Add experimental daemon for handling dm-user requests.
Right now this is open-coded. As the API stabilizes it will be
integrated into libdm.
Bug: 154536437
Test: manual test
Change-Id: I07bb811b6fb80d85d55e218d788023634c8158b7
diff --git a/fs_mgr/libdm/Android.bp b/fs_mgr/libdm/Android.bp
index 58241b3..e425284 100644
--- a/fs_mgr/libdm/Android.bp
+++ b/fs_mgr/libdm/Android.bp
@@ -42,6 +42,7 @@
enabled: false,
},
},
+ ramdisk_available: true,
}
filegroup {
diff --git a/fs_mgr/libsnapshot/Android.bp b/fs_mgr/libsnapshot/Android.bp
index 95301ff..eaef180 100644
--- a/fs_mgr/libsnapshot/Android.bp
+++ b/fs_mgr/libsnapshot/Android.bp
@@ -310,3 +310,36 @@
auto_gen_config: true,
require_root: true,
}
+
+cc_defaults {
+ name: "snapuserd_defaults",
+ srcs: [
+ "snapuserd.cpp",
+ ],
+
+ cflags: [
+ "-Wall",
+ "-Werror"
+ ],
+
+ static_libs: [
+ "libbase",
+ "liblog",
+ "libdm",
+ ],
+}
+
+cc_binary {
+ name: "snapuserd",
+ defaults: ["snapuserd_defaults"],
+}
+
+cc_binary {
+ name: "snapuserd_ramdisk",
+ stem: "snapuserd",
+ defaults: ["snapuserd_defaults"],
+
+ ramdisk: true,
+ static_executable: true,
+ system_shared_libs: [],
+}
diff --git a/fs_mgr/libsnapshot/snapuserd.cpp b/fs_mgr/libsnapshot/snapuserd.cpp
new file mode 100644
index 0000000..a6ff4fd
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright (C) 2020 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 <linux/types.h>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/stringprintf.h>
+#include <android-base/unique_fd.h>
+#include <libdm/dm.h>
+
+using android::base::unique_fd;
+
+#define DM_USER_MAP_READ 0
+#define DM_USER_MAP_WRITE 1
+
+struct dm_user_message {
+ __u64 seq;
+ __u64 type;
+ __u64 flags;
+ __u64 sector;
+ __u64 len;
+ __u8 buf[];
+};
+
+using namespace android::dm;
+
+static int daemon_main(const std::string& device) {
+ unique_fd block_fd(open(device.c_str(), O_RDWR));
+ if (block_fd < 0) {
+ PLOG(ERROR) << "Unable to open " << device;
+ return 1;
+ }
+
+ unique_fd ctrl_fd(open("/dev/dm-user", O_RDWR));
+ if (ctrl_fd < 0) {
+ PLOG(ERROR) << "Unable to open /dev/dm-user";
+ return 1;
+ }
+
+ size_t buf_size = 1UL << 16;
+ auto buf = std::make_unique<char>(buf_size);
+
+ /* Just keeps pumping messages between userspace and the kernel. We won't
+ * actually be doing anything, but the sequence numbers line up so it'll at
+ * least make forward progress. */
+ while (true) {
+ struct dm_user_message* msg = (struct dm_user_message*)buf.get();
+
+ memset(buf.get(), 0, buf_size);
+
+ ssize_t readed = read(ctrl_fd.get(), buf.get(), buf_size);
+ if (readed < 0) {
+ PLOG(ERROR) << "Control read failed, trying with more space";
+ buf_size *= 2;
+ buf = std::make_unique<char>(buf_size);
+ continue;
+ }
+
+ LOG(DEBUG) << android::base::StringPrintf("read() from dm-user returned %d bytes:",
+ (int)readed);
+ LOG(DEBUG) << android::base::StringPrintf(" msg->seq: 0x%016llx", msg->seq);
+ LOG(DEBUG) << android::base::StringPrintf(" msg->type: 0x%016llx", msg->type);
+ LOG(DEBUG) << android::base::StringPrintf(" msg->flags: 0x%016llx", msg->flags);
+ LOG(DEBUG) << android::base::StringPrintf(" msg->sector: 0x%016llx", msg->sector);
+ LOG(DEBUG) << android::base::StringPrintf(" msg->len: 0x%016llx", msg->len);
+
+ switch (msg->type) {
+ case DM_USER_MAP_READ: {
+ LOG(DEBUG) << android::base::StringPrintf(
+ "Responding to read of sector %lld with %lld bytes data", msg->sector,
+ msg->len);
+
+ if ((sizeof(*msg) + msg->len) > buf_size) {
+ auto old_buf = std::move(buf);
+ buf_size = sizeof(*msg) + msg->len;
+ buf = std::make_unique<char>(buf_size);
+ memcpy(buf.get(), old_buf.get(), sizeof(*msg));
+ msg = (struct dm_user_message*)buf.get();
+ }
+
+ if (lseek(block_fd.get(), msg->sector * 512, SEEK_SET) < 0) {
+ PLOG(ERROR) << "lseek failed: " << device;
+ return 7;
+ }
+ if (!android::base::ReadFully(block_fd.get(), msg->buf, msg->len)) {
+ PLOG(ERROR) << "read failed: " << device;
+ return 7;
+ }
+
+ if (!android::base::WriteFully(ctrl_fd.get(), buf.get(), sizeof(*msg) + msg->len)) {
+ PLOG(ERROR) << "write control failed";
+ return 3;
+ }
+ break;
+ }
+
+ case DM_USER_MAP_WRITE:
+ abort();
+ break;
+ }
+
+ LOG(DEBUG) << "read() finished, next message";
+ }
+
+ return 0;
+}
+
+int main([[maybe_unused]] int argc, char** argv) {
+ android::base::InitLogging(argv, &android::base::KernelLogger);
+ daemon_main(argv[1]);
+ return 0;
+}