Utils.cpp - platform/system/vold - Gitiles

 /*
  * Copyright (C) 2015 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "sehandle.h"
 #include "Utils.h"
 #include "Process.h"

 #include <base/file.h>
 #include <base/logging.h>
 #include <base/stringprintf.h>
 #include <cutils/fs.h>
 #include <private/android_filesystem_config.h>
 #include <logwrap/logwrap.h>

 #include <mutex>
 #include <dirent.h>
 #include <fcntl.h>
 #include <linux/fs.h>
 #include <stdlib.h>
 #include <sys/mount.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
 #include <sys/statvfs.h>

 #ifndef UMOUNT_NOFOLLOW
 #define UMOUNT_NOFOLLOW    0x00000008  /* Don't follow symlink on umount */
 #endif

 using android::base::ReadFileToString;
 using android::base::StringPrintf;

 namespace android {
 namespace vold {

 security_context_t sBlkidContext = nullptr;
 security_context_t sBlkidUntrustedContext = nullptr;
 security_context_t sFsckContext = nullptr;
 security_context_t sFsckUntrustedContext = nullptr;

 static const char* kBlkidPath = "/system/bin/blkid";

 static const char* kProcFilesystems = "/proc/filesystems";

 status_t CreateDeviceNode(const std::string& path, dev_t dev) {
     const char* cpath = path.c_str();
     status_t res = 0;

     char* secontext = nullptr;
     if (sehandle) {
         if (!selabel_lookup(sehandle, &secontext, cpath, S_IFBLK)) {
             setfscreatecon(secontext);
         }
     }

     mode_t mode = 0660 | S_IFBLK;
     if (mknod(cpath, mode, dev) < 0) {
         if (errno != EEXIST) {
             PLOG(ERROR) << "Failed to create device node for " << major(dev)
                     << ":" << minor(dev) << " at " << path;
             res = -errno;
         }
     }

     if (secontext) {
         setfscreatecon(nullptr);
         freecon(secontext);
     }

     return res;
 }

 status_t DestroyDeviceNode(const std::string& path) {
     const char* cpath = path.c_str();
     if (TEMP_FAILURE_RETRY(unlink(cpath))) {
         return -errno;
     } else {
         return OK;
     }
 }

 status_t PrepareDir(const std::string& path, mode_t mode, uid_t uid, gid_t gid) {
     const char* cpath = path.c_str();

     char* secontext = nullptr;
     if (sehandle) {
         if (!selabel_lookup(sehandle, &secontext, cpath, S_IFDIR)) {
             setfscreatecon(secontext);
         }
     }

     int res = fs_prepare_dir(cpath, mode, uid, gid);

     if (secontext) {
         setfscreatecon(nullptr);
         freecon(secontext);
     }

     if (res == 0) {
         return OK;
     } else {
         return -errno;
     }
 }

 status_t ForceUnmount(const std::string& path) {
     const char* cpath = path.c_str();
     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }
     PLOG(WARNING) << "Failed to unmount " << path;

     sleep(5);
     Process::killProcessesWithOpenFiles(cpath, SIGINT);

     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }
     PLOG(WARNING) << "Failed to unmount " << path;

     sleep(5);
     Process::killProcessesWithOpenFiles(cpath, SIGTERM);

     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }
     PLOG(WARNING) << "Failed to unmount " << path;

     sleep(5);
     Process::killProcessesWithOpenFiles(cpath, SIGKILL);

     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }
     PLOG(ERROR) << "Failed to unmount " << path;

     return -errno;
 }

 status_t BindMount(const std::string& source, const std::string& target) {
     if (::mount(source.c_str(), target.c_str(), "", MS_BIND, NULL)) {
         PLOG(ERROR) << "Failed to bind mount " << source << " to " << target;
         return -errno;
     }
     return OK;
 }

 static status_t readMetadata(const std::string& path, std::string& fsType,
         std::string& fsUuid, std::string& fsLabel, bool untrusted) {
     fsType.clear();
     fsUuid.clear();
     fsLabel.clear();

