diff options
Diffstat (limited to 'arch/arm64/kernel/hw_breakpoint.c')
| -rw-r--r-- | arch/arm64/kernel/hw_breakpoint.c | 1023 |
1 files changed, 1023 insertions, 0 deletions
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c new file mode 100644 index 000000000..35225632d --- /dev/null +++ b/arch/arm64/kernel/hw_breakpoint.c @@ -0,0 +1,1023 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility, + * using the CPU's debug registers. + * + * Copyright (C) 2012 ARM Limited + * Author: Will Deacon <will.deacon@arm.com> + */ + +#define pr_fmt(fmt) "hw-breakpoint: " fmt + +#include <linux/compat.h> +#include <linux/cpu_pm.h> +#include <linux/errno.h> +#include <linux/hw_breakpoint.h> +#include <linux/kprobes.h> +#include <linux/perf_event.h> +#include <linux/ptrace.h> +#include <linux/smp.h> +#include <linux/uaccess.h> + +#include <asm/current.h> +#include <asm/debug-monitors.h> +#include <asm/hw_breakpoint.h> +#include <asm/traps.h> +#include <asm/cputype.h> +#include <asm/system_misc.h> + +/* Breakpoint currently in use for each BRP. */ +static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]); + +/* Watchpoint currently in use for each WRP. */ +static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]); + +/* Currently stepping a per-CPU kernel breakpoint. */ +static DEFINE_PER_CPU(int, stepping_kernel_bp); + +/* Number of BRP/WRP registers on this CPU. */ +static int core_num_brps; +static int core_num_wrps; + +int hw_breakpoint_slots(int type) +{ + /* + * We can be called early, so don't rely on + * our static variables being initialised. + */ + switch (type) { + case TYPE_INST: + return get_num_brps(); + case TYPE_DATA: + return get_num_wrps(); + default: + pr_warn("unknown slot type: %d\n", type); + return 0; + } +} + +#define READ_WB_REG_CASE(OFF, N, REG, VAL) \ + case (OFF + N): \ + AARCH64_DBG_READ(N, REG, VAL); \ + break + +#define WRITE_WB_REG_CASE(OFF, N, REG, VAL) \ + case (OFF + N): \ + AARCH64_DBG_WRITE(N, REG, VAL); \ + break + +#define GEN_READ_WB_REG_CASES(OFF, REG, VAL) \ + READ_WB_REG_CASE(OFF, 0, REG, VAL); \ + READ_WB_REG_CASE(OFF, 1, REG, VAL); \ + READ_WB_REG_CASE(OFF, 2, REG, VAL); \ + READ_WB_REG_CASE(OFF, 3, REG, VAL); \ + READ_WB_REG_CASE(OFF, 4, REG, VAL); \ + READ_WB_REG_CASE(OFF, 5, REG, VAL); \ + READ_WB_REG_CASE(OFF, 6, REG, VAL); \ + READ_WB_REG_CASE(OFF, 7, REG, VAL); \ + READ_WB_REG_CASE(OFF, 8, REG, VAL); \ + READ_WB_REG_CASE(OFF, 9, REG, VAL); \ + READ_WB_REG_CASE(OFF, 10, REG, VAL); \ + READ_WB_REG_CASE(OFF, 11, REG, VAL); \ + READ_WB_REG_CASE(OFF, 12, REG, VAL); \ + READ_WB_REG_CASE(OFF, 13, REG, VAL); \ + READ_WB_REG_CASE(OFF, 14, REG, VAL); \ + READ_WB_REG_CASE(OFF, 15, REG, VAL) + +#define GEN_WRITE_WB_REG_CASES(OFF, REG, VAL) \ + WRITE_WB_REG_CASE(OFF, 0, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 1, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 2, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 3, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 4, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 5, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 6, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 7, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 8, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 9, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 10, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 11, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 12, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 13, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 14, REG, VAL); \ + WRITE_WB_REG_CASE(OFF, 15, REG, VAL) + +static u64 read_wb_reg(int reg, int n) +{ + u64 val = 0; + + switch (reg + n) { + GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val); + GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val); + GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val); + GEN_READ_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val); + default: + pr_warn("attempt to read from unknown breakpoint register %d\n", n); + } + + return val; +} +NOKPROBE_SYMBOL(read_wb_reg); + +static void write_wb_reg(int reg, int n, u64 val) +{ + switch (reg + n) { + GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val); + GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BCR, AARCH64_DBG_REG_NAME_BCR, val); + GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WVR, AARCH64_DBG_REG_NAME_WVR, val); + GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_WCR, AARCH64_DBG_REG_NAME_WCR, val); + default: + pr_warn("attempt to write to unknown breakpoint register %d\n", n); + } + isb(); +} +NOKPROBE_SYMBOL(write_wb_reg); + +/* + * Convert a breakpoint privilege level to the corresponding exception + * level. + */ +static enum dbg_active_el debug_exception_level(int privilege) +{ + switch (privilege) { + case AARCH64_BREAKPOINT_EL0: + return DBG_ACTIVE_EL0; + case AARCH64_BREAKPOINT_EL1: + return DBG_ACTIVE_EL1; + default: + pr_warn("invalid breakpoint privilege level %d\n", privilege); + return -EINVAL; + } +} +NOKPROBE_SYMBOL(debug_exception_level); + +enum hw_breakpoint_ops { + HW_BREAKPOINT_INSTALL, + HW_BREAKPOINT_UNINSTALL, + HW_BREAKPOINT_RESTORE +}; + +static int is_compat_bp(struct perf_event *bp) +{ + struct task_struct *tsk = bp->hw.target; + + /* + * tsk can be NULL for per-cpu (non-ptrace) breakpoints. + * In this case, use the native interface, since we don't have + * the notion of a "compat CPU" and could end up relying on + * deprecated behaviour if we use unaligned watchpoints in + * AArch64 state. + */ + return tsk && is_compat_thread(task_thread_info(tsk)); +} + +/** + * hw_breakpoint_slot_setup - Find and setup a perf slot according to + * operations + * + * @slots: pointer to array of slots + * @max_slots: max number of slots + * @bp: perf_event to setup + * @ops: operation to be carried out on the slot + * + * Return: + * slot index on success + * -ENOSPC if no slot is available/matches + * -EINVAL on wrong operations parameter + */ +static int hw_breakpoint_slot_setup(struct perf_event **slots, int max_slots, + struct perf_event *bp, + enum hw_breakpoint_ops ops) +{ + int i; + struct perf_event **slot; + + for (i = 0; i < max_slots; ++i) { + slot = &slots[i]; + switch (ops) { + case HW_BREAKPOINT_INSTALL: + if (!