2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License version 2 as
4 * published by the Free Software Foundation.
6 * This program is distributed in the hope that it will be useful,
7 * but WITHOUT ANY WARRANTY; without even the implied warranty of
8 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
9 * GNU General Public License for more details.
11 * You should have received a copy of the GNU General Public License
12 * along with this program; if not, write to the Free Software
13 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
15 * Copyright (C) 2009, 2010 ARM Limited
17 * Author: Will Deacon <will.deacon@arm.com>
21 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
22 * using the CPU's debug registers.
24 #define pr_fmt(fmt) "hw-breakpoint: " fmt
26 #include <linux/errno.h>
27 #include <linux/hardirq.h>
28 #include <linux/perf_event.h>
29 #include <linux/hw_breakpoint.h>
30 #include <linux/smp.h>
32 #include <asm/cacheflush.h>
33 #include <asm/cputype.h>
34 #include <asm/current.h>
35 #include <asm/hw_breakpoint.h>
36 #include <asm/kdebug.h>
37 #include <asm/traps.h>
39 /* Breakpoint currently in use for each BRP. */
40 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
42 /* Watchpoint currently in use for each WRP. */
43 static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
45 /* Number of BRP/WRP registers on this CPU. */
46 static int core_num_brps;
47 static int core_num_wrps;
49 /* Debug architecture version. */
52 /* Maximum supported watchpoint length. */
53 static u8 max_watchpoint_len;
55 #define READ_WB_REG_CASE(OP2, M, VAL) \
56 case ((OP2 << 4) + M): \
57 ARM_DBG_READ(c ## M, OP2, VAL); \
60 #define WRITE_WB_REG_CASE(OP2, M, VAL) \
61 case ((OP2 << 4) + M): \
62 ARM_DBG_WRITE(c ## M, OP2, VAL);\
65 #define GEN_READ_WB_REG_CASES(OP2, VAL) \
66 READ_WB_REG_CASE(OP2, 0, VAL); \
67 READ_WB_REG_CASE(OP2, 1, VAL); \
68 READ_WB_REG_CASE(OP2, 2, VAL); \
69 READ_WB_REG_CASE(OP2, 3, VAL); \
70 READ_WB_REG_CASE(OP2, 4, VAL); \
71 READ_WB_REG_CASE(OP2, 5, VAL); \
72 READ_WB_REG_CASE(OP2, 6, VAL); \
73 READ_WB_REG_CASE(OP2, 7, VAL); \
74 READ_WB_REG_CASE(OP2, 8, VAL); \
75 READ_WB_REG_CASE(OP2, 9, VAL); \
76 READ_WB_REG_CASE(OP2, 10, VAL); \
77 READ_WB_REG_CASE(OP2, 11, VAL); \
78 READ_WB_REG_CASE(OP2, 12, VAL); \
79 READ_WB_REG_CASE(OP2, 13, VAL); \
80 READ_WB_REG_CASE(OP2, 14, VAL); \
81 READ_WB_REG_CASE(OP2, 15, VAL)
83 #define GEN_WRITE_WB_REG_CASES(OP2, VAL) \
84 WRITE_WB_REG_CASE(OP2, 0, VAL); \
85 WRITE_WB_REG_CASE(OP2, 1, VAL); \
86 WRITE_WB_REG_CASE(OP2, 2, VAL); \
87 WRITE_WB_REG_CASE(OP2, 3, VAL); \
88 WRITE_WB_REG_CASE(OP2, 4, VAL); \
89 WRITE_WB_REG_CASE(OP2, 5, VAL); \
90 WRITE_WB_REG_CASE(OP2, 6, VAL); \
91 WRITE_WB_REG_CASE(OP2, 7, VAL); \
92 WRITE_WB_REG_CASE(OP2, 8, VAL); \
93 WRITE_WB_REG_CASE(OP2, 9, VAL); \
94 WRITE_WB_REG_CASE(OP2, 10, VAL); \
95 WRITE_WB_REG_CASE(OP2, 11, VAL); \
96 WRITE_WB_REG_CASE(OP2, 12, VAL); \
97 WRITE_WB_REG_CASE(OP2, 13, VAL); \
98 WRITE_WB_REG_CASE(OP2, 14, VAL); \
99 WRITE_WB_REG_CASE(OP2, 15, VAL)
101 static u32 read_wb_reg(int n)
106 GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
107 GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
108 GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
109 GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
111 pr_warning("attempt to read from unknown breakpoint "
118 static void write_wb_reg(int n, u32 val)
121 GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
122 GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
123 GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
124 GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
126 pr_warning("attempt to write to unknown breakpoint "