     std::vector<std::string> cmd;
     cmd.push_back(kBlkidPath);
     cmd.push_back("-c");
     cmd.push_back("/dev/null");
     cmd.push_back(path);

     std::vector<std::string> output;
     status_t res = ForkExecvp(cmd, output, untrusted ? sBlkidUntrustedContext : sBlkidContext);
     if (res != OK) {
         LOG(WARNING) << "blkid failed to identify " << path;
         return res;
     }

     char value[128];
     for (auto line : output) {
         // Extract values from blkid output, if defined
         const char* cline = line.c_str();
         char* start = strstr(cline, "TYPE=");
         if (start != nullptr && sscanf(start + 5, "\"%127[^\"]\"", value) == 1) {
             fsType = value;
         }

         start = strstr(cline, "UUID=");
         if (start != nullptr && sscanf(start + 5, "\"%127[^\"]\"", value) == 1) {
             fsUuid = value;
         }

         start = strstr(cline, "LABEL=");
         if (start != nullptr && sscanf(start + 6, "\"%127[^\"]\"", value) == 1) {
             fsLabel = value;
         }
     }

     return OK;
 }

 status_t ReadMetadata(const std::string& path, std::string& fsType,
         std::string& fsUuid, std::string& fsLabel) {
     return readMetadata(path, fsType, fsUuid, fsLabel, false);
 }

 status_t ReadMetadataUntrusted(const std::string& path, std::string& fsType,
         std::string& fsUuid, std::string& fsLabel) {
     return readMetadata(path, fsType, fsUuid, fsLabel, true);
 }

 status_t ForkExecvp(const std::vector<std::string>& args) {
     return ForkExecvp(args, nullptr);
 }

 status_t ForkExecvp(const std::vector<std::string>& args, security_context_t context) {
     size_t argc = args.size();
     char** argv = (char**) calloc(argc, sizeof(char*));
     for (size_t i = 0; i < argc; i++) {
         argv[i] = (char*) args[i].c_str();
         if (i == 0) {
             LOG(VERBOSE) << args[i];
         } else {
             LOG(VERBOSE) << "    " << args[i];
         }
     }

     if (setexeccon(context)) {
         LOG(ERROR) << "Failed to setexeccon";
         abort();
     }
     status_t res = android_fork_execvp(argc, argv, NULL, false, true);
     if (setexeccon(nullptr)) {
         LOG(ERROR) << "Failed to setexeccon";
         abort();
     }

     free(argv);
     return res;
 }

 status_t ForkExecvp(const std::vector<std::string>& args,
         std::vector<std::string>& output) {
     return ForkExecvp(args, output, nullptr);
 }

 status_t ForkExecvp(const std::vector<std::string>& args,
         std::vector<std::string>& output, security_context_t context) {
     std::string cmd;
     for (size_t i = 0; i < args.size(); i++) {
         cmd += args[i] + " ";
         if (i == 0) {
             LOG(VERBOSE) << args[i];
         } else {
             LOG(VERBOSE) << "    " << args[i];
         }
     }
     output.clear();

     if (setexeccon(context)) {
         LOG(ERROR) << "Failed to setexeccon";
         abort();
     }
     FILE* fp = popen(cmd.c_str(), "r");
     if (setexeccon(nullptr)) {
         LOG(ERROR) << "Failed to setexeccon";
         abort();
     }

     if (!fp) {
         PLOG(ERROR) << "Failed to popen " << cmd;
         return -errno;
     }
     char line[1024];
     while (fgets(line, sizeof(line), fp) != nullptr) {
         LOG(VERBOSE) << line;
         output.push_back(std::string(line));
     }
     if (pclose(fp) != 0) {
         PLOG(ERROR) << "Failed to pclose " << cmd;
         return -errno;
     }

     return OK;
 }

 pid_t ForkExecvpAsync(const std::vector<std::string>& args) {
     size_t argc = args.size();
     char** argv = (char**) calloc(argc + 1, sizeof(char*));
     for (size_t i = 0; i < argc; i++) {
         argv[i] = (char*) args[i].c_str();
         if (i == 0) {
             LOG(VERBOSE) << args[i];
         } else {
             LOG(VERBOSE) << "    " << args[i];
         }
     }

     pid_t pid = fork();
     if (pid == 0) {
         close(STDIN_FILENO);
         close(STDOUT_FILENO);
         close(STDERR_FILENO);

         if (execvp(argv[0], argv)) {
             PLOG(ERROR) << "Failed to exec";
         }

