620 lines
14 KiB
C
620 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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*
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* Copyright (C) 2007 Alan Stern
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* Copyright (C) 2009 IBM Corporation
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* Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
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*
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* Authors: Alan Stern <stern@rowland.harvard.edu>
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* K.Prasad <prasad@linux.vnet.ibm.com>
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* Frederic Weisbecker <fweisbec@gmail.com>
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*/
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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.
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*/
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#include <linux/perf_event.h>
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#include <linux/hw_breakpoint.h>
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#include <linux/irqflags.h>
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#include <linux/notifier.h>
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#include <linux/kallsyms.h>
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#include <linux/kprobes.h>
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#include <linux/percpu.h>
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#include <linux/kdebug.h>
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/sched.h>
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#include <linux/smp.h>
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#include <asm/hw_breakpoint.h>
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#include <asm/processor.h>
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#include <asm/debugreg.h>
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#include <asm/user.h>
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#include <asm/desc.h>
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#include <asm/tlbflush.h>
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/* Per cpu debug control register value */
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DEFINE_PER_CPU(unsigned long, cpu_dr7);
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EXPORT_PER_CPU_SYMBOL(cpu_dr7);
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/* Per cpu debug address registers values */
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static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
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/*
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* Stores the breakpoints currently in use on each breakpoint address
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* register for each cpus
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*/
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static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
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static inline unsigned long
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__encode_dr7(int drnum, unsigned int len, unsigned int type)
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{
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unsigned long bp_info;
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bp_info = (len | type) & 0xf;
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bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
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bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));
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return bp_info;
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}
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/*
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* Encode the length, type, Exact, and Enable bits for a particular breakpoint
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* as stored in debug register 7.
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*/
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unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
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{
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return __encode_dr7(drnum, len, type) | DR_GLOBAL_SLOWDOWN;
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}
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/*
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* Decode the length and type bits for a particular breakpoint as
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* stored in debug register 7. Return the "enabled" status.
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*/
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int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
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{
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int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
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*len = (bp_info & 0xc) | 0x40;
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*type = (bp_info & 0x3) | 0x80;
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return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
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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. Eventually we enable it in the debug control register.
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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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unsigned long *dr7;
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int i;
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lockdep_assert_irqs_disabled();
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for (i = 0; i < HBP_NUM; i++) {
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struct perf_event **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 == HBP_NUM, "Can't find any breakpoint slot"))
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return -EBUSY;
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set_debugreg(info->address, i);
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__this_cpu_write(cpu_debugreg[i], info->address);
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dr7 = this_cpu_ptr(&cpu_dr7);
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*dr7 |= encode_dr7(i, info->len, info->type);
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/*
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* Ensure we first write cpu_dr7 before we set the DR7 register.
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* This ensures an NMI never see cpu_dr7 0 when DR7 is not.
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*/
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barrier();
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set_debugreg(*dr7, 7);
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if (info->mask)
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set_dr_addr_mask(info->mask, i);
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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 *info = counter_arch_bp(bp);
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unsigned long dr7;
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int i;
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lockdep_assert_irqs_disabled();
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for (i = 0; i < HBP_NUM; i++) {
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struct perf_event **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 == HBP_NUM, "Can't find any breakpoint slot"))
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return;
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dr7 = this_cpu_read(cpu_dr7);
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dr7 &= ~__encode_dr7(i, info->len, info->type);
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set_debugreg(dr7, 7);
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if (info->mask)
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set_dr_addr_mask(0, i);
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/*
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* Ensure the write to cpu_dr7 is after we've set the DR7 register.
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* This ensures an NMI never see cpu_dr7 0 when DR7 is not.
