linux/arch/x86/kernel/hw_breakpoint.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (C) 2007 Alan Stern
 * Copyright (C) 2009 IBM Corporation
 * Copyright (C) 2009 Frederic Weisbecker <[email protected]>
 *
 * Authors: Alan Stern <[email protected]>
 *          K.Prasad <[email protected]>
 *          Frederic Weisbecker <[email protected]>
 */

/*
 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
 * using the CPU's debug registers.
 */

#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <linux/irqflags.h>
#include <linux/notifier.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/percpu.h>
#include <linux/kdebug.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/smp.h>

#include <asm/hw_breakpoint.h>
#include <asm/processor.h>
#include <asm/debugreg.h>
#include <asm/user.h>
#include <asm/desc.h>
#include <asm/tlbflush.h>

/* Per cpu debug control register value */
DEFINE_PER_CPU(unsigned long, cpu_dr7);
EXPORT_PER_CPU_SYMBOL(…);

/* Per cpu debug address registers values */
static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);

/*
 * Stores the breakpoints currently in use on each breakpoint address
 * register for each cpus
 */
static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);


static inline unsigned long
__encode_dr7(int drnum, unsigned int len, unsigned int type)
{ … }

/*
 * Encode the length, type, Exact, and Enable bits for a particular breakpoint
 * as stored in debug register 7.
 */
unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
{ … }

/*
 * Decode the length and type bits for a particular breakpoint as
 * stored in debug register 7.  Return the "enabled" status.
 */
int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
{ … }

/*
 * Install a perf counter breakpoint.
 *
 * We seek a free debug address register and use it for this
 * breakpoint. Eventually we enable it in the debug control register.
 *
 * Atomic: we hold the counter->ctx->lock and we only handle variables
 * and registers local to this cpu.
 */
int arch_install_hw_breakpoint(struct perf_event *bp)
{ … }

/*
 * Uninstall the breakpoint contained in the given counter.
 *
 * First we search the debug address register it uses and then we disable
 * it.
 *
 * Atomic: we hold the counter->ctx->lock and we only handle variables
 * and registers local to this cpu.
 */
void arch_uninstall_hw_breakpoint(struct perf_event *bp)
{ … }

static int arch_bp_generic_len(int x86_len)
{ … }

int arch_bp_generic_fields(int x86_len, int x86_type,
			   int *gen_len, int *gen_type)
{ … }

/*
 * Check for virtual address in kernel space.
 */
int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
{ … }

/*
 * Checks whether the range [addr, end], overlaps the area [base, base + size).
 */
static inline bool within_area(unsigned long addr, unsigned long end,
			       unsigned long base, unsigned long size)
{ … }

/*
 * Checks whether the range from addr to end, inclusive, overlaps the fixed
 * mapped CPU entry area range or other ranges used for CPU entry.
 */
static inline bool within_cpu_entry(unsigned long addr, unsigned long end)
{ … }

static int arch_build_bp_info(struct perf_event *bp,
			      const struct perf_event_attr *attr,
			      struct arch_hw_breakpoint *hw)
{ … }

/*
 * 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)
{ … }

/*
 * Release the user breakpoints used by ptrace
 */
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{ … }

void hw_breakpoint_restore(void)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * Handle debug exception notifications.
 *
 * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
 *
 * NOTIFY_DONE returned if one of the following conditions is true.
 * i) When the causative address is from user-space and the exception
 * is a valid one, i.e. not triggered as a result of lazy debug register
 * switching
 * ii) When there are more bits than trap<n> set in DR6 register (such
 * as BD, BS or BT) indicating that more than one debug condition is
 * met and requires some more action in do_debug().
 *
 * NOTIFY_STOP returned for all other cases
 *
 */
static int hw_breakpoint_handler(struct die_args *args)
{ … }

/*
 * Handle debug exception notifications.
 */
int hw_breakpoint_exceptions_notify(
		struct notifier_block *unused, unsigned long val, void *data)
{ … }

void hw_breakpoint_pmu_read(struct perf_event *bp)
{ … }