1
0
mirror of https://github.com/topjohnwu/Magisk.git synced 2024-12-22 16:07:39 +00:00
2021-11-29 19:56:37 -08:00

32 lines
881 B
C++

#include "memory.hpp"
namespace jni_hook {
// We know our minimum alignment is WORD size (size of pointer)
static constexpr size_t ALIGN = sizeof(long);
// 4MB is more than enough
static constexpr size_t CAPACITY = (1 << 22);
// No need to be thread safe as the initial mmap always happens on the main thread
static uint8_t *_area = nullptr;
static std::atomic<uint8_t *> _curr = nullptr;
void *memory_block::allocate(size_t sz) {
if (!_area) {
// Memory will not actually be allocated because physical pages are mapped in on-demand
_area = static_cast<uint8_t *>(xmmap(
nullptr, CAPACITY, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
_curr = _area;
}
return _curr.fetch_add(align_to(sz, ALIGN));
}
void memory_block::release() {
if (_area)
munmap(_area, CAPACITY);
}
} // namespace jni_hook