lib/sanitizer_common/sanitizer_linux.cc - platform/external/compiler-rt - Git at Google

 //===-- 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.
 //===----------------------------------------------------------------------===//
 #ifdef __linux__

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

 #include <fcntl.h>
 #include <pthread.h>
 #include <sched.h>
 #include <sys/mman.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <sys/prctl.h>
 #include <unistd.h>
 #include <unwind.h>
 #include <errno.h>

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

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

 namespace __sanitizer {

 // --------------- sanitizer_libc.h
 void *internal_mmap(void *addr, uptr length, int prot, int flags,
                     int fd, u64 offset) {
 #if SANITIZER_LINUX_USES_64BIT_SYSCALLS
   return (void *)syscall(__NR_mmap, addr, length, prot, flags, fd, offset);
 #else
   return (void *)syscall(__NR_mmap2, addr, length, prot, flags, fd, offset);
 #endif
 }

 int internal_munmap(void *addr, uptr length) {
   return syscall(__NR_munmap, addr, length);
 }

 int internal_close(fd_t fd) {
   return syscall(__NR_close, fd);
 }

 fd_t internal_open(const char *filename, int flags) {
   return syscall(__NR_open, filename, flags);
 }

 fd_t internal_open(const char *filename, int flags, u32 mode) {
   return syscall(__NR_open, filename, flags, mode);
 }

 fd_t OpenFile(const char *filename, bool write) {
   return internal_open(filename,
       write ? O_WRONLY | O_CREAT /*| O_CLOEXEC*/ : O_RDONLY, 0660);
 }

 uptr internal_read(fd_t fd, void *buf, uptr count) {
   sptr res;
   HANDLE_EINTR(res, (sptr)syscall(__NR_read, fd, buf, count));
   return res;
 }

 uptr internal_write(fd_t fd, const void *buf, uptr count) {
   sptr res;
   HANDLE_EINTR(res, (sptr)syscall(__NR_write, fd, buf, count));
   return res;
 }

 int internal_stat(const char *path, void *buf) {
 #if SANITIZER_LINUX_USES_64BIT_SYSCALLS
   return syscall(__NR_stat, path, buf);
 #else
   return syscall(__NR_stat64, path, buf);
 #endif
 }

 int internal_lstat(const char *path, void *buf) {
 #if SANITIZER_LINUX_USES_64BIT_SYSCALLS
   return syscall(__NR_lstat, path, buf);
 #else
   return syscall(__NR_lstat64, path, buf);
 #endif
 }

 int internal_fstat(fd_t fd, void *buf) {
 #if SANITIZER_LINUX_USES_64BIT_SYSCALLS
   return syscall(__NR_fstat, fd, buf);
 #else
   return syscall(__NR_fstat64, fd, buf);
 #endif
 }

 uptr internal_filesize(fd_t fd) {
 #if SANITIZER_LINUX_USES_64BIT_SYSCALLS
   struct stat st;
 #else
   struct stat64 st;
 #endif
   if (internal_fstat(fd, &st))
     return -1;
   return (uptr)st.st_size;
 }

 int internal_dup2(int oldfd, int newfd) {
   return syscall(__NR_dup2, oldfd, newfd);
 }

 uptr internal_readlink(const char *path, char *buf, uptr bufsize) {
   return (uptr)syscall(__NR_readlink, path, buf, bufsize);
 }

 int internal_sched_yield() {
   return syscall(__NR_sched_yield);
 }

 void internal__exit(int exitcode) {
   syscall(__NR_exit_group, exitcode);
   Die();  // Unreachable.
 }

 // ----------------- sanitizer_common.h
 bool FileExists(const char *filename) {
 #if SANITIZER_LINUX_USES_64BIT_SYSCALLS
   struct stat st;
   if (syscall(__NR_stat, filename, &st))
     return false;
 #else
   struct stat64 st;
   if (syscall(__NR_stat64, filename, &st))
     return false;
 #endif
   // Sanity check: filename is a regular file.
   return S_ISREG(st.st_mode);
 }

 uptr GetTid() {
   return syscall(__NR_gettid);
 }

 void GetThreadStackTopAndBottom(bool at_initialization, uptr *stack_top,
                                 uptr *stack_bottom) {
   static const uptr kMaxThreadStackSize = 256 * (1 << 20);  // 256M
   CHECK(stack_top);
   CHECK(stack_bottom);
   if (at_initialization) {
     // This is the main thread. Libpthread may not be initialized yet.
     struct rlimit rl;
     CHECK_EQ(getrlimit(RLIMIT_STACK, &rl), 0);

