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OpenCloudOS-Kernel/arch/arm/kernel/hw_breakpoint.c

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// 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 (is_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 (!is_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 (is_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 (is_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;
}
#ifdef CONFIG_ARM_ERRATA_764319
static int oslsr_fault;
static int debug_oslsr_trap(struct pt_regs *regs, unsigned int instr)
{
oslsr_fault = 1;
instruction_pointer(regs) += 4;
return 0;
}
static struct undef_hook debug_oslsr_hook = {
.instr_mask = 0xffffffff,
.instr_val = 0xee115e91,
.fn = debug_oslsr_trap,
};
#endif
/*
* 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:
#ifdef CONFIG_ARM_ERRATA_764319
oslsr_fault = 0;
register_undef_hook(&debug_oslsr_hook);
ARM_DBG_READ(c1, c1, 4, oslsr);
unregister_undef_hook(&debug_oslsr_hook);
if (oslsr_fault)
return false;
#else
ARM_DBG_READ(c1, c1, 4, oslsr);
#endif
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;
}
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