lib/msan/msan_linux.cc

//===-- msan_linux.cc -----------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of MemorySanitizer.
//
// Linux-specific code.
//===----------------------------------------------------------------------===//

#ifdef __linux__

#include "msan.h"

#include <algorithm>
#include <elf.h>
#include <link.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <unwind.h>
#include <execinfo.h>
#include <sys/time.h>
#include <sys/resource.h>

#include "sanitizer_common/sanitizer_common.h"
#include "sanitizer_common/sanitizer_procmaps.h"

namespace __msan {

static const uptr kMemBeg     = 0x600000000000;
static const uptr kMemEnd     = 0x7fffffffffff;
static const uptr kShadowBeg  = MEM_TO_SHADOW(kMemBeg);
static const uptr kShadowEnd  = MEM_TO_SHADOW(kMemEnd);
static const uptr kBad1Beg    = 0x100000000;  // 4G
static const uptr kBad1End    = kShadowBeg - 1;
static const uptr kBad2Beg    = kShadowEnd + 1;
static const uptr kBad2End    = kMemBeg - 1;
static const uptr kOriginsBeg = kBad2Beg;
static const uptr kOriginsEnd = kBad2End;

bool InitShadow(bool prot1, bool prot2, bool map_shadow, bool init_origins) {
  if (flags()->verbosity) {
    Printf("__msan_init %p\n", &__msan_init);
    Printf("Memory   : %p %p\n", kMemBeg, kMemEnd);
    Printf("Bad2     : %p %p\n", kBad2Beg, kBad2End);
    Printf("Origins  : %p %p\n", kOriginsBeg, kOriginsEnd);
    Printf("Shadow   : %p %p\n", kShadowBeg, kShadowEnd);
    Printf("Bad1     : %p %p\n", kBad1Beg, kBad1End);
  }

  if (!MemoryRangeIsAvailable(kShadowBeg,
                              init_origins ? kOriginsEnd : kShadowEnd)) {
    Printf("FATAL: Shadow memory range is not available.\n");
    return false;
  }

  if (prot1 && !Mprotect(kBad1Beg, kBad1End - kBad1Beg))
    return false;
  if (prot2 && !Mprotect(kBad2Beg, kBad2End - kBad2Beg))
    return false;
  if (map_shadow) {
    void *shadow = MmapFixedNoReserve(kShadowBeg, kShadowEnd - kShadowBeg);
    if (shadow != (void*)kShadowBeg) return false;
  }
  if (init_origins) {
    void *origins = MmapFixedNoReserve(kOriginsBeg, kOriginsEnd - kOriginsBeg);
    if (origins != (void*)kOriginsBeg) return false;
  }
  return true;
}

void MsanDie() {
  _exit(flags()->exit_code);
}

static void MsanAtExit(void) {
  if (msan_report_count > 0) {
    ReportAtExitStatistics();
    if (flags()->exit_code)
      _exit(flags()->exit_code);
  }
}

void InstallAtExitHandler() {
  atexit(MsanAtExit);
}

void UnpoisonMappedDSO(link_map *map) {
  typedef ElfW(Phdr) Elf_Phdr;
  typedef ElfW(Ehdr) Elf_Ehdr;
  char *base = (char *)map->l_addr;
  Elf_Ehdr *ehdr = (Elf_Ehdr *)base;
  char *phdrs = base + ehdr->e_phoff;
  char *phdrs_end = phdrs + ehdr->e_phnum * ehdr->e_phentsize;

  // Find the segment with the minimum base so we can "relocate" the p_vaddr
  // fields.  Typically ET_DYN objects (DSOs) have base of zero and ET_EXEC
  // objects have a non-zero base.
  uptr preferred_base = ~0ULL;
  for (char *iter = phdrs; iter != phdrs_end; iter += ehdr->e_phentsize) {
    Elf_Phdr *phdr = (Elf_Phdr *)iter;
    if (phdr->p_type == PT_LOAD)
      preferred_base = std::min(preferred_base, (uptr)phdr->p_vaddr);
  }

  // Compute the delta from the real base to get a relocation delta.
  sptr delta = (uptr)base - preferred_base;
  // Now we can figure out what the loader really mapped.
  for (char *iter = phdrs; iter != phdrs_end; iter += ehdr->e_phentsize) {
    Elf_Phdr *phdr = (Elf_Phdr *)iter;
    if (phdr->p_type == PT_LOAD) {
      uptr seg_start = phdr->p_vaddr + delta;
      uptr seg_end = seg_start + phdr->p_memsz;
      // None of these values are aligned.  We consider the ragged edges of the
      // load command as defined, since they are mapped from the file.
      seg_start = RoundDownTo(seg_start, GetPageSizeCached());
      seg_end = RoundUpTo(seg_end, GetPageSizeCached());
      __msan_unpoison((void *)seg_start, seg_end - seg_start);
    }
  }
}

}  // namespace __msan

#endif  // __linux__