mirror of https://gitee.com/openkylin/linux.git
782 lines
17 KiB
C
782 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
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* using the CPU's debug registers. Derived from
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* "arch/x86/kernel/hw_breakpoint.c"
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*
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* Copyright 2010 IBM Corporation
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* Author: K.Prasad <prasad@linux.vnet.ibm.com>
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*/
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#include <linux/hw_breakpoint.h>
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#include <linux/notifier.h>
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#include <linux/kprobes.h>
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#include <linux/percpu.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/smp.h>
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#include <linux/debugfs.h>
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#include <linux/init.h>
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#include <asm/hw_breakpoint.h>
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#include <asm/processor.h>
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#include <asm/sstep.h>
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#include <asm/debug.h>
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#include <asm/debugfs.h>
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#include <asm/hvcall.h>
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#include <asm/inst.h>
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#include <linux/uaccess.h>
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/*
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* Stores the breakpoints currently in use on each breakpoint address
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* register for every cpu
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*/
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static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM_MAX]);
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/*
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* Returns total number of data or instruction breakpoints available.
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*/
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int hw_breakpoint_slots(int type)
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{
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if (type == TYPE_DATA)
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return nr_wp_slots();
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return 0; /* no instruction breakpoints available */
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}
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static bool single_step_pending(void)
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{
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int i;
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for (i = 0; i < nr_wp_slots(); i++) {
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if (current->thread.last_hit_ubp[i])
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return true;
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}
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return false;
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}
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/*
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* Install a perf counter breakpoint.
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*
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* We seek a free debug address register and use it for this
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* breakpoint.
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*
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* Atomic: we hold the counter->ctx->lock and we only handle variables
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* and registers local to this cpu.
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*/
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int arch_install_hw_breakpoint(struct perf_event *bp)
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{
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struct arch_hw_breakpoint *info = counter_arch_bp(bp);
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struct perf_event **slot;
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int i;
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for (i = 0; i < nr_wp_slots(); i++) {
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slot = this_cpu_ptr(&bp_per_reg[i]);
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if (!*slot) {
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*slot = bp;
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break;
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}
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}
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if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
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return -EBUSY;
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/*
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* Do not install DABR values if the instruction must be single-stepped.
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* If so, DABR will be populated in single_step_dabr_instruction().
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*/
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if (!single_step_pending())
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__set_breakpoint(i, info);
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return 0;
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}
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/*
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* Uninstall the breakpoint contained in the given counter.
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*
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* First we search the debug address register it uses and then we disable
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* it.
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*
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* Atomic: we hold the counter->ctx->lock and we only handle variables
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* and registers local to this cpu.
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*/
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void arch_uninstall_hw_breakpoint(struct perf_event *bp)
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{
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struct arch_hw_breakpoint null_brk = {0};
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struct perf_event **slot;
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int i;
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for (i = 0; i < nr_wp_slots(); i++) {
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slot = this_cpu_ptr(&bp_per_reg[i]);
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if (*slot == bp) {
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*slot = NULL;
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break;
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}
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}
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if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
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return;
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__set_breakpoint(i, &null_brk);
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}
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static bool is_ptrace_bp(struct perf_event *bp)
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{
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return bp->overflow_handler == ptrace_triggered;
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}
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struct breakpoint {
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struct list_head list;
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struct perf_event *bp;
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bool ptrace_bp;
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};
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static DEFINE_PER_CPU(struct breakpoint *, cpu_bps[HBP_NUM_MAX]);
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static LIST_HEAD(task_bps);
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static struct breakpoint *alloc_breakpoint(struct perf_event *bp)
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{
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struct breakpoint *tmp;
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tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
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if (!tmp)
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return ERR_PTR(-ENOMEM);
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tmp->bp = bp;
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tmp->ptrace_bp = is_ptrace_bp(bp);