132 /* Determine debug architecture. */
133 static u8 get_debug_arch(void)
137 /* Do we implement the extended CPUID interface? */
138 if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
139 pr_warning("CPUID feature registers not supported. "
140 "Assuming v6 debug is present.\n");
141 return ARM_DEBUG_ARCH_V6;
144 ARM_DBG_READ(c0, 0, didr);
145 return (didr >> 16) & 0xf;
148 u8 arch_get_debug_arch(void)
153 static int debug_arch_supported(void)
155 u8 arch = get_debug_arch();
157 /* We don't support the memory-mapped interface. */
158 return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) ||
159 arch >= ARM_DEBUG_ARCH_V7_1;
162 /* Can we determine the watchpoint access type from the fsr? */
163 static int debug_exception_updates_fsr(void)
168 /* Determine number of WRP registers available. */
169 static int get_num_wrp_resources(void)
172 ARM_DBG_READ(c0, 0, didr);
173 return ((didr >> 28) & 0xf) + 1;
176 /* Determine number of BRP registers available. */
177 static int get_num_brp_resources(void)
180 ARM_DBG_READ(c0, 0, didr);
181 return ((didr >> 24) & 0xf) + 1;
184 /* Does this core support mismatch breakpoints? */
185 static int core_has_mismatch_brps(void)
187 return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
188 get_num_brp_resources() > 1);
191 /* Determine number of usable WRPs available. */
192 static int get_num_wrps(void)
195 * On debug architectures prior to 7.1, when a watchpoint fires, the
196 * only way to work out which watchpoint it was is by disassembling
197 * the faulting instruction and working out the address of the memory
200 * Furthermore, we can only do this if the watchpoint was precise
201 * since imprecise watchpoints prevent us from calculating register
204 * Providing we have more than 1 breakpoint register, we only report
205 * a single watchpoint register for the time being. This way, we always
206 * know which watchpoint fired. In the future we can either add a
207 * disassembler and address generation emulator, or we can insert a
208 * check to see if the DFAR is set on watchpoint exception entry
209 * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
210 * that it is set on some implementations].
212 if (get_debug_arch() < ARM_DEBUG_ARCH_V7_1)
215 return get_num_wrp_resources();
218 /* Determine number of usable BRPs available. */
219 static int get_num_brps(void)
221 int brps = get_num_brp_resources();
222 return core_has_mismatch_brps() ? brps - 1 : brps;
226 * In order to access the breakpoint/watchpoint control registers,
227 * we must be running in debug monitor mode. Unfortunately, we can
228 * be put into halting debug mode at any time by an external debugger
229 * but there is nothing we can do to prevent that.
231 static int enable_monitor_mode(void)
234 ARM_DBG_READ(c1, 0, dscr);
236 /* If monitor mode is already enabled, just return. */
237 if (dscr & ARM_DSCR_MDBGEN)
240 /* Write to the corresponding DSCR. */
241 switch (get_debug_arch()) {
242 case ARM_DEBUG_ARCH_V6:
243 case ARM_DEBUG_ARCH_V6_1:
244 ARM_DBG_WRITE(c1, 0, (dscr | ARM_DSCR_MDBGEN));
246 case ARM_DEBUG_ARCH_V7_ECP14:
247 case ARM_DEBUG_ARCH_V7_1:
248 ARM_DBG_WRITE(c2, 2, (dscr | ARM_DSCR_MDBGEN));
255 /* Check that the write made it through. */
256 ARM_DBG_READ(c1, 0, dscr);
257 if (WARN_ONCE(!(dscr & ARM_DSCR_MDBGEN),
258 "Failed to enable monitor mode on CPU %d.\n",
266 int hw_breakpoint_slots(int type)
268 if (!debug_arch_supported())
272 * We can be called early, so don't rely on
273 * our static variables being initialised.
277 return get_num_brps();
279 return get_num_wrps();
281 pr_warning("unknown slot type: %d\n", type);
287 * Check if 8-bit byte-address select is available.
288 * This clobbers WRP 0.
290 static u8 get_max_wp_len(void)
293 struct arch_hw_breakpoint_ctrl ctrl;
296 if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
299 memset(&ctrl, 0, sizeof(ctrl));
300 ctrl.len = ARM_BREAKPOINT_LEN_8;
301 ctrl_reg = encode_ctrl_reg(ctrl);
303 write_wb_reg(ARM_BASE_WVR, 0);
304 write_wb_reg(ARM_BASE_WCR, ctrl_reg);
305 if ((read_wb_reg(ARM_BASE_WCR) & ctrl_reg) == ctrl_reg)
312 u8 arch_get_max_wp_len(void)
314 return max_watchpoint_len;
318 * Install a perf counter breakpoint.
320 int arch_install_hw_breakpoint(struct perf_event *bp)
322 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
323 struct perf_event **slot, **slots;
324 int i, max_slots, ctrl_base, val_base, ret = 0;
327 /* Ensure that we are in monitor mode and halting mode is disabled. */
328 ret = enable_monitor_mode();
332 addr = info->address;
333 ctrl = encode_ctrl_reg(info->ctrl) | 0x1;
335 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
337 ctrl_base = ARM_BASE_BCR;
338 val_base = ARM_BASE_BVR;
339 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
340 max_slots = core_num_brps;
343 ctrl_base = ARM_BASE_WCR;
344 val_base = ARM_BASE_WVR;
345 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
346 max_slots = core_num_wrps;
349 for (i = 0; i < max_slots; ++i) {
358 if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n")) {
363 /* Override the breakpoint data with the step data. */
364 if (info->step_ctrl.enabled) {
365 addr = info->trigger & ~0x3;
366 ctrl = encode_ctrl_reg(info->step_ctrl);
367 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) {
369 ctrl_base = ARM_BASE_BCR + core_num_brps;
370 val_base = ARM_BASE_BVR + core_num_brps;
374 /* Setup the address register. */
375 write_wb_reg(val_base + i, addr);
377 /* Setup the control register. */
378 write_wb_reg(ctrl_base + i, ctrl);
384 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
386 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
387 struct perf_event **slot, **slots;
388 int i, max_slots, base;
390 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
393 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
394 max_slots = core_num_brps;
398 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
399 max_slots = core_num_wrps;
402 /* Remove the breakpoint. */
403 for (i = 0; i < max_slots; ++i) {
412 if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n"))
415 /* Ensure that we disable the mismatch breakpoint. */
416 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE &&
417 info->step_ctrl.enabled) {
419 base = ARM_BASE_BCR + core_num_brps;
422 /* Reset the control register. */
423 write_wb_reg(base + i, 0);
426 static int get_hbp_len(u8 hbp_len)
428 unsigned int len_in_bytes = 0;
431 case ARM_BREAKPOINT_LEN_1:
434 case ARM_BREAKPOINT_LEN_2:
437 case ARM_BREAKPOINT_LEN_4:
440 case ARM_BREAKPOINT_LEN_8:
449 * Check whether bp virtual address is in kernel space.
451 int arch_check_bp_in_kernelspace(struct perf_event *bp)
455 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
458 len = get_hbp_len(info->ctrl.len);
460 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
464 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
465 * Hopefully this will disappear when ptrace can bypass the conversion
466 * to generic breakpoint descriptions.
468 int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
469 int *gen_len, int *gen_type)
473 case ARM_BREAKPOINT_EXECUTE:
474 *gen_type = HW_BREAKPOINT_X;
476 case ARM_BREAKPOINT_LOAD:
477 *gen_type = HW_BREAKPOINT_R;
479 case ARM_BREAKPOINT_STORE:
480 *gen_type = HW_BREAKPOINT_W;
482 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
483 *gen_type = HW_BREAKPOINT_RW;
491 case ARM_BREAKPOINT_LEN_1:
492 *gen_len = HW_BREAKPOINT_LEN_1;
494 case ARM_BREAKPOINT_LEN_2:
495 *gen_len = HW_BREAKPOINT_LEN_2;
497 case ARM_BREAKPOINT_LEN_4:
498 *gen_len = HW_BREAKPOINT_LEN_4;
500 case ARM_BREAKPOINT_LEN_8:
501 *gen_len = HW_BREAKPOINT_LEN_8;
511 * Construct an arch_hw_breakpoint from a perf_event.
