diff options
| -rw-r--r-- | src/common/host_memory.cpp | 60 |
1 files changed, 58 insertions, 2 deletions
diff --git a/src/common/host_memory.cpp b/src/common/host_memory.cpp index ba22595e0..41ca12ab0 100644 --- a/src/common/host_memory.cpp +++ b/src/common/host_memory.cpp @@ -21,12 +21,14 @@ #include <boost/icl/interval_set.hpp> #include <fcntl.h> #include <sys/mman.h> +#include <sys/random.h> #include <unistd.h> #include "common/scope_exit.h" #endif // ^^^ Linux ^^^ #include <mutex> +#include <random> #include "common/alignment.h" #include "common/assert.h" @@ -353,6 +355,61 @@ private: #elif defined(__linux__) || defined(__FreeBSD__) // ^^^ Windows ^^^ vvv Linux vvv +#ifdef ARCHITECTURE_arm64 + +uint64_t GetRandomU64() { + uint64_t ret; + ASSERT(getrandom(&ret, sizeof(ret), 0) == 0); + return ret; +} + +void* ChooseVirtualBase(size_t virtual_size) { + constexpr uintptr_t Map39BitSize = (1ULL << 39); + constexpr uintptr_t Map36BitSize = (1ULL << 36); + + // Seed the MT with some initial strong randomness. + // + // This is not a cryptographic application, we just want something more + // random than the current time. + std::mt19937_64 rng(GetRandomU64()); + + // We want to ensure we are allocating at an address aligned to the L2 block size. + // For Qualcomm devices, we must also allocate memory above 36 bits. + const size_t lower = Map36BitSize / HugePageSize; + const size_t upper = (Map39BitSize - virtual_size) / HugePageSize; + const size_t range = upper - lower; + + // Try up to 64 times to allocate memory at random addresses in the range. + for (int i = 0; i < 64; i++) { + // Calculate a possible location. + uintptr_t hint_address = ((rng() % range) + lower) * HugePageSize; + + // Try to map. + // Note: we may be able to take advantage of MAP_FIXED_NOREPLACE here. + void* map_pointer = + mmap(reinterpret_cast<void*>(hint_address), virtual_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0); + + // If we successfully mapped, we're done. + if (reinterpret_cast<uintptr_t>(map_pointer) == hint_address) { + return map_pointer; + } + + // Unmap if necessary, and try again. + if (map_pointer != MAP_FAILED) { + munmap(map_pointer, virtual_size); + } + } + + return MAP_FAILED; +} +#else +void* ChooseVirtualBase(size_t virtual_size) { + return mmap(nullptr, virtual_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0); +} +#endif + class HostMemory::Impl { public: explicit Impl(size_t backing_size_, size_t virtual_size_) @@ -415,8 +472,7 @@ public: } } #else - virtual_base = static_cast<u8*>(mmap(nullptr, virtual_size, PROT_NONE, - MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0)); + virtual_base = static_cast<u8*>(ChooseVirtualBase(virtual_size)); if (virtual_base == MAP_FAILED) { LOG_CRITICAL(HW_Memory, "mmap failed: {}", strerror(errno)); throw std::bad_alloc{}; |