*slot) { + *slot = bp; + return i; + } + break; + case HW_BREAKPOINT_UNINSTALL: + if (*slot == bp) { + *slot = NULL; + return i; + } + break; + case HW_BREAKPOINT_RESTORE: + if (*slot == bp) + return i; + break; + default: + pr_warn_once("Unhandled hw breakpoint ops %d\n", ops); + return -EINVAL; + } + } + return -ENOSPC; +} + +static int hw_breakpoint_control(struct perf_event *bp, + enum hw_breakpoint_ops ops) +{ + struct arch_hw_breakpoint *info = counter_arch_bp(bp); + struct perf_event **slots; + struct debug_info *debug_info = ¤t->thread.debug; + int i, max_slots, ctrl_reg, val_reg, reg_enable; + enum dbg_active_el dbg_el = debug_exception_level(info->ctrl.privilege); + u32 ctrl; + + if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) { + /* Breakpoint */ + ctrl_reg = AARCH64_DBG_REG_BCR; + val_reg = AARCH64_DBG_REG_BVR; + slots = this_cpu_ptr(bp_on_reg); + max_slots = core_num_brps; + reg_enable = !debug_info->bps_disabled; + } else { + /* Watchpoint */ + ctrl_reg = AARCH64_DBG_REG_WCR; + val_reg = AARCH64_DBG_REG_WVR; + slots = this_cpu_ptr(wp_on_reg); + max_slots = core_num_wrps; + reg_enable = !debug_info->wps_disabled; + } + + i = hw_breakpoint_slot_setup(slots, max_slots, bp, ops); + + if (WARN_ONCE(i < 0, "Can't find any breakpoint slot")) + return i; + + switch (ops) { + case HW_BREAKPOINT_INSTALL: + /* + * Ensure debug monitors are enabled at the correct exception + * level. + */ + enable_debug_monitors(dbg_el); + fallthrough; + case HW_BREAKPOINT_RESTORE: + /* Setup the address register. */ + write_wb_reg(val_reg, i, info->address); + + /* Setup the control register. */ + ctrl = encode_ctrl_reg(info->ctrl); + write_wb_reg(ctrl_reg, i, + reg_enable ? ctrl | 0x1 : ctrl & ~0x1); + break; + case HW_BREAKPOINT_UNINSTALL: + /* Reset the control register. */ + write_wb_reg(ctrl_reg, i, 0); + + /* + * Release the debug monitors for the correct exception + * level. + */ + disable_debug_monitors(dbg_el); + break; + } + + return 0; +} + +/* + * Install a perf counter breakpoint. + */ +int arch_install_hw_breakpoint(struct perf_event *bp) +{ + return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL); +} + +void arch_uninstall_hw_breakpoint(struct perf_event *bp) +{ + hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL); +} + +static int get_hbp_len(u8 hbp_len) +{ + unsigned int len_in_bytes = 0; + + switch (hbp_len) { + case ARM_BREAKPOINT_LEN_1: + len_in_bytes = 1; + break; + case ARM_BREAKPOINT_LEN_2: + len_in_bytes = 2; + break; + case ARM_BREAKPOINT_LEN_3: + len_in_bytes = 3; + break; + case ARM_BREAKPOINT_LEN_4: + len_in_bytes = 4; + break; + case ARM_BREAKPOINT_LEN_5: + len_in_bytes = 5; + break; + case ARM_BREAKPOINT_LEN_6: + len_in_bytes = 6; + break; + case ARM_BREAKPOINT_LEN_7: + len_in_bytes = 7; + break; + case ARM_BREAKPOINT_LEN_8: + len_in_bytes = 8; + break; + } + + return len_in_bytes; +} + +/* + * Check whether bp virtual address is in kernel space. + */ +int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw) +{ + unsigned int len; + unsigned long va; + + va = hw->address; + len = get_hbp_len(hw->ctrl.len); + + return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE); +} + +/* + * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl. + * Hopefully this will disappear when ptrace can bypass the conversion + * to generic breakpoint descriptions. + */ +int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl, + int *gen_len, int *gen_type, int *offset) +{ + /* Type */ + switch (ctrl.type) { + case ARM_BREAKPOINT_EXECUTE: + *gen_type = HW_BREAKPOINT_X; + break; + case ARM_BREAKPOINT_LOAD: + *gen_type = HW_BREAKPOINT_R; + break; + case ARM_BREAKPOINT_STORE: + *gen_type = HW_BREAKPOINT_W; + break; + case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE: + *gen_type = HW_BREAKPOINT_RW; + break; + default: + return -EINVAL; + } + + if (!ctrl.len) + return -EINVAL; + *offset = __ffs(ctrl.len); + + /* Len */ + switch (ctrl.len >> *offset) { + case ARM_BREAKPOINT_LEN_1: + *gen_len = HW_BREAKPOINT_LEN_1; + break; + case ARM_BREAKPOINT_LEN_2: + *gen_len = HW_BREAKPOINT_LEN_2; + break; + case ARM_BREAKPOINT_LEN_3: + *gen_len = HW_BREAKPOINT_LEN_3; + break; + case ARM_BREAKPOINT_LEN_4: + *gen_len = HW_BREAKPOINT_LEN_4; + break; + case ARM_BREAKPOINT_LEN_5: + *gen_len = HW_BREAKPOINT_LEN_5; + break; + case ARM_BREAKPOINT_LEN_6: + *gen_len = HW_BREAKPOINT_LEN_6; + break; + case ARM_BREAKPOINT_LEN_7: + *gen_len = HW_BREAKPOINT_LEN_7; + break; + case ARM_BREAKPOINT_LEN_8: + *gen_len = HW_BREAKPOINT_LEN_8; + break; + default: + return -EINVAL; + } + + return 0; +} + +/* + * Construct an arch_hw_breakpoint from a perf_event. + */ +static int arch_build_bp_info(struct perf_event *bp, + const struct perf_event_attr *attr, + struct arch_hw_breakpoint *hw) +{ + /* Type */ + switch (attr->bp_type) { + case HW_BREAKPOINT_X: + hw->ctrl.type = ARM_BREAKPOINT_EXECUTE; + break; + case HW_BREAKPOINT_R: + hw->ctrl.type = ARM_BREAKPOINT_LOAD; + break; + case HW_BREAKPOINT_W: + hw->ctrl.type = ARM_BREAKPOINT_STORE; + break; + case HW_BREAKPOINT_RW: + hw->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE; + break; + default: + return -EINVAL; + } + + /* Len */ + switch (attr->bp_len) { + case HW_BREAKPOINT_LEN_1: + hw->ctrl.len = ARM_BREAKPOINT_LEN_1; + break; + case HW_BREAKPOINT_LEN_2: + hw->ctrl.len = ARM_BREAKPOINT_LEN_2; + break; + case HW_BREAKPOINT_LEN_3: + hw->ctrl.len = ARM_BREAKPOINT_LEN_3; + break; + case HW_BREAKPOINT_LEN_4: + hw->ctrl.len = ARM_BREAKPOINT_LEN_4; + break; + case HW_BREAKPOINT_LEN_5: + hw->ctrl.len = ARM_BREAKPOINT_LEN_5; + break; + case HW_BREAKPOINT_LEN_6: + hw->ctrl.len = ARM_BREAKPOINT_LEN_6; + break; + case HW_BREAKPOINT_LEN_7: + hw->ctrl.len = ARM_BREAKPOINT_LEN_7; + break; + case HW_BREAKPOINT_LEN_8: + hw->ctrl.len = ARM_BREAKPOINT_LEN_8; + break; + default: + return -EINVAL; + } + + /* + * On AArch64, we only permit breakpoints of length 4, whereas + * AArch32 also requires breakpoints of length 2 for Thumb. + * Watchpoints can be of length 1, 2, 4 or 8 bytes. + */ + if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE) { + if (is_compat_bp(bp)) { + if (hw->ctrl.len != ARM_BREAKPOINT_LEN_2 && + hw->ctrl.len != ARM_BREAKPOINT_LEN_4) + return -EINVAL; + } else if (hw->ctrl.len != ARM_BREAKPOINT_LEN_4) { + /* + * FIXME: Some tools (I'm looking at you perf) assume + * that breakpoints should be sizeof(long). This + * is nonsense. For now, we fix up the parameter + * but we should probably return -EINVAL instead. + */ + hw->ctrl.len = ARM_BREAKPOINT_LEN_4; + } + } + + /* Address */ + hw->address = attr->bp_addr; + + /* + * Privilege + * Note that we disallow combined EL0/EL1 breakpoints because + * that would complicate the stepping code. + */ + if (arch_check_bp_in_kernelspace(hw)) + hw->ctrl.privilege = AARCH64_BREAKPOINT_EL1; + else + hw->ctrl.privilege = AARCH64_BREAKPOINT_EL0; + + /* Enabled? */ + hw->ctrl.enabled = !attr->disabled; + + return 0; +} + +/* + * Validate the arch-specific HW Breakpoint register settings. + */ +int hw_breakpoint_arch_parse(struct