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*/
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barrier();
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this_cpu_write(cpu_dr7, dr7);
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}
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static int arch_bp_generic_len(int x86_len)
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{
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switch (x86_len) {
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case X86_BREAKPOINT_LEN_1:
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return HW_BREAKPOINT_LEN_1;
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case X86_BREAKPOINT_LEN_2:
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return HW_BREAKPOINT_LEN_2;
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case X86_BREAKPOINT_LEN_4:
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return HW_BREAKPOINT_LEN_4;
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#ifdef CONFIG_X86_64
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case X86_BREAKPOINT_LEN_8:
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return HW_BREAKPOINT_LEN_8;
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#endif
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default:
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return -EINVAL;
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}
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}
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int arch_bp_generic_fields(int x86_len, int x86_type,
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int *gen_len, int *gen_type)
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{
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int len;
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/* Type */
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switch (x86_type) {
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case X86_BREAKPOINT_EXECUTE:
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if (x86_len != X86_BREAKPOINT_LEN_X)
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return -EINVAL;
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*gen_type = HW_BREAKPOINT_X;
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*gen_len = sizeof(long);
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return 0;
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case X86_BREAKPOINT_WRITE:
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*gen_type = HW_BREAKPOINT_W;
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break;
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case X86_BREAKPOINT_RW:
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*gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
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break;
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default:
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return -EINVAL;
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}
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/* Len */
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len = arch_bp_generic_len(x86_len);
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if (len < 0)
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return -EINVAL;
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*gen_len = len;
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return 0;
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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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unsigned long va;
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int len;
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va = hw->address;
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len = arch_bp_generic_len(hw->len);
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WARN_ON_ONCE(len < 0);
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/*
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* We don't need to worry about va + len - 1 overflowing:
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* we already require that va is aligned to a multiple of len.
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*/
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return (va >= TASK_SIZE_MAX) || ((va + len - 1) >= TASK_SIZE_MAX);
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}
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/*
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* Checks whether the range [addr, end], overlaps the area [base, base + size).
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*/
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static inline bool within_area(unsigned long addr, unsigned long end,
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unsigned long base, unsigned long size)
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{
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return end >= base && addr < (base + size);
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}
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/*
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* Checks whether the range from addr to end, inclusive, overlaps the fixed
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* mapped CPU entry area range or other ranges used for CPU entry.
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*/
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static inline bool within_cpu_entry(unsigned long addr, unsigned long end)
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{
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int cpu;
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/* CPU entry erea is always used for CPU entry */
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if (within_area(addr, end, CPU_ENTRY_AREA_BASE,
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CPU_ENTRY_AREA_TOTAL_SIZE))
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return true;
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for_each_possible_cpu(cpu) {
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/* The original rw GDT is being used after load_direct_gdt() */
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if (within_area(addr, end, (unsigned long)get_cpu_gdt_rw(cpu),
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GDT_SIZE))
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return true;
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/*
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* cpu_tss_rw is not directly referenced by hardware, but
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* cpu_tss_rw is also used in CPU entry code,
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*/
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if (within_area(addr, end,
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(unsigned long)&per_cpu(cpu_tss_rw, cpu),
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sizeof(struct tss_struct)))
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return true;
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/*
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* cpu_tlbstate.user_pcid_flush_mask is used for CPU entry.
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* If a data breakpoint on it, it will cause an unwanted #DB.
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* Protect the full cpu_tlbstate structure to be sure.
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*/
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if (within_area(addr, end,
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(unsigned long)&per_cpu(cpu_tlbstate, cpu),
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sizeof(struct tlb_state)))
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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 arch_build_bp_info(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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unsigned long bp_end;
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bp_end = attr->bp_addr + attr->bp_len - 1;
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if (bp_end < attr->bp_addr)
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return -EINVAL;
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/*
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* Prevent any breakpoint of any type that overlaps the CPU
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* entry area and data. This protects the IST stacks and also
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* reduces the chance that we ever find out what happens if
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* there's a data breakpoint on the GDT, IDT, or TSS.
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*/
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if (within_cpu_entry(attr->bp_addr, bp_end))
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return -EINVAL;
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hw->address = attr->bp_addr;
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hw->mask = 0;
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/* Type */
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switch (attr->bp_type) {
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case HW_BREAKPOINT_W:
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hw->type = X86_BREAKPOINT_WRITE;
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break;
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case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
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hw->type = X86_BREAKPOINT_RW;
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break;
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case HW_BREAKPOINT_X:
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/*
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* We don't allow kernel breakpoints in places that are not
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* acceptable for kprobes. On non-kprobes kernels, we don't
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* allow kernel breakpoints at all.
