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Diffstat (limited to 'arch/arm/kernel/hw_breakpoint.c')
| -rw-r--r-- | arch/arm/kernel/hw_breakpoint.c | 1205 |
1 files changed, 1205 insertions, 0 deletions
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c new file mode 100644 index 000000000..8f1fa7aac --- /dev/null +++ b/arch/arm/kernel/hw_breakpoint.c @@ -0,0 +1,1205 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * + * Copyright (C) 2009, 2010 ARM Limited + * + * Author: Will Deacon <will.deacon@arm.com> + */ + +/* + * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility, + * using the CPU's debug registers. + */ +#define pr_fmt(fmt) "hw-breakpoint: " fmt + +#include <linux/errno.h> +#include <linux/hardirq.h> +#include <linux/perf_event.h> +#include <linux/hw_breakpoint.h> +#include <linux/smp.h> +#include <linux/cpu_pm.h> +#include <linux/coresight.h> + +#include <asm/cacheflush.h> +#include <asm/cputype.h> +#include <asm/current.h> +#include <asm/hw_breakpoint.h> +#include <asm/traps.h> + +/* Breakpoint currently in use for each BRP. */ +static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]); + +/* Watchpoint currently in use for each WRP. */ +static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]); + +/* Number of BRP/WRP registers on this CPU. */ +static int core_num_brps __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: + case ARM_DEBUG_ARCH_V8_1: + case ARM_DEBUG_ARCH_V8_2: + case ARM_DEBUG_ARCH_V8_4: + 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; + fallthrough; + 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; + fallthrough; + case 3: + /* Allow single byte watchpoint. */ + if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1) + break; + fallthrough; + 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"); + fallthrough; + 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; + fallthrough; + 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; +} |