perf_event *bp, + const struct perf_event_attr *attr, + struct arch_hw_breakpoint *hw) +{ + int ret; + u64 alignment_mask, offset; + + /* Build the arch_hw_breakpoint. */ + ret = arch_build_bp_info(bp, attr, hw); + if (ret) + return ret; + + /* + * Check address alignment. + * We don't do any clever alignment correction for watchpoints + * because using 64-bit unaligned addresses is deprecated for + * AArch64. + * + * AArch32 tasks expect some simple alignment fixups, so emulate + * that here. + */ + if (is_compat_bp(bp)) { + if (hw->ctrl.len == ARM_BREAKPOINT_LEN_8) + alignment_mask = 0x7; + else + alignment_mask = 0x3; + offset = hw->address & alignment_mask; + switch (offset) { + case 0: + /* Aligned */ + break; + case 1: + case 2: + /* Allow halfword watchpoints and breakpoints. */ + if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2) + break; + + fallthrough; + case 3: + /* Allow single byte watchpoint. */ + if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1) + break; + + fallthrough; + default: + return -EINVAL; + } + } else { + if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE) + alignment_mask = 0x3; + else + alignment_mask = 0x7; + offset = hw->address & alignment_mask; + } + + hw->address &= ~alignment_mask; + hw->ctrl.len <<= offset; + + /* + * Disallow per-task kernel breakpoints since these would + * complicate the stepping code. + */ + if (hw->ctrl.privilege == AARCH64_BREAKPOINT_EL1 && bp->hw.target) + return -EINVAL; + + return 0; +} + +/* + * Enable/disable all of the breakpoints active at the specified + * exception level at the register level. + * This is used when single-stepping after a breakpoint exception. + */ +static void toggle_bp_registers(int reg, enum dbg_active_el el, int enable) +{ + int i, max_slots, privilege; + u32 ctrl; + struct perf_event **slots; + + switch (reg) { + case AARCH64_DBG_REG_BCR: + slots = this_cpu_ptr(bp_on_reg); + max_slots = core_num_brps; + break; + case AARCH64_DBG_REG_WCR: + slots = this_cpu_ptr(wp_on_reg); + max_slots = core_num_wrps; + break; + default: + return; + } + + for (i = 0; i < max_slots; ++i) { + if (!slots[i]) + continue; + + privilege = counter_arch_bp(slots[i])->ctrl.privilege; + if (debug_exception_level(privilege) != el) + continue; + + ctrl = read_wb_reg(reg, i); + if (enable) + ctrl |= 0x1; + else + ctrl &= ~0x1; + write_wb_reg(reg, i, ctrl); + } +} +NOKPROBE_SYMBOL(toggle_bp_registers); + +/* + * Debug exception handlers. + */ +static int breakpoint_handler(unsigned long unused, unsigned long esr, + struct pt_regs *regs) +{ + int i, step = 0, *kernel_step; + u32 ctrl_reg; + u64 addr, val; + struct perf_event *bp, **slots; + struct debug_info *debug_info; + struct arch_hw_breakpoint_ctrl ctrl; + + slots = this_cpu_ptr(bp_on_reg); + addr = instruction_pointer(regs); + debug_info = ¤t->thread.debug; + + for (i = 0; i < core_num_brps; ++i) { + rcu_read_lock(); + + bp = slots[i]; + + if (bp == NULL) + goto unlock; + + /* Check if the breakpoint value matches. */ + val = read_wb_reg(AARCH64_DBG_REG_BVR, i); + if (val != (addr & ~0x3)) + goto unlock; + + /* Possible match, check the byte address select to confirm. */ + ctrl_reg = read_wb_reg(AARCH64_DBG_REG_BCR, i); + decode_ctrl_reg(ctrl_reg, &ctrl); + if (!