compiler-rt/lib/hwasan/hwasan_globals.cpp

   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