513 static int arch_build_bp_info(struct perf_event *bp)
515 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
518 switch (bp->attr.bp_type) {
519 case HW_BREAKPOINT_X:
520 info->ctrl.type = ARM_BREAKPOINT_EXECUTE;
522 case HW_BREAKPOINT_R:
523 info->ctrl.type = ARM_BREAKPOINT_LOAD;
525 case HW_BREAKPOINT_W:
526 info->ctrl.type = ARM_BREAKPOINT_STORE;
528 case HW_BREAKPOINT_RW:
529 info->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
536 switch (bp->attr.bp_len) {
537 case HW_BREAKPOINT_LEN_1:
538 info->ctrl.len = ARM_BREAKPOINT_LEN_1;
540 case HW_BREAKPOINT_LEN_2:
541 info->ctrl.len = ARM_BREAKPOINT_LEN_2;
543 case HW_BREAKPOINT_LEN_4:
544 info->ctrl.len = ARM_BREAKPOINT_LEN_4;
546 case HW_BREAKPOINT_LEN_8:
547 info->ctrl.len = ARM_BREAKPOINT_LEN_8;
548 if ((info->ctrl.type != ARM_BREAKPOINT_EXECUTE)
549 && max_watchpoint_len >= 8)
556 * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
557 * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
558 * by the hardware and must be aligned to the appropriate number of
561 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
562 info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
563 info->ctrl.len != ARM_BREAKPOINT_LEN_4)
567 info->address = bp->attr.bp_addr;
570 info->ctrl.privilege = ARM_BREAKPOINT_USER;
571 if (arch_check_bp_in_kernelspace(bp))
572 info->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
575 info->ctrl.enabled = !bp->attr.disabled;
578 info->ctrl.mismatch = 0;
584 * Validate the arch-specific HW Breakpoint register settings.
586 int arch_validate_hwbkpt_settings(struct perf_event *bp)
588 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
590 u32 offset, alignment_mask = 0x3;
592 /* Build the arch_hw_breakpoint. */
593 ret = arch_build_bp_info(bp);
597 /* Check address alignment. */
598 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
599 alignment_mask = 0x7;
600 offset = info->address & alignment_mask;
607 /* Allow halfword watchpoints and breakpoints. */
608 if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
611 /* Allow single byte watchpoint. */
612 if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
619 info->address &= ~alignment_mask;
620 info->ctrl.len <<= offset;
622 if (!bp->overflow_handler) {
624 * Mismatch breakpoints are required for single-stepping
627 if (!core_has_mismatch_brps())
630 /* We don't allow mismatch breakpoints in kernel space. */
631 if (arch_check_bp_in_kernelspace(bp))
635 * Per-cpu breakpoints are not supported by our stepping
638 if (!bp->hw.bp_target)
642 * We only support specific access types if the fsr
645 if (!debug_exception_updates_fsr() &&
646 (info->ctrl.type == ARM_BREAKPOINT_LOAD ||
647 info->ctrl.type == ARM_BREAKPOINT_STORE))
656 * Enable/disable single-stepping over the breakpoint bp at address addr.
658 static void enable_single_step(struct perf_event *bp, u32 addr)
660 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
662 arch_uninstall_hw_breakpoint(bp);
663 info->step_ctrl.mismatch = 1;
664 info->step_ctrl.len = ARM_BREAKPOINT_LEN_4;
665 info->step_ctrl.type = ARM_BREAKPOINT_EXECUTE;
666 info->step_ctrl.privilege = info->ctrl.privilege;
667 info->step_ctrl.enabled = 1;
668 info->trigger = addr;
669 arch_install_hw_breakpoint(bp);
672 static void disable_single_step(struct perf_event *bp)
674 arch_uninstall_hw_breakpoint(bp);
675 counter_arch_bp(bp)->step_ctrl.enabled = 0;
676 arch_install_hw_breakpoint(bp);
679 static void watchpoint_handler(unsigned long addr, unsigned int fsr,
680 struct pt_regs *regs)
683 u32 val, ctrl_reg, alignment_mask;
684 struct perf_event *wp, **slots;
685 struct arch_hw_breakpoint *info;
686 struct arch_hw_breakpoint_ctrl ctrl;
688 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
690 for (i = 0; i < core_num_wrps; ++i) {
698 info = counter_arch_bp(wp);
700 * The DFAR is an unknown value on debug architectures prior
701 * to 7.1. Since we only allow a single watchpoint on these
702 * older CPUs, we can set the trigger to the lowest possible
705 if (debug_arch < ARM_DEBUG_ARCH_V7_1) {
707 info->trigger = wp->attr.bp_addr;
709 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
710 alignment_mask = 0x7;
712 alignment_mask = 0x3;
714 /* Check if the watchpoint value matches. */
715 val = read_wb_reg(ARM_BASE_WVR + i);
716 if (val != (addr & ~alignment_mask))
719 /* Possible match, check the byte address select. */
720 ctrl_reg = read_wb_reg(ARM_BASE_WCR + i);
721 decode_ctrl_reg(ctrl_reg, &ctrl);
722 if (!((1 << (addr & alignment_mask)) & ctrl.len))
725 /* Check that the access type matches. */
726 if (debug_exception_updates_fsr()) {
727 access = (fsr & ARM_FSR_ACCESS_MASK) ?
