt_settings(struct perf_event *bp)
520 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
522 u64 alignment_mask, offset;
524 /* Build the arch_hw_breakpoint. */
525 ret = arch_build_bp_info(bp);
530 * Check address alignment.
531 * We don't do any clever alignment correction for watchpoints
532 * because using 64-bit unaligned addresses is deprecated for
535 * AArch32 tasks expect some simple alignment fixups, so emulate
538 if (is_compat_bp(bp)) {
539 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
540 alignment_mask = 0x7;
542 alignment_mask = 0x3;
543 offset = info->address & alignment_mask;
549 /* Allow single byte watchpoint. */
550 if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
553 /* Allow halfword watchpoints and breakpoints. */
554 if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
560 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE)
561 alignment_mask = 0x3;
563 alignment_mask = 0x7;
564 offset = info->address & alignment_mask;
567 info->address &= ~alignment_mask;
568 info->ctrl.len <<= offset;
571 * Disallow per-task kernel breakpoints since these would
572 * complicate the stepping code.
574 if (info->ctrl.privilege == AARCH64_BREAKPOINT_EL1 && bp->hw.target)
581 * Enable/disable all of the breakpoints active at the specified
582 * exception level at the register level.
583 * This is used when single-stepping after a breakpoint exception.
585 static void toggle_bp_registers(int reg, enum dbg_active_el el, int enable)
587 int i, max_slots, privilege;
589 struct perf_event **slots;
592 case AARCH64_DBG_REG_BCR:
593 slots = this_cpu_ptr(bp_on_reg);
594 max_slots = core_num_brps;
596 case AARCH64_DBG_REG_WCR:
597 slots = this_cpu_ptr(wp_on_reg);
598 max_slots = core_num_wrps;
604 for (i = 0; i < max_slots; ++i) {
608 privilege = counter_arch_bp(slots[i])->ctrl.privilege;
609 if (debug_exception_level(privilege) != el)
612 ctrl = read_wb_reg(reg, i);
617 write_wb_reg(reg, i, ctrl);
620 NOKPROBE_SYMBOL(toggle_bp_registers);
623 * Debug exception handlers.
625 static int breakpoint_handler(unsigned long unused, unsigned int esr,
626 struct pt_regs *regs)
628 int i, step = 0, *kernel_step;
631 struct perf_event *bp, **slots;
632 struct debug_info *debug_info;
633 struct arch_hw_breakpoint_ctrl ctrl;
635 slots = this_cpu_ptr(bp_on_reg);
636 addr = instruction_pointer(regs);
637 debug_info = ¤t->thread.debug;
639 for (i = 0; i < core_num_brps; ++i) {
647 /* Check if the breakpoint value matches. */
648 val = read_wb_reg(AARCH64_DBG_REG_BVR, i);
649 if (val != (addr & ~0x3))
652 /* Possible match, check the byte address select to confirm. */
653 ctrl_reg = read_wb_reg(AARCH64_DBG_REG_BCR, i);
654 decode_ctrl_reg(ctrl_reg, &ctrl);
655 if (!((1 << (addr & 0x3)) & ctrl.len))
658 counter_arch_bp(bp)->trigger = addr;
659 perf_bp_event(bp, regs);
661 /* Do we need to handle the stepping? */
662 if (is_default_overflow_handler(bp))
671 if (user_mode(regs)) {
672 debug_info->bps_disabled = 1;
673 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 0);
675 /* If we're already stepping a watchpoint, just return. */
676 if (debug_info->wps_disabled)
679 if (test_thread_flag(TIF_SINGLESTEP))
680 debug_info->suspended_step = 1;
682 user_enable_single_step(current);
684 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 0);
685 kernel_step = this_cpu_ptr(&stepping_kernel_bp);
687 if (*kernel_step != ARM_KERNEL_STEP_NONE)
690 if (kernel_active_single_step()) {
691 *kernel_step = ARM_KERNEL_STEP_SUSPEND;
693 *kernel_step = ARM_KERNEL_STEP_ACTIVE;
694 kernel_enable_single_step(regs);
700 NOKPROBE_SYMBOL(breakpoint_handler);
703 * Arm64 hardware does not always report a watchpoint hit address that matches
704 * one of the watchpoints set. It can also report an address "near" the
705 * watchpoint if a single instruction access both watched and unwatched
706 * addresses. There is no straight-forward way, short of disassembling the
707 * offending instruction, to map that address back to the watchpoint. This
708 * function computes the distance of the memory access from the watchpoint as a
709 * heuristic for the likelyhood that a given access triggered the watchpoint.
