1 files changed, 32 insertions, 2 deletions

diff --git a/src/common/host_memory.cpp b/src/common/host_memory.cpp
index 8e4f1f97a..ba22595e0 100644
--- a/src/common/host_memory.cpp
+++ b/src/common/host_memory.cpp
@@ -11,9 +11,14 @@
 
 #elif defined(__linux__) || defined(__FreeBSD__) // ^^^ Windows ^^^ vvv Linux vvv
 
+#ifdef ANDROID
+#include <android/sharedmem.h>
+#endif
+
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #endif
+#include <boost/icl/interval_set.hpp>
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <unistd.h>
@@ -366,17 +371,20 @@ public:
         }
 
         // Backing memory initialization
-#if defined(__FreeBSD__) && __FreeBSD__ < 13
+#ifdef ANDROID
+        fd = ASharedMemory_create("HostMemory", backing_size);
+#elif defined(__FreeBSD__) && __FreeBSD__ < 13
         // XXX Drop after FreeBSD 12.* reaches EOL on 2024-06-30
         fd = shm_open(SHM_ANON, O_RDWR, 0600);
 #else
         fd = memfd_create("HostMemory", 0);
 #endif
-        if (fd == -1) {
+        if (fd < 0) {
             LOG_CRITICAL(HW_Memory, "memfd_create failed: {}", strerror(errno));
             throw std::bad_alloc{};
         }
 
+#ifndef ANDROID
         // Defined to extend the file with zeros
         int ret = ftruncate(fd, backing_size);
         if (ret != 0) {
@@ -384,6 +392,7 @@ public:
                          strerror(errno));
             throw std::bad_alloc{};
         }
+#endif
 
         backing_base = static_cast<u8*>(
             mmap(nullptr, backing_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
@@ -415,6 +424,7 @@ public:
         madvise(virtual_base, virtual_size, MADV_HUGEPAGE);
 #endif
 
+        placeholders.add({0, virtual_size});
         good = true;
     }
 
@@ -423,6 +433,10 @@ public:
     }
 
     void Map(size_t virtual_offset, size_t host_offset, size_t length) {
+        {
+            std::scoped_lock lock{placeholder_mutex};
+            placeholders.subtract({virtual_offset, virtual_offset + length});
+        }
 
         void* ret = mmap(virtual_base + virtual_offset, length, PROT_READ | PROT_WRITE,
                          MAP_SHARED | MAP_FIXED, fd, host_offset);
@@ -433,6 +447,19 @@ public:
         // The method name is wrong. We're still talking about the virtual range.
         // We don't want to unmap, we want to reserve this memory.
 
+        {
+            std::scoped_lock lock{placeholder_mutex};
+            auto it = placeholders.find({virtual_offset - 1, virtual_offset + length + 1});
+
+            if (it != placeholders.end()) {
+                size_t prev_upper = virtual_offset + length;
+                virtual_offset = std::min(virtual_offset, it->lower());
+                length = std::max(it->upper(), prev_upper) - virtual_offset;
+            }
+
+            placeholders.add({virtual_offset, virtual_offset + length});
+        }
+
         void* ret = mmap(virtual_base + virtual_offset, length, PROT_NONE,
                          MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
         ASSERT_MSG(ret != MAP_FAILED, "mmap failed: {}", strerror(errno));
@@ -476,6 +503,9 @@ private:
     }
 
     int fd{-1}; // memfd file descriptor, -1 is the error value of memfd_create
+
+    boost::icl::interval_set<size_t> placeholders; ///< Mapped placeholders
+    std::mutex placeholder_mutex;                  ///< Mutex for placeholders
 };
 
 #else // ^^^ Linux ^^^ vvv Generic vvv