         _exit(1);
     }

     if (pid == -1) {
         PLOG(ERROR) << "Failed to exec";
     }

     free(argv);
     return pid;
 }

 status_t ReadRandomBytes(size_t bytes, std::string& out) {
     out.clear();

     int fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY | O_CLOEXEC | O_NOFOLLOW));
     if (fd == -1) {
         return -errno;
     }

     char buf[BUFSIZ];
     size_t n;
     while ((n = TEMP_FAILURE_RETRY(read(fd, &buf[0], std::min(sizeof(buf), bytes)))) > 0) {
         out.append(buf, n);
         bytes -= n;
     }
     close(fd);

     if (bytes == 0) {
         return OK;
     } else {
         return -EIO;
     }
 }

 status_t HexToStr(const std::string& hex, std::string& str) {
     str.clear();
     bool even = true;
     char cur = 0;
     for (size_t i = 0; i < hex.size(); i++) {
         int val = 0;
         switch (hex[i]) {
         case ' ': case '-': case ':': continue;
         case 'f': case 'F': val = 15; break;
         case 'e': case 'E': val = 14; break;
         case 'd': case 'D': val = 13; break;
         case 'c': case 'C': val = 12; break;
         case 'b': case 'B': val = 11; break;
         case 'a': case 'A': val = 10; break;
         case '9': val = 9; break;
         case '8': val = 8; break;
         case '7': val = 7; break;
         case '6': val = 6; break;
         case '5': val = 5; break;
         case '4': val = 4; break;
         case '3': val = 3; break;
         case '2': val = 2; break;
         case '1': val = 1; break;
         case '0': val = 0; break;
         default: return -EINVAL;
         }

         if (even) {
             cur = val << 4;
         } else {
             cur += val;
             str.push_back(cur);
             cur = 0;
         }
         even = !even;
     }
     return even ? OK : -EINVAL;
 }

 static const char* kLookup = "0123456789abcdef";

 status_t StrToHex(const std::string& str, std::string& hex) {
     hex.clear();
     for (size_t i = 0; i < str.size(); i++) {
         hex.push_back(kLookup[(str[i] & 0xF0) >> 4]);
         hex.push_back(kLookup[str[i] & 0x0F]);
     }
     return OK;
 }

 uint64_t GetFreeBytes(const std::string& path) {
     struct statvfs sb;
     if (statvfs(path.c_str(), &sb) == 0) {
         return sb.f_bfree * sb.f_bsize;
     } else {
         return -1;
     }
 }

 // TODO: borrowed from frameworks/native/libs/diskusage/ which should
 // eventually be migrated into system/
 static int64_t stat_size(struct stat *s) {
     int64_t blksize = s->st_blksize;
     // count actual blocks used instead of nominal file size
     int64_t size = s->st_blocks * 512;

     if (blksize) {
         /* round up to filesystem block size */
         size = (size + blksize - 1) & (~(blksize - 1));
     }

     return size;
 }

 // TODO: borrowed from frameworks/native/libs/diskusage/ which should
 // eventually be migrated into system/
 int64_t calculate_dir_size(int dfd) {
     int64_t size = 0;
     struct stat s;
     DIR *d;
     struct dirent *de;

     d = fdopendir(dfd);
     if (d == NULL) {
         close(dfd);
         return 0;
     }

     while ((de = readdir(d))) {
         const char *name = de->d_name;
         if (fstatat(dfd, name, &s, AT_SYMLINK_NOFOLLOW) == 0) {
             size += stat_size(&s);
         }
         if (de->d_type == DT_DIR) {
             int subfd;