     // Find the mapping that contains a stack variable.
     MemoryMappingLayout proc_maps;
     uptr start, end, offset;
     uptr prev_end = 0;
     while (proc_maps.Next(&start, &end, &offset, 0, 0)) {
       if ((uptr)&rl < end)
         break;
       prev_end = end;
     }
     CHECK((uptr)&rl >= start && (uptr)&rl < end);

     // Get stacksize from rlimit, but clip it so that it does not overlap
     // with other mappings.
     uptr stacksize = rl.rlim_cur;
     if (stacksize > end - prev_end)
       stacksize = end - prev_end;
     // When running with unlimited stack size, we still want to set some limit.
     // The unlimited stack size is caused by 'ulimit -s unlimited'.
     // Also, for some reason, GNU make spawns subprocesses with unlimited stack.
     if (stacksize > kMaxThreadStackSize)
       stacksize = kMaxThreadStackSize;
     *stack_top = end;
     *stack_bottom = end - stacksize;
     return;
   }
   pthread_attr_t attr;
   CHECK_EQ(pthread_getattr_np(pthread_self(), &attr), 0);
   uptr stacksize = 0;
   void *stackaddr = 0;
   pthread_attr_getstack(&attr, &stackaddr, (size_t*)&stacksize);
   pthread_attr_destroy(&attr);

   *stack_top = (uptr)stackaddr + stacksize;
   *stack_bottom = (uptr)stackaddr;
   CHECK(stacksize < kMaxThreadStackSize);  // Sanity check.
 }

 // Like getenv, but reads env directly from /proc and does not use libc.
 // This function should be called first inside __asan_init.
 const char *GetEnv(const char *name) {
   static char *environ;
   static uptr len;
   static bool inited;
   if (!inited) {
     inited = true;
     uptr environ_size;
     len = ReadFileToBuffer("/proc/self/environ",
                            &environ, &environ_size, 1 << 26);
   }
   if (!environ || len == 0) return 0;
   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 == 0)  // this entry isn't NUL terminated
       return 0;
     else if (!internal_memcmp(p, name, namelen) && p[namelen] == '=')  // Match.
       return p + namelen + 1;  // point after =
     p = endp + 1;
   }
   return 0;  // Not found.
 }

 #ifdef __GLIBC__

 extern "C" {
   extern void *__libc_stack_end;
 }

 static void GetArgsAndEnv(char ***argv, char ***envp) {
   uptr *stack_end = (uptr *)__libc_stack_end;
   int argc = *stack_end;
   *argv = (char**)(stack_end + 1);
   *envp = (char**)(stack_end + argc + 2);
 }

 #else  // __GLIBC__

 static void ReadNullSepFileToArray(const char *path, char ***arr,
                                    int arr_size) {
   char *buff;
   uptr buff_size = 0;
   *arr = (char **)MmapOrDie(arr_size * sizeof(char *), "NullSepFileArray");
   ReadFileToBuffer(path, &buff, &buff_size, 1024 * 1024);
   (*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] = 0;
 }

 static void GetArgsAndEnv(char ***argv, char ***envp) {
   static const int kMaxArgv = 2000, kMaxEnvp = 2000;
   ReadNullSepFileToArray("/proc/self/cmdline", argv, kMaxArgv);
   ReadNullSepFileToArray("/proc/self/environ", envp, kMaxEnvp);
 }

 #endif  // __GLIBC__

 void ReExec() {
   char **argv, **envp;
   GetArgsAndEnv(&argv, &envp);
   execve("/proc/self/exe", argv, envp);
   Printf("execve failed, errno %d\n", errno);
   Die();
 }

 void PrepareForSandboxing() {
   // Some kinds of sandboxes may forbid filesystem access, so we won't be able
   // to read the file mappings from /proc/self/maps. Luckily, neither the
   // process will be able to load additional libraries, so it's fine to use the
   // cached mappings.
   MemoryMappingLayout::CacheMemoryMappings();
 }

 // ----------------- sanitizer_procmaps.h
 // Linker initialized.
 ProcSelfMapsBuff MemoryMappingLayout::cached_proc_self_maps_;
 StaticSpinMutex MemoryMappingLayout::cache_lock_;  // Linker initialized.

