diff options
author | Bryan Cantrill <bryan@joyent.com> | 2012-09-18 15:35:29 -0700 |
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committer | Ben Noordhuis <info@bnoordhuis.nl> | 2012-09-22 02:57:33 +0200 |
commit | 7bd84de5ed7c5e8c072bcc02fb50037b8f3aac3f (patch) | |
tree | 785a4d6eb635f1bd7031530660ef19980a2d3dad | |
parent | 017009f8c5c691dcb76b63ff38def6fef50b4414 (diff) | |
download | node-7bd84de5ed7c5e8c072bcc02fb50037b8f3aac3f.tar.gz |
v8: loosen artificial mmap constraint
Fixes #4010.
-rw-r--r-- | deps/v8/src/platform-posix.cc | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/deps/v8/src/platform-posix.cc b/deps/v8/src/platform-posix.cc index 3bc83733c..2b8001516 100644 --- a/deps/v8/src/platform-posix.cc +++ b/deps/v8/src/platform-posix.cc @@ -109,11 +109,20 @@ void* OS::GetRandomMmapAddr() { raw_addr &= V8_UINT64_C(0x3ffffffff000); #else uint32_t raw_addr = V8::RandomPrivate(isolate); - // 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. + + // For our 32-bit 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); systems will + // either try the hint and if that fails move higher (MacOS and other BSD + // derivatives) or try the hint and if that fails allocate as if there were + // no hint at all (Linux, Solaris, illumos and derivatives). 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 &= 0x3ffff000; - raw_addr += 0x20000000; + raw_addr += 0x80000000; #endif return reinterpret_cast<void*>(raw_addr); } |