llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc

//===-- sanitizer_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 shared between AddressSanitizer and ThreadSanitizer
// run-time libraries and implements linux-specific functions from
// sanitizer_libc.h.
//===----------------------------------------------------------------------===//

#include "sanitizer_platform.h"

#if SANITIZER_FREEBSD || SANITIZER_LINUX

#include "sanitizer_common.h"
#include "sanitizer_flags.h"
#include "sanitizer_internal_defs.h"
#include "sanitizer_libc.h"
#include "sanitizer_linux.h"
#include "sanitizer_mutex.h"
#include "sanitizer_placement_new.h"
#include "sanitizer_procmaps.h"
#include "sanitizer_stacktrace.h"
#include "sanitizer_symbolizer.h"

#if !SANITIZER_FREEBSD
#include <asm/param.h>
#endif

// For mips64, syscall(__NR_stat) fills the buffer in the 'struct kernel_stat'
// format. Struct kernel_stat is defined as 'struct stat' in asm/stat.h. To
// access stat from asm/stat.h, without conflicting with definition in
// sys/stat.h, we use this trick.
#if defined(__mips64)
#include <asm/unistd.h>
#include <sys/types.h>
#define stat kernel_stat
#include <asm/stat.h>
#undef stat
#endif

#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <link.h>
#include <pthread.h>
#include <sched.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/utsname.h>
#include <ucontext.h>
#include <unistd.h>

#if SANITIZER_FREEBSD
#include <sys/exec.h>
#include <sys/sysctl.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <machine/atomic.h>
extern "C" {
// <sys/umtx.h> must be included after <errno.h> and <sys/types.h> on
// FreeBSD 9.2 and 10.0.
#include <sys/umtx.h>
}
extern char **environ;  // provided by crt1
#endif  // SANITIZER_FREEBSD

#if !SANITIZER_ANDROID
#include <sys/signal.h>
#endif

#if SANITIZER_LINUX
// <linux/time.h>
struct kernel_timeval {
  long tv_sec;
  long tv_usec;
};

// <linux/futex.h> is broken on some linux distributions.
const int FUTEX_WAIT = 0;
const int FUTEX_WAKE = 1;
#endif  // SANITIZER_LINUX

// Are we using 32-bit or 64-bit Linux syscalls?
// x32 (which defines __x86_64__) has SANITIZER_WORDSIZE == 32
// but it still needs to use 64-bit syscalls.
#if SANITIZER_LINUX && (defined(__x86_64__) || defined(__powerpc64__) || \
    SANITIZER_WORDSIZE == 64)
# define SANITIZER_LINUX_USES_64BIT_SYSCALLS 1
#else
# define SANITIZER_LINUX_USES_64BIT_SYSCALLS 0
#endif

namespace __sanitizer {

#if SANITIZER_LINUX && defined(__x86_64__)
#include "sanitizer_syscall_linux_x86_64.inc"
#elif SANITIZER_LINUX && defined(__aarch64__)
#include "sanitizer_syscall_linux_aarch64.inc"
#else
#include "sanitizer_syscall_generic.inc"
#endif

// --------------- sanitizer_libc.h
uptr internal_mmap(void *addr, uptr length, int prot, int flags, int fd,
                   OFF_T offset) {
#ifdef __s390__
  struct s390_mmap_params {
    unsigned long addr;
    unsigned long length;
    unsigned long prot;
    unsigned long flags;
    unsigned long fd;
    unsigned long offset;
  } params = {
    (unsigned long)addr,
    (unsigned long)length,
    (unsigned long)prot,
    (unsigned long)flags,
    (unsigned long)fd,
# ifdef __s390x__
    (unsigned long)offset,
# else
    (unsigned long)(offset / 4096),
# endif
  };
# ifdef __s390x__
  return internal_syscall(SYSCALL(mmap), &params);
# else
  return internal_syscall(SYSCALL(mmap2), &params);
# endif
#elif SANITIZER_FREEBSD || SANITIZER_LINUX_USES_64BIT_SYSCALLS
  return internal_syscall(SYSCALL(mmap), (uptr)addr, length, prot, flags, fd,
                          offset);
#else
  // mmap2 specifies file offset in 4096-byte units.
  CHECK(IsAligned(offset, 4096));
  return internal_syscall(SYSCALL(mmap2), addr, length, prot, flags, fd,
                          offset / 4096);
#endif
}

uptr internal_munmap(void *addr, uptr length) {
  return internal_syscall(SYSCALL(munmap), (uptr)addr, length);
}

int internal_mprotect(void *addr, uptr length, int prot) {
  return internal_syscall(SYSCALL(mprotect), (uptr)addr, length, prot);
}

uptr internal_close(fd_t fd) {
  return internal_syscall(SYSCALL(close), fd);
}

uptr internal_open(const char *filename, int flags) {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(openat), AT_FDCWD, (uptr)filename, flags);
#else
  return internal_syscall(SYSCALL(open), (uptr)filename, flags);
#endif
}

uptr internal_open(const char *filename, int flags, u32 mode) {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(openat), AT_FDCWD, (uptr)filename, flags,
                          mode);
#else
  return internal_syscall(SYSCALL(open), (uptr)filename, flags, mode);
#endif
}

uptr internal_read(fd_t fd, void *buf, uptr count) {
  sptr res;
  HANDLE_EINTR(res, (sptr)internal_syscall(SYSCALL(read), fd, (uptr)buf,
               count));
  return res;
}

uptr internal_write(fd_t fd, const void *buf, uptr count) {
  sptr res;
  HANDLE_EINTR(res, (sptr)internal_syscall(SYSCALL(write), fd, (uptr)buf,
               count));
  return res;
}

uptr internal_ftruncate(fd_t fd, uptr size) {
  sptr res;
  HANDLE_EINTR(res, (sptr)internal_syscall(SYSCALL(ftruncate), fd,
               (OFF_T)size));
  return res;
}

#if !SANITIZER_LINUX_USES_64BIT_SYSCALLS && !SANITIZER_FREEBSD
static void stat64_to_stat(struct stat64 *in, struct stat *out) {
  internal_memset(out, 0, sizeof(*out));
  out->st_dev = in->st_dev;
  out->st_ino = in->st_ino;
  out->st_mode = in->st_mode;
  out->st_nlink = in->st_nlink;
  out->st_uid = in->st_uid;
  out->st_gid = in->st_gid;
  out->st_rdev = in->st_rdev;
  out->st_size = in->st_size;
  out->st_blksize = in->st_blksize;
  out->st_blocks = in->st_blocks;
  out->st_atime = in->st_atime;
  out->st_mtime = in->st_mtime;
  out->st_ctime = in->st_ctime;
  out->st_ino = in->st_ino;
}
#endif

