js/src/util/NativeStack.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "util/NativeStack.h"
   8
   9 #include "mozilla/Assertions.h"  // MOZ_ASSERT, MOZ_RELEASE_ASSERT, MOZ_CRASH
  10
  11 #ifdef XP_WIN
  12 #  include "util/WindowsWrapper.h"
  13 #elif defined(__wasi__)
  14 // Nothing
  15 #elif defined(XP_DARWIN) || defined(DARWIN) || defined(XP_UNIX)
  16 #  include <pthread.h>
  17 #  if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
  18 #    include <pthread_np.h>
  19 #  endif
  20 #  if defined(SOLARIS) || defined(AIX)
  21 #    include <ucontext.h>
  22 #  endif
  23 #  if defined(ANDROID) && !defined(__aarch64__)
  24 #    include <sys/types.h>
  25 #    include <unistd.h>
  26 #  endif
  27 #  if defined(XP_LINUX) && !defined(ANDROID) && defined(__GLIBC__)
  28 #    include <dlfcn.h>
  29 #    include <sys/syscall.h>
  30 #    include <sys/types.h>
  31 #    include <unistd.h>
  32 #    define gettid() static_cast<pid_t>(syscall(__NR_gettid))
  33 #  endif
  34 #else
  35 #  error "Unsupported platform"
  36 #endif
  37
  38 #include "js/friend/StackLimits.h"  // JS_STACK_GROWTH_DIRECTION
  39
  40 #if defined(XP_WIN)
  41
  42 void* js::GetNativeStackBaseImpl() {
  43   PNT_TIB pTib = reinterpret_cast<PNT_TIB>(NtCurrentTeb());
  44   return static_cast<void*>(pTib->StackBase);
  45 }
  46
  47 #elif defined(SOLARIS)
  48
  49 static_assert(JS_STACK_GROWTH_DIRECTION < 0);
  50
  51 void* js::GetNativeStackBaseImpl() {
  52   stack_t st;
  53   stack_getbounds(&st);
  54   return static_cast<char*>(st.ss_sp) + st.ss_size;
  55 }
  56
  57 #elif defined(AIX)
  58
  59 static_assert(JS_STACK_GROWTH_DIRECTION < 0);
  60
  61 void* js::GetNativeStackBaseImpl() {
  62   ucontext_t context;
  63   getcontext(&context);
  64   return static_cast<char*>(context.uc_stack.ss_sp) + context.uc_stack.ss_size;
  65 }
  66
  67 #elif defined(XP_LINUX) && !defined(ANDROID) && defined(__GLIBC__)
  68 void* js::GetNativeStackBaseImpl() {
  69   // On the main thread, get stack base from glibc's __libc_stack_end rather
  70   // than pthread APIs to avoid filesystem calls /proc/self/maps.  Non-main
  71   // threads spawned with pthreads can read this information directly from their
  72   // pthread struct, but the main thread must go parse /proc/self/maps to figure
  73   // the mapped stack address space ranges.  We want to avoid reading from
  74   // /proc/ so that firefox can run in sandboxed environments where /proc may
  75   // not be mounted.
  76   if (gettid() == getpid()) {
  77     void** pLibcStackEnd = (void**)dlsym(RTLD_DEFAULT, "__libc_stack_end");
  78
  79     // If __libc_stack_end is not found, architecture specific frame pointer
  80     // hopping will need to be implemented.
  81     MOZ_RELEASE_ASSERT(
  82         pLibcStackEnd,
  83         "__libc_stack_end unavailable, unable to setup stack range for JS");
  84     void* stackBase = *pLibcStackEnd;
  85     MOZ_RELEASE_ASSERT(
  86         stackBase, "invalid stack base, unable to setup stack range for JS");
  87
  88     // We don't need to fix stackBase, as it already roughly points to beginning
  89     // of the stack
  90     return stackBase;
  91   }
  92
  93   // Non-main threads have the required info stored in memory, so no filesystem
  94   // calls are made.
  95   pthread_t thread = pthread_self();
  96   pthread_attr_t sattr;
  97   pthread_attr_init(&sattr);
  98   pthread_getattr_np(thread, &sattr);
  99
 100   // stackBase will be the *lowest* address on all architectures.
 101   void* stackBase = nullptr;
 102   size_t stackSize = 0;
 103   int rc = pthread_attr_getstack(&sattr, &stackBase, &stackSize);
 104   if (rc) {
 105     MOZ_CRASH(
 106         "call to pthread_attr_getstack failed, unable to setup stack range for "
 107         "JS");
 108   }
 109   MOZ_RELEASE_ASSERT(stackBase,
 110                      "invalid stack base, unable to setup stack range for JS");
 111   pthread_attr_destroy(&sattr);
 112
 113 #  if JS_STACK_GROWTH_DIRECTION > 0
 114   return stackBase;
 115 #  else
 116   return static_cast<char*>(stackBase) + stackSize;
 117 #  endif
 118 }
 119
 120 #elif defined(__wasi__)
 121
 122 // Since we rearrange the layout for wasi via --stack-first flag for the linker
 123 // the final layout is: 0x00 | <- stack | data | heap -> |.
 124 static void* const NativeStackBase = __builtin_frame_address(0);
 125
 126 void* js::GetNativeStackBaseImpl() {
 127   MOZ_ASSERT(JS_STACK_GROWTH_DIRECTION < 0);
 128   return NativeStackBase;
 129 }
 130
 131 #else  // __wasi__
 132
 133 void* js::GetNativeStackBaseImpl() {
 134   pthread_t thread = pthread_self();
 135 #  if defined(XP_DARWIN) || defined(DARWIN)
 136   return pthread_get_stackaddr_np(thread);
 137
 138 #  else
 139   pthread_attr_t sattr;
 140   pthread_attr_init(&sattr);
 141 #    if defined(__OpenBSD__)
 142   stack_t ss;
 143 #    elif defined(PTHREAD_NP_H) || defined(_PTHREAD_NP_H_) || defined(NETBSD)
 144   /* e.g. on FreeBSD 4.8 or newer, neundorf@kde.org */
 145   pthread_attr_get_np(thread, &sattr);
 146 #    else
 147   /*
 148    * FIXME: this function is non-portable;
 149    * other POSIX systems may have different np alternatives
 150    */
 151   pthread_getattr_np(thread, &sattr);
 152 #    endif
 153
 154   void* stackBase = 0;
 155   size_t stackSize = 0;
 156   int rc;
 157 #    if defined(__OpenBSD__)
 158   rc = pthread_stackseg_np(pthread_self(), &ss);
 159   stackBase = (void*)((size_t)ss.ss_sp - ss.ss_size);
 160   stackSize = ss.ss_size;
 161 #    elif defined(ANDROID) && !defined(__aarch64__)
 162   if (gettid() == getpid()) {
 163     // bionic's pthread_attr_getstack prior to API 21 doesn't tell the truth
 164     // for the main thread (see bug 846670). So we scan /proc/self/maps to
 165     // find the segment which contains the stack.
 166     rc = -1;
 167
 168     // Put the string on the stack, otherwise there is the danger that it
 169     // has not been decompressed by the the on-demand linker. Bug 1165460.
 170     //
 171     // The volatile keyword should stop the compiler from trying to omit
 172     // the stack copy in the future (hopefully).
 173     volatile char path[] = "/proc/self/maps";
 174     FILE* fs = fopen((const char*)path, "r");
 175
 176     if (fs) {
 177       char line[100];
 178       unsigned long stackAddr = (unsigned long)&sattr;
 179       while (fgets(line, sizeof(line), fs) != nullptr) {
 180         unsigned long stackStart;
 181         unsigned long stackEnd;
 182         if (sscanf(line, "%lx-%lx ", &stackStart, &stackEnd) == 2 &&
 183             stackAddr >= stackStart && stackAddr < stackEnd) {
 184           stackBase = (void*)stackStart;
 185           stackSize = stackEnd - stackStart;
 186           rc = 0;
 187           break;
 188         }
 189       }
 190       fclose(fs);
 191     }
 192   } else {
 193     // For non main-threads pthread allocates the stack itself so it tells
 194     // the truth.
 195     rc = pthread_attr_getstack(&sattr, &stackBase, &stackSize);
 196   }
 197 #    else
 198   rc = pthread_attr_getstack(&sattr, &stackBase, &stackSize);
 199 #    endif
 200   if (rc) {
 201     MOZ_CRASH();
 202   }
 203   MOZ_ASSERT(stackBase);
 204   pthread_attr_destroy(&sattr);
 205
 206 #    if JS_STACK_GROWTH_DIRECTION > 0
 207   return stackBase;
 208 #    else
 209   return static_cast<char*>(stackBase) + stackSize;
 210 #    endif
 211 #  endif
 212 }
 213
 214 #endif /* !XP_WIN */