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 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.
  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
  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