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-rw-r--r--arch/x86/kernel/hw_breakpoint.c592
1 files changed, 592 insertions, 0 deletions
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
new file mode 100644
index 000000000..668a4a653
--- /dev/null
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -0,0 +1,592 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ * Copyright (C) 2007 Alan Stern
+ * Copyright (C) 2009 IBM Corporation
+ * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Authors: Alan Stern <stern@rowland.harvard.edu>
+ * K.Prasad <prasad@linux.vnet.ibm.com>
+ * Frederic Weisbecker <fweisbec@gmail.com>
+ */
+
+/*
+ * 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(cpu_dr7);
+
+/* 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)
+{
+ unsigned long bp_info;
+
+ bp_info = (len | type) & 0xf;
+ bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
+ bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));
+
+ return bp_info;
+}
+
+/*
+ * 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)
+{
+ return __encode_dr7(drnum, len, type) | DR_GLOBAL_SLOWDOWN;
+}
+
+/*
+ * 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)
+{
+ int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
+
+ *len = (bp_info & 0xc) | 0x40;
+ *type = (bp_info & 0x3) | 0x80;
+
+ return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
+}
+
+/*
+ * 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)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ unsigned long *dr7;
+ int i;
+
+ lockdep_assert_irqs_disabled();
+
+ for (i = 0; i < HBP_NUM; i++) {
+ struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
+
+ if (!*slot) {
+ *slot = bp;
+ break;
+ }
+ }
+
+ if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+ return -EBUSY;
+
+ set_debugreg(info->address, i);
+ __this_cpu_write(cpu_debugreg[i], info->address);
+
+ dr7 = this_cpu_ptr(&cpu_dr7);
+ *dr7 |= encode_dr7(i, info->len, info->type);
+
+ /*
+ * Ensure we first write cpu_dr7 before we set the DR7 register.
+ * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
+ */
+ barrier();
+
+ set_debugreg(*dr7, 7);
+ if (info->mask)
+ set_dr_addr_mask(info->mask, i);
+
+ return 0;
+}
+
+/*
+ * 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)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ unsigned long dr7;
+ int i;
+
+ lockdep_assert_irqs_disabled();
+
+ for (i = 0; i < HBP_NUM; i++) {
+ struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
+
+ if (*slot == bp) {
+ *slot = NULL;
+ break;
+ }
+ }
+
+ if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+ return;
+
+ dr7 = this_cpu_read(cpu_dr7);
+ dr7 &= ~__encode_dr7(i, info->len, info->type);
+
+ set_debugreg(dr7, 7);
+ if (info->mask)
+ set_dr_addr_mask(0, i);
+
+ /*
+ * Ensure the write to cpu_dr7 is after we've set the DR7 register.
+ * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
+ */
+ barrier();
+
+ this_cpu_write(cpu_dr7, dr7);
+}
+
+static int arch_bp_generic_len(int x86_len)
+{
+ switch (x86_len) {
+ case X86_BREAKPOINT_LEN_1:
+ return HW_BREAKPOINT_LEN_1;
+ case X86_BREAKPOINT_LEN_2:
+ return HW_BREAKPOINT_LEN_2;
+ case X86_BREAKPOINT_LEN_4:
+ return HW_BREAKPOINT_LEN_4;
+#ifdef CONFIG_X86_64
+ case X86_BREAKPOINT_LEN_8:
+ return HW_BREAKPOINT_LEN_8;
+#endif
+ default:
+ return -EINVAL;
+ }
+}
+
+int arch_bp_generic_fields(int x86_len, int x86_type,
+ int *gen_len, int *gen_type)
+{
+ int len;
+
+ /* Type */
+ switch (x86_type) {
+ case X86_BREAKPOINT_EXECUTE:
+ if (x86_len != X86_BREAKPOINT_LEN_X)
+ return -EINVAL;
+
+ *gen_type = HW_BREAKPOINT_X;
+ *gen_len = sizeof(long);
+ return 0;
+ case X86_BREAKPOINT_WRITE:
+ *gen_type = HW_BREAKPOINT_W;
+ break;
+ case X86_BREAKPOINT_RW:
+ *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* Len */
+ len = arch_bp_generic_len(x86_len);
+ if (len < 0)
+ return -EINVAL;
+ *gen_len = len;
+
+ return 0;
+}
+
+/*
+ * Check for virtual address in kernel space.
+ */
+int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
+{
+ unsigned long va;
+ int len;
+
+ va = hw->address;
+ len = arch_bp_generic_len(hw->len);
+ WARN_ON_ONCE(len < 0);
+
+ /*
+ * We don't need to worry about va + len - 1 overflowing:
+ * we already require that va is aligned to a multiple of len.