 MemoryMappingLayout::MemoryMappingLayout() {
   proc_self_maps_.len =
       ReadFileToBuffer("/proc/self/maps", &proc_self_maps_.data,
                        &proc_self_maps_.mmaped_size, 1 << 26);
   if (proc_self_maps_.mmaped_size == 0) {
     LoadFromCache();
     CHECK_GT(proc_self_maps_.len, 0);
   }
   // internal_write(2, proc_self_maps_.data, proc_self_maps_.len);
   Reset();
   // FIXME: in the future we may want to cache the mappings on demand only.
   CacheMemoryMappings();
 }

 MemoryMappingLayout::~MemoryMappingLayout() {
   // Only unmap the buffer if it is different from the cached one. Otherwise
   // it will be unmapped when the cache is refreshed.
   if (proc_self_maps_.data != cached_proc_self_maps_.data) {
     UnmapOrDie(proc_self_maps_.data, proc_self_maps_.mmaped_size);
   }
 }

 void MemoryMappingLayout::Reset() {
   current_ = proc_self_maps_.data;
 }

 // static
 void MemoryMappingLayout::CacheMemoryMappings() {
   SpinMutexLock l(&cache_lock_);
   // Don't invalidate the cache if the mappings are unavailable.
   ProcSelfMapsBuff old_proc_self_maps;
   old_proc_self_maps = cached_proc_self_maps_;
   cached_proc_self_maps_.len =
       ReadFileToBuffer("/proc/self/maps", &cached_proc_self_maps_.data,
                        &cached_proc_self_maps_.mmaped_size, 1 << 26);
   if (cached_proc_self_maps_.mmaped_size == 0) {
     cached_proc_self_maps_ = old_proc_self_maps;
   } else {
     if (old_proc_self_maps.mmaped_size) {
       UnmapOrDie(old_proc_self_maps.data,
                  old_proc_self_maps.mmaped_size);
     }
   }
 }

 void MemoryMappingLayout::LoadFromCache() {
   SpinMutexLock l(&cache_lock_);
   if (cached_proc_self_maps_.data) {
     proc_self_maps_ = cached_proc_self_maps_;
   }
 }

 // Parse a hex value in str and update str.
 static uptr ParseHex(char **str) {
   uptr x = 0;
   char *s;
   for (s = *str; ; s++) {
     char c = *s;
     uptr v = 0;
     if (c >= '0' && c <= '9')
       v = c - '0';
     else if (c >= 'a' && c <= 'f')
       v = c - 'a' + 10;
     else if (c >= 'A' && c <= 'F')
       v = c - 'A' + 10;
     else
       break;
     x = x * 16 + v;
   }
   *str = s;
   return x;
 }

 static bool IsOnOf(char c, char c1, char c2) {
   return c == c1 || c == c2;
 }

 static bool IsDecimal(char c) {
   return c >= '0' && c <= '9';
 }

 bool MemoryMappingLayout::Next(uptr *start, uptr *end, uptr *offset,
                                char filename[], uptr filename_size) {
   char *last = proc_self_maps_.data + proc_self_maps_.len;
   if (current_ >= last) return false;
   uptr dummy;
   if (!start) start = &dummy;
   if (!end) end = &dummy;
   if (!offset) offset = &dummy;
   char *next_line = (char*)internal_memchr(current_, '\n', last - current_);
   if (next_line == 0)
     next_line = last;
   // Example: 08048000-08056000 r-xp 00000000 03:0c 64593   /foo/bar
   *start = ParseHex(&current_);
   CHECK_EQ(*current_++, '-');
   *end = ParseHex(&current_);
   CHECK_EQ(*current_++, ' ');
   CHECK(IsOnOf(*current_++, '-', 'r'));
   CHECK(IsOnOf(*current_++, '-', 'w'));
   CHECK(IsOnOf(*current_++, '-', 'x'));
   CHECK(IsOnOf(*current_++, 's', 'p'));
   CHECK_EQ(*current_++, ' ');
   *offset = ParseHex(&current_);
   CHECK_EQ(*current_++, ' ');
   ParseHex(&current_);
   CHECK_EQ(*current_++, ':');
   ParseHex(&current_);
   CHECK_EQ(*current_++, ' ');
   while (IsDecimal(*current_))
     current_++;
   CHECK_EQ(*current_++, ' ');
   // Skip spaces.
   while (current_ < next_line && *current_ == ' ')
     current_++;
   // Fill in the filename.
   uptr i = 0;
   while (current_ < next_line) {
     if (filename && i < filename_size - 1)
       filename[i++] = *current_;
     current_++;
   }
   if (filename && i < filename_size)
     filename[i] = 0;
   current_ = next_line + 1;
   return true;
 }

