Merge "Expand virtio_block check to other virtual devices" into pie-gsipie-gsi

4 files changed, 41 insertions, 43 deletions

diff --git a/Utils.cpp b/Utils.cpp
index d17de626..959658b4 100644
--- a/Utils.cpp
+++ b/Utils.cpp
@@ -65,6 +65,7 @@ bool sSleepOnUnmount = true;
 static const char* kBlkidPath = "/system/bin/blkid";
 static const char* kKeyPath = "/data/misc/vold";
 
+static const char* kProcDevices = "/proc/devices";
 static const char* kProcFilesystems = "/proc/filesystems";
 
 // Lock used to protect process-level SELinux changes from racing with each
@@ -732,8 +733,39 @@ bool Readlinkat(int dirfd, const std::string& path, std::string* result) {
     }
 }
 
-bool IsRunningInEmulator() {
-    return android::base::GetBoolProperty("ro.kernel.qemu", false);
+static unsigned int GetMajorBlockVirtioBlk() {
+    std::string devices;
+    if (!ReadFileToString(kProcDevices, &devices)) {
+        PLOG(ERROR) << "Unable to open /proc/devices";
+        return 0;
+    }
+
+    bool blockSection = false;
+    for (auto line : android::base::Split(devices, "\n")) {
+        if (line == "Block devices:") {
+            blockSection = true;
+        } else if (line == "Character devices:") {
+            blockSection = false;
+        } else if (blockSection) {
+            auto tokens = android::base::Split(line, " ");
+            if (tokens.size() == 2 && tokens[1] == "virtblk") {
+                return std::stoul(tokens[0]);
+            }
+        }
+    }
+
+    return 0;
+}
+
+bool IsVirtioBlkDevice(unsigned int major) {
+    // Most virtualized platforms expose block devices with the virtio-blk
+    // block device driver. Unfortunately, this driver does not use a fixed
+    // major number, but relies on the kernel to assign one from a specific
+    // range of block majors, which are allocated for "LOCAL/EXPERIMENAL USE"
+    // per Documentation/devices.txt. This is true even for the latest Linux
+    // kernel (4.4; see init() in drivers/block/virtio_blk.c).
+    static unsigned int kMajorBlockVirtioBlk = GetMajorBlockVirtioBlk();
+    return kMajorBlockVirtioBlk && major == kMajorBlockVirtioBlk;
 }
 
 // TODO(118708649): fix duplication with init/util.h
diff --git a/Utils.h b/Utils.h
index fb0d3893..234de70a 100644
--- a/Utils.h
+++ b/Utils.h
@@ -123,8 +123,8 @@ status_t RestoreconRecursive(const std::string& path);
 // TODO: promote to android::base
 bool Readlinkat(int dirfd, const std::string& path, std::string* result);
 
-/* Checks if Android is running in QEMU */
-bool IsRunningInEmulator();
+// Handles dynamic major assignment for virtio-block
+bool IsVirtioBlkDevice(unsigned int major);
 
 status_t WaitForFile(const char* filename, std::chrono::nanoseconds timeout);
 
diff --git a/VolumeManager.cpp b/VolumeManager.cpp
index 21e132a3..cf36c698 100644
--- a/VolumeManager.cpp
+++ b/VolumeManager.cpp
@@ -76,8 +76,6 @@ static const char* kPropVirtualDisk = "persist.sys.virtual_disk";
 static const unsigned int kSizeVirtualDisk = 536870912;
 
 static const unsigned int kMajorBlockMmc = 179;
-static const unsigned int kMajorBlockExperimentalMin = 240;
-static const unsigned int kMajorBlockExperimentalMax = 254;
 
 VolumeManager *VolumeManager::sInstance = NULL;
 
