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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 
ArmUsingHardFloat()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 
LocalTimezone(double time,TimezoneCache * cache)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 
LocalTimeOffset(TimezoneCache * cache)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 
Allocate(const size_t requested,size_t * allocated,bool is_executable)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 
GetSharedLibraryAddresses()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 
SignalCodeMovingGC()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 
VirtualMemory()210 VirtualMemory::VirtualMemory() : address_(NULL), size_(0) {}
211 
VirtualMemory(size_t size)212 VirtualMemory::VirtualMemory(size_t size)
213     : address_(ReserveRegion(size)), size_(size) {}
214 
VirtualMemory(size_t size,size_t alignment)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 
~VirtualMemory()254 VirtualMemory::~VirtualMemory() {
255   if (IsReserved()) {
256     bool result = ReleaseRegion(address(), size());
257     DCHECK(result);
258     USE(result);
259   }
260 }
261 
IsReserved()262 bool VirtualMemory::IsReserved() { return address_ != NULL; }
263 
Reset()264 void VirtualMemory::Reset() {
265   address_ = NULL;
266   size_ = 0;
267 }
268 
Commit(void * address,size_t size,bool is_executable)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 
Uncommit(void * address,size_t size)274 bool VirtualMemory::Uncommit(void* address, size_t size) {
275   CHECK(InVM(address, size));
276   return UncommitRegion(address, size);
277 }
278 
Guard(void * address)279 bool VirtualMemory::Guard(void* address) {
280   CHECK(InVM(address, OS::CommitPageSize()));
281   OS::Guard(address, OS::CommitPageSize());
282   return true;
283 }
284 
ReserveRegion(size_t size)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 
CommitRegion(void * base,size_t size,bool is_executable)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 
UncommitRegion(void * base,size_t size)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 
ReleasePartialRegion(void * base,size_t size,void * free_start,size_t free_size)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 
ReleaseRegion(void * base,size_t size)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 
HasLazyCommits()331 bool VirtualMemory::HasLazyCommits() { return true; }
332 
333 }  // namespace base
334 }  // namespace v8
335