1/*
2 ** Copyright 2016, The Android Open Source Project
3 **
4 ** Licensed under the Apache License, Version 2.0 (the "License");
5 ** you may not use this file except in compliance with the License.
6 ** You may obtain a copy of the License at
7 **
8 **     http://www.apache.org/licenses/LICENSE-2.0
9 **
10 ** Unless required by applicable law or agreed to in writing, software
11 ** distributed under the License is distributed on an "AS IS" BASIS,
12 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 ** See the License for the specific language governing permissions and
14 ** limitations under the License.
15 */
16
17#include <fcntl.h>
18#include <linux/unistd.h>
19#include <sys/mount.h>
20#include <sys/wait.h>
21
22#include <sstream>
23
24#include <android-base/logging.h>
25#include <android-base/macros.h>
26#include <android-base/stringprintf.h>
27
28#include "installd_constants.h"
29#include "otapreopt_utils.h"
30
31#ifndef LOG_TAG
32#define LOG_TAG "otapreopt"
33#endif
34
35using android::base::StringPrintf;
36
37namespace android {
38namespace installd {
39
40static void CloseDescriptor(int fd) {
41    if (fd >= 0) {
42        int result = close(fd);
43        UNUSED(result);  // Ignore result. Printing to logcat will open a new descriptor
44                         // that we do *not* want.
45    }
46}
47
48static void CloseDescriptor(const char* descriptor_string) {
49    int fd = -1;
50    std::istringstream stream(descriptor_string);
51    stream >> fd;
52    if (!stream.fail()) {
53        CloseDescriptor(fd);
54    }
55}
56
57// Entry for otapreopt_chroot. Expected parameters are:
58//   [cmd] [status-fd] [target-slot] "dexopt" [dexopt-params]
59// The file descriptor denoted by status-fd will be closed. The rest of the parameters will
60// be passed on to otapreopt in the chroot.
61static int otapreopt_chroot(const int argc, char **arg) {
62    // Validate arguments
63    // We need the command, status channel and target slot, at a minimum.
64    if(argc < 3) {
65        PLOG(ERROR) << "Not enough arguments.";
66        exit(208);
67    }
68    // Close all file descriptors. They are coming from the caller, we do not want to pass them
69    // on across our fork/exec into a different domain.
70    // 1) Default descriptors.
71    CloseDescriptor(STDIN_FILENO);
72    CloseDescriptor(STDOUT_FILENO);
73    CloseDescriptor(STDERR_FILENO);
74    // 2) The status channel.
75    CloseDescriptor(arg[1]);
76
77    // We need to run the otapreopt tool from the postinstall partition. As such, set up a
78    // mount namespace and change root.
79
80    // Create our own mount namespace.
81    if (unshare(CLONE_NEWNS) != 0) {
82        PLOG(ERROR) << "Failed to unshare() for otapreopt.";
83        exit(200);
84    }
85
86    // Make postinstall private, so that our changes don't propagate.
87    if (mount("", "/postinstall", nullptr, MS_PRIVATE, nullptr) != 0) {
88        PLOG(ERROR) << "Failed to mount private.";
89        exit(201);
90    }
91
92    // Bind mount necessary directories.
93    constexpr const char* kBindMounts[] = {
94            "/data", "/dev", "/proc", "/sys"
95    };
96    for (size_t i = 0; i < arraysize(kBindMounts); ++i) {
97        std::string trg = StringPrintf("/postinstall%s", kBindMounts[i]);
98        if (mount(kBindMounts[i], trg.c_str(), nullptr, MS_BIND, nullptr) != 0) {
99            PLOG(ERROR) << "Failed to bind-mount " << kBindMounts[i];
100            exit(202);
101        }
102    }
103
104    // Try to mount the vendor partition. update_engine doesn't do this for us, but we
105    // want it for vendor APKs.
106    // Notes:
107    //  1) We pretty much guess a name here and hope to find the partition by name.
108    //     It is just as complicated and brittle to scan /proc/mounts. But this requires
109    //     validating the target-slot so as not to try to mount some totally random path.
110    //  2) We're in a mount namespace here, so when we die, this will be cleaned up.
111    //  3) Ignore errors. Printing anything at this stage will open a file descriptor
112    //     for logging.
113    if (!ValidateTargetSlotSuffix(arg[2])) {
114        LOG(ERROR) << "Target slot suffix not legal: " << arg[2];
115        exit(207);
116    }
117    {
118      std::string vendor_partition = StringPrintf("/dev/block/by-name/vendor%s",
119                                                  arg[2]);
120      int vendor_result = mount(vendor_partition.c_str(),
121                                "/postinstall/vendor",
122                                "ext4",
123                                MS_RDONLY,
124                                /* data */ nullptr);
125      UNUSED(vendor_result);
126    }
127
128    // Try to mount the product partition. update_engine doesn't do this for us, but we
129    // want it for product APKs. Same notes as vendor above.
130    {
131      std::string product_partition = StringPrintf("/dev/block/by-name/product%s",
132                                                   arg[2]);
133      int product_result = mount(product_partition.c_str(),
134                                 "/postinstall/product",
135                                 "ext4",
136                                 MS_RDONLY,
137                                 /* data */ nullptr);
138      UNUSED(product_result);
139    }
140
141    // Chdir into /postinstall.
142    if (chdir("/postinstall") != 0) {
143        PLOG(ERROR) << "Unable to chdir into /postinstall.";
144        exit(203);
145    }
146
147    // Make /postinstall the root in our mount namespace.
148    if (chroot(".")  != 0) {
149        PLOG(ERROR) << "Failed to chroot";
150        exit(204);
151    }
152
153    if (chdir("/") != 0) {
154        PLOG(ERROR) << "Unable to chdir into /.";
155        exit(205);
156    }
157
158    // Now go on and run otapreopt.
159
160    // Incoming:  cmd + status-fd + target-slot + cmd... + null      | Incoming | = argc + 1
161    // Outgoing:  cmd             + target-slot + cmd... + null      | Outgoing | = argc
162    const char** argv = new const char*[argc];
163
164    argv[0] = "/system/bin/otapreopt";
165
166    // The first parameter is the status file descriptor, skip.
167    for (size_t i = 2; i <= static_cast<size_t>(argc); ++i) {
168        argv[i - 1] = arg[i];
169    }
170
171    execv(argv[0], static_cast<char * const *>(const_cast<char**>(argv)));
172    PLOG(ERROR) << "execv(OTAPREOPT) failed.";
173    exit(99);
174}
175
176}  // namespace installd
177}  // namespace android
178
179int main(const int argc, char *argv[]) {
180    return android::installd::otapreopt_chroot(argc, argv);
181}
182