#if defined(__mips64)
static void kernel_stat_to_stat(struct kernel_stat *in, struct stat *out) {
  internal_memset(out, 0, sizeof(*out));
  out->st_dev = in->st_dev;
  out->st_ino = in->st_ino;
  out->st_mode = in->st_mode;
  out->st_nlink = in->st_nlink;
  out->st_uid = in->st_uid;
  out->st_gid = in->st_gid;
  out->st_rdev = in->st_rdev;
  out->st_size = in->st_size;
  out->st_blksize = in->st_blksize;
  out->st_blocks = in->st_blocks;
  out->st_atime = in->st_atime_nsec;
  out->st_mtime = in->st_mtime_nsec;
  out->st_ctime = in->st_ctime_nsec;
  out->st_ino = in->st_ino;
}
#endif

uptr internal_stat(const char *path, void *buf) {
#if SANITIZER_FREEBSD
  return internal_syscall(SYSCALL(stat), path, buf);
#elif SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(newfstatat), AT_FDCWD, (uptr)path,
                          (uptr)buf, 0);
#elif SANITIZER_LINUX_USES_64BIT_SYSCALLS
# if defined(__mips64)
  // For mips64, stat syscall fills buffer in the format of kernel_stat
  struct kernel_stat kbuf;
  int res = internal_syscall(SYSCALL(stat), path, &kbuf);
  kernel_stat_to_stat(&kbuf, (struct stat *)buf);
  return res;
# else
  return internal_syscall(SYSCALL(stat), (uptr)path, (uptr)buf);
# endif
#else
  struct stat64 buf64;
  int res = internal_syscall(SYSCALL(stat64), path, &buf64);
  stat64_to_stat(&buf64, (struct stat *)buf);
  return res;
#endif
}

uptr internal_lstat(const char *path, void *buf) {
#if SANITIZER_FREEBSD
  return internal_syscall(SYSCALL(lstat), path, buf);
#elif SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(newfstatat), AT_FDCWD, (uptr)path,
                         (uptr)buf, AT_SYMLINK_NOFOLLOW);
#elif SANITIZER_LINUX_USES_64BIT_SYSCALLS
# if SANITIZER_MIPS64
  // For mips64, lstat syscall fills buffer in the format of kernel_stat
  struct kernel_stat kbuf;
  int res = internal_syscall(SYSCALL(lstat), path, &kbuf);
  kernel_stat_to_stat(&kbuf, (struct stat *)buf);
  return res;
# else
  return internal_syscall(SYSCALL(lstat), (uptr)path, (uptr)buf);
# endif
#else
  struct stat64 buf64;
  int res = internal_syscall(SYSCALL(lstat64), path, &buf64);
  stat64_to_stat(&buf64, (struct stat *)buf);
  return res;
#endif
}

uptr internal_fstat(fd_t fd, void *buf) {
#if SANITIZER_FREEBSD || SANITIZER_LINUX_USES_64BIT_SYSCALLS
# if SANITIZER_MIPS64
  // For mips64, fstat syscall fills buffer in the format of kernel_stat
  struct kernel_stat kbuf;
  int res = internal_syscall(SYSCALL(fstat), fd, &kbuf);
  kernel_stat_to_stat(&kbuf, (struct stat *)buf);
  return res;
# else
  return internal_syscall(SYSCALL(fstat), fd, (uptr)buf);
# endif
#else
  struct stat64 buf64;
  int res = internal_syscall(SYSCALL(fstat64), fd, &buf64);
  stat64_to_stat(&buf64, (struct stat *)buf);
  return res;
#endif
}

uptr internal_filesize(fd_t fd) {
  struct stat st;
  if (internal_fstat(fd, &st))
    return -1;
  return (uptr)st.st_size;
}

uptr internal_dup2(int oldfd, int newfd) {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(dup3), oldfd, newfd, 0);
#else
  return internal_syscall(SYSCALL(dup2), oldfd, newfd);
#endif
}

uptr internal_readlink(const char *path, char *buf, uptr bufsize) {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(readlinkat), AT_FDCWD,
                          (uptr)path, (uptr)buf, bufsize);
#else
  return internal_syscall(SYSCALL(readlink), (uptr)path, (uptr)buf, bufsize);
#endif
}

uptr internal_unlink(const char *path) {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(unlinkat), AT_FDCWD, (uptr)path, 0);
#else
  return internal_syscall(SYSCALL(unlink), (uptr)path);
#endif
}

uptr internal_rename(const char *oldpath, const char *newpath) {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(renameat), AT_FDCWD, (uptr)oldpath, AT_FDCWD,
                          (uptr)newpath);
#else
  return internal_syscall(SYSCALL(rename), (uptr)oldpath, (uptr)newpath);
#endif
}

uptr internal_sched_yield() {
  return internal_syscall(SYSCALL(sched_yield));
}

void internal__exit(int exitcode) {
#if SANITIZER_FREEBSD
  internal_syscall(SYSCALL(exit), exitcode);
#else
  internal_syscall(SYSCALL(exit_group), exitcode);
#endif
  Die();  // Unreachable.
}

uptr internal_execve(const char *filename, char *const argv[],
                     char *const envp[]) {
  return internal_syscall(SYSCALL(execve), (uptr)filename, (uptr)argv,
                          (uptr)envp);
}

// ----------------- sanitizer_common.h
bool FileExists(const char *filename) {
  struct stat st;
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  if (internal_syscall(SYSCALL(newfstatat), AT_FDCWD, filename, &st, 0))
#else
  if (internal_stat(filename, &st))
#endif
    return false;
  // Sanity check: filename is a regular file.
  return S_ISREG(st.st_mode);
}

uptr GetTid() {
#if SANITIZER_FREEBSD
  return (uptr)pthread_self();
#else
  return internal_syscall(SYSCALL(gettid));
#endif
}

u64 NanoTime() {
#if SANITIZER_FREEBSD
  timeval tv;
#else
  kernel_timeval tv;
#endif
  internal_memset(&tv, 0, sizeof(tv));
  internal_syscall(SYSCALL(gettimeofday), (uptr)&tv, 0);
  return (u64)tv.tv_sec * 1000*1000*1000 + tv.tv_usec * 1000;
}

