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| 1 /* Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
| 2 * Use of this source code is governed by a BSD-style license that can be | |
| 3 * found in the LICENSE file. | |
| 4 */ | |
| 5 #include "nacl_mounts/kernel_object.h" | |
| 6 | |
| 7 #include <assert.h> | |
| 8 #include <errno.h> | |
| 9 #include <fcntl.h> | |
| 10 #include <pthread.h> | |
| 11 | |
| 12 #include <algorithm> | |
| 13 #include <map> | |
| 14 #include <string> | |
| 15 #include <vector> | |
| 16 | |
| 17 #include "nacl_mounts/kernel_handle.h" | |
| 18 #include "nacl_mounts/mount.h" | |
| 19 #include "nacl_mounts/mount_node.h" | |
| 20 #include "utils/auto_lock.h" | |
| 21 | |
| 22 KernelObject::KernelObject() { | |
| 23 pthread_mutex_init(&kernel_lock_, NULL); | |
| 24 pthread_mutex_init(&process_lock_, NULL); | |
| 25 } | |
| 26 | |
| 27 KernelObject::~KernelObject() { | |
| 28 pthread_mutex_destroy(&process_lock_); | |
| 29 pthread_mutex_destroy(&kernel_lock_); | |
| 30 } | |
| 31 | |
| 32 // Uses longest prefix to find the mount for the give path, then | |
| 33 // acquires the mount and returns it with a relative path. | |
| 34 Mount* KernelObject::AcquireMountAndPath(const std::string& relpath, | |
| 35 Path* out_path) { | |
| 36 Path abs_path; | |
| 37 { | |
| 38 AutoLock lock(&process_lock_); | |
| 39 abs_path = GetAbsPathLocked(relpath); | |
| 40 } | |
| 41 | |
| 42 AutoLock lock(&kernel_lock_); | |
| 43 Mount* mount = NULL; | |
| 44 | |
| 45 | |
| 46 // Find longest prefix | |
| 47 size_t max = abs_path.Size(); | |
| 48 for (size_t len = 0; len < abs_path.Size(); len++) { | |
| 49 MountMap_t::iterator it = mounts_.find(abs_path.Range(0, max - len)); | |
| 50 if (it != mounts_.end()) { | |
| 51 out_path->Set("/"); | |
| 52 out_path->Append(abs_path.Range(max - len, max)); | |
| 53 mount = it->second; | |
| 54 break; | |
| 55 } | |
| 56 } | |
| 57 | |
| 58 if (NULL == mount) { | |
| 59 errno = ENOTDIR; | |
| 60 return NULL; | |
| 61 } | |
| 62 | |
| 63 // Acquire the mount while we hold the proxy lock | |
| 64 mount->Acquire(); | |
| 65 return mount; | |
| 66 } | |
| 67 | |
| 68 void KernelObject::ReleaseMount(Mount* mnt) { | |
| 69 AutoLock lock(&kernel_lock_); | |
| 70 mnt->Release(); | |
| 71 } | |
| 72 | |
| 73 KernelHandle* KernelObject::AcquireHandle(int fd) { | |
| 74 AutoLock lock(&process_lock_); | |
| 75 if (fd < 0 || fd >= static_cast<int>(handle_map_.size())) { | |
| 76 errno = EBADF; | |
| 77 return NULL; | |
| 78 } | |
| 79 | |
| 80 KernelHandle* handle = handle_map_[fd]; | |
| 81 if (NULL == handle) { | |
| 82 errno = EBADF; | |
| 83 return NULL; | |
| 84 } | |
| 85 | |
| 86 // Ref count while holding parent mutex | |
| 87 handle->Acquire(); | |
| 88 | |
| 89 lock.Unlock(); | |
| 90 if (handle->node_) handle->mount_->AcquireNode(handle->node_); | |
| 91 | |
| 92 return handle; | |
| 93 } | |
| 94 | |
| 95 void KernelObject::ReleaseHandle(KernelHandle* handle) { | |
| 96 // The handle must already be held before taking the | |
| 97 // kernel lock. | |
| 98 if (handle->node_) handle->mount_->ReleaseNode(handle->node_); | |
| 99 | |
| 100 AutoLock lock(&process_lock_); | |
| 101 handle->Release(); | |
| 102 } | |
| 103 | |
| 104 // Helper function to properly sort FD order in the heap, forcing | |
| 105 // lower numberd FD to be available first. | |
| 106 static bool FdOrder(int i, int j) { | |
| 107 return i > j; | |
| 108 } | |
| 109 | |
| 110 int KernelObject::AllocateFD(KernelHandle* handle) { | |
| 111 AutoLock lock(&process_lock_); | |
| 112 int id; | |
| 113 | |
| 114 // Acquire the handle and its mount since we are about to track it with | |
| 115 // this FD. | |
| 116 handle->Acquire(); | |
| 117 handle->mount_->Acquire(); | |
| 118 | |
| 119 // If we can recycle and FD, use that first | |
| 120 if (free_fds_.size()) { | |
| 121 id = free_fds_.front(); | |
| 122 std::pop_heap(free_fds_.begin(), free_fds_.end(), FdOrder); | |
| 123 free_fds_.pop_back(); | |
| 124 handle_map_[id] = handle; | |
| 125 } else { | |
| 126 id = handle_map_.size(); | |
| 127 handle_map_.push_back(handle); | |
| 128 } | |
| 129 return id; | |
| 130 } | |
| 131 | |
| 132 void KernelObject::AssignFD(int fd, KernelHandle* handle) { | |
| 133 AutoLock lock(&process_lock_); | |
| 134 | |
| 135 // Acquire the handle and its mount since we are about to track it with | |
| 136 // this FD. | |
| 137 handle->Acquire(); | |
| 138 handle->mount_->Acquire(); | |
| 139 | |
| 140 if (fd >= handle_map_.size()) | |
| 141 handle_map_.resize(fd + 1); | |
| 142 | |
| 143 assert(handle_map_[fd] == NULL); | |
| 144 handle_map_[fd] = handle; | |
| 145 } | |
| 146 | |
| 147 void KernelObject::FreeFD(int fd) { | |
| 148 AutoLock lock(&process_lock_); | |
| 149 | |
| 150 // Release the mount and handle since we no longer | |
| 151 // track them with this FD. | |
| 152 KernelHandle* handle = handle_map_[fd]; | |
| 153 handle->mount_->Release(); | |
| 154 handle->Release(); | |
| 155 | |
| 156 handle_map_[fd] = NULL; | |
| 157 free_fds_.push_back(fd); | |
| 158 std::push_heap(free_fds_.begin(), free_fds_.end(), FdOrder); | |
| 159 } | |
| 160 | |
| 161 Path KernelObject::GetAbsPathLocked(const std::string& path) { | |
| 162 // Generate absolute path | |
| 163 Path abs_path(cwd_); | |
| 164 if (path[0] == '/') { | |
| 165 abs_path = path; | |
| 166 } else { | |
| 167 abs_path = cwd_; | |
| 168 abs_path.Append(path); | |
| 169 } | |
| 170 | |
| 171 return abs_path; | |
| 172 } | |
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