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      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 // Platform-specific code for Linux goes here. For the POSIX-compatible
      6 // parts, the implementation is in platform-posix.cc.
      7 
      8 #include <pthread.h>
      9 #include <semaphore.h>
     10 #include <signal.h>
     11 #include <stdio.h>
     12 #include <stdlib.h>
     13 #include <sys/resource.h>
     14 #include <sys/time.h>
     15 
     16 // Ubuntu Dapper requires memory pages to be marked as
     17 // executable. Otherwise, OS raises an exception when executing code
     18 // in that page.
     19 #include <errno.h>
     20 #include <fcntl.h>      // open
     21 #include <stdarg.h>
     22 #include <strings.h>    // index
     23 #include <sys/mman.h>   // mmap & munmap
     24 #include <sys/stat.h>   // open
     25 #include <sys/types.h>  // mmap & munmap
     26 #include <unistd.h>     // sysconf
     27 
     28 // GLibc on ARM defines mcontext_t has a typedef for 'struct sigcontext'.
     29 // Old versions of the C library <signal.h> didn't define the type.
     30 #if defined(__ANDROID__) && !defined(__BIONIC_HAVE_UCONTEXT_T) && \
     31     (defined(__arm__) || defined(__aarch64__)) && \
     32     !defined(__BIONIC_HAVE_STRUCT_SIGCONTEXT)
     33 #include <asm/sigcontext.h>  // NOLINT
     34 #endif
     35 
     36 #if defined(LEAK_SANITIZER)
     37 #include <sanitizer/lsan_interface.h>
     38 #endif
     39 
     40 #include <cmath>
     41 
     42 #undef MAP_TYPE
     43 
     44 #include "src/base/macros.h"
     45 #include "src/base/platform/platform.h"
     46 
     47 #if V8_OS_NACL
     48 #if !defined(MAP_NORESERVE)
     49 // PNaCL doesn't have this, so we always grab all of the memory, which is bad.
     50 #define MAP_NORESERVE 0
     51 #endif
     52 #else
     53 #include <sys/prctl.h>
     54 #include <sys/syscall.h>
     55 #endif
     56 
     57 namespace v8 {
     58 namespace base {
     59 
     60 
     61 #ifdef __arm__
     62 
     63 bool OS::ArmUsingHardFloat() {
     64   // GCC versions 4.6 and above define __ARM_PCS or __ARM_PCS_VFP to specify
     65   // the Floating Point ABI used (PCS stands for Procedure Call Standard).
     66   // We use these as well as a couple of other defines to statically determine
     67   // what FP ABI used.
     68   // GCC versions 4.4 and below don't support hard-fp.
     69   // GCC versions 4.5 may support hard-fp without defining __ARM_PCS or
     70   // __ARM_PCS_VFP.
     71 
     72 #define GCC_VERSION (__GNUC__ * 10000                                          \
     73                      + __GNUC_MINOR__ * 100                                    \
     74                      + __GNUC_PATCHLEVEL__)
     75 #if GCC_VERSION >= 40600
     76 #if defined(__ARM_PCS_VFP)
     77   return true;
     78 #else
     79   return false;
     80 #endif
     81 
     82 #elif GCC_VERSION < 40500
     83   return false;
     84 
     85 #else
     86 #if defined(__ARM_PCS_VFP)
     87   return true;
     88 #elif defined(__ARM_PCS) || defined(__SOFTFP__) || defined(__SOFTFP) || \
     89       !defined(__VFP_FP__)
     90   return false;
     91 #else
     92 #error "Your version of GCC does not report the FP ABI compiled for."          \
     93        "Please report it on this issue"                                        \
     94        "http://code.google.com/p/v8/issues/detail?id=2140"
     95 
     96 #endif
     97 #endif
     98 #undef GCC_VERSION
     99 }
    100 
    101 #endif  // def __arm__
    102 
    103 
    104 const char* OS::LocalTimezone(double time, TimezoneCache* cache) {
    105 #if V8_OS_NACL
    106   // Missing support for tm_zone field.
    107   return "";
    108 #else
    109   if (std::isnan(time)) return "";
    110   time_t tv = static_cast<time_t>(std::floor(time/msPerSecond));
    111   struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
    112   if (!t || !t->tm_zone) return "";
    113   return t->tm_zone;
    114 #endif
    115 }
    116 
    117 
    118 double OS::LocalTimeOffset(TimezoneCache* cache) {
    119 #if V8_OS_NACL
    120   // Missing support for tm_zone field.
    121   return 0;
    122 #else
    123   time_t tv = time(NULL);
    124   struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
    125   // tm_gmtoff includes any daylight savings offset, so subtract it.
    126   return static_cast<double>(t->tm_gmtoff * msPerSecond -
    127                              (t->tm_isdst > 0 ? 3600 * msPerSecond : 0));
    128 #endif
    129 }
    130 
    131 
    132 void* OS::Allocate(const size_t requested,
    133                    size_t* allocated,
    134                    bool is_executable) {
    135   const size_t msize = RoundUp(requested, AllocateAlignment());
    136   int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
    137   void* addr = OS::GetRandomMmapAddr();
    138   void* mbase = mmap(addr, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    139   if (mbase == MAP_FAILED) return NULL;
    140   *allocated = msize;
    141   return mbase;
    142 }
    143 
    144 
    145 std::vector<OS::SharedLibraryAddress> OS::GetSharedLibraryAddresses() {
    146   std::vector<SharedLibraryAddress> result;
    147   // This function assumes that the layout of the file is as follows:
    148   // hex_start_addr-hex_end_addr rwxp <unused data> [binary_file_name]
    149   // If we encounter an unexpected situation we abort scanning further entries.
    150   FILE* fp = fopen("/proc/self/maps", "r");
    151   if (fp == NULL) return result;
    152 
    153   // Allocate enough room to be able to store a full file name.
    154   const int kLibNameLen = FILENAME_MAX + 1;
    155   char* lib_name = reinterpret_cast<char*>(malloc(kLibNameLen));
    156 
    157   // This loop will terminate once the scanning hits an EOF.
    158   while (true) {
    159     uintptr_t start, end;
    160     char attr_r, attr_w, attr_x, attr_p;
    161     // Parse the addresses and permission bits at the beginning of the line.
    162     if (fscanf(fp, "%" V8PRIxPTR "-%" V8PRIxPTR, &start, &end) != 2) break;
    163     if (fscanf(fp, " %c%c%c%c", &attr_r, &attr_w, &attr_x, &attr_p) != 4) break;
    164 
    165     int c;
    166     if (attr_r == 'r' && attr_w != 'w' && attr_x == 'x') {
    167       // Found a read-only executable entry. Skip characters until we reach
    168       // the beginning of the filename or the end of the line.
    169       do {
    170         c = getc(fp);
    171       } while ((c != EOF) && (c != '\n') && (c != '/') && (c != '['));
    172       if (c == EOF) break;  // EOF: Was unexpected, just exit.
    173 
    174       // Process the filename if found.
    175       if ((c == '/') || (c == '[')) {
    176         // Push the '/' or '[' back into the stream to be read below.
    177         ungetc(c, fp);
    178 
    179         // Read to the end of the line. Exit if the read fails.
    180         if (fgets(lib_name, kLibNameLen, fp) == NULL) break;
    181 
    182         // Drop the newline character read by fgets. We do not need to check
    183         // for a zero-length string because we know that we at least read the
    184         // '/' or '[' character.
    185         lib_name[strlen(lib_name) - 1] = '\0';
    186       } else {
    187         // No library name found, just record the raw address range.
    188         snprintf(lib_name, kLibNameLen,
    189                  "%08" V8PRIxPTR "-%08" V8PRIxPTR, start, end);
    190       }
    191       result.push_back(SharedLibraryAddress(lib_name, start, end));
    192     } else {
    193       // Entry not describing executable data. Skip to end of line to set up
    194       // reading the next entry.
    195       do {
    196         c = getc(fp);
    197       } while ((c != EOF) && (c != '\n'));
    198       if (c == EOF) break;
    199     }
    200   }
    201   free(lib_name);
    202   fclose(fp);
    203   return result;
    204 }
    205 
    206 
    207 void OS::SignalCodeMovingGC() {
    208   // Support for ll_prof.py.
    209   //
    210   // The Linux profiler built into the kernel logs all mmap's with
    211   // PROT_EXEC so that analysis tools can properly attribute ticks. We
    212   // do a mmap with a name known by ll_prof.py and immediately munmap
    213   // it. This injects a GC marker into the stream of events generated
    214   // by the kernel and allows us to synchronize V8 code log and the
    215   // kernel log.
    216   long size = sysconf(_SC_PAGESIZE);  // NOLINT(runtime/int)
    217   FILE* f = fopen(OS::GetGCFakeMMapFile(), "w+");
    218   if (f == NULL) {
    219     OS::PrintError("Failed to open %s\n", OS::GetGCFakeMMapFile());
    220     OS::Abort();
    221   }
    222   void* addr = mmap(OS::GetRandomMmapAddr(), size,
    223 #if V8_OS_NACL
    224                     // The Native Client port of V8 uses an interpreter,
    225                     // so code pages don't need PROT_EXEC.
    226                     PROT_READ,
    227 #else
    228                     PROT_READ | PROT_EXEC,
    229 #endif
    230                     MAP_PRIVATE, fileno(f), 0);
    231   DCHECK_NE(MAP_FAILED, addr);
    232   OS::Free(addr, size);
    233   fclose(f);
    234 }
    235 
    236 
    237 // Constants used for mmap.