// Like getenv, but reads env directly from /proc (on Linux) or parses the
// 'environ' array (on FreeBSD) and does not use libc. This function should be
// called first inside __asan_init.
const char *GetEnv(const char *name) {
#if SANITIZER_FREEBSD
  if (::environ != 0) {
    uptr NameLen = internal_strlen(name);
    for (char **Env = ::environ; *Env != 0; Env++) {
      if (internal_strncmp(*Env, name, NameLen) == 0 && (*Env)[NameLen] == '=')
        return (*Env) + NameLen + 1;
    }
  }
  return 0;  // Not found.
#elif SANITIZER_LINUX
  static char *environ;
  static uptr len;
  static bool inited;
  if (!inited) {
    inited = true;
    uptr environ_size;
    if (!ReadFileToBuffer("/proc/self/environ", &environ, &environ_size, &len))
      environ = nullptr;
  }
  if (!environ || len == 0) return nullptr;
  uptr namelen = internal_strlen(name);
  const char *p = environ;
  while (*p != '\0') {  // will happen at the \0\0 that terminates the buffer
    // proc file has the format NAME=value\0NAME=value\0NAME=value\0...
    const char* endp =
        (char*)internal_memchr(p, '\0', len - (p - environ));
    if (!endp)  // this entry isn't NUL terminated
      return nullptr;
    else if (!internal_memcmp(p, name, namelen) && p[namelen] == '=')  // Match.
      return p + namelen + 1;  // point after =
    p = endp + 1;
  }
  return nullptr;  // Not found.
#else
#error "Unsupported platform"
#endif
}

#if !SANITIZER_FREEBSD
extern "C" {
  SANITIZER_WEAK_ATTRIBUTE extern void *__libc_stack_end;
}
#endif

#if !SANITIZER_GO && !SANITIZER_FREEBSD
static void ReadNullSepFileToArray(const char *path, char ***arr,
                                   int arr_size) {
  char *buff;
  uptr buff_size;
  uptr buff_len;
  *arr = (char **)MmapOrDie(arr_size * sizeof(char *), "NullSepFileArray");
  if (!ReadFileToBuffer(path, &buff, &buff_size, &buff_len, 1024 * 1024)) {
    (*arr)[0] = nullptr;
    return;
  }
  (*arr)[0] = buff;
  int count, i;
  for (count = 1, i = 1; ; i++) {
    if (buff[i] == 0) {
      if (buff[i+1] == 0) break;
      (*arr)[count] = &buff[i+1];
      CHECK_LE(count, arr_size - 1);  // FIXME: make this more flexible.
      count++;
    }
  }
  (*arr)[count] = nullptr;
}
#endif

static void GetArgsAndEnv(char ***argv, char ***envp) {
#if !SANITIZER_FREEBSD
#if !SANITIZER_GO
  if (&__libc_stack_end) {
#endif
    uptr* stack_end = (uptr*)__libc_stack_end;
    int argc = *stack_end;
    *argv = (char**)(stack_end + 1);
    *envp = (char**)(stack_end + argc + 2);
#if !SANITIZER_GO
  } else {
    static const int kMaxArgv = 2000, kMaxEnvp = 2000;
    ReadNullSepFileToArray("/proc/self/cmdline", argv, kMaxArgv);
    ReadNullSepFileToArray("/proc/self/environ", envp, kMaxEnvp);
  }
#endif
#else
  // On FreeBSD, retrieving the argument and environment arrays is done via the
  // kern.ps_strings sysctl, which returns a pointer to a structure containing
  // this information. See also <sys/exec.h>.
  ps_strings *pss;
  size_t sz = sizeof(pss);
  if (sysctlbyname("kern.ps_strings", &pss, &sz, NULL, 0) == -1) {
    Printf("sysctl kern.ps_strings failed\n");
    Die();
  }
  *argv = pss->ps_argvstr;
  *envp = pss->ps_envstr;
#endif
}

char **GetArgv() {
  char **argv, **envp;
  GetArgsAndEnv(&argv, &envp);
  return argv;
}

void ReExec() {
  char **argv, **envp;
  GetArgsAndEnv(&argv, &envp);
  uptr rv = internal_execve("/proc/self/exe", argv, envp);
  int rverrno;
  CHECK_EQ(internal_iserror(rv, &rverrno), true);
  Printf("execve failed, errno %d\n", rverrno);
  Die();
}

enum MutexState {
  MtxUnlocked = 0,
  MtxLocked = 1,
  MtxSleeping = 2
};

BlockingMutex::BlockingMutex() {
  internal_memset(this, 0, sizeof(*this));
}

void BlockingMutex::Lock() {
  CHECK_EQ(owner_, 0);
  atomic_uint32_t *m = reinterpret_cast<atomic_uint32_t *>(&opaque_storage_);
  if (atomic_exchange(m, MtxLocked, memory_order_acquire) == MtxUnlocked)
    return;
  while (atomic_exchange(m, MtxSleeping, memory_order_acquire) != MtxUnlocked) {
#if SANITIZER_FREEBSD
    _umtx_op(m, UMTX_OP_WAIT_UINT, MtxSleeping, 0, 0);
#else
    internal_syscall(SYSCALL(futex), (uptr)m, FUTEX_WAIT, MtxSleeping, 0, 0, 0);
#endif
  }
}

void BlockingMutex::Unlock() {
  atomic_uint32_t *m = reinterpret_cast<atomic_uint32_t *>(&opaque_storage_);
  u32 v = atomic_exchange(m, MtxUnlocked, memory_order_relaxed);
  CHECK_NE(v, MtxUnlocked);
  if (v == MtxSleeping) {
#if SANITIZER_FREEBSD
    _umtx_op(m, UMTX_OP_WAKE, 1, 0, 0);
#else
    internal_syscall(SYSCALL(futex), (uptr)m, FUTEX_WAKE, 1, 0, 0, 0);
#endif
  }
}

void BlockingMutex::CheckLocked() {
  atomic_uint32_t *m = reinterpret_cast<atomic_uint32_t *>(&opaque_storage_);
  CHECK_NE(MtxUnlocked, atomic_load(m, memory_order_relaxed));
}

