lib/hwasan/hwasan_linux.cc

//===-- hwasan_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 HWAddressSanitizer.
//
// Linux-, NetBSD- and FreeBSD-specific code.
//===----------------------------------------------------------------------===//

#include "sanitizer_common/sanitizer_platform.h"
#if SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD

#include "hwasan.h"
#include "hwasan_thread.h"

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

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

namespace __hwasan {

void ReserveShadowMemoryRange(uptr beg, uptr end, const char *name) {
  CHECK_EQ((beg % GetMmapGranularity()), 0);
  CHECK_EQ(((end + 1) % GetMmapGranularity()), 0);
  uptr size = end - beg + 1;
  DecreaseTotalMmap(size);  // Don't count the shadow against mmap_limit_mb.
  void *res = MmapFixedNoReserve(beg, size, name);
  if (res != (void *)beg) {
    Report(
        "ReserveShadowMemoryRange failed while trying to map 0x%zx bytes. "
        "Perhaps you're using ulimit -v\n",
        size);
    Abort();
  }
  if (common_flags()->no_huge_pages_for_shadow) NoHugePagesInRegion(beg, size);
  if (common_flags()->use_madv_dontdump) DontDumpShadowMemory(beg, size);
}

static void ProtectGap(uptr addr, uptr size) {
  void *res = MmapFixedNoAccess(addr, size, "shadow gap");
  if (addr == (uptr)res) return;
  // A few pages at the start of the address space can not be protected.
  // But we really want to protect as much as possible, to prevent this memory
  // being returned as a result of a non-FIXED mmap().
  if (addr == 0) {
    uptr step = GetMmapGranularity();
    while (size > step) {
      addr += step;
      size -= step;
      void *res = MmapFixedNoAccess(addr, size, "shadow gap");
      if (addr == (uptr)res) return;
    }
  }

  Report(
      "ERROR: Failed to protect the shadow gap. "
      "ASan cannot proceed correctly. ABORTING.\n");
  DumpProcessMap();
  Die();
}

bool InitShadow() {
  const uptr maxVirtualAddress = GetMaxUserVirtualAddress();

  // LowMem covers as much of the first 4GB as possible.
  const uptr kLowMemEnd = 1UL<<32;
  const uptr kLowShadowEnd = kLowMemEnd >> kShadowScale;
  const uptr kLowShadowStart = kLowShadowEnd >> kShadowScale;

  // HighMem covers the upper part of the address space.
  const uptr kHighShadowEnd = (maxVirtualAddress >> kShadowScale) + 1;
  const uptr kHighShadowStart = Max(kLowMemEnd, kHighShadowEnd >> kShadowScale);
  CHECK(kHighShadowStart < kHighShadowEnd);

  const uptr kHighMemStart = kHighShadowStart << kShadowScale;
  CHECK(kHighShadowEnd <= kHighMemStart);

  if (Verbosity()) {
    Printf("|| `[%p, %p]` || HighMem    ||\n", (void *)kHighMemStart,
           (void *)maxVirtualAddress);
    if (kHighMemStart > kHighShadowEnd)
      Printf("|| `[%p, %p]` || ShadowGap2 ||\n", (void *)kHighShadowEnd,
             (void *)kHighMemStart);
    Printf("|| `[%p, %p]` || HighShadow ||\n", (void *)kHighShadowStart,
           (void *)kHighShadowEnd);
    if (kHighShadowStart > kLowMemEnd)
      Printf("|| `[%p, %p]` || ShadowGap2 ||\n", (void *)kHighShadowEnd,
             (void *)kHighMemStart);
    Printf("|| `[%p, %p]` || LowMem     ||\n", (void *)kLowShadowEnd,
           (void *)kLowMemEnd);
    Printf("|| `[%p, %p]` || LowShadow  ||\n", (void *)kLowShadowStart,
           (void *)kLowShadowEnd);
    Printf("|| `[%p, %p]` || ShadowGap1 ||\n", (void *)0,
           (void *)kLowShadowStart);
  }