728 HW_BREAKPOINT_W : HW_BREAKPOINT_R;
729 if (!(access & hw_breakpoint_type(wp)))
733 /* We have a winner. */
734 info->trigger = addr;
737 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
738 perf_bp_event(wp, regs);
741 * If no overflow handler is present, insert a temporary
742 * mismatch breakpoint so we can single-step over the
743 * watchpoint trigger.
745 if (!wp->overflow_handler)
746 enable_single_step(wp, instruction_pointer(regs));
753 static void watchpoint_single_step_handler(unsigned long pc)
756 struct perf_event *wp, **slots;
757 struct arch_hw_breakpoint *info;
759 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
761 for (i = 0; i < core_num_wrps; ++i) {
769 info = counter_arch_bp(wp);
770 if (!info->step_ctrl.enabled)
774 * Restore the original watchpoint if we've completed the
777 if (info->trigger != pc)
778 disable_single_step(wp);
785 static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
788 u32 ctrl_reg, val, addr;
789 struct perf_event *bp, **slots;
790 struct arch_hw_breakpoint *info;
791 struct arch_hw_breakpoint_ctrl ctrl;
793 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
795 /* The exception entry code places the amended lr in the PC. */
798 /* Check the currently installed breakpoints first. */
799 for (i = 0; i < core_num_brps; ++i) {
807 info = counter_arch_bp(bp);
809 /* Check if the breakpoint value matches. */
810 val = read_wb_reg(ARM_BASE_BVR + i);
811 if (val != (addr & ~0x3))
814 /* Possible match, check the byte address select to confirm. */
815 ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
816 decode_ctrl_reg(ctrl_reg, &ctrl);
817 if ((1 << (addr & 0x3)) & ctrl.len) {
818 info->trigger = addr;
819 pr_debug("breakpoint fired: address = 0x%x\n", addr);
820 perf_bp_event(bp, regs);
821 if (!bp->overflow_handler)
822 enable_single_step(bp, addr);
827 /* If we're stepping a breakpoint, it can now be restored. */
828 if (info->step_ctrl.enabled)
829 disable_single_step(bp);
834 /* Handle any pending watchpoint single-step breakpoints. */
835 watchpoint_single_step_handler(addr);
839 * Called from either the Data Abort Handler [watchpoint] or the
840 * Prefetch Abort Handler [breakpoint] with interrupts disabled.
842 static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
843 struct pt_regs *regs)
850 if (interrupts_enabled(regs))
853 /* We only handle watchpoints and hardware breakpoints. */
854 ARM_DBG_READ(c1, 0, dscr);
856 /* Perform perf callbacks. */
857 switch (ARM_DSCR_MOE(dscr)) {
858 case ARM_ENTRY_BREAKPOINT:
859 breakpoint_handler(addr, regs);
861 case ARM_ENTRY_ASYNC_WATCHPOINT:
862 WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
863 case ARM_ENTRY_SYNC_WATCHPOINT:
864 watchpoint_handler(addr, fsr, regs);
867 ret = 1; /* Unhandled fault. */
876 * One-time initialisation.
878 static cpumask_t debug_err_mask;
880 static int debug_reg_trap(struct pt_regs *regs, unsigned int instr)
882 int cpu = smp_processor_id();
884 pr_warning("Debug register access (0x%x) caused undefined instruction on CPU %d\n",
887 /* Set the error flag for this CPU and skip the faulting instruction. */
888 cpumask_set_cpu(cpu, &debug_err_mask);
889 instruction_pointer(regs) += 4;
893 static struct undef_hook debug_reg_hook = {
894 .instr_mask = 0x0fe80f10,
895 .instr_val = 0x0e000e10,
896 .fn = debug_reg_trap,
899 static void reset_ctrl_regs(void *unused)
901 int i, raw_num_brps, err = 0, cpu = smp_processor_id();
905 * v7 debug contains save and restore registers so that debug state
906 * can be maintained across low-power modes without leaving the debug
907 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
908 * the debug registers out of reset, so we must unlock the OS Lock
909 * Access Register to avoid taking undefined instruction exceptions
912 switch (debug_arch) {
913 case ARM_DEBUG_ARCH_V6:
914 case ARM_DEBUG_ARCH_V6_1:
915 /* ARMv6 cores clear the registers out of reset. */
917 case ARM_DEBUG_ARCH_V7_ECP14:
919 * Ensure sticky power-down is clear (i.e. debug logic is
922 asm volatile("mrc p14, 0, %0, c1, c5, 4" : "=r" (val));
923 if ((val & 0x1) == 0)
927 * Check whether we implement OS save and restore.
929 asm volatile("mrc p14, 0, %0, c1, c1, 4" : "=r" (val));
930 if ((val & 0x9) == 0)
933 case ARM_DEBUG_ARCH_V7_1:
935 * Ensure the OS double lock is clear.
937 asm volatile("mrc p14, 0, %0, c1, c3, 4" : "=r" (val));
938 if ((val & 0x1) == 1)
944 pr_warning("CPU %d debug is powered down!\n", cpu);
945 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
950 * Unconditionally clear the OS lock by writing a value
951 * other than 0xC5ACCE55 to the access register.
953 asm volatile("mcr p14, 0, %0, c1, c0, 4" : : "r" (0));
957 * Clear any configured vector-catch events before
958 * enabling monitor mode.
961 asm volatile("mcr p14, 0, %0, c0, c7, 0" : : "r" (0));
964 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
965 pr_warning("CPU %d failed to disable vector catch\n", cpu);
970 * The control/value register pairs are UNKNOWN out of reset so
971 * clear them to avoid spurious debug events.
973 raw_num_brps = get_num_brp_resources();
974 for (i = 0; i < raw_num_brps; ++i) {
975 write_wb_reg(ARM_BASE_BCR + i, 0UL);
976 write_wb_reg(ARM_BASE_BVR + i, 0UL);
979 for (i = 0; i < core_num_wrps; ++i) {
980 write_wb_reg(ARM_BASE_WCR + i, 0UL);
981 write_wb_reg(ARM_BASE_WVR + i, 0UL);
984 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
985 pr_warning("CPU %d failed to clear debug register pairs\n", cpu);
990 * Have a crack at enabling monitor mode. We don't actually need
991 * it yet, but reporting an error early is useful if it fails.
994 if (enable_monitor_mode())
995 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
998 static int __cpuinit dbg_reset_notify(struct notifier_block *self,
999 unsigned long action, void *cpu)
1001 if (action == CPU_ONLINE)
1002 smp_call_function_single((int)cpu, reset_ctrl_regs, NULL, 1);
1007 static struct notifier_block __cpuinitdata dbg_reset_nb = {
1008 .notifier_call = dbg_reset_notify,
1011 static int __init arch_hw_breakpoint_init(void)
1013 debug_arch = get_debug_arch();
1015 if (!debug_arch_supported()) {
1016 pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
1020 /* Determine how many BRPs/WRPs are available. */
1021 core_num_brps = get_num_brps();
1022 core_num_wrps = get_num_wrps();
1025 * We need to tread carefully here because DBGSWENABLE may be
1026 * driven low on this core and there isn't an architected way to
1029 register_undef_hook(&debug_reg_hook);
1032 * Reset the breakpoint resources. We assume that a halting
1033 * debugger will leave the world in a nice state for us.
1035 on_each_cpu(reset_ctrl_regs, NULL, 1);
1036 unregister_undef_hook(&debug_reg_hook);
1037 if (!cpumask_empty(&debug_err_mask)) {
1043 pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
1044 core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
1047 /* Work out the maximum supported watchpoint length. */
1048 max_watchpoint_len = get_max_wp_len();
1049 pr_info("maximum watchpoint size is %u bytes.\n",
1050 max_watchpoint_len);
1052 /* Register debug fault handler. */
1053 hook_fault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1054 TRAP_HWBKPT, "watchpoint debug exception");
1055 hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1056 TRAP_HWBKPT, "breakpoint debug exception");
1058 /* Register hotplug notifier. */
1059 register_cpu_notifier(&dbg_reset_nb);
1062 arch_initcall(arch_hw_breakpoint_init);
1064 void hw_breakpoint_pmu_read(struct perf_event *bp)
1069 * Dummy function to register with die_notifier.
1071 int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
1072 unsigned long val, void *data)