1 //===-- hwasan_checks.h -----------------------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file is a part of HWAddressSanitizer.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef HWASAN_CHECKS_H
14 #define HWASAN_CHECKS_H
15 
16 #include "hwasan_mapping.h"
17 #include "sanitizer_common/sanitizer_common.h"
18 
19 namespace __hwasan {
20 template <unsigned X>
21 __attribute__((always_inline)) static void SigTrap(uptr p) {
22 #if defined(__aarch64__)
23   (void)p;
24   // 0x900 is added to do not interfere with the kernel use of lower values of
25   // brk immediate.
26   register uptr x0 asm("x0") = p;
27   asm("brk %1\n\t" ::"r"(x0), "n"(0x900 + X));
28 #elif defined(__x86_64__)
29   // INT3 + NOP DWORD ptr [EAX + X] to pass X to our signal handler, 5 bytes
30   // total. The pointer is passed via rdi.
31   // 0x40 is added as a safeguard, to help distinguish our trap from others and
32   // to avoid 0 offsets in the command (otherwise it'll be reduced to a
33   // different nop command, the three bytes one).
34   asm volatile(
35       "int3\n"
36       "nopl %c0(%%rax)\n" ::"n"(0x40 + X),
37       "D"(p));
38 #else
39   // FIXME: not always sigill.
40   __builtin_trap();
41 #endif
42   // __builtin_unreachable();
43 }
44 
45 // Version with access size which is not power of 2
46 template <unsigned X>
47 __attribute__((always_inline)) static void SigTrap(uptr p, uptr size) {
48 #if defined(__aarch64__)
49   register uptr x0 asm("x0") = p;
50   register uptr x1 asm("x1") = size;
51   asm("brk %2\n\t" ::"r"(x0), "r"(x1), "n"(0x900 + X));
52 #elif defined(__x86_64__)
53   // Size is stored in rsi.
54   asm volatile(
55       "int3\n"
56       "nopl %c0(%%rax)\n" ::"n"(0x40 + X),
57       "D"(p), "S"(size));
58 #else
59   __builtin_trap();
60 #endif
61   // __builtin_unreachable();
62 }
63 
64 __attribute__((always_inline, nodebug)) static bool PossiblyShortTagMatches(
65     tag_t mem_tag, uptr ptr, uptr sz) {
66   tag_t ptr_tag = GetTagFromPointer(ptr);
67   if (ptr_tag == mem_tag)
68     return true;
69   if (mem_tag >= kShadowAlignment)
70     return false;
71   if ((ptr & (kShadowAlignment - 1)) + sz > mem_tag)
72     return false;
73 #ifndef __aarch64__
74   ptr = UntagAddr(ptr);
75 #endif
76   return *(u8 *)(ptr | (kShadowAlignment - 1)) == ptr_tag;
77 }
78 
79 enum class ErrorAction { Abort, Recover };
80 enum class AccessType { Load, Store };
81 
82 template <ErrorAction EA, AccessType AT, unsigned LogSize>
83 __attribute__((always_inline, nodebug)) static void CheckAddress(uptr p) {
84   uptr ptr_raw = p & ~kAddressTagMask;
85   tag_t mem_tag = *(tag_t *)MemToShadow(ptr_raw);
86   if (UNLIKELY(!PossiblyShortTagMatches(mem_tag, p, 1 << LogSize))) {
87     SigTrap<0x20 * (EA == ErrorAction::Recover) +
88             0x10 * (AT == AccessType::Store) + LogSize>(p);
89     if (EA == ErrorAction::Abort)
90       __builtin_unreachable();
91   }
92 }
93 
94 template <ErrorAction EA, AccessType AT>
95 __attribute__((always_inline, nodebug)) static void CheckAddressSized(uptr p,
96                                                                       uptr sz) {
97   if (sz == 0)
98     return;
99   tag_t ptr_tag = GetTagFromPointer(p);
100   uptr ptr_raw = p & ~kAddressTagMask;
101   tag_t *shadow_first = (tag_t *)MemToShadow(ptr_raw);
102   tag_t *shadow_last = (tag_t *)MemToShadow(ptr_raw + sz);
103   for (tag_t *t = shadow_first; t < shadow_last; ++t)
104     if (UNLIKELY(ptr_tag != *t)) {
105       SigTrap<0x20 * (EA == ErrorAction::Recover) +
106               0x10 * (AT == AccessType::Store) + 0xf>(p, sz);
107       if (EA == ErrorAction::Abort)
108         __builtin_unreachable();
109     }
110   uptr end = p + sz;
111   uptr tail_sz = end & 0xf;
112   if (UNLIKELY(tail_sz != 0 &&
113                !PossiblyShortTagMatches(
114                    *shadow_last, end & ~(kShadowAlignment - 1), tail_sz))) {
115     SigTrap<0x20 * (EA == ErrorAction::Recover) +
116             0x10 * (AT == AccessType::Store) + 0xf>(p, sz);
117     if (EA == ErrorAction::Abort)
118       __builtin_unreachable();
119   }
120 }
121 
122 }  // end namespace __hwasan
123 
124 #endif  // HWASAN_CHECKS_H
125