mirror of
https://github.com/flutter/flutter.git
synced 2026-02-20 02:29:02 +08:00
e0fd75b5ab
This caused us to lose our gn check certification. :( Turns out gn check was just ignoring all the header paths it didn't understand and so gn check passing for sky wasn't meaning much. I tried to straighten out some of the mess in this CL, but its going to take several more rounds of massaging before gn check passes again. On the bright side (almost) all of our headers are absolute now. Turns out my script (attached to the bug) didn't notice ../ includes but I'll fix that in the next patch. R=abarth@chromium.org BUG=435361 Review URL: https://codereview.chromium.org/746023002
100 lines
2.6 KiB
C++
100 lines
2.6 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file.
|
|
|
|
#include "sky/engine/config.h"
|
|
#include "sky/engine/wtf/AddressSpaceRandomization.h"
|
|
|
|
#include "sky/engine/wtf/PageAllocator.h"
|
|
#include "sky/engine/wtf/ProcessID.h"
|
|
#include "sky/engine/wtf/SpinLock.h"
|
|
|
|
namespace WTF {
|
|
|
|
namespace {
|
|
|
|
// This is the same PRNG as used by tcmalloc for mapping address randomness;
|
|
// see http://burtleburtle.net/bob/rand/smallprng.html
|
|
struct ranctx {
|
|
int lock;
|
|
bool initialized;
|
|
uint32_t a;
|
|
uint32_t b;
|
|
uint32_t c;
|
|
uint32_t d;
|
|
};
|
|
|
|
#define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
|
|
|
|
uint32_t ranvalInternal(ranctx* x)
|
|
{
|
|
uint32_t e = x->a - rot(x->b, 27);
|
|
x->a = x->b ^ rot(x->c, 17);
|
|
x->b = x->c + x->d;
|
|
x->c = x->d + e;
|
|
x->d = e + x->a;
|
|
return x->d;
|
|
}
|
|
|
|
#undef rot
|
|
|
|
uint32_t ranval(ranctx* x)
|
|
{
|
|
spinLockLock(&x->lock);
|
|
if (UNLIKELY(!x->initialized)) {
|
|
x->initialized = true;
|
|
char c;
|
|
uint32_t seed = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(&c));
|
|
seed ^= static_cast<uint32_t>(getCurrentProcessID());
|
|
x->a = 0xf1ea5eed;
|
|
x->b = x->c = x->d = seed;
|
|
for (int i = 0; i < 20; ++i) {
|
|
(void) ranvalInternal(x);
|
|
}
|
|
}
|
|
uint32_t ret = ranvalInternal(x);
|
|
spinLockUnlock(&x->lock);
|
|
return ret;
|
|
}
|
|
|
|
static struct ranctx s_ranctx;
|
|
|
|
}
|
|
|
|
// Calculates a random preferred mapping address. In calculating an
|
|
// address, we balance good ASLR against not fragmenting the address
|
|
// space too badly.
|
|
void* getRandomPageBase()
|
|
{
|
|
uintptr_t random;
|
|
random = static_cast<uintptr_t>(ranval(&s_ranctx));
|
|
#if CPU(X86_64)
|
|
random <<= 32UL;
|
|
random |= static_cast<uintptr_t>(ranval(&s_ranctx));
|
|
// This address mask gives a low liklihood of address space collisions.
|
|
// We handle the situation gracefully if there is a collision.
|
|
#if OS(WIN)
|
|
// 64-bit Windows has a bizarrely small 8TB user address space.
|
|
// Allocates in the 1-5TB region.
|
|
random &= 0x3ffffffffffUL;
|
|
random += 0x10000000000UL;
|
|
#else
|
|
// Linux and OS X support the full 47-bit user space of x64 processors.
|
|
random &= 0x3fffffffffffUL;
|
|
#endif
|
|
#elif CPU(ARM64)
|
|
// ARM64 on Linux has 39-bit user space.
|
|
random &= 0x3fffffffffUL;
|
|
random += 0x1000000000UL;
|
|
#else // !CPU(X86_64) && !CPU(ARM64)
|
|
// This is a good range on Windows, Linux and Mac.
|
|
// Allocates in the 0.5-1.5GB region.
|
|
random &= 0x3fffffff;
|
|
random += 0x20000000;
|
|
#endif // CPU(X86_64)
|
|
random &= kPageAllocationGranularityBaseMask;
|
|
return reinterpret_cast<void*>(random);
|
|
}
|
|
|
|
}
|