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return tmp;
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}
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static bool bp_addr_range_overlap(struct perf_event *bp1, struct perf_event *bp2)
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{
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__u64 bp1_saddr, bp1_eaddr, bp2_saddr, bp2_eaddr;
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bp1_saddr = ALIGN_DOWN(bp1->attr.bp_addr, HW_BREAKPOINT_SIZE);
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bp1_eaddr = ALIGN(bp1->attr.bp_addr + bp1->attr.bp_len, HW_BREAKPOINT_SIZE);
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bp2_saddr = ALIGN_DOWN(bp2->attr.bp_addr, HW_BREAKPOINT_SIZE);
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bp2_eaddr = ALIGN(bp2->attr.bp_addr + bp2->attr.bp_len, HW_BREAKPOINT_SIZE);
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return (bp1_saddr < bp2_eaddr && bp1_eaddr > bp2_saddr);
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}
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static bool alternate_infra_bp(struct breakpoint *b, struct perf_event *bp)
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{
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return is_ptrace_bp(bp) ? !b->ptrace_bp : b->ptrace_bp;
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}
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static bool can_co_exist(struct breakpoint *b, struct perf_event *bp)
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{
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return !(alternate_infra_bp(b, bp) && bp_addr_range_overlap(b->bp, bp));
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}
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static int task_bps_add(struct perf_event *bp)
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{
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struct breakpoint *tmp;
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tmp = alloc_breakpoint(bp);
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if (IS_ERR(tmp))
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return PTR_ERR(tmp);
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list_add(&tmp->list, &task_bps);
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return 0;
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}
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static void task_bps_remove(struct perf_event *bp)
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{
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struct list_head *pos, *q;
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list_for_each_safe(pos, q, &task_bps) {
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struct breakpoint *tmp = list_entry(pos, struct breakpoint, list);
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if (tmp->bp == bp) {
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list_del(&tmp->list);
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kfree(tmp);
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break;
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}
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}
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}
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/*
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* If any task has breakpoint from alternate infrastructure,
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* return true. Otherwise return false.
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*/
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static bool all_task_bps_check(struct perf_event *bp)
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{
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struct breakpoint *tmp;
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list_for_each_entry(tmp, &task_bps, list) {
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if (!can_co_exist(tmp, bp))
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return true;
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}
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return false;
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}
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/*
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* If same task has breakpoint from alternate infrastructure,
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* return true. Otherwise return false.
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*/
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static bool same_task_bps_check(struct perf_event *bp)
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{
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struct breakpoint *tmp;
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list_for_each_entry(tmp, &task_bps, list) {
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if (tmp->bp->hw.target == bp->hw.target &&
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!can_co_exist(tmp, bp))
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return true;
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}
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return false;
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}
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static int cpu_bps_add(struct perf_event *bp)
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{
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struct breakpoint **cpu_bp;
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struct breakpoint *tmp;
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int i = 0;
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tmp = alloc_breakpoint(bp);
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if (IS_ERR(tmp))
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return PTR_ERR(tmp);
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cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
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for (i = 0; i < nr_wp_slots(); i++) {
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if (!cpu_bp[i]) {
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cpu_bp[i] = tmp;
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break;
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}
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}
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return 0;
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}
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static void cpu_bps_remove(struct perf_event *bp)
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{
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struct breakpoint **cpu_bp;
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int i = 0;
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cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
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for (i = 0; i < nr_wp_slots(); i++) {
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if (!cpu_bp[i])
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continue;
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if (cpu_bp[i]->bp == bp) {
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kfree(cpu_bp[i]);
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cpu_bp[i] = NULL;
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break;
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}
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}
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}
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static bool cpu_bps_check(int cpu, struct perf_event *bp)
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{
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struct breakpoint **cpu_bp;
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int i;
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cpu_bp = per_cpu_ptr(cpu_bps, cpu);
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for (i = 0; i < nr_wp_slots(); i++) {
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if (cpu_bp[i] && !can_co_exist(cpu_bp[i], bp))
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return true;
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}
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return false;
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}
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static bool all_cpu_bps_check(struct perf_event *bp)
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{
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int cpu;
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for_each_online_cpu(cpu) {
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if (cpu_bps_check(cpu, bp))
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return true;
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}
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return false;
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}
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/*
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* We don't use any locks to serialize accesses to cpu_bps or task_bps
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* because are already inside nr_bp_mutex.
