arch/arm64/kernel/probes/uprobes.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2014-2016 Pratyush Anand <[email protected]>
   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         /*
  21          * Initial cache maintenance of the xol page done via set_pte_at().
  22          * Subsequent CMOs only needed if the xol slot changes.
  23          */
  24         if (!memcmp(dst, src, len))
  25                 goto done;
  26
  27         /* Initialize the slot */
  28         memcpy(dst, src, len);
  29
  30         /* flush caches (dcache/icache) */
  31         sync_icache_aliases((unsigned long)dst, (unsigned long)dst + len);
  32
  33 done:
  34         kunmap_atomic(xol_page_kaddr);
  35 }
  36
  37 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
  38 {
  39         return instruction_pointer(regs);
  40 }
  41
  42 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
  43                 unsigned long addr)
  44 {
  45         u32 insn;
  46
  47         /* TODO: Currently we do not support AARCH32 instruction probing */
  48         if (mm->context.flags & MMCF_AARCH32)
  49                 return -EOPNOTSUPP;
  50         else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
  51                 return -EINVAL;
  52
  53         insn = le32_to_cpu(auprobe->insn);
  54
  55         switch (arm_probe_decode_insn(insn, &auprobe->api)) {
  56         case INSN_REJECTED:
  57                 return -EINVAL;
  58
  59         case INSN_GOOD_NO_SLOT:
  60                 auprobe->simulate = true;
  61                 break;
  62
  63         default:
  64                 break;
  65         }
  66
  67         return 0;
  68 }
  69
  70 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  71 {
  72         struct uprobe_task *utask = current->utask;
  73
  74         /* Initialize with an invalid fault code to detect if ol insn trapped */
  75         current->thread.fault_code = UPROBE_INV_FAULT_CODE;
  76
  77         /* Instruction points to execute ol */
  78         instruction_pointer_set(regs, utask->xol_vaddr);
  79
  80         user_enable_single_step(current);
  81
  82         return 0;
  83 }
  84
  85 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  86 {
  87         struct uprobe_task *utask = current->utask;
  88
  89         WARN_ON_ONCE(current->thread.fault_code != UPROBE_INV_FAULT_CODE);
  90
  91         /* Instruction points to execute next to breakpoint address */
  92         instruction_pointer_set(regs, utask->vaddr + 4);
  93
  94         user_disable_single_step(current);
  95
  96         return 0;
  97 }
  98 bool arch_uprobe_xol_was_trapped(struct task_struct *t)
  99 {
 100         /*
 101          * Between arch_uprobe_pre_xol and arch_uprobe_post_xol, if an xol
 102          * insn itself is trapped, then detect the case with the help of
 103          * invalid fault code which is being set in arch_uprobe_pre_xol
 104          */
 105         if (t->thread.fault_code != UPROBE_INV_FAULT_CODE)
 106                 return true;
 107
 108         return false;
 109 }
 110
 111 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 112 {
 113         u32 insn;
 114         unsigned long addr;
 115
 116         if (!auprobe->simulate)
 117                 return false;
 118
 119         insn = le32_to_cpu(auprobe->insn);
 120         addr = instruction_pointer(regs);
 121
 122         if (auprobe->api.handler)
 123                 auprobe->api.handler(insn, addr, regs);
 124
 125         return true;
 126 }
 127
 128 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 129 {
 130         struct uprobe_task *utask = current->utask;
 131
 132         /*
 133          * Task has received a fatal signal, so reset back to probbed
 134          * address.
 135          */
 136         instruction_pointer_set(regs, utask->vaddr);
 137
 138         user_disable_single_step(current);
 139 }
 140
 141 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
 142                 struct pt_regs *regs)
 143 {
 144         /*
 145          * If a simple branch instruction (B) was called for retprobed
 146          * assembly label then return true even when regs->sp and ret->stack
 147          * are same. It will ensure that cleanup and reporting of return
 148          * instances corresponding to callee label is done when
 149          * handle_trampoline for called function is executed.
 150          */
 151         if (ctx == RP_CHECK_CHAIN_CALL)
 152                 return regs->sp <= ret->stack;
 153         else
 154                 return regs->sp < ret->stack;
 155 }
 156
 157 unsigned long
 158 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
 159                                   struct pt_regs *regs)
 160 {
 161         unsigned long orig_ret_vaddr;
 162
 163         orig_ret_vaddr = procedure_link_pointer(regs);
 164         /* Replace the return addr with trampoline addr */
 165         procedure_link_pointer_set(regs, trampoline_vaddr);
 166
 167         return orig_ret_vaddr;
 168 }
 169
 170 int arch_uprobe_exception_notify(struct notifier_block *self,
 171                                  unsigned long val, void *data)
 172 {
 173         return NOTIFY_DONE;
 174 }
 175
 176 static int uprobe_breakpoint_handler(struct pt_regs *regs,
 177                                      unsigned long esr)
 178 {
 179         if (uprobe_pre_sstep_notifier(regs))
 180                 return DBG_HOOK_HANDLED;
 181
 182         return DBG_HOOK_ERROR;
 183 }
 184
 185 static int uprobe_single_step_handler(struct pt_regs *regs,
 186                                       unsigned long esr)
 187 {
 188         struct uprobe_task *utask = current->utask;
 189
 190         WARN_ON(utask && (instruction_pointer(regs) != utask->xol_vaddr + 4));
 191         if (uprobe_post_sstep_notifier(regs))
 192                 return DBG_HOOK_HANDLED;
 193
 194         return DBG_HOOK_ERROR;
 195 }
 196
 197 /* uprobe breakpoint handler hook */
 198 static struct break_hook uprobes_break_hook = {
 199         .imm = UPROBES_BRK_IMM,
 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_user_break_hook(&uprobes_break_hook);
 211         register_user_step_hook(&uprobes_step_hook);
 212
 213         return 0;
 214 }
 215
 216 device_initcall(arch_init_uprobes);