 // Gets the object name and the offset by walking MemoryMappingLayout.
 bool MemoryMappingLayout::GetObjectNameAndOffset(uptr addr, uptr *offset,
                                                  char filename[],
                                                  uptr filename_size) {
   return IterateForObjectNameAndOffset(addr, offset, filename, filename_size);
 }

 bool SanitizerSetThreadName(const char *name) {
 #ifdef PR_SET_NAME
   return 0 == prctl(PR_SET_NAME, (unsigned long)name, 0, 0, 0);  // NOLINT
 #else
   return false;
 #endif
 }

 bool SanitizerGetThreadName(char *name, int max_len) {
 #ifdef PR_GET_NAME
   char buff[17];
   if (prctl(PR_GET_NAME, (unsigned long)buff, 0, 0, 0))  // NOLINT
     return false;
   internal_strncpy(name, buff, max_len);
   name[max_len] = 0;
   return true;
 #else
   return false;
 #endif
 }

 #ifndef SANITIZER_GO
 //------------------------- SlowUnwindStack -----------------------------------
 #ifdef __arm__
 #define UNWIND_STOP _URC_END_OF_STACK
 #define UNWIND_CONTINUE _URC_NO_REASON
 #else
 #define UNWIND_STOP _URC_NORMAL_STOP
 #define UNWIND_CONTINUE _URC_NO_REASON
 #endif

 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
 #ifdef __arm__
   uptr val;
   _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
       15 /* r15 = PC */, _UVRSD_UINT32, &val);
   CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
   // Clear the Thumb bit.
   return val & ~(uptr)1;
 #else
   return _Unwind_GetIP(ctx);
 #endif
 }

 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
   StackTrace *b = (StackTrace*)param;
   CHECK(b->size < b->max_size);
   uptr pc = Unwind_GetIP(ctx);
   b->trace[b->size++] = pc;
   if (b->size == b->max_size) return UNWIND_STOP;
   return UNWIND_CONTINUE;
 }

 static bool MatchPc(uptr cur_pc, uptr trace_pc) {
   return cur_pc - trace_pc <= 64 || trace_pc - cur_pc <= 64;
 }

 void StackTrace::SlowUnwindStack(uptr pc, uptr max_depth) {
   this->size = 0;
   this->max_size = max_depth;
   if (max_depth > 1) {
     _Unwind_Backtrace(Unwind_Trace, this);
     // We need to pop a few frames so that pc is on top.
     // trace[0] belongs to the current function so we always pop it.
     int to_pop = 1;
     /**/ if (size > 1 && MatchPc(pc, trace[1])) to_pop = 1;
     else if (size > 2 && MatchPc(pc, trace[2])) to_pop = 2;
     else if (size > 3 && MatchPc(pc, trace[3])) to_pop = 3;
     else if (size > 4 && MatchPc(pc, trace[4])) to_pop = 4;
     else if (size > 5 && MatchPc(pc, trace[5])) to_pop = 5;
     this->PopStackFrames(to_pop);
   }
   this->trace[0] = pc;
 }

 #endif  // #ifndef SANITIZER_GO

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

 BlockingMutex::BlockingMutex(LinkerInitialized) {
   CHECK_EQ(owner_, 0);
 }

 void BlockingMutex::Lock() {
   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)
     syscall(__NR_futex, m, FUTEX_WAIT, MtxSleeping, 0, 0, 0);
 }

 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)
     syscall(__NR_futex, m, FUTEX_WAKE, 1, 0, 0, 0);
 }