// ----------------- sanitizer_linux.h
// The actual size of this structure is specified by d_reclen.
// Note that getdents64 uses a different structure format. We only provide the
// 32-bit syscall here.
struct linux_dirent {
#if SANITIZER_X32 || defined(__aarch64__)
  u64 d_ino;
  u64 d_off;
#else
  unsigned long      d_ino;
  unsigned long      d_off;
#endif
  unsigned short     d_reclen;
#ifdef __aarch64__
  unsigned char      d_type;
#endif
  char               d_name[256];
};

// Syscall wrappers.
uptr internal_ptrace(int request, int pid, void *addr, void *data) {
  return internal_syscall(SYSCALL(ptrace), request, pid, (uptr)addr,
                          (uptr)data);
}

uptr internal_waitpid(int pid, int *status, int options) {
  return internal_syscall(SYSCALL(wait4), pid, (uptr)status, options,
                          0 /* rusage */);
}

uptr internal_getpid() {
  return internal_syscall(SYSCALL(getpid));
}

uptr internal_getppid() {
  return internal_syscall(SYSCALL(getppid));
}

uptr internal_getdents(fd_t fd, struct linux_dirent *dirp, unsigned int count) {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(getdents64), fd, (uptr)dirp, count);
#else
  return internal_syscall(SYSCALL(getdents), fd, (uptr)dirp, count);
#endif
}

uptr internal_lseek(fd_t fd, OFF_T offset, int whence) {
  return internal_syscall(SYSCALL(lseek), fd, offset, whence);
}

#if SANITIZER_LINUX
uptr internal_prctl(int option, uptr arg2, uptr arg3, uptr arg4, uptr arg5) {
  return internal_syscall(SYSCALL(prctl), option, arg2, arg3, arg4, arg5);
}
#endif

uptr internal_sigaltstack(const struct sigaltstack *ss,
                         struct sigaltstack *oss) {
  return internal_syscall(SYSCALL(sigaltstack), (uptr)ss, (uptr)oss);
}

int internal_fork() {
#if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
  return internal_syscall(SYSCALL(clone), SIGCHLD, 0);
#else
  return internal_syscall(SYSCALL(fork));
#endif
}

#if SANITIZER_LINUX
#define SA_RESTORER 0x04000000
// Doesn't set sa_restorer, use with caution (see below).
int internal_sigaction_norestorer(int signum, const void *act, void *oldact) {
  __sanitizer_kernel_sigaction_t k_act, k_oldact;
  internal_memset(&k_act, 0, sizeof(__sanitizer_kernel_sigaction_t));
  internal_memset(&k_oldact, 0, sizeof(__sanitizer_kernel_sigaction_t));
  const __sanitizer_sigaction *u_act = (const __sanitizer_sigaction *)act;
  __sanitizer_sigaction *u_oldact = (__sanitizer_sigaction *)oldact;
  if (u_act) {
    k_act.handler = u_act->handler;
    k_act.sigaction = u_act->sigaction;
    internal_memcpy(&k_act.sa_mask, &u_act->sa_mask,
                    sizeof(__sanitizer_kernel_sigset_t));
    // Without SA_RESTORER kernel ignores the calls (probably returns EINVAL).
    k_act.sa_flags = u_act->sa_flags | SA_RESTORER;
    // FIXME: most often sa_restorer is unset, however the kernel requires it
    // to point to a valid signal restorer that calls the rt_sigreturn syscall.
    // If sa_restorer passed to the kernel is NULL, the program may crash upon
    // signal delivery or fail to unwind the stack in the signal handler.
    // libc implementation of sigaction() passes its own restorer to
    // rt_sigaction, so we need to do the same (we'll need to reimplement the
    // restorers; for x86_64 the restorer address can be obtained from
    // oldact->sa_restorer upon a call to sigaction(xxx, NULL, oldact).
#if !SANITIZER_ANDROID || !SANITIZER_MIPS32
    k_act.sa_restorer = u_act->sa_restorer;
#endif
  }

  uptr result = internal_syscall(SYSCALL(rt_sigaction), (uptr)signum,
      (uptr)(u_act ? &k_act : nullptr),
      (uptr)(u_oldact ? &k_oldact : nullptr),
      (uptr)sizeof(__sanitizer_kernel_sigset_t));

  if ((result == 0) && u_oldact) {
    u_oldact->handler = k_oldact.handler;
    u_oldact->sigaction = k_oldact.sigaction;
    internal_memcpy(&u_oldact->sa_mask, &k_oldact.sa_mask,
                    sizeof(__sanitizer_kernel_sigset_t));
    u_oldact->sa_flags = k_oldact.sa_flags;
#if !SANITIZER_ANDROID || !SANITIZER_MIPS32
    u_oldact->sa_restorer = k_oldact.sa_restorer;
#endif
  }
  return result;
}
#endif  // SANITIZER_LINUX

uptr internal_sigprocmask(int how, __sanitizer_sigset_t *set,
    __sanitizer_sigset_t *oldset) {
#if SANITIZER_FREEBSD
  return internal_syscall(SYSCALL(sigprocmask), how, set, oldset);
#else
  __sanitizer_kernel_sigset_t *k_set = (__sanitizer_kernel_sigset_t *)set;
  __sanitizer_kernel_sigset_t *k_oldset = (__sanitizer_kernel_sigset_t *)oldset;
  return internal_syscall(SYSCALL(rt_sigprocmask), (uptr)how,
                          (uptr)&k_set->sig[0], (uptr)&k_oldset->sig[0],
                          sizeof(__sanitizer_kernel_sigset_t));
#endif
}

void internal_sigfillset(__sanitizer_sigset_t *set) {
  internal_memset(set, 0xff, sizeof(*set));
}

#if SANITIZER_LINUX
void internal_sigdelset(__sanitizer_sigset_t *set, int signum) {
  signum -= 1;
  CHECK_GE(signum, 0);
  CHECK_LT(signum, sizeof(*set) * 8);
  __sanitizer_kernel_sigset_t *k_set = (__sanitizer_kernel_sigset_t *)set;
  const uptr idx = signum / (sizeof(k_set->sig[0]) * 8);
  const uptr bit = signum % (sizeof(k_set->sig[0]) * 8);
  k_set->sig[idx] &= ~(1 << bit);
}
#endif  // SANITIZER_LINUX

// ThreadLister implementation.
ThreadLister::ThreadLister(int pid)
  : pid_(pid),
    descriptor_(-1),
    buffer_(4096),
    error_(true),
    entry_((struct linux_dirent *)buffer_.data()),
    bytes_read_(0) {
  char task_directory_path[80];
  internal_snprintf(task_directory_path, sizeof(task_directory_path),
                    "/proc/%d/task/", pid);
  uptr openrv = internal_open(task_directory_path, O_RDONLY | O_DIRECTORY);
  if (internal_iserror(openrv)) {
    error_ = true;
    Report("Can't open /proc/%d/task for reading.\n", pid);
  } else {
    error_ = false;
    descriptor_ = openrv;
  }
}

int ThreadLister::GetNextTID() {
  int tid = -1;
  do {
    if (error_)
      return -1;
    if ((char *)entry_ >= &buffer_[bytes_read_] && !GetDirectoryEntries())
      return -1;
    if (entry_->d_ino != 0 && entry_->d_name[0] >= '0' &&
        entry_->d_name[0] <= '9') {
      // Found a valid tid.
      tid = (int)internal_atoll(entry_->d_name);
    }
    entry_ = (struct linux_dirent *)(((char *)entry_) + entry_->d_reclen);
  } while (tid < 0);
  return tid;
}

void ThreadLister::Reset() {
  if (error_ || descriptor_ < 0)
    return;
  internal_lseek(descriptor_, 0, SEEK_SET);
}

ThreadLister::~ThreadLister() {
  if (descriptor_ >= 0)
    internal_close(descriptor_);
}

bool ThreadLister::error() { return error_; }

bool ThreadLister::GetDirectoryEntries() {
  CHECK_GE(descriptor_, 0);
  CHECK_NE(error_, true);
  bytes_read_ = internal_getdents(descriptor_,
                                  (struct linux_dirent *)buffer_.data(),
                                  buffer_.size());
  if (internal_iserror(bytes_read_)) {
    Report("Can't read directory entries from /proc/%d/task.\n", pid_);
    error_ = true;
    return false;
  } else if (bytes_read_ == 0) {
    return false;
  }
  entry_ = (struct linux_dirent *)buffer_.data();
  return true;
}

uptr GetPageSize() {
// Android post-M sysconf(_SC_PAGESIZE) crashes if called from .preinit_array.
#if (SANITIZER_LINUX && (defined(__x86_64__) || defined(__i386__))) || \
    SANITIZER_ANDROID
  return EXEC_PAGESIZE;
#else
  return sysconf(_SC_PAGESIZE);  // EXEC_PAGESIZE may not be trustworthy.
#endif
}

uptr ReadBinaryName(/*out*/char *buf, uptr buf_len) {
#if SANITIZER_FREEBSD
  const int Mib[] = { CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1 };
  const char *default_module_name = "kern.proc.pathname";
  size_t Size = buf_len;
  bool IsErr = (sysctl(Mib, ARRAY_SIZE(Mib), buf, &Size, NULL, 0) != 0);
  int readlink_error = IsErr ? errno : 0;
  uptr module_name_len = Size;
#else
  const char *default_module_name = "/proc/self/exe";
  uptr module_name_len = internal_readlink(
      default_module_name, buf, buf_len);
  int readlink_error;
  bool IsErr = internal_iserror(module_name_len, &readlink_error);
#endif
  if (IsErr) {
    // We can't read binary name for some reason, assume it's unknown.
    Report("WARNING: reading executable name failed with errno %d, "
           "some stack frames may not be symbolized\n", readlink_error);
    module_name_len = internal_snprintf(buf, buf_len, "%s",
                                        default_module_name);
    CHECK_LT(module_name_len, buf_len);
  }
  return module_name_len;
}

uptr ReadLongProcessName(/*out*/ char *buf, uptr buf_len) {
#if SANITIZER_LINUX
  char *tmpbuf;
  uptr tmpsize;
  uptr tmplen;
  if (ReadFileToBuffer("/proc/self/cmdline", &tmpbuf, &tmpsize, &tmplen,
                       1024 * 1024)) {
    internal_strncpy(buf, tmpbuf, buf_len);
    UnmapOrDie(tmpbuf, tmpsize);
    return internal_strlen(buf);
  }
#endif
  return ReadBinaryName(buf, buf_len);
}

// Match full names of the form /path/to/base_name{-,.}*
bool LibraryNameIs(const char *full_name, const char *base_name) {
  const char *name = full_name;
  // Strip path.
  while (*name != '\0') name++;
  while (name > full_name && *name != '/') name--;
  if (*name == '/') name++;
  uptr base_name_length = internal_strlen(base_name);
  if (internal_strncmp(name, base_name, base_name_length)) return false;
  return (name[base_name_length] == '-' || name[base_name_length] == '.');
}

#if !SANITIZER_ANDROID
// Call cb for each region mapped by map.
void ForEachMappedRegion(link_map *map, void (*cb)(const void *, uptr)) {
  CHECK_NE(map, nullptr);
#if !SANITIZER_FREEBSD
  typedef ElfW(Phdr) Elf_Phdr;
  typedef ElfW(Ehdr) Elf_Ehdr;
#endif  // !SANITIZER_FREEBSD
  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 = (uptr)-1;
  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 > (uptr)phdr->p_vaddr)
      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());
      cb((void *)seg_start, seg_end - seg_start);
    }
  }
}
#endif

#if defined(__x86_64__) && SANITIZER_LINUX
// We cannot use glibc's clone wrapper, because it messes with the child
// task's TLS. It writes the PID and TID of the child task to its thread
// descriptor, but in our case the child task shares the thread descriptor with
// the parent (because we don't know how to allocate a new thread
// descriptor to keep glibc happy). So the stock version of clone(), when
// used with CLONE_VM, would end up corrupting the parent's thread descriptor.
uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,
                    int *parent_tidptr, void *newtls, int *child_tidptr) {
  long long res;
  if (!fn || !child_stack)
    return -EINVAL;
  CHECK_EQ(0, (uptr)child_stack % 16);
  child_stack = (char *)child_stack - 2 * sizeof(unsigned long long);
  ((unsigned long long *)child_stack)[0] = (uptr)fn;
  ((unsigned long long *)child_stack)[1] = (uptr)arg;
  register void *r8 __asm__("r8") = newtls;
  register int *r10 __asm__("r10") = child_tidptr;
  __asm__ __volatile__(
                       /* %rax = syscall(%rax = SYSCALL(clone),
                        *                %rdi = flags,
                        *                %rsi = child_stack,
                        *                %rdx = parent_tidptr,
                        *                %r8  = new_tls,
                        *                %r10 = child_tidptr)
                        */
                       "syscall\n"

