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 #include "MemFd.hpp"
16 #include "../Debug.hpp"
17
18 #include <errno.h>
19 #include <fcntl.h>
20 #include <string.h>
21 #include <sys/mman.h>
22 #include <unistd.h>
23
24 #ifndef MFD_CLOEXEC
25 # define MFD_CLOEXEC 0x0001U
26 #endif
27
28 #if __aarch64__
29 # define __NR_memfd_create 279
30 #elif __arm__
31 # define __NR_memfd_create 279
32 #elif __powerpc64__
33 # define __NR_memfd_create 360
34 #elif __i386__
35 # define __NR_memfd_create 356
36 #elif __x86_64__
37 # define __NR_memfd_create 319
38 #endif /* __NR_memfd_create__ */
39
~LinuxMemFd()40 LinuxMemFd::~LinuxMemFd()
41 {
42 close();
43 }
44
importFd(int fd)45 void LinuxMemFd::importFd(int fd)
46 {
47 close();
48 fd_ = fd;
49 }
50
exportFd() const51 int LinuxMemFd::exportFd() const
52 {
53 if(fd_ < 0)
54 {
55 return fd_;
56 }
57
58 // Duplicate file descriptor while setting the clo-on-exec flag (Linux specific).
59 return ::fcntl(fd_, F_DUPFD_CLOEXEC, 0);
60 }
61
allocate(const char * name,size_t size)62 bool LinuxMemFd::allocate(const char *name, size_t size)
63 {
64 close();
65
66 #ifndef __NR_memfd_create
67 TRACE("memfd_create() not supported on this system!");
68 return false;
69 #else
70 // In the event of no system call this returns -1 with errno set
71 // as ENOSYS.
72 fd_ = syscall(__NR_memfd_create, name, MFD_CLOEXEC);
73 if(fd_ < 0)
74 {
75 TRACE("memfd_create() returned %d: %s", errno, strerror(errno));
76 return false;
77 }
78 // Ensure there is enough space.
79 if(size > 0 && ::ftruncate(fd_, size) < 0)
80 {
81 TRACE("ftruncate() %lld returned %d: %s", (long long)size, errno, strerror(errno));
82 close();
83 return false;
84 }
85 #endif
86 return true;
87 }
88
close()89 void LinuxMemFd::close()
90 {
91 if(fd_ >= 0)
92 {
93 // WARNING: Never retry on close() failure, even with EINTR, see
94 // https://lwn.net/Articles/576478/ for example.
95 int ret = ::close(fd_);
96 if(ret < 0)
97 {
98 TRACE("LinuxMemFd::close() failed with: %s", strerror(errno));
99 assert(false);
100 }
101 fd_ = -1;
102 }
103 }
104
mapReadWrite(size_t offset,size_t size)105 void *LinuxMemFd::mapReadWrite(size_t offset, size_t size)
106 {
107 void *addr = ::mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_,
108 static_cast<off_t>(offset));
109 return (addr == MAP_FAILED) ? nullptr : addr;
110 }
111
unmap(void * addr,size_t size)112 bool LinuxMemFd::unmap(void *addr, size_t size)
113 {
114 return ::munmap(addr, size) == 0;
115 }
116