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