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linux-zen-server/arch/arm64/kernel/hw_breakpoint.c

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Initial commit
2023-08-30 17:53:23 +02:00
// 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 = &current->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 = &current->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 (is_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 = is_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 = &current->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 = &current->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 = &current->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;
}
#ifdef CONFIG_CPU_PM
extern void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int));
#else
static inline void cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
{
}
#endif
/*
* 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;
}