 }  // namespace __sanitizer

 #endif  // __linux__
	//===-- 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.
	//===----------------------------------------------------------------------===//
	#ifdef __linux__

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

	#include <fcntl.h>
	#include <pthread.h>
	#include <sched.h>
	#include <sys/mman.h>
	#include <sys/resource.h>
	#include <sys/stat.h>
	#include <sys/syscall.h>
	#include <sys/time.h>
	#include <sys/types.h>
	#include <sys/prctl.h>
	#include <unistd.h>
	#include <unwind.h>
	#include <errno.h>

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

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

	namespace __sanitizer {

	// --------------- sanitizer_libc.h
	void internal_mmap(void addr, uptr length, int prot, int flags,
	int fd, u64 offset) {
	#if SANITIZER_LINUX_USES_64BIT_SYSCALLS
	return (void *)syscall(__NR_mmap, addr, length, prot, flags, fd, offset);
	#else
	return (void *)syscall(__NR_mmap2, addr, length, prot, flags, fd, offset);
	#endif
	}

	int internal_munmap(void *addr, uptr length) {
	return syscall(__NR_munmap, addr, length);
	}

	int internal_close(fd_t fd) {
	return syscall(__NR_close, fd);
	}

	fd_t internal_open(const char *filename, int flags) {
	return syscall(__NR_open, filename, flags);
	}

	fd_t internal_open(const char *filename, int flags, u32 mode) {
	return syscall(__NR_open, filename, flags, mode);
	}

	fd_t OpenFile(const char *filename, bool write) {
	return internal_open(filename,
	write ? O_WRONLY \| O_CREAT /\| O_CLOEXEC/ : O_RDONLY, 0660);
	}

	uptr internal_read(fd_t fd, void *buf, uptr count) {
	sptr res;
	HANDLE_EINTR(res, (sptr)syscall(__NR_read, fd, buf, count));
	return res;
	}

	uptr internal_write(fd_t fd, const void *buf, uptr count) {
	sptr res;
	HANDLE_EINTR(res, (sptr)syscall(__NR_write, fd, buf, count));
	return res;
	}

	int internal_stat(const char path, void buf) {
	#if SANITIZER_LINUX_USES_64BIT_SYSCALLS
	return syscall(__NR_stat, path, buf);
	#else
	return syscall(__NR_stat64, path, buf);
	#endif
	}

	int internal_lstat(const char path, void buf) {
	#if SANITIZER_LINUX_USES_64BIT_SYSCALLS
	return syscall(__NR_lstat, path, buf);
	#else
	return syscall(__NR_lstat64, path, buf);
	#endif
	}

	int internal_fstat(fd_t fd, void *buf) {
	#if SANITIZER_LINUX_USES_64BIT_SYSCALLS
	return syscall(__NR_fstat, fd, buf);
	#else
	return syscall(__NR_fstat64, fd, buf);
	#endif
	}

	uptr internal_filesize(fd_t fd) {
	#if SANITIZER_LINUX_USES_64BIT_SYSCALLS
	struct stat st;
	#else
	struct stat64 st;
	#endif
	if (internal_fstat(fd, &st))
	return -1;
	return (uptr)st.st_size;
	}

	int internal_dup2(int oldfd, int newfd) {
	return syscall(__NR_dup2, oldfd, newfd);
	}

	uptr internal_readlink(const char path, char buf, uptr bufsize) {
	return (uptr)syscall(__NR_readlink, path, buf, bufsize);
	}

	int internal_sched_yield() {
	return syscall(__NR_sched_yield);
	}

	void internal__exit(int exitcode) {
	syscall(__NR_exit_group, exitcode);
	Die(); // Unreachable.
	}

	// ----------------- sanitizer_common.h
	bool FileExists(const char *filename) {
	#if SANITIZER_LINUX_USES_64BIT_SYSCALLS
	struct stat st;
	if (syscall(__NR_stat, filename, &st))
	return false;
	#else
	struct stat64 st;
	if (syscall(__NR_stat64, filename, &st))
	return false;
	#endif
	// Sanity check: filename is a regular file.
	return S_ISREG(st.st_mode);
	}

	uptr GetTid() {
	return syscall(__NR_gettid);
	}

	void GetThreadStackTopAndBottom(bool at_initialization, uptr *stack_top,
	uptr *stack_bottom) {
	static const uptr kMaxThreadStackSize = 256 * (1 << 20); // 256M
	CHECK(stack_top);
	CHECK(stack_bottom);
	if (at_initialization) {
	// This is the main thread. Libpthread may not be initialized yet.
	struct rlimit rl;
	CHECK_EQ(getrlimit(RLIMIT_STACK, &rl), 0);

