xref: /freebsd/contrib/llvm-project/compiler-rt/lib/hwasan/hwasan_globals.cpp (revision f126890ac5386406dadf7c4cfa9566cbb56537c5)
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 #include "sanitizer_common/sanitizer_array_ref.h"
17 
18 namespace __hwasan {
19 
20 enum { NT_LLVM_HWASAN_GLOBALS = 3 };
21 struct hwasan_global_note {
22   s32 begin_relptr;
23   s32 end_relptr;
24 };
25 
26 // Check that the given library meets the code model requirements for tagged
27 // globals. These properties are not checked at link time so they need to be
28 // checked at runtime.
29 static void CheckCodeModel(ElfW(Addr) base, const ElfW(Phdr) * phdr,
30                            ElfW(Half) phnum) {
31   ElfW(Addr) min_addr = -1ull, max_addr = 0;
32   for (unsigned i = 0; i != phnum; ++i) {
33     if (phdr[i].p_type != PT_LOAD)
34       continue;
35     ElfW(Addr) lo = base + phdr[i].p_vaddr, hi = lo + phdr[i].p_memsz;
36     if (min_addr > lo)
37       min_addr = lo;
38     if (max_addr < hi)
39       max_addr = hi;
40   }
41 
42   if (max_addr - min_addr > 1ull << 32) {
43     Report("FATAL: HWAddressSanitizer: library size exceeds 2^32\n");
44     Die();
45   }
46   if (max_addr > 1ull << 48) {
47     Report("FATAL: HWAddressSanitizer: library loaded above address 2^48\n");
48     Die();
49   }
50 }
51 
52 ArrayRef<const hwasan_global> HwasanGlobalsFor(ElfW(Addr) base,
53                                                const ElfW(Phdr) * phdr,
54                                                ElfW(Half) phnum) {
55   // Read the phdrs from this DSO.
56   for (unsigned i = 0; i != phnum; ++i) {
57     if (phdr[i].p_type != PT_NOTE)
58       continue;
59 
60     const char *note = reinterpret_cast<const char *>(base + phdr[i].p_vaddr);
61     const char *nend = note + phdr[i].p_memsz;
62 
63     // Traverse all the notes until we find a HWASan note.
64     while (note < nend) {
65       auto *nhdr = reinterpret_cast<const ElfW(Nhdr) *>(note);
66       const char *name = note + sizeof(ElfW(Nhdr));
67       const char *desc = name + RoundUpTo(nhdr->n_namesz, 4);
68 
69       // Discard non-HWASan-Globals notes.
70       if (nhdr->n_type != NT_LLVM_HWASAN_GLOBALS ||
71           internal_strcmp(name, "LLVM") != 0) {
72         note = desc + RoundUpTo(nhdr->n_descsz, 4);
73         continue;
74       }
75 
76       // Only libraries with instrumented globals need to be checked against the
77       // code model since they use relocations that aren't checked at link time.
78       CheckCodeModel(base, phdr, phnum);
79 
80       auto *global_note = reinterpret_cast<const hwasan_global_note *>(desc);
81       auto *globals_begin = reinterpret_cast<const hwasan_global *>(
82           note + global_note->begin_relptr);
83       auto *globals_end = reinterpret_cast<const hwasan_global *>(
84           note + global_note->end_relptr);
85 
86       return {globals_begin, globals_end};
87     }
88   }
89 
90   return {};
91 }
92 
93 }  // namespace __hwasan
94