711 * See Section D2.10.5 "Determining the memory location that caused a Watchpoint
712 * exception" of ARMv8 Architecture Reference Manual for details.
714 * The function returns the distance of the address from the bytes watched by
715 * the watchpoint. In case of an exact match, it returns 0.
717 static u64 get_distance_from_watchpoint(unsigned long addr, u64 val,
718 struct arch_hw_breakpoint_ctrl *ctrl)
723 addr = untagged_addr(addr);
725 lens = __ffs(ctrl->len);
726 lene = __fls(ctrl->len);
729 wp_high = val + lene;
731 return wp_low - addr;
732 else if (addr > wp_high)
733 return addr - wp_high;
738 static int watchpoint_handler(unsigned long addr, unsigned int esr,
739 struct pt_regs *regs)
741 int i, step = 0, *kernel_step, access, closest_match = 0;
742 u64 min_dist = -1, dist;
745 struct perf_event *wp, **slots;
746 struct debug_info *debug_info;
747 struct arch_hw_breakpoint *info;
748 struct arch_hw_breakpoint_ctrl ctrl;
750 slots = this_cpu_ptr(wp_on_reg);
751 debug_info = ¤t->thread.debug;
754 * Find all watchpoints that match the reported address. If no exact
755 * match is found. Attribute the hit to the closest watchpoint.
758 for (i = 0; i < core_num_wrps; ++i) {
764 * Check that the access type matches.
765 * 0 => load, otherwise => store
767 access = (esr & AARCH64_ESR_ACCESS_MASK) ? HW_BREAKPOINT_W :
769 if (!(access & hw_breakpoint_type(wp)))
772 /* Check if the watchpoint value and byte select match. */
773 val = read_wb_reg(AARCH64_DBG_REG_WVR, i);
774 ctrl_reg = read_wb_reg(AARCH64_DBG_REG_WCR, i);
775 decode_ctrl_reg(ctrl_reg, &ctrl);
776 dist = get_distance_from_watchpoint(addr, val, &ctrl);
777 if (dist < min_dist) {
781 /* Is this an exact match? */
785 info = counter_arch_bp(wp);
786 info->trigger = addr;
787 perf_bp_event(wp, regs);
789 /* Do we need to handle the stepping? */
790 if (is_default_overflow_handler(wp))
793 if (min_dist > 0 && min_dist != -1) {
794 /* No exact match found. */
795 wp = slots[closest_match];
796 info = counter_arch_bp(wp);
797 info->trigger = addr;
798 perf_bp_event(wp, regs);
800 /* Do we need to handle the stepping? */
801 if (is_default_overflow_handler(wp))
810 * We always disable EL0 watchpoints because the kernel can
811 * cause these to fire via an unprivileged access.
813 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 0);
815 if (user_mode(regs)) {
816 debug_info->wps_disabled = 1;
818 /* If we're already stepping a breakpoint, just return. */
819 if (debug_info->bps_disabled)
822 if (test_thread_flag(TIF_SINGLESTEP))
823 debug_info->suspended_step = 1;
825 user_enable_single_step(current);
827 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 0);
828 kernel_step = this_cpu_ptr(&stepping_kernel_bp);
830 if (*kernel_step != ARM_KERNEL_STEP_NONE)
833 if (kernel_active_single_step()) {
834 *kernel_step = ARM_KERNEL_STEP_SUSPEND;
836 *kernel_step = ARM_KERNEL_STEP_ACTIVE;
837 kernel_enable_single_step(regs);
843 NOKPROBE_SYMBOL(watchpoint_handler);
846 * Handle single-step exception.
848 int reinstall_suspended_bps(struct pt_regs *regs)
850 struct debug_info *debug_info = ¤t->thread.debug;
851 int handled_exception = 0, *kernel_step;
853 kernel_step = this_cpu_ptr(&stepping_kernel_bp);
856 * Called from single-step exception handler.