                       /* if (%rax != 0)
                        *   return;
                        */
                       "testq  %%rax,%%rax\n"
                       "jnz    1f\n"

                       /* In the child. Terminate unwind chain. */
                       // XXX: We should also terminate the CFI unwind chain
                       // here. Unfortunately clang 3.2 doesn't support the
                       // necessary CFI directives, so we skip that part.
                       "xorq   %%rbp,%%rbp\n"

                       /* Call "fn(arg)". */
                       "popq   %%rax\n"
                       "popq   %%rdi\n"
                       "call   *%%rax\n"

                       /* Call _exit(%rax). */
                       "movq   %%rax,%%rdi\n"
                       "movq   %2,%%rax\n"
                       "syscall\n"

                       /* Return to parent. */
                     "1:\n"
                       : "=a" (res)
                       : "a"(SYSCALL(clone)), "i"(SYSCALL(exit)),
                         "S"(child_stack),
                         "D"(flags),
                         "d"(parent_tidptr),
                         "r"(r8),
                         "r"(r10)
                       : "rsp", "memory", "r11", "rcx");
  return res;
}
#elif defined(__mips__)
uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,
                    int *parent_tidptr, void *newtls, int *child_tidptr) {
  long long res;
  if (!fn || !child_stack)
    return -EINVAL;
  CHECK_EQ(0, (uptr)child_stack % 16);
  child_stack = (char *)child_stack - 2 * sizeof(unsigned long long);
  ((unsigned long long *)child_stack)[0] = (uptr)fn;
  ((unsigned long long *)child_stack)[1] = (uptr)arg;
  register void *a3 __asm__("$7") = newtls;
  register int *a4 __asm__("$8") = child_tidptr;
  // We don't have proper CFI directives here because it requires alot of code
  // for very marginal benefits.
  __asm__ __volatile__(
                       /* $v0 = syscall($v0 = __NR_clone,
                        * $a0 = flags,
                        * $a1 = child_stack,
                        * $a2 = parent_tidptr,
                        * $a3 = new_tls,
                        * $a4 = child_tidptr)
                        */
                       ".cprestore 16;\n"
                       "move $4,%1;\n"
                       "move $5,%2;\n"
                       "move $6,%3;\n"
                       "move $7,%4;\n"
                       /* Store the fifth argument on stack
                        * if we are using 32-bit abi.
                        */
#if SANITIZER_WORDSIZE == 32
                       "lw %5,16($29);\n"
#else
                       "move $8,%5;\n"
#endif
                       "li $2,%6;\n"
                       "syscall;\n"

                       /* if ($v0 != 0)
                        * return;
                        */
                       "bnez $2,1f;\n"

                       /* Call "fn(arg)". */
                       "ld $25,0($29);\n"
                       "ld $4,8($29);\n"
                       "jal $25;\n"

                       /* Call _exit($v0). */
                       "move $4,$2;\n"
                       "li $2,%7;\n"
                       "syscall;\n"

                       /* Return to parent. */
                     "1:\n"
                       : "=r" (res)
                       : "r"(flags),
                         "r"(child_stack),
                         "r"(parent_tidptr),
                         "r"(a3),
                         "r"(a4),
                         "i"(__NR_clone),
                         "i"(__NR_exit)
                       : "memory", "$29" );
  return res;
}
#elif defined(__aarch64__)
uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,
                    int *parent_tidptr, void *newtls, int *child_tidptr) {
  long long res;
  if (!fn || !child_stack)
    return -EINVAL;
  CHECK_EQ(0, (uptr)child_stack % 16);
  child_stack = (char *)child_stack - 2 * sizeof(unsigned long long);
  ((unsigned long long *)child_stack)[0] = (uptr)fn;
  ((unsigned long long *)child_stack)[1] = (uptr)arg;

  register int (*__fn)(void *)  __asm__("x0") = fn;
  register void *__stack __asm__("x1") = child_stack;
  register int   __flags __asm__("x2") = flags;
  register void *__arg   __asm__("x3") = arg;
  register int  *__ptid  __asm__("x4") = parent_tidptr;
  register void *__tls   __asm__("x5") = newtls;
  register int  *__ctid  __asm__("x6") = child_tidptr;

  __asm__ __volatile__(
                       "mov x0,x2\n" /* flags  */
                       "mov x2,x4\n" /* ptid  */
                       "mov x3,x5\n" /* tls  */
                       "mov x4,x6\n" /* ctid  */
                       "mov x8,%9\n" /* clone  */

                       "svc 0x0\n"

                       /* if (%r0 != 0)
                        *   return %r0;
                        */
                       "cmp x0, #0\n"
                       "bne 1f\n"

                       /* In the child, now. Call "fn(arg)". */
                       "ldp x1, x0, [sp], #16\n"
                       "blr x1\n"

                       /* Call _exit(%r0).  */
                       "mov x8, %10\n"
                       "svc 0x0\n"
                     "1:\n"

                       : "=r" (res)
                       : "i"(-EINVAL),
                         "r"(__fn), "r"(__stack), "r"(__flags), "r"(__arg),
                         "r"(__ptid), "r"(__tls), "r"(__ctid),
                         "i"(__NR_clone), "i"(__NR_exit)
                       : "x30", "memory");
  return res;
}
#elif defined(__powerpc64__)
uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,
                   int *parent_tidptr, void *newtls, int *child_tidptr) {
  long long res;
/* Stack frame offsets.  */
#if _CALL_ELF != 2
#define FRAME_MIN_SIZE         112
#define FRAME_TOC_SAVE         40
#else
#define FRAME_MIN_SIZE         32
#define FRAME_TOC_SAVE         24
#endif
  if (!fn || !child_stack)
    return -EINVAL;
  CHECK_EQ(0, (uptr)child_stack % 16);
  child_stack = (char *)child_stack - 2 * sizeof(unsigned long long);
  ((unsigned long long *)child_stack)[0] = (uptr)fn;
  ((unsigned long long *)child_stack)[1] = (uptr)arg;

  register int (*__fn)(void *) __asm__("r3") = fn;
  register void *__cstack      __asm__("r4") = child_stack;
  register int __flags         __asm__("r5") = flags;
  register void * __arg        __asm__("r6") = arg;
  register int * __ptidptr     __asm__("r7") = parent_tidptr;
  register void * __newtls     __asm__("r8") = newtls;
  register int * __ctidptr     __asm__("r9") = child_tidptr;