((1 << (addr & 0x3)) & ctrl.len)) + goto unlock; + + counter_arch_bp(bp)->trigger = addr; + perf_bp_event(bp, regs); + + /* Do we need to handle the stepping? */ + if (uses_default_overflow_handler(bp)) + step = 1; +unlock: + rcu_read_unlock(); + } + + if (!step) + return 0; + + if (user_mode(regs)) { + debug_info->bps_disabled = 1; + toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 0); + + /* If we're already stepping a watchpoint, just return. */ + if (debug_info->wps_disabled) + return 0; + + if (test_thread_flag(TIF_SINGLESTEP)) + debug_info->suspended_step = 1; + else + user_enable_single_step(current); + } else { + toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 0); + kernel_step = this_cpu_ptr(&stepping_kernel_bp); + + if (*kernel_step != ARM_KERNEL_STEP_NONE) + return 0; + + if (kernel_active_single_step()) { + *kernel_step = ARM_KERNEL_STEP_SUSPEND; + } else { + *kernel_step = ARM_KERNEL_STEP_ACTIVE; + kernel_enable_single_step(regs); + } + } + + return 0; +} +NOKPROBE_SYMBOL(breakpoint_handler); + +/* + * Arm64 hardware does not always report a watchpoint hit address that matches + * one of the watchpoints set. It can also report an address "near" the + * watchpoint if a single instruction access both watched and unwatched + * addresses. There is no straight-forward way, short of disassembling the + * offending instruction, to map that address back to the watchpoint. This + * function computes the distance of the memory access from the watchpoint as a + * heuristic for the likelihood that a given access triggered the watchpoint. + * + * See Section D2.10.5 "Determining the memory location that caused a Watchpoint + * exception" of ARMv8 Architecture Reference Manual for details. + * + * The function returns the distance of the address from the bytes watched by + * the watchpoint. In case of an exact match, it returns 0. + */ +static u64 get_distance_from_watchpoint(unsigned long addr, u64 val, + struct arch_hw_breakpoint_ctrl *ctrl) +{ + u64 wp_low, wp_high; + u32 lens, lene; + + addr = untagged_addr(addr); + + lens = __ffs(ctrl->len); + lene = __fls(ctrl->len); + + wp_low = val + lens; + wp_high = val + lene; + if (addr < wp_low) + return wp_low - addr; + else if (addr > wp_high) + return addr - wp_high; + else + return 0; +} + +static int watchpoint_report(struct perf_event *wp, unsigned long addr, + struct pt_regs *regs) +{ + int step = uses_default_overflow_handler(wp); + struct arch_hw_breakpoint *info = counter_arch_bp(wp); + + info->trigger = addr; + + /* + * If we triggered a user watchpoint from a uaccess routine, then + * handle the stepping ourselves since userspace really can't help + * us with this. + */ + if (!user_mode(regs) && info->ctrl.privilege == AARCH64_BREAKPOINT_EL0) + step = 1; + else + perf_bp_event(wp, regs); + + return step; +} + +static int watchpoint_handler(unsigned long addr, unsigned long esr, + struct pt_regs *regs) +{ + int i, step = 0, *kernel_step, access, closest_match = 0; + u64 min_dist = -1, dist; + u32 ctrl_reg; + u64 val; + struct perf_event *wp, **slots; + struct debug_info *debug_info; + struct arch_hw_breakpoint_ctrl ctrl; + + slots = this_cpu_ptr(wp_on_reg); + debug_info = ¤t->thread.debug; + + /* + * Find all watchpoints that match the reported address. If no exact + * match is found. Attribute the hit to the closest watchpoint. + */ + rcu_read_lock(); + for (i = 0; i < core_num_wrps; ++i) { + wp = slots[i]; + if (wp == NULL) + continue; + + /* + * Check that the access type matches. + * 0 => load, otherwise => store + */ + access = (esr & AARCH64_ESR_ACCESS_MASK) ? HW_BREAKPOINT_W : + HW_BREAKPOINT_R; + if (!