    238 static const int kMmapFd = -1;
    239 static const int kMmapFdOffset = 0;
    240 
    241 
    242 VirtualMemory::VirtualMemory() : address_(NULL), size_(0) { }
    243 
    244 
    245 VirtualMemory::VirtualMemory(size_t size)
    246     : address_(ReserveRegion(size)), size_(size) { }
    247 
    248 
    249 VirtualMemory::VirtualMemory(size_t size, size_t alignment)
    250     : address_(NULL), size_(0) {
    251   DCHECK((alignment % OS::AllocateAlignment()) == 0);
    252   size_t request_size = RoundUp(size + alignment,
    253                                 static_cast<intptr_t>(OS::AllocateAlignment()));
    254   void* reservation = mmap(OS::GetRandomMmapAddr(),
    255                            request_size,
    256                            PROT_NONE,
    257                            MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
    258                            kMmapFd,
    259                            kMmapFdOffset);
    260   if (reservation == MAP_FAILED) return;
    261 
    262   uint8_t* base = static_cast<uint8_t*>(reservation);
    263   uint8_t* aligned_base = RoundUp(base, alignment);
    264   DCHECK_LE(base, aligned_base);
    265 
    266   // Unmap extra memory reserved before and after the desired block.
    267   if (aligned_base != base) {
    268     size_t prefix_size = static_cast<size_t>(aligned_base - base);
    269     OS::Free(base, prefix_size);
    270     request_size -= prefix_size;
    271   }
    272 
    273   size_t aligned_size = RoundUp(size, OS::AllocateAlignment());
    274   DCHECK_LE(aligned_size, request_size);
    275 
    276   if (aligned_size != request_size) {
    277     size_t suffix_size = request_size - aligned_size;
    278     OS::Free(aligned_base + aligned_size, suffix_size);
    279     request_size -= suffix_size;
    280   }
    281 
    282   DCHECK(aligned_size == request_size);
    283 
    284   address_ = static_cast<void*>(aligned_base);
    285   size_ = aligned_size;
    286 #if defined(LEAK_SANITIZER)
    287   __lsan_register_root_region(address_, size_);
    288 #endif
    289 }
    290 
    291 
    292 VirtualMemory::~VirtualMemory() {
    293   if (IsReserved()) {
    294     bool result = ReleaseRegion(address(), size());
    295     DCHECK(result);
    296     USE(result);
    297   }
    298 }
    299 
    300 
    301 bool VirtualMemory::IsReserved() {
    302   return address_ != NULL;
    303 }
    304 
    305 
    306 void VirtualMemory::Reset() {
    307   address_ = NULL;
    308   size_ = 0;
    309 }
    310 
    311 
    312 bool VirtualMemory::Commit(void* address, size_t size, bool is_executable) {
    313   CHECK(InVM(address, size));
    314   return CommitRegion(address, size, is_executable);
    315 }
    316 
    317 
    318 bool VirtualMemory::Uncommit(void* address, size_t size) {
    319   CHECK(InVM(address, size));
    320   return UncommitRegion(address, size);
    321 }
    322 
    323 
    324 bool VirtualMemory::Guard(void* address) {
    325   CHECK(InVM(address, OS::CommitPageSize()));
    326   OS::Guard(address, OS::CommitPageSize());
    327   return true;
    328 }
    329 
    330 
    331 void* VirtualMemory::ReserveRegion(size_t size) {
    332   void* result = mmap(OS::GetRandomMmapAddr(),
    333                       size,
    334                       PROT_NONE,
    335                       MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
    336                       kMmapFd,
    337                       kMmapFdOffset);
    338 
    339   if (result == MAP_FAILED) return NULL;
    340 
    341 #if defined(LEAK_SANITIZER)
    342   __lsan_register_root_region(result, size);
    343 #endif
    344   return result;
    345 }
    346 
    347 
    348 bool VirtualMemory::CommitRegion(void* base, size_t size, bool is_executable) {
    349 #if V8_OS_NACL
    350   // The Native Client port of V8 uses an interpreter,
    351   // so code pages don't need PROT_EXEC.
    352   int prot = PROT_READ | PROT_WRITE;
    353 #else
    354   int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
    355 #endif
    356   if (MAP_FAILED == mmap(base,
    357                          size,
    358                          prot,
    359                          MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
    360                          kMmapFd,
    361                          kMmapFdOffset)) {
    362     return false;
    363   }
    364 
    365   return true;
    366 }
    367 
    368 
    369 bool VirtualMemory::UncommitRegion(void* base, size_t size) {
    370   return mmap(base,
    371               size,
    372               PROT_NONE,
    373               MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE | MAP_FIXED,
    374               kMmapFd,
    375               kMmapFdOffset) != MAP_FAILED;
    376 }
    377 
    378 
    379 bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
    380 #if defined(LEAK_SANITIZER)
    381   __lsan_unregister_root_region(base, size);
    382 #endif
    383   return munmap(base, size) == 0;
    384 }
    385 
    386 
    387 bool VirtualMemory::HasLazyCommits() {
    388   return true;
    389 }
    390 
    391 }  // namespace base
    392 }  // namespace v8
    393