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*/
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int arch_reserve_bp_slot(struct perf_event *bp)
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{
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int ret;
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/* ptrace breakpoint */
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if (is_ptrace_bp(bp)) {
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if (all_cpu_bps_check(bp))
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return -ENOSPC;
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if (same_task_bps_check(bp))
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return -ENOSPC;
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return task_bps_add(bp);
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}
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/* perf breakpoint */
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if (is_kernel_addr(bp->attr.bp_addr))
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return 0;
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if (bp->hw.target && bp->cpu == -1) {
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if (same_task_bps_check(bp))
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return -ENOSPC;
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return task_bps_add(bp);
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} else if (!bp->hw.target && bp->cpu != -1) {
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if (all_task_bps_check(bp))
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return -ENOSPC;
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return cpu_bps_add(bp);
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}
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if (same_task_bps_check(bp))
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return -ENOSPC;
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ret = cpu_bps_add(bp);
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if (ret)
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return ret;
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ret = task_bps_add(bp);
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if (ret)
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cpu_bps_remove(bp);
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return ret;
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}
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void arch_release_bp_slot(struct perf_event *bp)
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{
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if (!is_kernel_addr(bp->attr.bp_addr)) {
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if (bp->hw.target)
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task_bps_remove(bp);
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if (bp->cpu != -1)
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cpu_bps_remove(bp);
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}
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}
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/*
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* Perform cleanup of arch-specific counters during unregistration
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* of the perf-event
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*/
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void arch_unregister_hw_breakpoint(struct perf_event *bp)
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{
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/*
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* If the breakpoint is unregistered between a hw_breakpoint_handler()
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* and the single_step_dabr_instruction(), then cleanup the breakpoint
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* restoration variables to prevent dangling pointers.
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* FIXME, this should not be using bp->ctx at all! Sayeth peterz.
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*/
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if (bp->ctx && bp->ctx->task && bp->ctx->task != ((void *)-1L)) {
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int i;
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for (i = 0; i < nr_wp_slots(); i++) {
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if (bp->ctx->task->thread.last_hit_ubp[i] == bp)
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bp->ctx->task->thread.last_hit_ubp[i] = NULL;
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}
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}
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}
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/*
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* Check for virtual address in kernel space.
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*/
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int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
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{
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return is_kernel_addr(hw->address);
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}
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int arch_bp_generic_fields(int type, int *gen_bp_type)
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{
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*gen_bp_type = 0;
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if (type & HW_BRK_TYPE_READ)
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*gen_bp_type |= HW_BREAKPOINT_R;
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if (type & HW_BRK_TYPE_WRITE)
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*gen_bp_type |= HW_BREAKPOINT_W;
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if (*gen_bp_type == 0)
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return -EINVAL;
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return 0;
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}
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/*
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* Watchpoint match range is always doubleword(8 bytes) aligned on
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* powerpc. If the given range is crossing doubleword boundary, we
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* need to increase the length such that next doubleword also get
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* covered. Ex,
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*
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* address len = 6 bytes
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* |=========.
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* |------------v--|------v--------|
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* | | | | | | | | | | | | | | | | |
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* |---------------|---------------|
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* <---8 bytes--->
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*
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* In this case, we should configure hw as:
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* start_addr = address & ~(HW_BREAKPOINT_SIZE - 1)
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* len = 16 bytes
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*
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* @start_addr is inclusive but @end_addr is exclusive.
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*/
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static int hw_breakpoint_validate_len(struct arch_hw_breakpoint *hw)
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{
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u16 max_len = DABR_MAX_LEN;
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u16 hw_len;
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unsigned long start_addr, end_addr;
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start_addr = ALIGN_DOWN(hw->address, HW_BREAKPOINT_SIZE);
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end_addr = ALIGN(hw->address + hw->len, HW_BREAKPOINT_SIZE);
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hw_len = end_addr - start_addr;
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if (dawr_enabled()) {
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max_len = DAWR_MAX_LEN;
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/* DAWR region can't cross 512 bytes boundary on p10 predecessors */
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if (!cpu_has_feature(CPU_FTR_ARCH_31) &&
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(ALIGN_DOWN(start_addr, SZ_512) != ALIGN_DOWN(end_addr - 1, SZ_512)))
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return -EINVAL;
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} else if (IS_ENABLED(CONFIG_PPC_8xx)) {
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/* 8xx can setup a range without limitation */
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max_len = U16_MAX;
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}
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if (hw_len > max_len)
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return -EINVAL;
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hw->hw_len = hw_len;
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return 0;
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}
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/*
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* Validate the arch-specific HW Breakpoint register settings
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*/
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int hw_breakpoint_arch_parse(struct perf_event *bp,
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const struct perf_event_attr *attr,
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struct arch_hw_breakpoint *hw)
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{
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int ret = -EINVAL;
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if (!bp || !attr->bp_len)
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return ret;
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hw->type = HW_BRK_TYPE_TRANSLATE;
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if (attr->bp_type & HW_BREAKPOINT_R)
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hw->type |= HW_BRK_TYPE_READ;
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if (attr->bp_type & HW_BREAKPOINT_W)
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hw->type |= HW_BRK_TYPE_WRITE;
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if (hw->type == HW_BRK_TYPE_TRANSLATE)
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/* must set alteast read or write */
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return ret;
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if (!attr->exclude_user)
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hw->type |= HW_BRK_TYPE_USER;
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if (!attr->exclude_kernel)
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hw->type |= HW_BRK_TYPE_KERNEL;
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if (!attr->exclude_hv)
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hw->type |= HW_BRK_TYPE_HYP;
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hw->address = attr->bp_addr;
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hw->len = attr->bp_len;
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if (!ppc_breakpoint_available())
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return -ENODEV;
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return hw_breakpoint_validate_len(hw);
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}
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/*
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* Restores the breakpoint on the debug registers.
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* Invoke this function if it is known that the execution context is
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* about to change to cause loss of MSR_SE settings.
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*/
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void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
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{
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struct arch_hw_breakpoint *info;
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int i;
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for (i = 0; i < nr_wp_slots(); i++) {
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if (unlikely(tsk->thread.last_hit_ubp[i]))
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goto reset;
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}
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return;
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reset:
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regs->msr &= ~MSR_SE;
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for (i = 0; i < nr_wp_slots(); i++) {
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info = counter_arch_bp(__this_cpu_read(bp_per_reg[i]));
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__set_breakpoint(i, info);
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tsk->thread.last_hit_ubp[i] = NULL;
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}
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}
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static bool is_larx_stcx_instr(int type)
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{
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return type == LARX || type == STCX;
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}
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/*
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* We've failed in reliably handling the hw-breakpoint. Unregister
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* it and throw a warning message to let the user know about it.
