diff options
author | Bryan Cantrill <bryan@joyent.com> | 2012-09-19 02:35:29 +0400 |
---|---|---|
committer | isaacs <i@izs.me> | 2012-09-22 05:51:44 +0400 |
commit | 4165f736e65215bc39b38186582022039068c108 (patch) | |
tree | 3a4bdc9d53804ed5541ce750187a3222476d9380 /deps | |
parent | 040057167653e8e6ce4d5a368fbc6d73bb541e28 (diff) |
v8: loosen artificial mmap constraint
Fixes #4010.
Diffstat (limited to 'deps')
-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 d942d78a557..7ac114b4536 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); } |