  ReserveShadowMemoryRange(kLowShadowStart, kLowShadowEnd - 1, "low shadow");
  ReserveShadowMemoryRange(kHighShadowStart, kHighShadowEnd - 1, "high shadow");
  ProtectGap(0, kLowShadowStart);
  if (kHighShadowStart > kLowMemEnd)
    ProtectGap(kLowMemEnd, kHighShadowStart - kLowMemEnd);
  if (kHighMemStart > kHighShadowEnd)
    ProtectGap(kHighShadowEnd, kHighMemStart - kHighShadowEnd);

  return true;
}

static void HwasanAtExit(void) {
  if (flags()->print_stats && (flags()->atexit || hwasan_report_count > 0))
    ReportStats();
  if (hwasan_report_count > 0) {
    // ReportAtExitStatistics();
    if (common_flags()->exitcode)
      internal__exit(common_flags()->exitcode);
  }
}

void InstallAtExitHandler() {
  atexit(HwasanAtExit);
}

// ---------------------- TSD ---------------- {{{1

static pthread_key_t tsd_key;
static bool tsd_key_inited = false;

void HwasanTSDInit(void (*destructor)(void *tsd)) {
  CHECK(!tsd_key_inited);
  tsd_key_inited = true;
  CHECK_EQ(0, pthread_key_create(&tsd_key, destructor));
}

HwasanThread *GetCurrentThread() {
  return (HwasanThread*)pthread_getspecific(tsd_key);
}

void SetCurrentThread(HwasanThread *t) {
  // Make sure that HwasanTSDDtor gets called at the end.
  CHECK(tsd_key_inited);
  // Make sure we do not reset the current HwasanThread.
  CHECK_EQ(0, pthread_getspecific(tsd_key));
  pthread_setspecific(tsd_key, (void *)t);
}

void HwasanTSDDtor(void *tsd) {
  HwasanThread *t = (HwasanThread*)tsd;
  if (t->destructor_iterations_ > 1) {
    t->destructor_iterations_--;
    CHECK_EQ(0, pthread_setspecific(tsd_key, tsd));
    return;
  }
  // Make sure that signal handler can not see a stale current thread pointer.
  atomic_signal_fence(memory_order_seq_cst);
  HwasanThread::TSDDtor(tsd);
}

struct AccessInfo {
  uptr addr;
  uptr size;
  bool is_store;
  bool is_load;
  bool recover;
};

#if defined(__aarch64__)
static AccessInfo GetAccessInfo(siginfo_t *info, ucontext_t *uc) {
  // Access type is encoded in HLT immediate as 0x1XY,
  // where X&1 is 1 for store, 0 for load,
  // and X&2 is 1 if the error is recoverable.
  // Valid values of Y are 0 to 4, which are interpreted as log2(access_size),
  // and 0xF, which means that access size is stored in X1 register.
  // Access address is always in X0 register.
  AccessInfo ai;
  uptr pc = (uptr)info->si_addr;
  unsigned code = ((*(u32 *)pc) >> 5) & 0xffff;
  if ((code & 0xff00) != 0x100)
    return AccessInfo{0, 0, false, false}; // Not ours.
  bool is_store = code & 0x10;
  bool recover = code & 0x20;
  unsigned size_log = code & 0xf;
  if (size_log > 4 && size_log != 0xf)
    return AccessInfo{0, 0, false, false}; // Not ours.

  ai.is_store = is_store;
  ai.is_load = !is_store;
  ai.addr = uc->uc_mcontext.regs[0];
  if (size_log == 0xf)
    ai.size = uc->uc_mcontext.regs[1];
  else
    ai.size = 1U << size_log;
  ai.recover = recover;
  return ai;
}
#else
static AccessInfo GetAccessInfo(siginfo_t *info, ucontext_t *uc) {
  return AccessInfo{0, 0, false, false};
}
#endif

static bool HwasanOnSIGILL(int signo, siginfo_t *info, ucontext_t *uc) {
  SignalContext sig{info, uc};
  AccessInfo ai = GetAccessInfo(info, uc);
  if (!ai.is_store && !ai.is_load)
    return false;

  InternalScopedBuffer<BufferedStackTrace> stack_buffer(1);
  BufferedStackTrace *stack = stack_buffer.data();
  stack->Reset();
  GetStackTrace(stack, kStackTraceMax, sig.pc, sig.bp, uc,
                common_flags()->fast_unwind_on_fatal);

  ReportTagMismatch(stack, ai.addr, ai.size, ai.is_store);

  ++hwasan_report_count;
  if (flags()->halt_on_error || !ai.recover)
    Die();

  uc->uc_mcontext.pc += 4;
  return true;
}

static void OnStackUnwind(const SignalContext &sig, const void *,
                          BufferedStackTrace *stack) {
  GetStackTrace(stack, kStackTraceMax, sig.pc, sig.bp, sig.context,
                common_flags()->fast_unwind_on_fatal);
}

void HwasanOnDeadlySignal(int signo, void *info, void *context) {
  // Probably a tag mismatch.
  if (signo == SIGILL)
    if (HwasanOnSIGILL(signo, (siginfo_t *)info, (ucontext_t*)context))
      return;

  HandleDeadlySignal(info, context, GetTid(), &OnStackUnwind, nullptr);
}


} // namespace __hwasan

#endif // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD