lib/hwasan/hwasan_linux.cpp

//===-- hwasan_linux.cpp ----------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file is a part of HWAddressSanitizer and contains Linux-, NetBSD- and
/// FreeBSD-specific code.
///
//===----------------------------------------------------------------------===//

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

#include "hwasan.h"
#include "hwasan_dynamic_shadow.h"
#include "hwasan_interface_internal.h"
#include "hwasan_mapping.h"
#include "hwasan_report.h"
#include "hwasan_thread.h"
#include "hwasan_thread_list.h"

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

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

// Configurations of HWASAN_WITH_INTERCEPTORS and SANITIZER_ANDROID.
//
// HWASAN_WITH_INTERCEPTORS=OFF, SANITIZER_ANDROID=OFF
//   Not currently tested.
// HWASAN_WITH_INTERCEPTORS=OFF, SANITIZER_ANDROID=ON
//   Integration tests downstream exist.
// HWASAN_WITH_INTERCEPTORS=ON, SANITIZER_ANDROID=OFF
//    Tested with check-hwasan on x86_64-linux.
// HWASAN_WITH_INTERCEPTORS=ON, SANITIZER_ANDROID=ON
//    Tested with check-hwasan on aarch64-linux-android.
#if !SANITIZER_ANDROID
SANITIZER_INTERFACE_ATTRIBUTE
THREADLOCAL uptr __hwasan_tls;
#endif

namespace __hwasan {

// With the zero shadow base we can not actually map pages starting from 0.
// This constant is somewhat arbitrary.
constexpr uptr kZeroBaseShadowStart = 0;
constexpr uptr kZeroBaseMaxShadowStart = 1 << 18;

static void ProtectGap(uptr addr, uptr size) {
  __sanitizer::ProtectGap(addr, size, kZeroBaseShadowStart,
                          kZeroBaseMaxShadowStart);
}

uptr kLowMemStart;
uptr kLowMemEnd;
uptr kLowShadowEnd;
uptr kLowShadowStart;
uptr kHighShadowStart;
uptr kHighShadowEnd;
uptr kHighMemStart;
uptr kHighMemEnd;

uptr kAliasRegionStart;  // Always 0 when aliases aren't used.

static void PrintRange(uptr start, uptr end, const char *name) {
  Printf("|| [%p, %p] || %.*s ||\n", (void *)start, (void *)end, 10, name);
}

static void PrintAddressSpaceLayout() {
  PrintRange(kHighMemStart, kHighMemEnd, "HighMem");
  if (kHighShadowEnd + 1 < kHighMemStart)
    PrintRange(kHighShadowEnd + 1, kHighMemStart - 1, "ShadowGap");
  else
    CHECK_EQ(kHighShadowEnd + 1, kHighMemStart);
  PrintRange(kHighShadowStart, kHighShadowEnd, "HighShadow");
  if (kLowShadowEnd + 1 < kHighShadowStart)
    PrintRange(kLowShadowEnd + 1, kHighShadowStart - 1, "ShadowGap");
  else
    CHECK_EQ(kLowMemEnd + 1, kHighShadowStart);
  PrintRange(kLowShadowStart, kLowShadowEnd, "LowShadow");
  if (kLowMemEnd + 1 < kLowShadowStart)
    PrintRange(kLowMemEnd + 1, kLowShadowStart - 1, "ShadowGap");
  else
    CHECK_EQ(kLowMemEnd + 1, kLowShadowStart);
  PrintRange(kLowMemStart, kLowMemEnd, "LowMem");
  CHECK_EQ(0, kLowMemStart);
}

static uptr GetHighMemEnd() {
  // HighMem covers the upper part of the address space.
  uptr max_address = GetMaxUserVirtualAddress();
  // Adjust max address to make sure that kHighMemEnd and kHighMemStart are
  // properly aligned:
  max_address |= (GetMmapGranularity() << kShadowScale) - 1;
  return max_address;
}

static void InitializeShadowBaseAddress(uptr shadow_size_bytes) {
  __hwasan_shadow_memory_dynamic_address =
      FindDynamicShadowStart(shadow_size_bytes);
}

void InitPrctl() {
#define PR_SET_TAGGED_ADDR_CTRL 55
#define PR_GET_TAGGED_ADDR_CTRL 56
#define PR_TAGGED_ADDR_ENABLE (1UL << 0)
  // Check we're running on a kernel that can use the tagged address ABI.
  int local_errno = 0;
  if (internal_iserror(internal_prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0),
                       &local_errno) &&
      local_errno == EINVAL) {
#  if SANITIZER_ANDROID || defined(HWASAN_ALIASING_MODE)
    // Some older Android kernels have the tagged pointer ABI on
    // unconditionally, and hence don't have the tagged-addr prctl while still
    // allow the ABI.
    // If targeting Android and the prctl is not around we assume this is the
    // case.
    return;
#  else
    if (flags()->fail_without_syscall_abi) {
      Printf(
          "FATAL: "
          "HWAddressSanitizer requires a kernel with tagged address ABI.\n");
      Die();
    }
#  endif
  }

  // Turn on the tagged address ABI.
  if ((internal_iserror(internal_prctl(PR_SET_TAGGED_ADDR_CTRL,
                                       PR_TAGGED_ADDR_ENABLE, 0, 0, 0)) ||
       !internal_prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0))) {
#  if defined(__x86_64__) && !defined(HWASAN_ALIASING_MODE)
    // Try the new prctl API for Intel LAM.  The API is based on a currently
    // unsubmitted patch to the Linux kernel (as of May 2021) and is thus
    // subject to change.  Patch is here:
    // https://lore.kernel.org/linux-mm/[email protected]/
    int tag_bits = kTagBits;
    int tag_shift = kAddressTagShift;
    if (!internal_iserror(
            internal_prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE,
                           reinterpret_cast<unsigned long>(&tag_bits),
                           reinterpret_cast<unsigned long>(&tag_shift), 0))) {
      CHECK_EQ(tag_bits, kTagBits);
      CHECK_EQ(tag_shift, kAddressTagShift);
      return;
    }
#  endif  // defined(__x86_64__) && !defined(HWASAN_ALIASING_MODE)
    if (flags()->fail_without_syscall_abi) {
      Printf(
          "FATAL: HWAddressSanitizer failed to enable tagged address syscall "
          "ABI.\nSuggest check `sysctl abi.tagged_addr_disabled` "
          "configuration.\n");
      Die();
    }
  }
#undef PR_SET_TAGGED_ADDR_CTRL
#undef PR_GET_TAGGED_ADDR_CTRL
#undef PR_TAGGED_ADDR_ENABLE
}

bool InitShadow() {
  // Define the entire memory range.
  kHighMemEnd = GetHighMemEnd();

  // Determine shadow memory base offset.
  InitializeShadowBaseAddress(MemToShadowSize(kHighMemEnd));

  // Place the low memory first.
  kLowMemEnd = __hwasan_shadow_memory_dynamic_address - 1;
  kLowMemStart = 0;

  // Define the low shadow based on the already placed low memory.
  kLowShadowEnd = MemToShadow(kLowMemEnd);
  kLowShadowStart = __hwasan_shadow_memory_dynamic_address;

  // High shadow takes whatever memory is left up there (making sure it is not
  // interfering with low memory in the fixed case).
  kHighShadowEnd = MemToShadow(kHighMemEnd);
  kHighShadowStart = Max(kLowMemEnd, MemToShadow(kHighShadowEnd)) + 1;

  // High memory starts where allocated shadow allows.
  kHighMemStart = ShadowToMem(kHighShadowStart);

#  if defined(HWASAN_ALIASING_MODE)
  constexpr uptr kAliasRegionOffset = 1ULL << (kTaggableRegionCheckShift - 1);
  kAliasRegionStart =
      __hwasan_shadow_memory_dynamic_address + kAliasRegionOffset;

  CHECK_EQ(kAliasRegionStart >> kTaggableRegionCheckShift,
           __hwasan_shadow_memory_dynamic_address >> kTaggableRegionCheckShift);
  CHECK_EQ(
      (kAliasRegionStart + kAliasRegionOffset - 1) >> kTaggableRegionCheckShift,
      __hwasan_shadow_memory_dynamic_address >> kTaggableRegionCheckShift);
#  endif

  // Check the sanity of the defined memory ranges (there might be gaps).
  CHECK_EQ(kHighMemStart % GetMmapGranularity(), 0);
  CHECK_GT(kHighMemStart, kHighShadowEnd);
  CHECK_GT(kHighShadowEnd, kHighShadowStart);
  CHECK_GT(kHighShadowStart, kLowMemEnd);
  CHECK_GT(kLowMemEnd, kLowMemStart);
  CHECK_GT(kLowShadowEnd, kLowShadowStart);
  CHECK_GT(kLowShadowStart, kLowMemEnd);

  if (Verbosity())
    PrintAddressSpaceLayout();

  // Reserve shadow memory.
  ReserveShadowMemoryRange(kLowShadowStart, kLowShadowEnd, "low shadow");
  ReserveShadowMemoryRange(kHighShadowStart, kHighShadowEnd, "high shadow");

  // Protect all the gaps.
  ProtectGap(0, Min(kLowMemStart, kLowShadowStart));
  if (kLowMemEnd + 1 < kLowShadowStart)
    ProtectGap(kLowMemEnd + 1, kLowShadowStart - kLowMemEnd - 1);
  if (kLowShadowEnd + 1 < kHighShadowStart)
    ProtectGap(kLowShadowEnd + 1, kHighShadowStart - kLowShadowEnd - 1);
  if (kHighShadowEnd + 1 < kHighMemStart)
    ProtectGap(kHighShadowEnd + 1, kHighMemStart - kHighShadowEnd - 1);

  return true;
}

void InitThreads() {
  CHECK(__hwasan_shadow_memory_dynamic_address);
  uptr guard_page_size = GetMmapGranularity();
  uptr thread_space_start =
      __hwasan_shadow_memory_dynamic_address - (1ULL << kShadowBaseAlignment);
  uptr thread_space_end =
      __hwasan_shadow_memory_dynamic_address - guard_page_size;
  ReserveShadowMemoryRange(thread_space_start, thread_space_end - 1,
                           "hwasan threads", /*madvise_shadow*/ false);
  ProtectGap(thread_space_end,
             __hwasan_shadow_memory_dynamic_address - thread_space_end);
  InitThreadList(thread_space_start, thread_space_end - thread_space_start);
}

bool MemIsApp(uptr p) {
// Memory outside the alias range has non-zero tags.
#  if !defined(HWASAN_ALIASING_MODE)
  CHECK(GetTagFromPointer(p) == 0);
#  endif

  return p >= kHighMemStart || (p >= kLowMemStart && p <= kLowMemEnd);
}

static void HwasanAtExit(void) {
  if (common_flags()->print_module_map)
    DumpProcessMap();
  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

extern "C" void __hwasan_thread_enter() {
  hwasanThreadList().CreateCurrentThread()->InitRandomState();
}

extern "C" void __hwasan_thread_exit() {
  Thread *t = GetCurrentThread();
  // Make sure that signal handler can not see a stale current thread pointer.
  atomic_signal_fence(memory_order_seq_cst);
  if (t)
    hwasanThreadList().ReleaseThread(t);
}

#if HWASAN_WITH_INTERCEPTORS
static pthread_key_t tsd_key;
static bool tsd_key_inited = false;

void HwasanTSDThreadInit() {
  if (tsd_key_inited)
    CHECK_EQ(0, pthread_setspecific(tsd_key,
                                    (void *)GetPthreadDestructorIterations()));
}

void HwasanTSDDtor(void *tsd) {
  uptr iterations = (uptr)tsd;
  if (iterations > 1) {
    CHECK_EQ(0, pthread_setspecific(tsd_key, (void *)(iterations - 1)));
    return;
  }
  __hwasan_thread_exit();
}

void HwasanTSDInit() {
  CHECK(!tsd_key_inited);
  tsd_key_inited = true;
  CHECK_EQ(0, pthread_key_create(&tsd_key, HwasanTSDDtor));
}
#else
void HwasanTSDInit() {}
void HwasanTSDThreadInit() {}
#endif

#if SANITIZER_ANDROID
uptr *GetCurrentThreadLongPtr() {
  return (uptr *)get_android_tls_ptr();
}
#else
uptr *GetCurrentThreadLongPtr() {
  return &__hwasan_tls;
}
#endif

#if SANITIZER_ANDROID
void AndroidTestTlsSlot() {
  uptr kMagicValue = 0x010203040A0B0C0D;
  uptr *tls_ptr = GetCurrentThreadLongPtr();
  uptr old_value = *tls_ptr;
  *tls_ptr = kMagicValue;
  dlerror();
  if (*(uptr *)get_android_tls_ptr() != kMagicValue) {
    Printf(
        "ERROR: Incompatible version of Android: TLS_SLOT_SANITIZER(6) is used "
        "for dlerror().\n");
    Die();
  }
  *tls_ptr = old_value;
}
#else
void AndroidTestTlsSlot() {}
#endif

Thread *GetCurrentThread() {
  uptr *ThreadLongPtr = GetCurrentThreadLongPtr();
  if (UNLIKELY(*ThreadLongPtr == 0))
    return nullptr;
  auto *R = (StackAllocationsRingBuffer *)ThreadLongPtr;
  return hwasanThreadList().GetThreadByBufferAddress((uptr)R->Next());
}

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

static AccessInfo GetAccessInfo(siginfo_t *info, ucontext_t *uc) {
  // Access type is passed in a platform dependent way (see below) and encoded
  // as 0xXY, 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 passed via
  // platform dependent register (see below).
#if defined(__aarch64__)
  // Access type is encoded in BRK immediate as 0x900 + 0xXY. For Y == 0xF,
  // access size is stored in X1 register. Access address is always in X0
  // register.
  uptr pc = (uptr)info->si_addr;
  const unsigned code = ((*(u32 *)pc) >> 5) & 0xffff;
  if ((code & 0xff00) != 0x900)
    return AccessInfo{}; // Not ours.

  const bool is_store = code & 0x10;
  const bool recover = code & 0x20;
  const uptr addr = uc->uc_mcontext.regs[0];
  const unsigned size_log = code & 0xf;
  if (size_log > 4 && size_log != 0xf)
    return AccessInfo{}; // Not ours.
  const uptr size = size_log == 0xf ? uc->uc_mcontext.regs[1] : 1U << size_log;

#elif defined(__x86_64__)
  // Access type is encoded in the instruction following INT3 as
  // NOP DWORD ptr [EAX + 0x40 + 0xXY]. For Y == 0xF, access size is stored in
  // RSI register. Access address is always in RDI register.
  uptr pc = (uptr)uc->uc_mcontext.gregs[REG_RIP];
  uint8_t *nop = (uint8_t*)pc;
  if (*nop != 0x0f || *(nop + 1) != 0x1f || *(nop + 2) != 0x40  ||
      *(nop + 3) < 0x40)
    return AccessInfo{}; // Not ours.
  const unsigned code = *(nop + 3);

  const bool is_store = code & 0x10;
  const bool recover = code & 0x20;
  const uptr addr = uc->uc_mcontext.gregs[REG_RDI];
  const unsigned size_log = code & 0xf;
  if (size_log > 4 && size_log != 0xf)
    return AccessInfo{}; // Not ours.
  const uptr size =
      size_log == 0xf ? uc->uc_mcontext.gregs[REG_RSI] : 1U << size_log;

#else
# error Unsupported architecture
#endif

  return AccessInfo{addr, size, is_store, !is_store, recover};
}

static void HandleTagMismatch(AccessInfo ai, uptr pc, uptr frame,
                              ucontext_t *uc, uptr *registers_frame = nullptr) {
  InternalMmapVector<BufferedStackTrace> stack_buffer(1);
  BufferedStackTrace *stack = stack_buffer.data();
  stack->Reset();
  stack->Unwind(pc, frame, uc, common_flags()->fast_unwind_on_fatal);

  // The second stack frame contains the failure __hwasan_check function, as
  // we have a stack frame for the registers saved in __hwasan_tag_mismatch that
  // we wish to ignore. This (currently) only occurs on AArch64, as x64
  // implementations use SIGTRAP to implement the failure, and thus do not go
  // through the stack saver.
  if (registers_frame && stack->trace && stack->size > 0) {
    stack->trace++;
    stack->size--;
  }

  bool fatal = flags()->halt_on_error || !ai.recover;
  ReportTagMismatch(stack, ai.addr, ai.size, ai.is_store, fatal,
                    registers_frame);
}

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

  SignalContext sig{info, uc};
  HandleTagMismatch(ai, StackTrace::GetNextInstructionPc(sig.pc), sig.bp, uc);

#if defined(__aarch64__)
  uc->uc_mcontext.pc += 4;
#elif defined(__x86_64__)
#else
# error Unsupported architecture
#endif
  return true;
}

static void OnStackUnwind(const SignalContext &sig, const void *,
                          BufferedStackTrace *stack) {
  stack->Unwind(StackTrace::GetNextInstructionPc(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 == SIGTRAP)
    if (HwasanOnSIGTRAP(signo, (siginfo_t *)info, (ucontext_t*)context))
      return;

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


} // namespace __hwasan

// Entry point for interoperability between __hwasan_tag_mismatch (ASM) and the
// rest of the mismatch handling code (C++).
void __hwasan_tag_mismatch4(uptr addr, uptr access_info, uptr *registers_frame,
                            size_t outsize) {
  __hwasan::AccessInfo ai;
  ai.is_store = access_info & 0x10;
  ai.is_load = !ai.is_store;
  ai.recover = access_info & 0x20;
  ai.addr = addr;
  if ((access_info & 0xf) == 0xf)
    ai.size = outsize;
  else
    ai.size = 1 << (access_info & 0xf);

  __hwasan::HandleTagMismatch(ai, (uptr)__builtin_return_address(0),
                              (uptr)__builtin_frame_address(0), nullptr,
                              registers_frame);
  __builtin_unreachable();
}

#endif // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD