1 //===-- hwasan_globals.cpp ------------------------------------------------===//
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 // HWAddressSanitizer globals-specific runtime.
12 //===----------------------------------------------------------------------===//
13
14 #include "hwasan_globals.h"
15
16 namespace __hwasan {
17
18 enum { NT_LLVM_HWASAN_GLOBALS = 3 };
19 struct hwasan_global_note {
20 s32 begin_relptr;
21 s32 end_relptr;
22 };
23
24 // Check that the given library meets the code model requirements for tagged
25 // globals. These properties are not checked at link time so they need to be
26 // checked at runtime.
CheckCodeModel(ElfW (Addr)base,const ElfW (Phdr)* phdr,ElfW (Half)phnum)27 static void CheckCodeModel(ElfW(Addr) base, const ElfW(Phdr) * phdr,
28 ElfW(Half) phnum) {
29 ElfW(Addr) min_addr = -1ull, max_addr = 0;
30 for (unsigned i = 0; i != phnum; ++i) {
31 if (phdr[i].p_type != PT_LOAD)
32 continue;
33 ElfW(Addr) lo = base + phdr[i].p_vaddr, hi = lo + phdr[i].p_memsz;
34 if (min_addr > lo)
35 min_addr = lo;
36 if (max_addr < hi)
37 max_addr = hi;
38 }
39
40 if (max_addr - min_addr > 1ull << 32) {
41 Report("FATAL: HWAddressSanitizer: library size exceeds 2^32\n");
42 Die();
43 }
44 if (max_addr > 1ull << 48) {
45 Report("FATAL: HWAddressSanitizer: library loaded above address 2^48\n");
46 Die();
47 }
48 }
49
HwasanGlobalsFor(ElfW (Addr)base,const ElfW (Phdr)* phdr,ElfW (Half)phnum)50 ArrayRef<const hwasan_global> HwasanGlobalsFor(ElfW(Addr) base,
51 const ElfW(Phdr) * phdr,
52 ElfW(Half) phnum) {
53 // Read the phdrs from this DSO.
54 for (unsigned i = 0; i != phnum; ++i) {
55 if (phdr[i].p_type != PT_NOTE)
56 continue;
57
58 const char *note = reinterpret_cast<const char *>(base + phdr[i].p_vaddr);
59 const char *nend = note + phdr[i].p_memsz;
60
61 // Traverse all the notes until we find a HWASan note.
62 while (note < nend) {
63 auto *nhdr = reinterpret_cast<const ElfW(Nhdr) *>(note);
64 const char *name = note + sizeof(ElfW(Nhdr));
65 const char *desc = name + RoundUpTo(nhdr->n_namesz, 4);
66
67 // Discard non-HWASan-Globals notes.
68 if (nhdr->n_type != NT_LLVM_HWASAN_GLOBALS ||
69 internal_strcmp(name, "LLVM") != 0) {
70 note = desc + RoundUpTo(nhdr->n_descsz, 4);
71 continue;
72 }
73
74 // Only libraries with instrumented globals need to be checked against the
75 // code model since they use relocations that aren't checked at link time.
76 CheckCodeModel(base, phdr, phnum);
77
78 auto *global_note = reinterpret_cast<const hwasan_global_note *>(desc);
79 auto *globals_begin = reinterpret_cast<const hwasan_global *>(
80 note + global_note->begin_relptr);
81 auto *globals_end = reinterpret_cast<const hwasan_global *>(
82 note + global_note->end_relptr);
83
84 return {globals_begin, globals_end};
85 }
86 }
87
88 return {};
89 }
90
91 } // namespace __hwasan
92