1 // Copyright 2019 The SwiftShader Authors. All Rights Reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef MEMFD_LINUX 16 #define MEMFD_LINUX 17 18 #include <cstddef> 19 20 // Implementation of shared-memory regions backed by memfd_create(), which 21 // unfortunately is not exported by older GLibc versions, though it has been 22 // supported by the Linux kernel since 3.17 (good enough for Android and desktop 23 // Linux). 24 25 class LinuxMemFd 26 { 27 public: 28 LinuxMemFd() = default; 29 LinuxMemFd(const char * name,size_t size)30 LinuxMemFd(const char *name, size_t size) 31 : LinuxMemFd() 32 { 33 allocate(name, size); 34 } 35 36 ~LinuxMemFd(); 37 38 // Return true iff the region is valid/allocated. isValid() const39 bool isValid() const { return fd_ >= 0; } 40 41 // Return region's internal file descriptor value. Useful for mapping. fd() const42 int fd() const { return fd_; } 43 44 // Set the internal handle to |fd|. 45 void importFd(int fd); 46 47 // Return a copy of this instance's file descriptor (with CLO_EXEC set). 48 int exportFd() const; 49 50 // Implement memfd_create() through direct syscalls if possible. 51 // On success, return true and sets |fd| accordingly. On failure, return 52 // false and sets errno. 53 bool allocate(const char *name, size_t size); 54 55 // Map a segment of |size| bytes from |offset| from the region. 56 // Both |offset| and |size| should be page-aligned. Returns nullptr/errno 57 // on failure. 58 void *mapReadWrite(size_t offset, size_t size); 59 60 // Unmap a region segment starting at |addr| of |size| bytes. 61 // Both |addr| and |size| should be page-aligned. Returns true on success 62 // or false/errno on failure. 63 bool unmap(void *addr, size_t size); 64 65 void close(); 66 67 private: 68 int fd_ = -1; 69 }; 70 71 #endif // MEMFD_LINUX 72