(access & hw_breakpoint_type(wp))) + continue; + + /* Check if the watchpoint value and byte select match. */ + val = read_wb_reg(AARCH64_DBG_REG_WVR, i); + ctrl_reg = read_wb_reg(AARCH64_DBG_REG_WCR, i); + decode_ctrl_reg(ctrl_reg, &ctrl); + dist = get_distance_from_watchpoint(addr, val, &ctrl); + if (dist < min_dist) { + min_dist = dist; + closest_match = i; + } + /* Is this an exact match? */ + if (dist != 0) + continue; + + step = watchpoint_report(wp, addr, regs); + } + + /* No exact match found? */ + if (min_dist > 0 && min_dist != -1) + step = watchpoint_report(slots[closest_match], addr, regs); + + rcu_read_unlock(); + + if (!step) + return 0; + + /* + * We always disable EL0 watchpoints because the kernel can + * cause these to fire via an unprivileged access. + */ + toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 0); + + if (user_mode(regs)) { + debug_info->wps_disabled = 1; + + /* If we're already stepping a breakpoint, just return. */ + if (debug_info->bps_disabled) + return 0; + + if (test_thread_flag(TIF_SINGLESTEP)) + debug_info->suspended_step = 1; + else + user_enable_single_step(current); + } else { + toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 0); + kernel_step = this_cpu_ptr(&stepping_kernel_bp); + + if (*kernel_step != ARM_KERNEL_STEP_NONE) + return 0; + + if (kernel_active_single_step()) { + *kernel_step = ARM_KERNEL_STEP_SUSPEND; + } else { + *kernel_step = ARM_KERNEL_STEP_ACTIVE; + kernel_enable_single_step(regs); + } + } + + return 0; +} +NOKPROBE_SYMBOL(watchpoint_handler); + +/* + * Handle single-step exception. + */ +int reinstall_suspended_bps(struct pt_regs *regs) +{ + struct debug_info *debug_info = ¤t->thread.debug; + int handled_exception = 0, *kernel_step; + + kernel_step = this_cpu_ptr(&stepping_kernel_bp); + + /* + * Called from single-step exception handler. + * Return 0 if execution can resume, 1 if a SIGTRAP should be + * reported. + */ + if (user_mode(regs)) { + if (debug_info->bps_disabled) { + debug_info->bps_disabled = 0; + toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL0, 1); + handled_exception = 1; + } + + if (debug_info->wps_disabled) { + debug_info->wps_disabled = 0; + toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1); + handled_exception = 1; + } + + if (handled_exception) { + if (debug_info->suspended_step) { + debug_info->suspended_step = 0; + /* Allow exception handling to fall-through. */ + handled_exception = 0; + } else { + user_disable_single_step(current); + } + } + } else if (*kernel_step != ARM_KERNEL_STEP_NONE) { + toggle_bp_registers(AARCH64_DBG_REG_BCR, DBG_ACTIVE_EL1, 1); + toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL1, 1); + + if (!debug_info->wps_disabled) + toggle_bp_registers(AARCH64_DBG_REG_WCR, DBG_ACTIVE_EL0, 1); + + if (*kernel_step != ARM_KERNEL_STEP_SUSPEND) { + kernel_disable_single_step(); + handled_exception = 1; + } else { + handled_exception = 0; + } + + *kernel_step = ARM_KERNEL_STEP_NONE; + } + + return !handled_exception; +} +NOKPROBE_SYMBOL(reinstall_suspended_bps); + +/* + * Context-switcher for restoring