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*/
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if (attr->bp_addr >= TASK_SIZE_MAX) {
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if (within_kprobe_blacklist(attr->bp_addr))
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return -EINVAL;
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}
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hw->type = X86_BREAKPOINT_EXECUTE;
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/*
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* x86 inst breakpoints need to have a specific undefined len.
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* But we still need to check userspace is not trying to setup
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* an unsupported length, to get a range breakpoint for example.
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*/
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if (attr->bp_len == sizeof(long)) {
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hw->len = X86_BREAKPOINT_LEN_X;
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return 0;
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}
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fallthrough;
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default:
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return -EINVAL;
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}
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/* Len */
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switch (attr->bp_len) {
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case HW_BREAKPOINT_LEN_1:
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hw->len = X86_BREAKPOINT_LEN_1;
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break;
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case HW_BREAKPOINT_LEN_2:
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hw->len = X86_BREAKPOINT_LEN_2;
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break;
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case HW_BREAKPOINT_LEN_4:
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hw->len = X86_BREAKPOINT_LEN_4;
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break;
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#ifdef CONFIG_X86_64
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case HW_BREAKPOINT_LEN_8:
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hw->len = X86_BREAKPOINT_LEN_8;
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break;
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#endif
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default:
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/* AMD range breakpoint */
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if (!is_power_of_2(attr->bp_len))
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return -EINVAL;
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if (attr->bp_addr & (attr->bp_len - 1))
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return -EINVAL;
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if (!boot_cpu_has(X86_FEATURE_BPEXT))
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return -EOPNOTSUPP;
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/*
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* It's impossible to use a range breakpoint to fake out
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* user vs kernel detection because bp_len - 1 can't
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* have the high bit set. If we ever allow range instruction
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* breakpoints, then we'll have to check for kprobe-blacklisted
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* addresses anywhere in the range.
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*/
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hw->mask = attr->bp_len - 1;
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hw->len = X86_BREAKPOINT_LEN_1;
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}
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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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unsigned int align;
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int ret;
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ret = arch_build_bp_info(bp, attr, hw);
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if (ret)
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return ret;
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switch (hw->len) {
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case X86_BREAKPOINT_LEN_1:
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align = 0;
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if (hw->mask)
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align = hw->mask;
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break;
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case X86_BREAKPOINT_LEN_2:
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align = 1;
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break;
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case X86_BREAKPOINT_LEN_4:
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align = 3;
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break;
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#ifdef CONFIG_X86_64
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case X86_BREAKPOINT_LEN_8:
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align = 7;
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break;
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#endif
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default:
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WARN_ON_ONCE(1);
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return -EINVAL;
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}
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/*
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* Check that the low-order bits of the address are appropriate
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* for the alignment implied by len.
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*/
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if (hw->address & align)
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return -EINVAL;
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return 0;
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}
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/*
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* Dump the debug register contents to the user.
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* We can't dump our per cpu values because it
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* may contain cpu wide breakpoint, something that
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* doesn't belong to the current task.
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*
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* TODO: include non-ptrace user breakpoints (perf)
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*/
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void aout_dump_debugregs(struct user *dump)
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{
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int i;
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int dr7 = 0;
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struct perf_event *bp;
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struct arch_hw_breakpoint *info;
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struct thread_struct *thread = ¤t->thread;
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for (i = 0; i < HBP_NUM; i++) {
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bp = thread->ptrace_bps[i];
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if (bp && !bp->attr.disabled) {
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dump->u_debugreg[i] = bp->attr.bp_addr;
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info = counter_arch_bp(bp);
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dr7 |= encode_dr7(i, info->len, info->type);
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} else {
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dump->u_debugreg[i] = 0;
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}
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}
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dump->u_debugreg[4] = 0;
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dump->u_debugreg[5] = 0;
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dump->u_debugreg[6] = current->thread.debugreg6;
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dump->u_debugreg[7] = dr7;
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}
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EXPORT_SYMBOL_GPL(aout_dump_debugregs);
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/*
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* Release the user breakpoints used by ptrace
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*/
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void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
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{
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int i;
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struct thread_struct *t = &tsk->thread;
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for (i = 0; i < HBP_NUM; i++) {
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unregister_hw_breakpoint(t->ptrace_bps[i]);
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t->ptrace_bps[i] = NULL;
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}
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t->debugreg6 = 0;
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t->ptrace_dr7 = 0;
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}
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void hw_breakpoint_restore(void)
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{
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set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
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set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
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set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
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set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
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set_debugreg(current->thread.debugreg6, 6);
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set_debugreg(__this_cpu_read(cpu_dr7), 7);
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}
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EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
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/*
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* Handle debug exception notifications.