@@ -196,13 +194,10 @@ void VolumeManager::handleBlockEvent(NetlinkEvent *evt) {
         for (const auto& source : mDiskSources) {
             if (source->matches(eventPath)) {
                 // For now, assume that MMC and virtio-blk (the latter is
-                // emulator-specific; see Disk.cpp for details) devices are SD,
-                // and that everything else is USB
+                // specific to virtual platforms; see Utils.cpp for details)
+                // devices are SD, and that everything else is USB
                 int flags = source->getFlags();
-                if (major == kMajorBlockMmc
-                    || (android::vold::IsRunningInEmulator()
-                    && major >= (int) kMajorBlockExperimentalMin
-                    && major <= (int) kMajorBlockExperimentalMax)) {
+                if (major == kMajorBlockMmc || android::vold::IsVirtioBlkDevice(major)) {
                     flags |= android::vold::Disk::Flags::kSd;
                 } else {
                     flags |= android::vold::Disk::Flags::kUsb;
diff --git a/model/Disk.cpp b/model/Disk.cpp
index d7b19ac3..7b77af28 100644
--- a/model/Disk.cpp
+++ b/model/Disk.cpp
@@ -74,8 +74,6 @@ static const unsigned int kMajorBlockScsiN = 133;
 static const unsigned int kMajorBlockScsiO = 134;
 static const unsigned int kMajorBlockScsiP = 135;
 static const unsigned int kMajorBlockMmc = 179;
-static const unsigned int kMajorBlockExperimentalMin = 240;
-static const unsigned int kMajorBlockExperimentalMax = 254;
 
 static const char* kGptBasicData = "EBD0A0A2-B9E5-4433-87C0-68B6B72699C7";
 static const char* kGptAndroidMeta = "19A710A2-B3CA-11E4-B026-10604B889DCF";
@@ -87,33 +85,6 @@ enum class Table {
     kGpt,
 };
 
-static bool isVirtioBlkDevice(unsigned int major) {
-    /*
-     * The new emulator's "ranchu" virtual board no longer includes a goldfish
-     * MMC-based SD card device; instead, it emulates SD cards with virtio-blk,
-     * which has been supported by upstream kernel and QEMU for quite a while.
-     * Unfortunately, the virtio-blk block device driver does not use a fixed
-     * major number, but relies on the kernel to assign one from a specific
-     * range of block majors, which are allocated for "LOCAL/EXPERIMENAL USE"
-     * per Documentation/devices.txt. This is true even for the latest Linux
-     * kernel (4.4; see init() in drivers/block/virtio_blk.c).
-     *
-     * This makes it difficult for vold to detect a virtio-blk based SD card.
-     * The current solution checks two conditions (both must be met):
-     *
-     *  a) If the running environment is the emulator;
-     *  b) If the major number is an experimental block device major number (for
-     *     x86/x86_64 3.10 ranchu kernels, virtio-blk always gets major number
-     *     253, but it is safer to match the range than just one value).
-     *
-     * Other conditions could be used, too, e.g. the hardware name should be
-     * "ranchu", the device's sysfs path should end with "/block/vd[d-z]", etc.
-     * But just having a) and b) is enough for now.
-     */
-    return IsRunningInEmulator() && major >= kMajorBlockExperimentalMin
-            && major <= kMajorBlockExperimentalMax;
-}
-
 Disk::Disk(const std::string& eventPath, dev_t device,
         const std::string& nickname, int flags) :
         mDevice(device), mSize(-1), mNickname(nickname), mFlags(flags), mCreated(
@@ -286,7 +257,7 @@ status_t Disk::readMetadata() {
         break;
     }
     default: {
-        if (isVirtioBlkDevice(majorId)) {
+        if (IsVirtioBlkDevice(majorId)) {
             LOG(DEBUG) << "Recognized experimental block major ID " << majorId
                     << " as virtio-blk (emulator's virtual SD card device)";
             mLabel = "Virtual";
@@ -571,7 +542,7 @@ int Disk::getMaxMinors() {
         return std::stoi(tmp);
     }
     default: {
-        if (isVirtioBlkDevice(majorId)) {
+        if (IsVirtioBlkDevice(majorId)) {
             // drivers/block/virtio_blk.c has "#define PART_BITS 4", so max is
             // 2^4 - 1 = 15
             return 15;