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*/
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static void handler_error(struct perf_event *bp, struct arch_hw_breakpoint *info)
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{
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WARN(1, "Unable to handle hardware breakpoint. Breakpoint at 0x%lx will be disabled.",
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info->address);
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perf_event_disable_inatomic(bp);
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}
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static void larx_stcx_err(struct perf_event *bp, struct arch_hw_breakpoint *info)
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{
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printk_ratelimited("Breakpoint hit on instruction that can't be emulated. Breakpoint at 0x%lx will be disabled.\n",
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info->address);
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perf_event_disable_inatomic(bp);
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}
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static bool stepping_handler(struct pt_regs *regs, struct perf_event **bp,
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struct arch_hw_breakpoint **info, int *hit,
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struct ppc_inst instr)
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{
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int i;
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int stepped;
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/* Do not emulate user-space instructions, instead single-step them */
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if (user_mode(regs)) {
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for (i = 0; i < nr_wp_slots(); i++) {
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if (!hit[i])
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continue;
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current->thread.last_hit_ubp[i] = bp[i];
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info[i] = NULL;
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}
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regs->msr |= MSR_SE;
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return false;
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}
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stepped = emulate_step(regs, instr);
|
|
if (!stepped) {
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
if (!hit[i])
|
|
continue;
|
|
handler_error(bp[i], info[i]);
|
|
info[i] = NULL;
|
|
}
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
int hw_breakpoint_handler(struct die_args *args)
|
|
{
|
|
bool err = false;
|
|
int rc = NOTIFY_STOP;
|
|
struct perf_event *bp[HBP_NUM_MAX] = { NULL };
|
|
struct pt_regs *regs = args->regs;
|
|
struct arch_hw_breakpoint *info[HBP_NUM_MAX] = { NULL };
|
|
int i;
|
|
int hit[HBP_NUM_MAX] = {0};
|
|
int nr_hit = 0;
|
|
bool ptrace_bp = false;
|
|
struct ppc_inst instr = ppc_inst(0);
|
|
int type = 0;
|
|
int size = 0;
|
|
unsigned long ea;
|
|
|
|
/* Disable breakpoints during exception handling */
|
|
hw_breakpoint_disable();
|
|
|
|
/*
|
|
* The counter may be concurrently released but that can only
|
|
* occur from a call_rcu() path. We can then safely fetch
|
|
* the breakpoint, use its callback, touch its counter
|
|
* while we are in an rcu_read_lock() path.
|
|
*/
|
|
rcu_read_lock();
|
|
|
|
if (!IS_ENABLED(CONFIG_PPC_8xx))
|
|
wp_get_instr_detail(regs, &instr, &type, &size, &ea);
|
|
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
bp[i] = __this_cpu_read(bp_per_reg[i]);
|
|
if (!bp[i])
|
|
continue;
|
|
|
|
info[i] = counter_arch_bp(bp[i]);
|
|
info[i]->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
|
|
|
|
if (wp_check_constraints(regs, instr, ea, type, size, info[i])) {
|
|
if (!IS_ENABLED(CONFIG_PPC_8xx) &&
|
|
ppc_inst_equal(instr, ppc_inst(0))) {
|
|
handler_error(bp[i], info[i]);
|
|
info[i] = NULL;
|
|
err = 1;
|
|
continue;
|
|
}
|
|
|
|
if (is_ptrace_bp(bp[i]))
|
|
ptrace_bp = true;
|
|
hit[i] = 1;
|
|
nr_hit++;
|
|
}
|
|
}
|
|
|
|
if (err)
|
|
goto reset;
|
|
|
|
if (!nr_hit) {
|
|
rc = NOTIFY_DONE;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Return early after invoking user-callback function without restoring
|
|
* DABR if the breakpoint is from ptrace which always operates in
|
|
* one-shot mode. The ptrace-ed process will receive the SIGTRAP signal
|
|
* generated in do_dabr().
|
|
*/
|
|
if (ptrace_bp) {
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
if (!hit[i])
|
|
continue;
|
|
perf_bp_event(bp[i], regs);
|
|
info[i] = NULL;
|
|
}
|
|
rc = NOTIFY_DONE;
|
|
goto reset;
|
|
}
|
|
|
|
if (!IS_ENABLED(CONFIG_PPC_8xx)) {
|
|
if (is_larx_stcx_instr(type)) {
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
if (!hit[i])
|
|
continue;
|
|
larx_stcx_err(bp[i], info[i]);
|
|
info[i] = NULL;
|
|
}
|
|
goto reset;
|
|
}
|
|
|
|
if (!stepping_handler(regs, bp, info, hit, instr))
|
|
goto reset;
|
|
}
|
|
|
|
/*
|
|
* As a policy, the callback is invoked in a 'trigger-after-execute'
|
|
* fashion
|
|
*/
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
if (!hit[i])
|
|
continue;
|
|
if (!(info[i]->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
|
|
perf_bp_event(bp[i], regs);
|
|
}
|
|
|
|
reset:
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
if (!info[i])
|
|
continue;
|
|
__set_breakpoint(i, info[i]);
|
|
}
|
|
|
|
out:
|
|
rcu_read_unlock();
|
|
return rc;
|
|
}
|
|
NOKPROBE_SYMBOL(hw_breakpoint_handler);
|
|
|
|
/*
|
|
* Handle single-step exceptions following a DABR hit.
