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-rw-r--r--src/common/host_memory.cpp60
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{};