	// Find the mapping that contains a stack variable.
	MemoryMappingLayout proc_maps;
	uptr start, end, offset;
	uptr prev_end = 0;
	while (proc_maps.Next(&start, &end, &offset, 0, 0)) {
	if ((uptr)&rl < end)
	break;
	prev_end = end;
	}
	CHECK((uptr)&rl >= start && (uptr)&rl < end);

	// Get stacksize from rlimit, but clip it so that it does not overlap
	// with other mappings.
	uptr stacksize = rl.rlim_cur;
	if (stacksize > end - prev_end)
	stacksize = end - prev_end;
	// When running with unlimited stack size, we still want to set some limit.
	// The unlimited stack size is caused by 'ulimit -s unlimited'.
	// Also, for some reason, GNU make spawns subprocesses with unlimited stack.
	if (stacksize > kMaxThreadStackSize)
	stacksize = kMaxThreadStackSize;
	*stack_top = end;
	*stack_bottom = end - stacksize;
	return;
	}
	pthread_attr_t attr;
	CHECK_EQ(pthread_getattr_np(pthread_self(), &attr), 0);
	uptr stacksize = 0;
	void *stackaddr = 0;
	pthread_attr_getstack(&attr, &stackaddr, (size_t*)&stacksize);
	pthread_attr_destroy(&attr);

	*stack_top = (uptr)stackaddr + stacksize;
	*stack_bottom = (uptr)stackaddr;
	CHECK(stacksize < kMaxThreadStackSize); // Sanity check.
	}

	// Like getenv, but reads env directly from /proc and does not use libc.
	// This function should be called first inside __asan_init.
	const char GetEnv(const char name) {
	static char *environ;
	static uptr len;
	static bool inited;
	if (!inited) {
	inited = true;
	uptr environ_size;
	len = ReadFileToBuffer("/proc/self/environ",
	&environ, &environ_size, 1 << 26);
	}
	if (!environ \|\| len == 0) return 0;
	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 == 0) // this entry isn't NUL terminated
	return 0;
	else if (!internal_memcmp(p, name, namelen) && p[namelen] == '=') // Match.
	return p + namelen + 1; // point after =
	p = endp + 1;
	}
	return 0; // Not found.
	}

	#ifdef __GLIBC__

	extern "C" {
	extern void *__libc_stack_end;
	}

	static void GetArgsAndEnv(char *argv, char *envp) {
	uptr stack_end = (uptr )__libc_stack_end;
	int argc = *stack_end;
	argv = (char*)(stack_end + 1);
	envp = (char*)(stack_end + argc + 2);
	}

	#else // __GLIBC__

	static void ReadNullSepFileToArray(const char path, char **arr,
	int arr_size) {
	char *buff;
	uptr buff_size = 0;
	arr = (char )MmapOrDie(arr_size sizeof(char *), "NullSepFileArray");
	ReadFileToBuffer(path, &buff, &buff_size, 1024 * 1024);
	(*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] = 0;
	}

	static void GetArgsAndEnv(char *argv, char *envp) {
	static const int kMaxArgv = 2000, kMaxEnvp = 2000;
	ReadNullSepFileToArray("/proc/self/cmdline", argv, kMaxArgv);
	ReadNullSepFileToArray("/proc/self/environ", envp, kMaxEnvp);
	}

	#endif // __GLIBC__

	void ReExec() {
	char argv, envp;
	GetArgsAndEnv(&argv, &envp);
	execve("/proc/self/exe", argv, envp);
	Printf("execve failed, errno %d\n", errno);
	Die();
	}

	void PrepareForSandboxing() {
	// Some kinds of sandboxes may forbid filesystem access, so we won't be able
	// to read the file mappings from /proc/self/maps. Luckily, neither the
	// process will be able to load additional libraries, so it's fine to use the
	// cached mappings.
	MemoryMappingLayout::CacheMemoryMappings();
	}

	// ----------------- sanitizer_procmaps.h
	// Linker initialized.
	ProcSelfMapsBuff MemoryMappingLayout::cached_proc_self_maps_;
	StaticSpinMutex MemoryMappingLayout::cache_lock_; // Linker initialized.