suspended breakpoints. + */ +void hw_breakpoint_thread_switch(struct task_struct *next) +{ + /* + * current next + * disabled: 0 0 => The usual case, NOTIFY_DONE + * 0 1 => Disable the registers + * 1 0 => Enable the registers + * 1 1 => NOTIFY_DONE. per-task bps will + * get taken care of by perf. + */ + + struct debug_info *current_debug_info, *next_debug_info; + + current_debug_info = ¤t->thread.debug; + next_debug_info = &next->thread.debug; + + /* Update breakpoints. */ + if (current_debug_info->bps_disabled != next_debug_info->bps_disabled) + toggle_bp_registers(AARCH64_DBG_REG_BCR, + DBG_ACTIVE_EL0, + !next_debug_info->bps_disabled); + + /* Update watchpoints. */ + if (current_debug_info->wps_disabled != next_debug_info->wps_disabled) + toggle_bp_registers(AARCH64_DBG_REG_WCR, + DBG_ACTIVE_EL0, + !next_debug_info->wps_disabled); +} + +/* + * CPU initialisation. + */ +static int hw_breakpoint_reset(unsigned int cpu) +{ + int i; + struct perf_event **slots; + /* + * When a CPU goes through cold-boot, it does not have any installed + * slot, so it is safe to share the same function for restoring and + * resetting breakpoints; when a CPU is hotplugged in, it goes + * through the slots, which are all empty, hence it just resets control + * and value for debug registers. + * When this function is triggered on warm-boot through a CPU PM + * notifier some slots might be initialized; if so they are + * reprogrammed according to the debug slots content. + */ + for (slots = this_cpu_ptr(bp_on_reg), i = 0; i < core_num_brps; ++i) { + if (slots[i]) { + hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE); + } else { + write_wb_reg(AARCH64_DBG_REG_BCR, i, 0UL); + write_wb_reg(AARCH64_DBG_REG_BVR, i, 0UL); + } + } + + for (slots = this_cpu_ptr(wp_on_reg), i = 0; i < core_num_wrps; ++i) { + if (slots[i]) { + hw_breakpoint_control(slots[i], HW_BREAKPOINT_RESTORE); + } else { + write_wb_reg(AARCH64_DBG_REG_WCR, i, 0UL); + write_wb_reg(AARCH64_DBG_REG_WVR, i, 0UL); + } + } + + return 0; +} + +/* + * One-time initialisation. + */ +static int __init arch_hw_breakpoint_init(void) +{ + int ret; + + core_num_brps = get_num_brps(); + core_num_wrps = get_num_wrps(); + + pr_info("found %d breakpoint and %d watchpoint registers.\n", + core_num_brps, core_num_wrps); + + /* Register debug fault handlers. */ + hook_debug_fault_code(DBG_ESR_EVT_HWBP, breakpoint_handler, SIGTRAP, + TRAP_HWBKPT, "hw-breakpoint handler"); + hook_debug_fault_code(DBG_ESR_EVT_HWWP, watchpoint_handler, SIGTRAP, + TRAP_HWBKPT, "hw-watchpoint handler"); + + /* + * Reset the breakpoint resources. We assume that a halting + * debugger will leave the world in a nice state for us. + */ + ret = cpuhp_setup_state(CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING, + "perf/arm64/hw_breakpoint:starting", + hw_breakpoint_reset, NULL); + if (ret) + pr_err("failed to register CPU hotplug notifier: %d\n", ret); + + /* Register cpu_suspend hw breakpoint restore hook */ + cpu_suspend_set_dbg_restorer(hw_breakpoint_reset); + + return ret; +} +arch_initcall(arch_hw_breakpoint_init); + +void hw_breakpoint_pmu_read(struct perf_event *bp) +{ +} + +/* + * Dummy function to register with die_notifier. + */ +int hw_breakpoint_exceptions_notify(struct notifier_block *unused, + unsigned long val, void *data) +{ + return NOTIFY_DONE; +} |