|
|
*/
|
|
static int single_step_dabr_instruction(struct die_args *args)
|
|
{
|
|
struct pt_regs *regs = args->regs;
|
|
struct perf_event *bp = NULL;
|
|
struct arch_hw_breakpoint *info;
|
|
int i;
|
|
bool found = false;
|
|
|
|
/*
|
|
* Check if we are single-stepping as a result of a
|
|
* previous HW Breakpoint exception
|
|
*/
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
bp = current->thread.last_hit_ubp[i];
|
|
|
|
if (!bp)
|
|
continue;
|
|
|
|
found = true;
|
|
info = counter_arch_bp(bp);
|
|
|
|
/*
|
|
* We shall invoke the user-defined callback function in the
|
|
* single stepping handler to confirm to 'trigger-after-execute'
|
|
* semantics
|
|
*/
|
|
if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
|
|
perf_bp_event(bp, regs);
|
|
current->thread.last_hit_ubp[i] = NULL;
|
|
}
|
|
|
|
if (!found)
|
|
return NOTIFY_DONE;
|
|
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
bp = __this_cpu_read(bp_per_reg[i]);
|
|
if (!bp)
|
|
continue;
|
|
|
|
info = counter_arch_bp(bp);
|
|
__set_breakpoint(i, info);
|
|
}
|
|
|
|
/*
|
|
* If the process was being single-stepped by ptrace, let the
|
|
* other single-step actions occur (e.g. generate SIGTRAP).
|
|
*/
|
|
if (test_thread_flag(TIF_SINGLESTEP))
|
|
return NOTIFY_DONE;
|
|
|
|
return NOTIFY_STOP;
|
|
}
|
|
NOKPROBE_SYMBOL(single_step_dabr_instruction);
|
|
|
|
/*
|
|
* Handle debug exception notifications.
|
|
*/
|
|
int hw_breakpoint_exceptions_notify(
|
|
struct notifier_block *unused, unsigned long val, void *data)
|
|
{
|
|
int ret = NOTIFY_DONE;
|
|
|
|
switch (val) {
|
|
case DIE_DABR_MATCH:
|
|
ret = hw_breakpoint_handler(data);
|
|
break;
|
|
case DIE_SSTEP:
|
|
ret = single_step_dabr_instruction(data);
|
|
break;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
NOKPROBE_SYMBOL(hw_breakpoint_exceptions_notify);
|
|
|
|
/*
|
|
* Release the user breakpoints used by ptrace
|
|
*/
|
|
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
|
|
{
|
|
int i;
|
|
struct thread_struct *t = &tsk->thread;
|
|
|
|
for (i = 0; i < nr_wp_slots(); i++) {
|
|
unregister_hw_breakpoint(t->ptrace_bps[i]);
|
|
t->ptrace_bps[i] = NULL;
|
|
}
|
|
}
|
|
|
|
void hw_breakpoint_pmu_read(struct perf_event *bp)
|
|
{
|
|
/* TODO */
|
|
}
|
|
|
|
void ptrace_triggered(struct perf_event *bp,
|
|
struct perf_sample_data *data, struct pt_regs *regs)
|
|
{
|
|
struct perf_event_attr attr;
|
|
|
|
/*
|
|
* Disable the breakpoint request here since ptrace has defined a
|
|
* one-shot behaviour for breakpoint exceptions in PPC64.
|
|
* The SIGTRAP signal is generated automatically for us in do_dabr().
|
|
* We don't have to do anything about that here
|
|
*/
|
|
attr = bp->attr;
|
|
attr.disabled = true;
|
|
modify_user_hw_breakpoint(bp, &attr);
|
|
}
|