fs_mgr: libdm: add support android-verity target.

The support for android-verity makes it possible for us to test
raw verified filesystem images to be attached to android-verity
target and have it verified by the kernel.

This makes the testing of android-verity device mapper target
much easier as it doesn't _have_ to be used for root mount.

Bug: 72722987
Test:
 $ losetup /dev/block/loop0 /data/local/tmp/verity_fs.img
 $ dmctl create verity-fs android-verity 0 4200 \
   Android:7e4333f9bba00adfe0ede979e28ed1920492b40f 7:0

Change-Id: Ica6bf5c6e1fd758fdb4005fc8a09755f369a8a0f
Signed-off-by: Sandeep Patil <sspatil@google.com>

fs_mgr/libdm/dm_target.cpp

@@ -111,5 +111,9 @@ std::string DmTargetVerity::GetParameterString() const {
     return base + " " + std::to_string(optional_args_.size()) + " " + optional;
 }
 
+std::string DmTargetAndroidVerity::GetParameterString() const {
+    return keyid_ + " " + block_device_;
+}
+
 }  // namespace dm
 }  // namespace android

fs_mgr/libdm/include/libdm/dm_target.h

@@ -128,6 +128,20 @@ class DmTargetVerity final : public DmTarget {
     bool valid_;
 };
 
+class DmTargetAndroidVerity final : public DmTarget {
+  public:
+    DmTargetAndroidVerity(uint64_t start, uint64_t length, const std::string& block_device,
+                          const std::string& keyid)
+        : DmTarget(start, length), keyid_(keyid), block_device_(block_device) {}
+
+    std::string name() const override { return "android-verity"; }
+    std::string GetParameterString() const override;
+
+  private:
+    std::string keyid_;
+    std::string block_device_;
+};
+
 // This is the same as DmTargetVerity, but the table may be specified as a raw
 // string. This code exists only for fs_mgr_verity and should be avoided. Use
 // DmTargetVerity for new code instead.

fs_mgr/tools/dmctl.cpp

@@ -40,6 +40,7 @@ using DmTable = ::android::dm::DmTable;
 using DmTarget = ::android::dm::DmTarget;
 using DmTargetLinear = ::android::dm::DmTargetLinear;
 using DmTargetZero = ::android::dm::DmTargetZero;
+using DmTargetAndroidVerity = ::android::dm::DmTargetAndroidVerity;
 using DmTargetTypeInfo = ::android::dm::DmTargetTypeInfo;
 using DmBlockDevice = ::android::dm::DeviceMapper::DmBlockDevice;
 
@@ -96,6 +97,16 @@ class TargetParser final {
             }
             return std::make_unique<DmTargetLinear>(start_sector, num_sectors, block_device,
                                                     physical_sector);
+        } else if (target_type == "android-verity") {
+            if (!HasArgs(2)) {
+                std::cerr << "Expected \"android-verity\" <public-key-id> <block_device>"
+                          << std::endl;
+                return nullptr;
+            }
+            std::string keyid = NextArg();
+            std::string block_device = NextArg();
+            return std::make_unique<DmTargetAndroidVerity>(start_sector, num_sectors, keyid,
+                                                           block_device);
         } else {
             std::cerr << "Unrecognized target type: " << target_type << std::endl;
             return nullptr;