arch/arm64/kernel/probes/uprobes.c

   1 /*
   2  * Copyright (C) 2014-2016 Pratyush Anand <panand@redhat.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8 #include <linux/highmem.h>
   9 #include <linux/ptrace.h>
  10 #include <linux/uprobes.h>
  11 #include <asm/cacheflush.h>
  12
  13 #include "decode-insn.h"
  14
  15 #define UPROBE_INV_FAULT_CODE   UINT_MAX
  16
  17 void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
  18                 void *src, unsigned long len)
  19 {
  20         void *xol_page_kaddr = kmap_atomic(page);
  21         void *dst = xol_page_kaddr + (vaddr & ~PAGE_MASK);
  22
  23         /* Initialize the slot */
  24         memcpy(dst, src, len);
  25
  26         /* flush caches (dcache/icache) */
  27         sync_icache_aliases(dst, len);
  28
  29         kunmap_atomic(xol_page_kaddr);
  30 }
  31
  32 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
  33 {
  34         return instruction_pointer(regs);
  35 }
  36
  37 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
  38                 unsigned long addr)
  39 {
  40         probe_opcode_t insn;
  41
  42         /* TODO: Currently we do not support AARCH32 instruction probing */
  43         if (test_bit(TIF_32BIT, &mm->context.flags))
  44                 return -ENOTSUPP;
  45         else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
  46                 return -EINVAL;
  47
  48         insn = *(probe_opcode_t *)(&auprobe->insn[0]);
  49
  50         switch (arm_probe_decode_insn(insn, &auprobe->api)) {
  51         case INSN_REJECTED:
  52                 return -EINVAL;
  53
  54         case INSN_GOOD_NO_SLOT:
  55                 auprobe->simulate = true;
  56                 break;
  57
  58         default:
  59                 break;
  60         }
  61
  62         return 0;
  63 }
  64
  65 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  66 {
  67         struct uprobe_task *utask = current->utask;
  68
  69         /* Initialize with an invalid fault code to detect if ol insn trapped */
  70         current->thread.fault_code = UPROBE_INV_FAULT_CODE;
  71
  72         /* Instruction points to execute ol */
  73         instruction_pointer_set(regs, utask->xol_vaddr);
  74
  75         user_enable_single_step(current);
  76
  77         return 0;
  78 }
  79
  80 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  81 {
  82         struct uprobe_task *utask = current->utask;
  83
  84         WARN_ON_ONCE(current->thread.fault_code != UPROBE_INV_FAULT_CODE);
  85
  86         /* Instruction points to execute next to breakpoint address */
  87         instruction_pointer_set(regs, utask->vaddr + 4);
  88
  89         user_disable_single_step(current);
  90
  91         return 0;
  92 }
  93 bool arch_uprobe_xol_was_trapped(struct task_struct *t)
  94 {
  95         /*
  96          * Between arch_uprobe_pre_xol and arch_uprobe_post_xol, if an xol
  97          * insn itself is trapped, then detect the case with the help of
  98          * invalid fault code which is being set in arch_uprobe_pre_xol
  99          */
 100         if (t->thread.fault_code != UPROBE_INV_FAULT_CODE)
 101                 return true;
 102
 103         return false;
 104 }
 105
 106 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 107 {
 108         probe_opcode_t insn;
 109         unsigned long addr;
 110
 111         if (!auprobe->simulate)
 112                 return false;
 113
 114         insn = *(probe_opcode_t *)(&auprobe->insn[0]);
 115         addr = instruction_pointer(regs);
 116
 117         if (auprobe->api.handler)
 118                 auprobe->api.handler(insn, addr, regs);
 119
 120         return true;
 121 }
 122
 123 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 124 {
 125         struct uprobe_task *utask = current->utask;
 126
 127         /*
 128          * Task has received a fatal signal, so reset back to probbed
 129          * address.
 130          */
 131         instruction_pointer_set(regs, utask->vaddr);
 132
 133         user_disable_single_step(current);
 134 }
 135
 136 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
 137                 struct pt_regs *regs)
 138 {
 139         /*
 140          * If a simple branch instruction (B) was called for retprobed
 141          * assembly label then return true even when regs->sp and ret->stack
 142          * are same. It will ensure that cleanup and reporting of return
 143          * instances corresponding to callee label is done when
 144          * handle_trampoline for called function is executed.
 145          */
 146         if (ctx == RP_CHECK_CHAIN_CALL)
 147                 return regs->sp <= ret->stack;
 148         else
 149                 return regs->sp < ret->stack;
 150 }
 151
 152 unsigned long
 153 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
 154                                   struct pt_regs *regs)
 155 {
 156         unsigned long orig_ret_vaddr;
 157
 158         orig_ret_vaddr = procedure_link_pointer(regs);
 159         /* Replace the return addr with trampoline addr */
 160         procedure_link_pointer_set(regs, trampoline_vaddr);
 161
 162         return orig_ret_vaddr;
 163 }
 164
 165 int arch_uprobe_exception_notify(struct notifier_block *self,
 166                                  unsigned long val, void *data)
 167 {
 168         return NOTIFY_DONE;
 169 }
 170
 171 static int uprobe_breakpoint_handler(struct pt_regs *regs,
 172                 unsigned int esr)
 173 {
 174         if (user_mode(regs) && uprobe_pre_sstep_notifier(regs))
 175                 return DBG_HOOK_HANDLED;
 176
 177         return DBG_HOOK_ERROR;
 178 }
 179
 180 static int uprobe_single_step_handler(struct pt_regs *regs,
 181                 unsigned int esr)
 182 {
 183         struct uprobe_task *utask = current->utask;
 184
 185         if (user_mode(regs)) {
 186                 WARN_ON(utask &&
 187                         (instruction_pointer(regs) != utask->xol_vaddr + 4));
 188
 189                 if (uprobe_post_sstep_notifier(regs))
 190                         return DBG_HOOK_HANDLED;
 191         }
 192
 193         return DBG_HOOK_ERROR;
 194 }
 195
 196 /* uprobe breakpoint handler hook */
 197 static struct break_hook uprobes_break_hook = {
 198         .esr_mask = BRK64_ESR_MASK,
 199         .esr_val = BRK64_ESR_UPROBES,
 200         .fn = uprobe_breakpoint_handler,
 201 };
 202
 203 /* uprobe single step handler hook */
 204 static struct step_hook uprobes_step_hook = {
 205         .fn = uprobe_single_step_handler,
 206 };
 207
 208 static int __init arch_init_uprobes(void)
 209 {
 210         register_break_hook(&uprobes_break_hook);
 211         register_step_hook(&uprobes_step_hook);
 212
 213         return 0;
 214 }
 215
 216 device_initcall(arch_init_uprobes);