 __asm__ __volatile__(
           /* fn, arg, child_stack are saved acrVoss the syscall */
           "mr 28, %5\n\t"
           "mr 29, %6\n\t"
           "mr 27, %8\n\t"

           /* syscall
             r3 == flags
             r4 == child_stack
             r5 == parent_tidptr
             r6 == newtls
             r7 == child_tidptr */
           "mr 3, %7\n\t"
           "mr 5, %9\n\t"
           "mr 6, %10\n\t"
           "mr 7, %11\n\t"
           "li 0, %3\n\t"
           "sc\n\t"

           /* Test if syscall was successful */
           "cmpdi  cr1, 3, 0\n\t"
           "crandc cr1*4+eq, cr1*4+eq, cr0*4+so\n\t"
           "bne-   cr1, 1f\n\t"

           /* Do the function call */
           "std   2, %13(1)\n\t"
#if _CALL_ELF != 2
           "ld    0, 0(28)\n\t"
           "ld    2, 8(28)\n\t"
           "mtctr 0\n\t"
#else
           "mr    12, 28\n\t"
           "mtctr 12\n\t"
#endif
           "mr    3, 27\n\t"
           "bctrl\n\t"
           "ld    2, %13(1)\n\t"

           /* Call _exit(r3) */
           "li 0, %4\n\t"
           "sc\n\t"

           /* Return to parent */
           "1:\n\t"
           "mr %0, 3\n\t"
             : "=r" (res)
             : "0" (-1), "i" (EINVAL),
               "i" (__NR_clone), "i" (__NR_exit),
               "r" (__fn), "r" (__cstack), "r" (__flags),
               "r" (__arg), "r" (__ptidptr), "r" (__newtls),
               "r" (__ctidptr), "i" (FRAME_MIN_SIZE), "i" (FRAME_TOC_SAVE)
             : "cr0", "cr1", "memory", "ctr",
               "r0", "r29", "r27", "r28");
  return res;
}
#endif  // defined(__x86_64__) && SANITIZER_LINUX

#if SANITIZER_ANDROID
#if __ANDROID_API__ < 21
extern "C" __attribute__((weak)) int dl_iterate_phdr(
    int (*)(struct dl_phdr_info *, size_t, void *), void *);
#endif

static int dl_iterate_phdr_test_cb(struct dl_phdr_info *info, size_t size,
                                   void *data) {
  // Any name starting with "lib" indicates a bug in L where library base names
  // are returned instead of paths.
  if (info->dlpi_name && info->dlpi_name[0] == 'l' &&
      info->dlpi_name[1] == 'i' && info->dlpi_name[2] == 'b') {
    *(bool *)data = true;
    return 1;
  }
  return 0;
}

static atomic_uint32_t android_api_level;

static AndroidApiLevel AndroidDetectApiLevel() {
  if (!&dl_iterate_phdr)
    return ANDROID_KITKAT; // K or lower
  bool base_name_seen = false;
  dl_iterate_phdr(dl_iterate_phdr_test_cb, &base_name_seen);
  if (base_name_seen)
    return ANDROID_LOLLIPOP_MR1; // L MR1
  return ANDROID_POST_LOLLIPOP;   // post-L
  // Plain L (API level 21) is completely broken wrt ASan and not very
  // interesting to detect.
}

AndroidApiLevel AndroidGetApiLevel() {
  AndroidApiLevel level =
      (AndroidApiLevel)atomic_load(&android_api_level, memory_order_relaxed);
  if (level) return level;
  level = AndroidDetectApiLevel();
  atomic_store(&android_api_level, level, memory_order_relaxed);
  return level;
}

#endif

bool IsHandledDeadlySignal(int signum) {
  if (common_flags()->handle_abort && signum == SIGABRT)
    return true;
  if (common_flags()->handle_sigill && signum == SIGILL)
    return true;
  if (common_flags()->handle_sigfpe && signum == SIGFPE)
    return true;
  return (signum == SIGSEGV || signum == SIGBUS) && common_flags()->handle_segv;
}

#ifndef SANITIZER_GO
void *internal_start_thread(void(*func)(void *arg), void *arg) {
  // Start the thread with signals blocked, otherwise it can steal user signals.
  __sanitizer_sigset_t set, old;
  internal_sigfillset(&set);
#if SANITIZER_LINUX && !SANITIZER_ANDROID
  // Glibc uses SIGSETXID signal during setuid call. If this signal is blocked
  // on any thread, setuid call hangs (see test/tsan/setuid.c).
  internal_sigdelset(&set, 33);
#endif
  internal_sigprocmask(SIG_SETMASK, &set, &old);
  void *th;
  real_pthread_create(&th, nullptr, (void*(*)(void *arg))func, arg);
  internal_sigprocmask(SIG_SETMASK, &old, nullptr);
  return th;
}

void internal_join_thread(void *th) {
  real_pthread_join(th, nullptr);
}
#else
void *internal_start_thread(void (*func)(void *), void *arg) { return 0; }

void internal_join_thread(void *th) {}
#endif

#if defined(__aarch64__)
// Android headers in the older NDK releases miss this definition.
struct __sanitizer_esr_context {
  struct _aarch64_ctx head;
  uint64_t esr;
};

static bool Aarch64GetESR(ucontext_t *ucontext, u64 *esr) {
  static const u32 kEsrMagic = 0x45535201;
  u8 *aux = ucontext->uc_mcontext.__reserved;
  while (true) {
    _aarch64_ctx *ctx = (_aarch64_ctx *)aux;
    if (ctx->size == 0) break;
    if (ctx->magic == kEsrMagic) {
      *esr = ((__sanitizer_esr_context *)ctx)->esr;
      return true;
    }
    aux += ctx->size;
  }
  return false;
}
#endif