             /* always skip "." and ".." */
             if (name[0] == '.') {
                 if (name[1] == 0)
                     continue;
                 if ((name[1] == '.') && (name[2] == 0))
                     continue;
             }

             subfd = openat(dfd, name, O_RDONLY | O_DIRECTORY);
             if (subfd >= 0) {
                 size += calculate_dir_size(subfd);
             }
         }
     }
     closedir(d);
     return size;
 }

 uint64_t GetTreeBytes(const std::string& path) {
     int dirfd = open(path.c_str(), O_DIRECTORY, O_RDONLY);
     if (dirfd < 0) {
         PLOG(WARNING) << "Failed to open " << path;
         return -1;
     } else {
         uint64_t res = calculate_dir_size(dirfd);
         close(dirfd);
         return res;
     }
 }

 bool IsFilesystemSupported(const std::string& fsType) {
     std::string supported;
     if (!ReadFileToString(kProcFilesystems, &supported)) {
         PLOG(ERROR) << "Failed to read supported filesystems";
         return false;
     }
     return supported.find(fsType + "\n") != std::string::npos;
 }

 status_t WipeBlockDevice(const std::string& path) {
     status_t res = -1;
     const char* c_path = path.c_str();
     unsigned long nr_sec = 0;
     unsigned long long range[2];

     int fd = TEMP_FAILURE_RETRY(open(c_path, O_RDWR | O_CLOEXEC));
     if (fd == -1) {
         PLOG(ERROR) << "Failed to open " << path;
         goto done;
     }

     if ((ioctl(fd, BLKGETSIZE, nr_sec)) == -1) {
         PLOG(ERROR) << "Failed to determine size of " << path;
         goto done;
     }

     range[0] = 0;
     range[1] = (unsigned long long) nr_sec * 512;

     LOG(INFO) << "About to discard " << range[1] << " on " << path;
     if (ioctl(fd, BLKDISCARD, &range) == 0) {
         LOG(INFO) << "Discard success on " << path;
         res = 0;
     } else {
         PLOG(ERROR) << "Discard failure on " << path;
     }

 done:
     close(fd);
     return res;
 }

 }  // namespace vold
 }  // namespace android
	/*
	* Copyright (C) 2015 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "sehandle.h"
	#include "Utils.h"
	#include "Process.h"

	#include <base/file.h>
	#include <base/logging.h>
	#include <base/stringprintf.h>
	#include <cutils/fs.h>
	#include <private/android_filesystem_config.h>
	#include <logwrap/logwrap.h>

	#include <mutex>
	#include <dirent.h>
	#include <fcntl.h>
	#include <linux/fs.h>
	#include <stdlib.h>
	#include <sys/mount.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <sys/wait.h>
	#include <sys/statvfs.h>

	#ifndef UMOUNT_NOFOLLOW
	#define UMOUNT_NOFOLLOW 0x00000008 /* Don't follow symlink on umount */
	#endif

	using android::base::ReadFileToString;
	using android::base::StringPrintf;

	namespace android {
	namespace vold {

	security_context_t sBlkidContext = nullptr;
	security_context_t sBlkidUntrustedContext = nullptr;
	security_context_t sFsckContext = nullptr;
	security_context_t sFsckUntrustedContext = nullptr;

	static const char* kBlkidPath = "/system/bin/blkid";

	static const char* kProcFilesystems = "/proc/filesystems";

	status_t CreateDeviceNode(const std::string& path, dev_t dev) {
	const char* cpath = path.c_str();
	status_t res = 0;

	char* secontext = nullptr;
	if (sehandle) {
	if (!selabel_lookup(sehandle, &secontext, cpath, S_IFBLK)) {
	setfscreatecon(secontext);
	}
	}

	mode_t mode = 0660 \| S_IFBLK;
	if (mknod(cpath, mode, dev) < 0) {
	if (errno != EEXIST) {
	PLOG(ERROR) << "Failed to create device node for " << major(dev)
	<< ":" << minor(dev) << " at " << path;
	res = -errno;
	}
	}

	if (secontext) {
	setfscreatecon(nullptr);
	freecon(secontext);
	}

	return res;
	}

	status_t DestroyDeviceNode(const std::string& path) {
	const char* cpath = path.c_str();
	if (TEMP_FAILURE_RETRY(unlink(cpath))) {
	return -errno;
	} else {
	return OK;
	}
	}

	status_t PrepareDir(const std::string& path, mode_t mode, uid_t uid, gid_t gid) {
	const char* cpath = path.c_str();

	char* secontext = nullptr;
	if (sehandle) {
	if (!selabel_lookup(sehandle, &secontext, cpath, S_IFDIR)) {
	setfscreatecon(secontext);
	}
	}

	int res = fs_prepare_dir(cpath, mode, uid, gid);

	if (secontext) {
	setfscreatecon(nullptr);
	freecon(secontext);
	}

	if (res == 0) {
	return OK;
	} else {
	return -errno;
	}
	}

	status_t ForceUnmount(const std::string& path) {
	const char* cpath = path.c_str();
	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}
	PLOG(WARNING) << "Failed to unmount " << path;

	sleep(5);
	Process::killProcessesWithOpenFiles(cpath, SIGINT);

	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}
	PLOG(WARNING) << "Failed to unmount " << path;

	sleep(5);
	Process::killProcessesWithOpenFiles(cpath, SIGTERM);

	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}
	PLOG(WARNING) << "Failed to unmount " << path;

	sleep(5);
	Process::killProcessesWithOpenFiles(cpath, SIGKILL);

	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}
	PLOG(ERROR) << "Failed to unmount " << path;

	return -errno;
	}

	status_t BindMount(const std::string& source, const std::string& target) {
	if (::mount(source.c_str(), target.c_str(), "", MS_BIND, NULL)) {
	PLOG(ERROR) << "Failed to bind mount " << source << " to " << target;
	return -errno;
	}
	return OK;
	}

	static status_t readMetadata(const std::string& path, std::string& fsType,
	std::string& fsUuid, std::string& fsLabel, bool untrusted) {
	fsType.clear();
	fsUuid.clear();
	fsLabel.clear();

	std::vector<std::string> cmd;
	cmd.push_back(kBlkidPath);
	cmd.push_back("-c");
	cmd.push_back("/dev/null");
	cmd.push_back(path);

	std::vector<std::string> output;
	status_t res = ForkExecvp(cmd, output, untrusted ? sBlkidUntrustedContext : sBlkidContext);
	if (res != OK) {
	LOG(WARNING) << "blkid failed to identify " << path;
	return res;
	}

	char value[128];
	for (auto line : output) {
	// Extract values from blkid output, if defined
	const char* cline = line.c_str();
	char* start = strstr(cline, "TYPE=");
	if (start != nullptr && sscanf(start + 5, "\"%127[^\"]\"", value) == 1) {
	fsType = value;
	}

	start = strstr(cline, "UUID=");
	if (start != nullptr && sscanf(start + 5, "\"%127[^\"]\"", value) == 1) {
	fsUuid = value;
	}

	start = strstr(cline, "LABEL=");
	if (start != nullptr && sscanf(start + 6, "\"%127[^\"]\"", value) == 1) {
	fsLabel = value;
	}
	}

	return OK;
	}

	status_t ReadMetadata(const std::string& path, std::string& fsType,
	std::string& fsUuid, std::string& fsLabel) {
	return readMetadata(path, fsType, fsUuid, fsLabel, false);
	}

	status_t ReadMetadataUntrusted(const std::string& path, std::string& fsType,
	std::string& fsUuid, std::string& fsLabel) {
	return readMetadata(path, fsType, fsUuid, fsLabel, true);
	}

	status_t ForkExecvp(const std::vector<std::string>& args) {
	return ForkExecvp(args, nullptr);
	}

	status_t ForkExecvp(const std::vector<std::string>& args, security_context_t context) {
	size_t argc = args.size();
	char argv = (char) calloc(argc, sizeof(char*));
	for (size_t i = 0; i < argc; i++) {
	argv[i] = (char*) args[i].c_str();
	if (i == 0) {
	LOG(VERBOSE) << args[i];
	} else {
	LOG(VERBOSE) << " " << args[i];
	}
	}

	if (setexeccon(context)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}
	status_t res = android_fork_execvp(argc, argv, NULL, false, true);
	if (setexeccon(nullptr)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}

	free(argv);
	return res;
	}

	status_t ForkExecvp(const std::vector<std::string>& args,
	std::vector<std::string>& output) {
	return ForkExecvp(args, output, nullptr);
	}

	status_t ForkExecvp(const std::vector<std::string>& args,
	std::vector<std::string>& output, security_context_t context) {
	std::string cmd;
	for (size_t i = 0; i < args.size(); i++) {
	cmd += args[i] + " ";
	if (i == 0) {
	LOG(VERBOSE) << args[i];
	} else {
	LOG(VERBOSE) << " " << args[i];
	}
	}
	output.clear();

	if (setexeccon(context)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}
	FILE* fp = popen(cmd.c_str(), "r");
	if (setexeccon(nullptr)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}

	if (!fp) {
	PLOG(ERROR) << "Failed to popen " << cmd;
	return -errno;
	}
	char line[1024];
	while (fgets(line, sizeof(line), fp) != nullptr) {
	LOG(VERBOSE) << line;
	output.push_back(std::string(line));
	}
	if (pclose(fp) != 0) {
	PLOG(ERROR) << "Failed to pclose " << cmd;
	return -errno;
	}

	return OK;
	}

	pid_t ForkExecvpAsync(const std::vector<std::string>& args) {
	size_t argc = args.size();
	char argv = (char) calloc(argc + 1, sizeof(char*));
	for (size_t i = 0; i < argc; i++) {
	argv[i] = (char*) args[i].c_str();
	if (i == 0) {
	LOG(VERBOSE) << args[i];
	} else {
	LOG(VERBOSE) << " " << args[i];
	}
	}

	pid_t pid = fork();
	if (pid == 0) {
	close(STDIN_FILENO);
	close(STDOUT_FILENO);
	close(STDERR_FILENO);

	if (execvp(argv[0], argv)) {
	PLOG(ERROR) << "Failed to exec";
	}

	_exit(1);
	}

	if (pid == -1) {
	PLOG(ERROR) << "Failed to exec";
	}

	free(argv);
	return pid;
	}

	status_t ReadRandomBytes(size_t bytes, std::string& out) {
	out.clear();

	int fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY \| O_CLOEXEC \| O_NOFOLLOW));
	if (fd == -1) {
	return -errno;
	}

	char buf[BUFSIZ];
	size_t n;
	while ((n = TEMP_FAILURE_RETRY(read(fd, &buf[0], std::min(sizeof(buf), bytes)))) > 0) {
	out.append(buf, n);
	bytes -= n;
	}
	close(fd);

	if (bytes == 0) {
	return OK;
	} else {
	return -EIO;
	}
	}

	status_t HexToStr(const std::string& hex, std::string& str) {
	str.clear();
	bool even = true;
	char cur = 0;
	for (size_t i = 0; i < hex.size(); i++) {
	int val = 0;
	switch (hex[i]) {
	case ' ': case '-': case ':': continue;
	case 'f': case 'F': val = 15; break;
	case 'e': case 'E': val = 14; break;
	case 'd': case 'D': val = 13; break;
	case 'c': case 'C': val = 12; break;
	case 'b': case 'B': val = 11; break;
	case 'a': case 'A': val = 10; break;
	case '9': val = 9; break;
	case '8': val = 8; break;
	case '7': val = 7; break;
	case '6': val = 6; break;
	case '5': val = 5; break;
	case '4': val = 4; break;
	case '3': val = 3; break;
	case '2': val = 2; break;
	case '1': val = 1; break;
	case '0': val = 0; break;
	default: return -EINVAL;
	}