+ */
+ return (va >= TASK_SIZE_MAX) || ((va + len - 1) >= TASK_SIZE_MAX);
+}
+
+/*
+ * 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)
+{
+ return end >= base && addr < (base + 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)
+{
+ int cpu;
+
+ /* CPU entry erea is always used for CPU entry */
+ if (within_area(addr, end, CPU_ENTRY_AREA_BASE,
+ CPU_ENTRY_AREA_TOTAL_SIZE))
+ return true;
+
+ /*
+ * When FSGSBASE is enabled, paranoid_entry() fetches the per-CPU
+ * GSBASE value via __per_cpu_offset or pcpu_unit_offsets.
+ */
+#ifdef CONFIG_SMP
+ if (within_area(addr, end, (unsigned long)__per_cpu_offset,
+ sizeof(unsigned long) * nr_cpu_ids))
+ return true;
+#else
+ if (within_area(addr, end, (unsigned long)&pcpu_unit_offsets,
+ sizeof(pcpu_unit_offsets)))
+ return true;
+#endif
+
+ for_each_possible_cpu(cpu) {
+ /* The original rw GDT is being used after load_direct_gdt() */
+ if (within_area(addr, end, (unsigned long)get_cpu_gdt_rw(cpu),
+ GDT_SIZE))
+ return true;
+
+ /*
+ * cpu_tss_rw is not directly referenced by hardware, but
+ * cpu_tss_rw is also used in CPU entry code,
+ */
+ if (within_area(addr, end,
+ (unsigned long)&per_cpu(cpu_tss_rw, cpu),
+ sizeof(struct tss_struct)))
+ return true;
+
+ /*
+ * cpu_tlbstate.user_pcid_flush_mask is used for CPU entry.
+ * If a data breakpoint on it, it will cause an unwanted #DB.
+ * Protect the full cpu_tlbstate structure to be sure.
+ */
+ if (within_area(addr, end,
+ (unsigned long)&per_cpu(cpu_tlbstate, cpu),
+ sizeof(struct tlb_state)))
+ return true;
+
+ /*
+ * When in guest (X86_FEATURE_HYPERVISOR), local_db_save()
+ * will read per-cpu cpu_dr7 before clear dr7 register.
+ */
+ if (within_area(addr, end, (unsigned long)&per_cpu(cpu_dr7, cpu),
+ sizeof(cpu_dr7)))
+ return true;
+ }
+
+ return false;
+}
+
+static int arch_build_bp_info(struct perf_event *bp,
+ const struct perf_event_attr *attr,
+ struct arch_hw_breakpoint *hw)
+{
+ unsigned long bp_end;
+
+ bp_end = attr->bp_addr + attr->bp_len - 1;
+ if (bp_end < attr->bp_addr)
+ return -EINVAL;
+
+ /*
+ * Prevent any breakpoint of any type that overlaps the CPU
+ * entry area and data. This protects the IST stacks and also
+ * reduces the chance that we ever find out what happens if
+ * there's a data breakpoint on the GDT, IDT, or TSS.
+ */
+ if (within_cpu_entry(attr->bp_addr, bp_end))
+ return -EINVAL;
+
+ hw->address = attr->bp_addr;
+ hw->mask = 0;
+
+ /* Type */
+ switch (attr->bp_type) {
+ case HW_BREAKPOINT_W:
+ hw->type = X86_BREAKPOINT_WRITE;
+ break;
+ case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+ hw->type = X86_BREAKPOINT_RW;
+ break;
+ case HW_BREAKPOINT_X:
+ /*
+ * We don't allow kernel breakpoints in places that are not
+ * acceptable for kprobes. On non-kprobes kernels, we don't
+ * allow kernel breakpoints at all.
+ */
+ if (attr->bp_addr >= TASK_SIZE_MAX) {
+ if (within_kprobe_blacklist(attr->bp_addr))
+ return -EINVAL;
+ }
+
+ hw->type = X86_BREAKPOINT_EXECUTE;
+ /*
+ * x86 inst breakpoints need to have a specific undefined len.
+ * But we still need to check userspace is not trying to setup
+ * an unsupported length, to get a range breakpoint for example.
