diff options
| -rw-r--r-- | deps/v8/src/platform-posix.cc | 46 |
1 files changed, 28 insertions, 18 deletions
diff --git a/deps/v8/src/platform-posix.cc b/deps/v8/src/platform-posix.cc index 3c868688a..5c3529d44 100644 --- a/deps/v8/src/platform-posix.cc +++ b/deps/v8/src/platform-posix.cc @@ -92,6 +92,33 @@ void OS::Guard(void* address, const size_t size) { } #endif // __CYGWIN__ +// For our illumos/Solaris mmap hint, we pick a random address in the bottom +// half of the top half of the address space (that is, the third quarter). +// Because we do not MAP_FIXED, this will be treated only as a hint -- the +// system will not fail to mmap() because something else happens to already be +// mapped at our random address. We deliberately set the hint high enough to +// get well above the system's break (that is, the heap); illumos and Solaris +// will try the hint and if that fails allocate as if there were no hint at +// all. The high hint prevents the break from getting hemmed in at low values, +// ceding half of the address space to the system heap. + +// On all other 32bit platforms the range 0x20000000 - 0x60000000 is relatively +// unpopulated across a variety of ASLR modes (PAE kernel, NX compat mode, etc) +// and on macos 10.6 and 10.7. + +#ifdef V8_TARGET_ARCH_X64 +# ifdef __sun +# define V8_ASLR_MEMORY_SHIFT 0x400000000000ULL +# else +# define V8_ASLR_MEMORY_SHIFT 0 +# endif // __sun +#else +# ifdef __sun +# define V8_ASLR_MEMORY_SHIFT 0x80000000 +# else +# define V8_ASLR_MEMORY_SHIFT 0x20000000 +# endif // __sun +#endif // V8_TARGET_ARCH_X64 void* OS::GetRandomMmapAddr() { Isolate* isolate = Isolate::UncheckedCurrent(); @@ -111,25 +138,8 @@ void* OS::GetRandomMmapAddr() { uint32_t raw_addr = V8::RandomPrivate(isolate); raw_addr &= 0x3ffff000; - -# ifdef __sun - // For our Solaris/illumos mmap hint, we pick a random address in the bottom - // half of the top half of the address space (that is, the third quarter). - // Because we do not MAP_FIXED, this will be treated only as a hint -- the - // system will not fail to mmap() because something else happens to already - // be mapped at our random address. We deliberately set the hint high enough - // to get well above the system's break (that is, the heap); Solaris and - // illumos will try the hint and if that fails allocate as if there were - // no hint at all. The high hint prevents the break from getting hemmed in - // at low values, ceding half of the address space to the system heap. - raw_addr += 0x80000000; -# else - // The range 0x20000000 - 0x60000000 is relatively unpopulated across a - // variety of ASLR modes (PAE kernel, NX compat mode, etc) and on macos - // 10.6 and 10.7. - raw_addr += 0x20000000; -# endif #endif + raw_addr += V8_ASLR_MEMORY_SHIFT; return reinterpret_cast<void*>(raw_addr); } return NULL; |