	MemoryMappingLayout::MemoryMappingLayout() {
	proc_self_maps_.len =
	ReadFileToBuffer("/proc/self/maps", &proc_self_maps_.data,
	&proc_self_maps_.mmaped_size, 1 << 26);
	if (proc_self_maps_.mmaped_size == 0) {
	LoadFromCache();
	CHECK_GT(proc_self_maps_.len, 0);
	}
	// internal_write(2, proc_self_maps_.data, proc_self_maps_.len);
	Reset();
	// FIXME: in the future we may want to cache the mappings on demand only.
	CacheMemoryMappings();
	}

	MemoryMappingLayout::~MemoryMappingLayout() {
	// Only unmap the buffer if it is different from the cached one. Otherwise
	// it will be unmapped when the cache is refreshed.
	if (proc_self_maps_.data != cached_proc_self_maps_.data) {
	UnmapOrDie(proc_self_maps_.data, proc_self_maps_.mmaped_size);
	}
	}

	void MemoryMappingLayout::Reset() {
	current_ = proc_self_maps_.data;
	}

	// static
	void MemoryMappingLayout::CacheMemoryMappings() {
	SpinMutexLock l(&cache_lock_);
	// Don't invalidate the cache if the mappings are unavailable.
	ProcSelfMapsBuff old_proc_self_maps;
	old_proc_self_maps = cached_proc_self_maps_;
	cached_proc_self_maps_.len =
	ReadFileToBuffer("/proc/self/maps", &cached_proc_self_maps_.data,
	&cached_proc_self_maps_.mmaped_size, 1 << 26);
	if (cached_proc_self_maps_.mmaped_size == 0) {
	cached_proc_self_maps_ = old_proc_self_maps;
	} else {
	if (old_proc_self_maps.mmaped_size) {
	UnmapOrDie(old_proc_self_maps.data,
	old_proc_self_maps.mmaped_size);
	}
	}
	}

	void MemoryMappingLayout::LoadFromCache() {
	SpinMutexLock l(&cache_lock_);
	if (cached_proc_self_maps_.data) {
	proc_self_maps_ = cached_proc_self_maps_;
	}
	}

	// Parse a hex value in str and update str.
	static uptr ParseHex(char **str) {
	uptr x = 0;
	char *s;
	for (s = *str; ; s++) {
	char c = *s;
	uptr v = 0;
	if (c >= '0' && c <= '9')
	v = c - '0';
	else if (c >= 'a' && c <= 'f')
	v = c - 'a' + 10;
	else if (c >= 'A' && c <= 'F')
	v = c - 'A' + 10;
	else
	break;
	x = x * 16 + v;
	}
	*str = s;
	return x;
	}

	static bool IsOnOf(char c, char c1, char c2) {
	return c == c1 \|\| c == c2;
	}

	static bool IsDecimal(char c) {
	return c >= '0' && c <= '9';
	}

	bool MemoryMappingLayout::Next(uptr start, uptr end, uptr *offset,
	char filename[], uptr filename_size) {
	char *last = proc_self_maps_.data + proc_self_maps_.len;
	if (current_ >= last) return false;
	uptr dummy;
	if (!start) start = &dummy;
	if (!end) end = &dummy;
	if (!offset) offset = &dummy;
	char next_line = (char)internal_memchr(current_, '\n', last - current_);
	if (next_line == 0)
	next_line = last;
	// Example: 08048000-08056000 r-xp 00000000 03:0c 64593 /foo/bar
	*start = ParseHex(&current_);
	CHECK_EQ(*current_++, '-');
	*end = ParseHex(&current_);
	CHECK_EQ(*current_++, ' ');
	CHECK(IsOnOf(*current_++, '-', 'r'));
	CHECK(IsOnOf(*current_++, '-', 'w'));
	CHECK(IsOnOf(*current_++, '-', 'x'));
	CHECK(IsOnOf(*current_++, 's', 'p'));
	CHECK_EQ(*current_++, ' ');
	*offset = ParseHex(&current_);
	CHECK_EQ(*current_++, ' ');
	ParseHex(&current_);
	CHECK_EQ(*current_++, ':');
	ParseHex(&current_);
	CHECK_EQ(*current_++, ' ');
	while (IsDecimal(*current_))
	current_++;
	CHECK_EQ(*current_++, ' ');
	// Skip spaces.
	while (current_ < next_line && *current_ == ' ')
	current_++;
	// Fill in the filename.
	uptr i = 0;
	while (current_ < next_line) {
	if (filename && i < filename_size - 1)
	filename[i++] = *current_;
	current_++;
	}
	if (filename && i < filename_size)
	filename[i] = 0;
	current_ = next_line + 1;
	return true;
	}