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*
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* Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
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*
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* NOTIFY_DONE returned if one of the following conditions is true.
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* i) When the causative address is from user-space and the exception
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* is a valid one, i.e. not triggered as a result of lazy debug register
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* switching
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* ii) When there are more bits than trap<n> set in DR6 register (such
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* as BD, BS or BT) indicating that more than one debug condition is
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* met and requires some more action in do_debug().
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*
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* NOTIFY_STOP returned for all other cases
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*
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*/
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static int hw_breakpoint_handler(struct die_args *args)
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{
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int i, cpu, rc = NOTIFY_STOP;
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struct perf_event *bp;
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unsigned long dr6;
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unsigned long *dr6_p;
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/* The DR6 value is pointed by args->err */
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dr6_p = (unsigned long *)ERR_PTR(args->err);
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dr6 = *dr6_p;
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/* If it's a single step, TRAP bits are random */
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if (dr6 & DR_STEP)
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return NOTIFY_DONE;
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/* Do an early return if no trap bits are set in DR6 */
|
|
if ((dr6 & DR_TRAP_BITS) == 0)
|
|
return NOTIFY_DONE;
|
|
|
|
/*
|
|
* Assert that local interrupts are disabled
|
|
* Reset the DRn bits in the virtualized register value.
|
|
* The ptrace trigger routine will add in whatever is needed.
|
|
*/
|
|
current->thread.debugreg6 &= ~DR_TRAP_BITS;
|
|
cpu = get_cpu();
|
|
|
|
/* Handle all the breakpoints that were triggered */
|
|
for (i = 0; i < HBP_NUM; ++i) {
|
|
if (likely(!(dr6 & (DR_TRAP0 << i))))
|
|
continue;
|
|
|
|
/*
|
|
* 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();
|
|
|
|
bp = per_cpu(bp_per_reg[i], cpu);
|
|
/*
|
|
* Reset the 'i'th TRAP bit in dr6 to denote completion of
|
|
* exception handling
|
|
*/
|
|
(*dr6_p) &= ~(DR_TRAP0 << i);
|
|
/*
|
|
* bp can be NULL due to lazy debug register switching
|
|
* or due to concurrent perf counter removing.
|
|
*/
|
|
if (!bp) {
|
|
rcu_read_unlock();
|
|
break;
|
|
}
|
|
|
|
perf_bp_event(bp, args->regs);
|
|
|
|
/*
|
|
* Set up resume flag to avoid breakpoint recursion when
|
|
* returning back to origin.
|
|
*/
|
|
if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
|
|
args->regs->flags |= X86_EFLAGS_RF;
|
|
|
|
rcu_read_unlock();
|
|
}
|
|
/*
|
|
* Further processing in do_debug() is needed for a) user-space
|
|
* breakpoints (to generate signals) and b) when the system has
|
|
* taken exception due to multiple causes
|
|
*/
|
|
if ((current->thread.debugreg6 & DR_TRAP_BITS) ||
|
|
(dr6 & (~DR_TRAP_BITS)))
|
|
rc = NOTIFY_DONE;
|
|
|
|
put_cpu();
|
|
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* Handle debug exception notifications.
|
|
*/
|
|
int hw_breakpoint_exceptions_notify(
|
|
struct notifier_block *unused, unsigned long val, void *data)
|
|
{
|
|
if (val != DIE_DEBUG)
|
|
return NOTIFY_DONE;
|
|
|
|
return hw_breakpoint_handler(data);
|
|
}
|
|
|
|
void hw_breakpoint_pmu_read(struct perf_event *bp)
|
|
{
|
|
/* TODO */
|
|
}
|