arch/arm64/kernel/probes/uprobes.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2014-2016 Pratyush Anand <panand@redhat.com>
   4  */
   5 #include <linux/highmem.h>
   6 #include <linux/ptrace.h>
   7 #include <linux/uprobes.h>
   8 #include <asm/cacheflush.h>
   9
  10 #include "decode-insn.h"
  11
  12 #define UPROBE_INV_FAULT_CODE   UINT_MAX
  13
  14 void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
  15                 void *src, unsigned long len)
  16 {
  17         void *xol_page_kaddr = kmap_atomic(page);
  18         void *dst = xol_page_kaddr + (vaddr & ~PAGE_MASK);
  19
  20         /* Initialize the slot */
  21         memcpy(dst, src, len);
  22
  23         /* flush caches (dcache/icache) */
  24         sync_icache_aliases(dst, len);
  25
  26         kunmap_atomic(xol_page_kaddr);
  27 }
  28
  29 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
  30 {
  31         return instruction_pointer(regs);
  32 }
  33
  34 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
  35                 unsigned long addr)
  36 {
  37         probe_opcode_t insn;
  38
  39         /* TODO: Currently we do not support AARCH32 instruction probing */
  40         if (mm->context.flags & MMCF_AARCH32)
  41                 return -ENOTSUPP;
  42         else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
  43                 return -EINVAL;
  44
  45         insn = *(probe_opcode_t *)(&auprobe->insn[0]);
  46
  47         switch (arm_probe_decode_insn(insn, &auprobe->api)) {
  48         case INSN_REJECTED:
  49                 return -EINVAL;
  50
  51         case INSN_GOOD_NO_SLOT:
  52                 auprobe->simulate = true;
  53                 break;
  54
  55         default:
  56                 break;
  57         }
  58
  59         return 0;
  60 }
  61
  62 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  63 {
  64         struct uprobe_task *utask = current->utask;
  65
  66         /* Initialize with an invalid fault code to detect if ol insn trapped */
  67         current->thread.fault_code = UPROBE_INV_FAULT_CODE;
  68
  69         /* Instruction points to execute ol */
  70         instruction_pointer_set(regs, utask->xol_vaddr);
  71
  72         user_enable_single_step(current);
  73
  74         return 0;
  75 }
  76
  77 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  78 {
  79         struct uprobe_task *utask = current->utask;
  80
  81         WARN_ON_ONCE(current->thread.fault_code != UPROBE_INV_FAULT_CODE);
  82
  83         /* Instruction points to execute next to breakpoint address */
  84         instruction_pointer_set(regs, utask->vaddr + 4);
  85
  86         user_disable_single_step(current);
  87
  88         return 0;
  89 }
  90 bool arch_uprobe_xol_was_trapped(struct task_struct *t)
  91 {
  92         /*
  93          * Between arch_uprobe_pre_xol and arch_uprobe_post_xol, if an xol
  94          * insn itself is trapped, then detect the case with the help of
  95          * invalid fault code which is being set in arch_uprobe_pre_xol
  96          */
  97         if (t->thread.fault_code != UPROBE_INV_FAULT_CODE)
  98                 return true;
  99
 100         return false;
 101 }
 102
 103 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 104 {
 105         probe_opcode_t insn;
 106         unsigned long addr;
 107
 108         if (!auprobe->simulate)
 109                 return false;
 110
 111         insn = *(probe_opcode_t *)(&auprobe->insn[0]);
 112         addr = instruction_pointer(regs);
 113
 114         if (auprobe->api.handler)
 115                 auprobe->api.handler(insn, addr, regs);
 116
 117         return true;
 118 }
 119
 120 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 121 {
 122         struct uprobe_task *utask = current->utask;
 123
 124         /*
 125          * Task has received a fatal signal, so reset back to probbed
 126          * address.
 127          */
 128         instruction_pointer_set(regs, utask->vaddr);
 129
 130         user_disable_single_step(current);
 131 }
 132
 133 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
 134                 struct pt_regs *regs)
 135 {
 136         /*
 137          * If a simple branch instruction (B) was called for retprobed
 138          * assembly label then return true even when regs->sp and ret->stack
 139          * are same. It will ensure that cleanup and reporting of return
 140          * instances corresponding to callee label is done when
 141          * handle_trampoline for called function is executed.
 142          */
 143         if (ctx == RP_CHECK_CHAIN_CALL)
 144                 return regs->sp <= ret->stack;
 145         else
 146                 return regs->sp < ret->stack;
 147 }
 148
 149 unsigned long
 150 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
 151                                   struct pt_regs *regs)
 152 {
 153         unsigned long orig_ret_vaddr;
 154
 155         orig_ret_vaddr = procedure_link_pointer(regs);
 156         /* Replace the return addr with trampoline addr */
 157         procedure_link_pointer_set(regs, trampoline_vaddr);
 158
 159         return orig_ret_vaddr;
 160 }
 161
 162 int arch_uprobe_exception_notify(struct notifier_block *self,
 163                                  unsigned long val, void *data)
 164 {
 165         return NOTIFY_DONE;
 166 }
 167
 168 static int uprobe_breakpoint_handler(struct pt_regs *regs,
 169                 unsigned int esr)
 170 {
 171         if (uprobe_pre_sstep_notifier(regs))
 172                 return DBG_HOOK_HANDLED;
 173
 174         return DBG_HOOK_ERROR;
 175 }
 176
 177 static int uprobe_single_step_handler(struct pt_regs *regs,
 178                 unsigned int esr)
 179 {
 180         struct uprobe_task *utask = current->utask;
 181
 182         WARN_ON(utask && (instruction_pointer(regs) != utask->xol_vaddr + 4));
 183         if (uprobe_post_sstep_notifier(regs))
 184                 return DBG_HOOK_HANDLED;
 185
 186         return DBG_HOOK_ERROR;
 187 }
 188
 189 /* uprobe breakpoint handler hook */
 190 static struct break_hook uprobes_break_hook = {
 191         .imm = UPROBES_BRK_IMM,
 192         .fn = uprobe_breakpoint_handler,
 193 };
 194
 195 /* uprobe single step handler hook */
 196 static struct step_hook uprobes_step_hook = {
 197         .fn = uprobe_single_step_handler,
 198 };
 199
 200 static int __init arch_init_uprobes(void)
 201 {
 202         register_user_break_hook(&uprobes_break_hook);
 203         register_user_step_hook(&uprobes_step_hook);
 204
 205         return 0;
 206 }
 207
 208 device_initcall(arch_init_uprobes);