+ */
+ if (attr->bp_len == sizeof(long)) {
+ hw->len = X86_BREAKPOINT_LEN_X;
+ return 0;
+ }
+ fallthrough;
+ default:
+ return -EINVAL;
+ }
+
+ /* Len */
+ switch (attr->bp_len) {
+ case HW_BREAKPOINT_LEN_1:
+ hw->len = X86_BREAKPOINT_LEN_1;
+ break;
+ case HW_BREAKPOINT_LEN_2:
+ hw->len = X86_BREAKPOINT_LEN_2;
+ break;
+ case HW_BREAKPOINT_LEN_4:
+ hw->len = X86_BREAKPOINT_LEN_4;
+ break;
+#ifdef CONFIG_X86_64
+ case HW_BREAKPOINT_LEN_8:
+ hw->len = X86_BREAKPOINT_LEN_8;
+ break;
+#endif
+ default:
+ /* AMD range breakpoint */
+ if (!is_power_of_2(attr->bp_len))
+ return -EINVAL;
+ if (attr->bp_addr & (attr->bp_len - 1))
+ return -EINVAL;
+
+ if (!boot_cpu_has(X86_FEATURE_BPEXT))
+ return -EOPNOTSUPP;
+
+ /*
+ * It's impossible to use a range breakpoint to fake out
+ * user vs kernel detection because bp_len - 1 can't
+ * have the high bit set. If we ever allow range instruction
+ * breakpoints, then we'll have to check for kprobe-blacklisted
+ * addresses anywhere in the range.
+ */
+ hw->mask = attr->bp_len - 1;
+ hw->len = X86_BREAKPOINT_LEN_1;
+ }
+
+ 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)
+{
+ unsigned int align;
+ int ret;
+
+
+ ret = arch_build_bp_info(bp, attr, hw);
+ if (ret)
+ return ret;
+
+ switch (hw->len) {
+ case X86_BREAKPOINT_LEN_1:
+ align = 0;
+ if (hw->mask)
+ align = hw->mask;
+ break;
+ case X86_BREAKPOINT_LEN_2:
+ align = 1;
+ break;
+ case X86_BREAKPOINT_LEN_4:
+ align = 3;
+ break;
+#ifdef CONFIG_X86_64
+ case X86_BREAKPOINT_LEN_8:
+ align = 7;
+ break;
+#endif
+ default:
+ WARN_ON_ONCE(1);
+ return -EINVAL;
+ }
+
+ /*
+ * Check that the low-order bits of the address are appropriate
+ * for the alignment implied by len.
+ */
+ if (hw->address & align)
+ return -EINVAL;
+
+ return 0;
+}
+
+/*
+ * 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 < HBP_NUM; i++) {
+ unregister_hw_breakpoint(t->ptrace_bps[i]);
+ t->ptrace_bps[i] = NULL;
+ }
+
+ t->virtual_dr6 = 0;
+ t->ptrace_dr7 = 0;
+}
+
+void hw_breakpoint_restore(void)
+{
+ set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
+ set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
+ set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
+ set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
+ set_debugreg(DR6_RESERVED, 6);
+ set_debugreg(__this_cpu_read(cpu_dr7), 7);
+}
+EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
+
+/*
+ * 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)
+{
+ int i, rc = NOTIFY_STOP;
+ struct perf_event *bp;
+ unsigned long *dr6_p;
+ unsigned long dr6;
+ bool bpx;
+
+ /* The DR6 value is pointed by args->err */
+ dr6_p = (unsigned long *)ERR_PTR(args->err);
+ dr6 = *dr6_p;
+
+ /* Do an early return if no trap bits are set in DR6 */
+ if ((dr6 & DR_TRAP_BITS) == 0)
+ return NOTIFY_DONE;
+
+ /* Handle all the breakpoints that were triggered */
+ for (i = 0; i < HBP_NUM; ++i) {
+ if (likely(!(dr6 & (DR_TRAP0 << i))))
+ continue;
+
+ bp = this_cpu_read(bp_per_reg[i]);
+ if (!bp)
+ continue;
+
+ bpx = bp->hw.info.type == X86_BREAKPOINT_EXECUTE;
+
+ /*
+ * TF and data breakpoints are traps and can be merged, however
+ * instruction breakpoints are faults and will be raised
+ * separately.
+ *
+ * However DR6 can indicate both TF and instruction
+ * breakpoints. In that case take TF as that has precedence and
+ * delay the instruction breakpoint for the next exception.
+ */
+ if (bpx && (dr6 & DR_STEP))
+ continue;
+
+ /*
+ * Reset the 'i'th TRAP bit in dr6 to denote completion of
+ * exception handling
+ */
+ (*dr6_p) &= ~(DR_TRAP0 << i);
+
+ perf_bp_event(bp, args->regs);
+
+ /*
+ * Set up resume flag to avoid breakpoint recursion when
+ * returning back to origin.
+ */
+ if (bpx)
+ args->regs->flags |= X86_EFLAGS_RF;
+ }
+
+ /*
+ * 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.virtual_dr6 & DR_TRAP_BITS) ||
+ (dr6 & (~DR_TRAP_BITS)))
+ rc = NOTIFY_DONE;
+
+ 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 */
+}
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