	if (even) {
	cur = val << 4;
	} else {
	cur += val;
	str.push_back(cur);
	cur = 0;
	}
	even = !even;
	}
	return even ? OK : -EINVAL;
	}

	static const char* kLookup = "0123456789abcdef";

	status_t StrToHex(const std::string& str, std::string& hex) {
	hex.clear();
	for (size_t i = 0; i < str.size(); i++) {
	hex.push_back(kLookup[(str[i] & 0xF0) >> 4]);
	hex.push_back(kLookup[str[i] & 0x0F]);
	}
	return OK;
	}

	uint64_t GetFreeBytes(const std::string& path) {
	struct statvfs sb;
	if (statvfs(path.c_str(), &sb) == 0) {
	return sb.f_bfree * sb.f_bsize;
	} else {
	return -1;
	}
	}

	// TODO: borrowed from frameworks/native/libs/diskusage/ which should
	// eventually be migrated into system/
	static int64_t stat_size(struct stat *s) {
	int64_t blksize = s->st_blksize;
	// count actual blocks used instead of nominal file size
	int64_t size = s->st_blocks * 512;

	if (blksize) {
	/* round up to filesystem block size */
	size = (size + blksize - 1) & (~(blksize - 1));
	}

	return size;
	}

	// TODO: borrowed from frameworks/native/libs/diskusage/ which should
	// eventually be migrated into system/
	int64_t calculate_dir_size(int dfd) {
	int64_t size = 0;
	struct stat s;
	DIR *d;
	struct dirent *de;

	d = fdopendir(dfd);
	if (d == NULL) {
	close(dfd);
	return 0;
	}

	while ((de = readdir(d))) {
	const char *name = de->d_name;
	if (fstatat(dfd, name, &s, AT_SYMLINK_NOFOLLOW) == 0) {
	size += stat_size(&s);
	}
	if (de->d_type == DT_DIR) {
	int subfd;

	/* always skip "." and ".." */
	if (name[0] == '.') {
	if (name[1] == 0)
	continue;
	if ((name[1] == '.') && (name[2] == 0))
	continue;
	}

	subfd = openat(dfd, name, O_RDONLY \| O_DIRECTORY);
	if (subfd >= 0) {
	size += calculate_dir_size(subfd);
	}
	}
	}
	closedir(d);
	return size;
	}

	uint64_t GetTreeBytes(const std::string& path) {
	int dirfd = open(path.c_str(), O_DIRECTORY, O_RDONLY);
	if (dirfd < 0) {
	PLOG(WARNING) << "Failed to open " << path;
	return -1;
	} else {
	uint64_t res = calculate_dir_size(dirfd);
	close(dirfd);
	return res;
	}
	}

	bool IsFilesystemSupported(const std::string& fsType) {
	std::string supported;
	if (!ReadFileToString(kProcFilesystems, &supported)) {
	PLOG(ERROR) << "Failed to read supported filesystems";
	return false;
	}
	return supported.find(fsType + "\n") != std::string::npos;
	}

	status_t WipeBlockDevice(const std::string& path) {
	status_t res = -1;
	const char* c_path = path.c_str();
	unsigned long nr_sec = 0;
	unsigned long long range[2];

	int fd = TEMP_FAILURE_RETRY(open(c_path, O_RDWR \| O_CLOEXEC));
	if (fd == -1) {
	PLOG(ERROR) << "Failed to open " << path;
	goto done;
	}

	if ((ioctl(fd, BLKGETSIZE, nr_sec)) == -1) {
	PLOG(ERROR) << "Failed to determine size of " << path;
	goto done;
	}

	range[0] = 0;
	range[1] = (unsigned long long) nr_sec * 512;

	LOG(INFO) << "About to discard " << range[1] << " on " << path;
	if (ioctl(fd, BLKDISCARD, &range) == 0) {
	LOG(INFO) << "Discard success on " << path;
	res = 0;
	} else {
	PLOG(ERROR) << "Discard failure on " << path;
	}

	done:
	close(fd);
	return res;
	}

	} // namespace vold
	} // namespace android