	// Gets the object name and the offset by walking MemoryMappingLayout.
	bool MemoryMappingLayout::GetObjectNameAndOffset(uptr addr, uptr *offset,
	char filename[],
	uptr filename_size) {
	return IterateForObjectNameAndOffset(addr, offset, filename, filename_size);
	}

	bool SanitizerSetThreadName(const char *name) {
	#ifdef PR_SET_NAME
	return 0 == prctl(PR_SET_NAME, (unsigned long)name, 0, 0, 0); // NOLINT
	#else
	return false;
	#endif
	}

	bool SanitizerGetThreadName(char *name, int max_len) {
	#ifdef PR_GET_NAME
	char buff[17];
	if (prctl(PR_GET_NAME, (unsigned long)buff, 0, 0, 0)) // NOLINT
	return false;
	internal_strncpy(name, buff, max_len);
	name[max_len] = 0;
	return true;
	#else
	return false;
	#endif
	}

	#ifndef SANITIZER_GO
	//------------------------- SlowUnwindStack -----------------------------------
	#ifdef __arm__
	#define UNWIND_STOP _URC_END_OF_STACK
	#define UNWIND_CONTINUE _URC_NO_REASON
	#else
	#define UNWIND_STOP _URC_NORMAL_STOP
	#define UNWIND_CONTINUE _URC_NO_REASON
	#endif

	uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
	#ifdef __arm__
	uptr val;
	_Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
	15 /* r15 = PC */, _UVRSD_UINT32, &val);
	CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
	// Clear the Thumb bit.
	return val & ~(uptr)1;
	#else
	return _Unwind_GetIP(ctx);
	#endif
	}

	_Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context ctx, void param) {
	StackTrace b = (StackTrace)param;
	CHECK(b->size < b->max_size);
	uptr pc = Unwind_GetIP(ctx);
	b->trace[b->size++] = pc;
	if (b->size == b->max_size) return UNWIND_STOP;
	return UNWIND_CONTINUE;
	}

	static bool MatchPc(uptr cur_pc, uptr trace_pc) {
	return cur_pc - trace_pc <= 64 \|\| trace_pc - cur_pc <= 64;
	}

	void StackTrace::SlowUnwindStack(uptr pc, uptr max_depth) {
	this->size = 0;
	this->max_size = max_depth;
	if (max_depth > 1) {
	_Unwind_Backtrace(Unwind_Trace, this);
	// We need to pop a few frames so that pc is on top.
	// trace[0] belongs to the current function so we always pop it.
	int to_pop = 1;
	/**/ if (size > 1 && MatchPc(pc, trace[1])) to_pop = 1;
	else if (size > 2 && MatchPc(pc, trace[2])) to_pop = 2;
	else if (size > 3 && MatchPc(pc, trace[3])) to_pop = 3;
	else if (size > 4 && MatchPc(pc, trace[4])) to_pop = 4;
	else if (size > 5 && MatchPc(pc, trace[5])) to_pop = 5;
	this->PopStackFrames(to_pop);
	}
	this->trace[0] = pc;
	}

	#endif // #ifndef SANITIZER_GO

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

	BlockingMutex::BlockingMutex(LinkerInitialized) {
	CHECK_EQ(owner_, 0);
	}

	void BlockingMutex::Lock() {
	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)
	syscall(__NR_futex, m, FUTEX_WAIT, MtxSleeping, 0, 0, 0);
	}

	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)
	syscall(__NR_futex, m, FUTEX_WAKE, 1, 0, 0, 0);
	}

	} // namespace __sanitizer

	#endif // __linux__