SignalContext::WriteFlag SignalContext::GetWriteFlag(void *context) {
  ucontext_t *ucontext = (ucontext_t *)context;
#if defined(__x86_64__) || defined(__i386__)
  static const uptr PF_WRITE = 1U << 1;
#if SANITIZER_FREEBSD
  uptr err = ucontext->uc_mcontext.mc_err;
#else
  uptr err = ucontext->uc_mcontext.gregs[REG_ERR];
#endif
  return err & PF_WRITE ? WRITE : READ;
#elif defined(__arm__)
  static const uptr FSR_WRITE = 1U << 11;
  uptr fsr = ucontext->uc_mcontext.error_code;
  // FSR bits 5:0 describe the abort type, and are never 0 (or so it seems).
  // Zero FSR indicates an older kernel that does not pass this information to
  // the userspace.
  if (fsr == 0) return UNKNOWN;
  return fsr & FSR_WRITE ? WRITE : READ;
#elif defined(__aarch64__)
  static const u64 ESR_ELx_WNR = 1U << 6;
  u64 esr;
  if (!Aarch64GetESR(ucontext, &esr)) return UNKNOWN;
  return esr & ESR_ELx_WNR ? WRITE : READ;
#else
  (void)ucontext;
  return UNKNOWN;  // FIXME: Implement.
#endif
}

void GetPcSpBp(void *context, uptr *pc, uptr *sp, uptr *bp) {
#if defined(__arm__)
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.arm_pc;
  *bp = ucontext->uc_mcontext.arm_fp;
  *sp = ucontext->uc_mcontext.arm_sp;
#elif defined(__aarch64__)
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.pc;
  *bp = ucontext->uc_mcontext.regs[29];
  *sp = ucontext->uc_mcontext.sp;
#elif defined(__hppa__)
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.sc_iaoq[0];
  /* GCC uses %r3 whenever a frame pointer is needed.  */
  *bp = ucontext->uc_mcontext.sc_gr[3];
  *sp = ucontext->uc_mcontext.sc_gr[30];
#elif defined(__x86_64__)
# if SANITIZER_FREEBSD
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.mc_rip;
  *bp = ucontext->uc_mcontext.mc_rbp;
  *sp = ucontext->uc_mcontext.mc_rsp;
# else
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.gregs[REG_RIP];
  *bp = ucontext->uc_mcontext.gregs[REG_RBP];
  *sp = ucontext->uc_mcontext.gregs[REG_RSP];
# endif
#elif defined(__i386__)
# if SANITIZER_FREEBSD
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.mc_eip;
  *bp = ucontext->uc_mcontext.mc_ebp;
  *sp = ucontext->uc_mcontext.mc_esp;
# else
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.gregs[REG_EIP];
  *bp = ucontext->uc_mcontext.gregs[REG_EBP];
  *sp = ucontext->uc_mcontext.gregs[REG_ESP];
# endif
#elif defined(__powerpc__) || defined(__powerpc64__)
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.regs->nip;
  *sp = ucontext->uc_mcontext.regs->gpr[PT_R1];
  // The powerpc{,64}-linux ABIs do not specify r31 as the frame
  // pointer, but GCC always uses r31 when we need a frame pointer.
  *bp = ucontext->uc_mcontext.regs->gpr[PT_R31];
#elif defined(__sparc__)
  ucontext_t *ucontext = (ucontext_t*)context;
  uptr *stk_ptr;
# if defined (__arch64__)
  *pc = ucontext->uc_mcontext.mc_gregs[MC_PC];
  *sp = ucontext->uc_mcontext.mc_gregs[MC_O6];
  stk_ptr = (uptr *) (*sp + 2047);
  *bp = stk_ptr[15];
# else
  *pc = ucontext->uc_mcontext.gregs[REG_PC];
  *sp = ucontext->uc_mcontext.gregs[REG_O6];
  stk_ptr = (uptr *) *sp;
  *bp = stk_ptr[15];
# endif
#elif defined(__mips__)
  ucontext_t *ucontext = (ucontext_t*)context;
  *pc = ucontext->uc_mcontext.pc;
  *bp = ucontext->uc_mcontext.gregs[30];
  *sp = ucontext->uc_mcontext.gregs[29];
#else
# error "Unsupported arch"
#endif
}

void MaybeReexec() {
  // No need to re-exec on Linux.
}

#ifdef __s390x__
static bool FixedCVE_2016_2143() {
  // Try to determine if the running kernel has a fix for CVE-2016-2143,
  // return false if in doubt (better safe than sorry).  Distros may want to
  // adjust this for their own kernels.
  struct utsname buf;
  unsigned int major, minor, patch = 0;
  // This should never fail, but just in case...
  if (uname(&buf))
    return false;
  char *ptr = buf.release;
  major = internal_simple_strtoll(ptr, &ptr, 10);
  // At least first 2 should be matched.
  if (ptr[0] != '.')
    return false;
  minor = internal_simple_strtoll(ptr+1, &ptr, 10);
  // Third is optional.
  if (ptr[0] == '.')
    patch = internal_simple_strtoll(ptr+1, &ptr, 10);
  if (major < 3) {
    // <3.0 is bad.
    return false;
  } else if (major == 3) {
    // 3.2.79+ is OK.
    if (minor == 2 && patch >= 79)
      return true;
    // Otherwise, bad.
    return false;
  } else if (major == 4) {
    // 4.1.21+ is OK.
    if (minor == 1 && patch >= 21)
      return true;
    // 4.4.6+ is OK.
    if (minor == 4 && patch >= 6)
      return true;
    // Otherwise, OK if 4.5+.
    return minor >= 5;
  } else {
    // Linux 5 and up are fine.
    return true;
  }
}

void AvoidCVE_2016_2143() {
  // Older kernels are affected by CVE-2016-2143 - they will crash hard
  // if someone uses 4-level page tables (ie. virtual addresses >= 4TB)
  // and fork() in the same process.  Unfortunately, sanitizers tend to
  // require such addresses.  Since this is very likely to crash the whole
  // machine (sanitizers themselves use fork() for llvm-symbolizer, for one),
  // abort the process at initialization instead.
  if (FixedCVE_2016_2143())
    return;
  if (GetEnv("SANITIZER_IGNORE_CVE_2016_2143"))
    return;
  Report(
    "ERROR: Your kernel seems to be vulnerable to CVE-2016-2143.  Using ASan,\n"
    "MSan or TSan with such kernel can and will crash your machine, or worse.\n"
    "\n"
    "If you are certain your kernel is not vulnerable (you have compiled it\n"
    "yourself, are are using an unrecognized distribution kernel), you can\n"
    "override this safety check by exporting SANITIZER_IGNORE_CVE_2016_2143\n"
    "with any value.\n");
  Die();
}
#endif

} // namespace __sanitizer

#endif // SANITIZER_FREEBSD || SANITIZER_LINUX