/* * 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 */ /* * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility, * using the CPU's debug registers. */ #define pr_fmt(fmt) "hw-breakpoint: " fmt #include #include #include #include #include #include #include #include #include #include #include #include /* 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 __ro_after_init; static int core_num_wrps __ro_after_init; /* Debug architecture version. */ static u8 debug_arch __ro_after_init; /* Does debug architecture support OS Save and Restore? */ static bool has_ossr __ro_after_init; /* Maximum supported watchpoint length. */ static u8 max_watchpoint_len __ro_after_init; #define READ_WB_REG_CASE(OP2, M, VAL) \ case ((OP2 << 4) + M): \ ARM_DBG_READ(c0, c ## M, OP2, VAL); \ break #define WRITE_WB_REG_CASE(OP2, M, VAL) \ case ((OP2 << 4) + M): \ ARM_DBG_WRITE(c0, 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_warn("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_warn("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 (((read_cpuid_id() >> 16) & 0xf) != 0xf) { pr_warn_once("CPUID feature registers not supported. " "Assuming v6 debug is present.\n"); return ARM_DEBUG_ARCH_V6; } ARM_DBG_READ(c0, 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(); /* We don't support the memory-mapped interface. */ return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) || arch >= ARM_DEBUG_ARCH_V7_1; } /* Can we determine the watchpoint access type from the fsr? */ static int debug_exception_updates_fsr(void) { return get_debug_arch() >= ARM_DEBUG_ARCH_V8; } /* Determine number of WRP registers available. */ static int get_num_wrp_resources(void) { u32 didr; ARM_DBG_READ(c0, c0, 0, didr); return ((didr >> 28) & 0xf) + 1; } /* Determine number of BRP registers available. */ static int get_num_brp_resources(void) { u32 didr; ARM_DBG_READ(c0, 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) { /* * On debug architectures prior to 7.1, 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 (get_debug_arch() < ARM_DEBUG_ARCH_V7_1) return 1; return get_num_wrp_resources(); } /* Determine number of usable BRPs available. */ static int get_num_brps(void) { int brps = get_num_brp_resources(); return core_has_mismatch_brps() ? brps - 1 : 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 monitor_mode_enabled(void) { u32 dscr; ARM_DBG_READ(c0, c1, 0, dscr); return !!(dscr & ARM_DSCR_MDBGEN); } static int enable_monitor_mode(void) { u32 dscr; ARM_DBG_READ(c0, c1, 0, dscr); /* 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(c0, c1, 0, (dscr | ARM_DSCR_MDBGEN)); break; case ARM_DEBUG_ARCH_V7_ECP14: case ARM_DEBUG_ARCH_V7_1: case ARM_DEBUG_ARCH_V8: ARM_DBG_WRITE(c0, c2, 2, (dscr | ARM_DSCR_MDBGEN)); isb(); break; default: return -ENODEV; } /* Check that the write made it through. */ ARM_DBG_READ(c0, c1, 0, dscr); if (!(dscr & ARM_DSCR_MDBGEN)) { pr_warn_once("Failed to enable monitor mode on CPU %d.\n", smp_processor_id()); return -EPERM; } out: return 0; } 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_warn("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; u32 addr, ctrl; 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 = this_cpu_ptr(bp_on_reg); max_slots = core_num_brps; } else { /* Watchpoint */ ctrl_base = ARM_BASE_WCR; val_base = ARM_BASE_WVR; slots = this_cpu_ptr(wp_on_reg); max_slots = core_num_wrps; } for (i = 0; i < max_slots; ++i) { slot = &slots[i]; if (!*slot) { *slot = bp; break; } } if (i == max_slots) { pr_warn("Can't find any breakpoint slot\n"); return -EBUSY; } /* Override the breakpoint data with the step data. */ if (info->step_ctrl.enabled) { addr = info->trigger & ~0x3; ctrl = encode_ctrl_reg(info->step_ctrl); if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) { i = 0; ctrl_base = ARM_BASE_BCR + core_num_brps; val_base = ARM_BASE_BVR + core_num_brps; } } /* Setup the address register. */ write_wb_reg(val_base + i, addr); /* Setup the control register. */ write_wb_reg(ctrl_base + i, ctrl); return 0; } 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 = this_cpu_ptr(bp_on_reg); max_slots = core_num_brps; } else { /* Watchpoint */ base = ARM_BASE_WCR; slots = this_cpu_ptr(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 (i == max_slots) { pr_warn("Can't find any breakpoint slot\n"); return; } /* Ensure that we disable the mismatch breakpoint. */ if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE && info->step_ctrl.enabled) { i = 0; base = ARM_BASE_BCR + core_num_brps; } /* 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 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) { /* 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, 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_4: hw->ctrl.len = ARM_BREAKPOINT_LEN_4; break; case HW_BREAKPOINT_LEN_8: hw->ctrl.len = ARM_BREAKPOINT_LEN_8; if ((hw->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 (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE && hw->ctrl.len != ARM_BREAKPOINT_LEN_2 && hw->ctrl.len != ARM_BREAKPOINT_LEN_4) return -EINVAL; /* Address */ hw->address = attr->bp_addr; /* Privilege */ hw->ctrl.privilege = ARM_BREAKPOINT_USER; if (arch_check_bp_in_kernelspace(hw)) hw->ctrl.privilege |= ARM_BREAKPOINT_PRIV; /* Enabled? */ hw->ctrl.enabled = !attr->disabled; /* Mismatch */ hw->ctrl.mismatch = 0; 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 = 0; u32 offset, alignment_mask = 0x3; /* Ensure that we are in monitor debug mode. */ if (!monitor_mode_enabled()) return -ENODEV; /* Build the arch_hw_breakpoint. */ ret = arch_build_bp_info(bp, attr, hw); if (ret) goto out; /* Check address alignment. */ if (hw->ctrl.len == ARM_BREAKPOINT_LEN_8) alignment_mask = 0x7; 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; case 3: /* Allow single byte watchpoint. */ if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1) break; default: ret = -EINVAL; goto out; } hw->address &= ~alignment_mask; hw->ctrl.len <<= offset; if (uses_default_overflow_handler(bp)) { /* * Mismatch breakpoints are required for single-stepping * breakpoints. */ if (!core_has_mismatch_brps()) return -EINVAL; /* We don't allow mismatch breakpoints in kernel space. */ if (arch_check_bp_in_kernelspace(hw)) return -EPERM; /* * Per-cpu breakpoints are not supported by our stepping * mechanism. */ if (!bp->hw.target) return -EINVAL; /* * We only support specific access types if the fsr * reports them. */ if (!debug_exception_updates_fsr() && (hw->ctrl.type == ARM_BREAKPOINT_LOAD || hw->ctrl.type == ARM_BREAKPOINT_STORE)) return -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); } /* * Arm32 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 this same function in the arm64 platform code, which has the same * problem. * * 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 u32 get_distance_from_watchpoint(unsigned long addr, u32 val, struct arch_hw_breakpoint_ctrl *ctrl) { u32 wp_low, wp_high; u32 lens, lene; 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_fault_on_uaccess(struct pt_regs *regs, struct arch_hw_breakpoint *info) { return !user_mode(regs) && info->ctrl.privilege == ARM_BREAKPOINT_USER; } static void watchpoint_handler(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { int i, access, closest_match = 0; u32 min_dist = -1, dist; u32 val, ctrl_reg; struct perf_event *wp, **slots; struct arch_hw_breakpoint *info; struct arch_hw_breakpoint_ctrl ctrl; slots = this_cpu_ptr(wp_on_reg); /* * 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; /* * The DFAR is an unknown value on debug architectures prior * to 7.1. Since we only allow a single watchpoint on these * older CPUs, we can set the trigger to the lowest possible * faulting address. */ if (debug_arch < ARM_DEBUG_ARCH_V7_1) { BUG_ON(i > 0); info = counter_arch_bp(wp); info->trigger = wp->attr.bp_addr; } else { /* Check that the access type matches. */ if (debug_exception_updates_fsr()) { access = (fsr & ARM_FSR_ACCESS_MASK) ? HW_BREAKPOINT_W : HW_BREAKPOINT_R; if (!(access & hw_breakpoint_type(wp))) continue; } val = read_wb_reg(ARM_BASE_WVR + i); ctrl_reg = read_wb_reg(ARM_BASE_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; /* We have a winner. */ info = counter_arch_bp(wp); info->trigger = addr; } pr_debug("watchpoint fired: address = 0x%x\n", info->trigger); /* * 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 (watchpoint_fault_on_uaccess(regs, info)) goto step; perf_bp_event(wp, regs); /* * Defer stepping to the overflow handler if one is installed. * Otherwise, insert a temporary mismatch breakpoint so that * we can single-step over the watchpoint trigger. */ if (!uses_default_overflow_handler(wp)) continue; step: enable_single_step(wp, instruction_pointer(regs)); } if (min_dist > 0 && min_dist != -1) { /* No exact match found. */ wp = slots[closest_match]; info = counter_arch_bp(wp); info->trigger = addr; pr_debug("watchpoint fired: address = 0x%x\n", info->trigger); perf_bp_event(wp, regs); if (uses_default_overflow_handler(wp)) 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 = this_cpu_ptr(wp_on_reg); for (i = 0; i < core_num_wrps; ++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 = this_cpu_ptr(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 (uses_default_overflow_handler(bp)) 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 interrupts disabled. */ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { int ret = 0; u32 dscr; preempt_disable(); if (interrupts_enabled(regs)) local_irq_enable(); /* We only handle watchpoints and hardware breakpoints. */ ARM_DBG_READ(c0, 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, fsr, regs); break; default: ret = 1; /* Unhandled fault. */ } preempt_enable(); return ret; } /* * One-time initialisation. */ static cpumask_t debug_err_mask; static int debug_reg_trap(struct pt_regs *regs, unsigned int instr) { int cpu = smp_processor_id(); pr_warn("Debug register access (0x%x) caused undefined instruction on CPU %d\n", instr, cpu); /* Set the error flag for this CPU and skip the faulting instruction. */ cpumask_set_cpu(cpu, &debug_err_mask); instruction_pointer(regs) += 4; return 0; } static struct undef_hook debug_reg_hook = { .instr_mask = 0x0fe80f10, .instr_val = 0x0e000e10, .fn = debug_reg_trap, }; /* Does this core support OS Save and Restore? */ static bool core_has_os_save_restore(void) { u32 oslsr; switch (get_debug_arch()) { case ARM_DEBUG_ARCH_V7_1: return true; case ARM_DEBUG_ARCH_V7_ECP14: ARM_DBG_READ(c1, c1, 4, oslsr); if (oslsr & ARM_OSLSR_OSLM0) return true; default: return false; } } static void reset_ctrl_regs(unsigned int cpu) { int i, raw_num_brps, err = 0; u32 val; /* * 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. */ switch (debug_arch) { case ARM_DEBUG_ARCH_V6: case ARM_DEBUG_ARCH_V6_1: /* ARMv6 cores clear the registers out of reset. */ goto out_mdbgen; case ARM_DEBUG_ARCH_V7_ECP14: /* * Ensure sticky power-down is clear (i.e. debug logic is * powered up). */ ARM_DBG_READ(c1, c5, 4, val); if ((val & 0x1) == 0) err = -EPERM; if (!has_ossr) goto clear_vcr; break; case ARM_DEBUG_ARCH_V7_1: /* * Ensure the OS double lock is clear. */ ARM_DBG_READ(c1, c3, 4, val); if ((val & 0x1) == 1) err = -EPERM; break; } if (err) { pr_warn_once("CPU %d debug is powered down!\n", cpu); cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu)); return; } /* * Unconditionally clear the OS lock by writing a value * other than CS_LAR_KEY to the access register. */ ARM_DBG_WRITE(c1, c0, 4, ~CORESIGHT_UNLOCK); isb(); /* * Clear any configured vector-catch events before * enabling monitor mode. */ clear_vcr: ARM_DBG_WRITE(c0, c7, 0, 0); isb(); if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) { pr_warn_once("CPU %d failed to disable vector catch\n", cpu); return; } /* * The control/value register pairs are UNKNOWN out of reset so * clear them to avoid spurious debug events. */ raw_num_brps = get_num_brp_resources(); for (i = 0; i < raw_num_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); } if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) { pr_warn_once("CPU %d failed to clear debug register pairs\n", cpu); return; } /* * Have a crack at enabling monitor mode. We don't actually need * it yet, but reporting an error early is useful if it fails. */ out_mdbgen: if (enable_monitor_mode()) cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu)); } static int dbg_reset_online(unsigned int cpu) { local_irq_disable(); reset_ctrl_regs(cpu); local_irq_enable(); return 0; } #ifdef CONFIG_CPU_PM static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action, void *v) { if (action == CPU_PM_EXIT) reset_ctrl_regs(smp_processor_id()); return NOTIFY_OK; } static struct notifier_block dbg_cpu_pm_nb = { .notifier_call = dbg_cpu_pm_notify, }; static void __init pm_init(void) { cpu_pm_register_notifier(&dbg_cpu_pm_nb); } #else static inline void pm_init(void) { } #endif static int __init arch_hw_breakpoint_init(void) { int ret; debug_arch = get_debug_arch(); if (!debug_arch_supported()) { pr_info("debug architecture 0x%x unsupported.\n", debug_arch); return 0; } /* * Scorpion CPUs (at least those in APQ8060) seem to set DBGPRSR.SPD * whenever a WFI is issued, even if the core is not powered down, in * violation of the architecture. When DBGPRSR.SPD is set, accesses to * breakpoint and watchpoint registers are treated as undefined, so * this results in boot time and runtime failures when these are * accessed and we unexpectedly take a trap. * * It's not clear if/how this can be worked around, so we blacklist * Scorpion CPUs to avoid these issues. */ if (read_cpuid_part() == ARM_CPU_PART_SCORPION) { pr_info("Scorpion CPU detected. Hardware breakpoints and watchpoints disabled\n"); return 0; } has_ossr = core_has_os_save_restore(); /* Determine how many BRPs/WRPs are available. */ core_num_brps = get_num_brps(); core_num_wrps = get_num_wrps(); /* * We need to tread carefully here because DBGSWENABLE may be * driven low on this core and there isn't an architected way to * determine that. */ cpus_read_lock(); register_undef_hook(&debug_reg_hook); /* * Register CPU notifier which resets the breakpoint resources. We * assume that a halting debugger will leave the world in a nice state * for us. */ ret = cpuhp_setup_state_cpuslocked(CPUHP_AP_ONLINE_DYN, "arm/hw_breakpoint:online", dbg_reset_online, NULL); unregister_undef_hook(&debug_reg_hook); if (WARN_ON(ret < 0) || !cpumask_empty(&debug_err_mask)) { core_num_brps = 0; core_num_wrps = 0; if (ret > 0) cpuhp_remove_state_nocalls_cpuslocked(ret); cpus_read_unlock(); return 0; } pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n", core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " : "", core_num_wrps); /* 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(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT, "watchpoint debug exception"); hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT, "breakpoint debug exception"); cpus_read_unlock(); /* Register PM notifiers. */ pm_init(); 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; }