857 * Return 0 if execution can resume, 1 if a SIGTRAP should be
860 if (user_mode(regs)) {
861 if (debug_info->bps_disabled) {
862 debug_info->bps_disabled = 0;
863 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 1);
864 handled_exception = 1;
867 if (debug_info->wps_disabled) {
868 debug_info->wps_disabled = 0;
869 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1);
870 handled_exception = 1;
873 if (handled_exception) {
874 if (debug_info->suspended_step) {
875 debug_info->suspended_step = 0;
876 /* Allow exception handling to fall-through. */
877 handled_exception = 0;
879 user_disable_single_step(current);
882 } else if (*kernel_step != ARM_KERNEL_STEP_NONE) {
883 toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 1);
884 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 1);
886 if (!debug_info->wps_disabled)
887 toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1);
889 if (*kernel_step != ARM_KERNEL_STEP_SUSPEND) {
890 kernel_disable_single_step();
891 handled_exception = 1;
893 handled_exception = 0;
896 *kernel_step = ARM_KERNEL_STEP_NONE;
899 return !handled_exception;
901 NOKPROBE_SYMBOL(reinstall_suspended_bps);
904 * Context-switcher for restoring suspended breakpoints.
906 void hw_breakpoint_thread_switch(struct task_struct *next)
910 * disabled: 0 0 => The usual case, NOTIFY_DONE
911 * 0 1 => Disable the registers
912 * 1 0 => Enable the registers
913 * 1 1 => NOTIFY_DONE. per-task bps will
914 * get taken care of by perf.
917 struct debug_info *current_debug_info, *next_debug_info;
919 current_debug_info = ¤t->thread.debug;
920 next_debug_info = &next->thread.debug;
922 /* Update breakpoints. */
923 if (current_debug_info->bps_disabled != next_debug_info->bps_disabled)
924 toggle_bp_registers(AARCH64_DBG_REG_BCR,
926 !next_debug_info->bps_disabled);
928 /* Update watchpoints. */
929 if (current_debug_info->wps_disabled != next_debug_info->wps_disabled)
930 toggle_bp_registers(AARCH64_DBG_REG_WCR,
932 !next_debug_info->wps_disabled);
936 * CPU initialisation.
938 static int hw_breakpoint_reset(unsigned int cpu)
941 struct perf_event **slots;
943 * When a CPU goes through cold-boot, it does not have any installed
944 * slot, so it is safe to share the same function for restoring and
945 * resetting breakpoints; when a CPU is hotplugged in, it goes
946 * through the slots, which are all empty, hence it just resets control
947 * and value for debug registers.
948 * When this function is triggered on warm-boot through a CPU PM
949 * notifier some slots might be initialized; if so they are
950 * reprogrammed according to the debug slots content.
952 for (slots = this_cpu_ptr(bp_on_reg), i = 0; i < core_num_brps; ++i) {
954 hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE);
956 write_wb_reg(AARCH64_DBG_REG_BCR, i, 0UL);
957 write_wb_reg(AARCH64_DBG_REG_BVR, i, 0UL);
961 for (slots = this_cpu_ptr(wp_on_reg), i = 0; i < core_num_wrps; ++i) {
963 hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE);
965 write_wb_reg(AARCH64_DBG_REG_WCR, i, 0UL);
966 write_wb_reg(AARCH64_DBG_REG_WVR, i, 0UL);
974 extern void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int));
976 static inline void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
982 * One-time initialisation.
984 static int __init arch_hw_breakpoint_init(void)
988 core_num_brps = get_num_brps();
989 core_num_wrps = get_num_wrps();
991 pr_info("found %d breakpoint and %d watchpoint registers.\n",
992 core_num_brps, core_num_wrps);
994 /* Register debug fault handlers. */
995 hook_debug_fault_code(DBG_ESR_EVT_HWBP, breakpoint_handler, SIGTRAP,
996 TRAP_HWBKPT, "hw-breakpoint handler");
997 hook_debug_fault_code(DBG_ESR_EVT_HWWP, watchpoint_handler, SIGTRAP,
998 TRAP_HWBKPT, "hw-watchpoint handler");
1001 * Reset the breakpoint resources. We assume that a halting
1002 * debugger will leave the world in a nice state for us.
1004 ret = cpuhp_setup_state(CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING,
1005 "perf/arm64/hw_breakpoint:starting",
1006 hw_breakpoint_reset, NULL);
1008 pr_err("failed to register CPU hotplug notifier: %d\n", ret);
1010 /* Register cpu_suspend hw breakpoint restore hook */
1011 cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);
1015 arch_initcall(arch_hw_breakpoint_init);
1017 void hw_breakpoint_pmu_read(struct perf_event *bp)
1022 * Dummy function to register with die_notifier.
1024 int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
1025 unsigned long val, void *data)