Merge "Use apex/com.android.resolv/lib64/libned_resolv.so by default"
diff --git a/base/file.cpp b/base/file.cpp
index d5bb7fe..2f4a517 100644
--- a/base/file.cpp
+++ b/base/file.cpp
@@ -22,6 +22,7 @@
 #include <libgen.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
diff --git a/base/logging.cpp b/base/logging.cpp
index bd09069..f89168c 100644
--- a/base/logging.cpp
+++ b/base/logging.cpp
@@ -417,6 +417,14 @@
   }
   std::string msg(data_->ToString());
 
+  if (data_->GetSeverity() == FATAL) {
+#ifdef __ANDROID__
+    // Set the bionic abort message early to avoid liblog doing it
+    // with the individual lines, so that we get the whole message.
+    android_set_abort_message(msg.c_str());
+#endif
+  }
+
   {
     // Do the actual logging with the lock held.
     std::lock_guard<std::mutex> lock(LoggingLock());
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index fee0857..b717aef 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -1541,7 +1541,7 @@
         return false;
     }
     auto path = find_item_given_name("super_empty.img");
-    if (path.empty()) {
+    if (path.empty() || access(path.c_str(), R_OK)) {
         return false;
     }
     auto metadata = android::fs_mgr::ReadFromImageFile(path);
diff --git a/fs_mgr/README.overlayfs.md b/fs_mgr/README.overlayfs.md
index 2d42d6c..fbb5f5d 100644
--- a/fs_mgr/README.overlayfs.md
+++ b/fs_mgr/README.overlayfs.md
@@ -89,6 +89,18 @@
   if higher than 4.6.
 - *adb enable-verity* will free up overlayfs and as a bonus the
   device will be reverted pristine to before any content was updated.
+  Update engine does not take advantage of this, will perform a full OTA.
+- Update engine will not run if *fs_mgr_overlayfs_is_setup*() reports
+  true as adb remount overrides are incompatable with an OTA for
+  multiple reasons.
+  NB: This is not a problem for fastbootd or recovery as overrides are
+  disabled for those special boot scenarios.
+- For implementation simplicity on retrofit dynamic partition devices,
+  take the whole alternate super (eg: if "*a*" slot, then the whole of
+  "*system_b*").
+  Since landing a filesystem on the alternate super physical device
+  without differentiating if it is setup to support logical or physical,
+  the alternate slot metadata and previous content will be lost.
 - If dynamic partitions runs out of space, resizing a logical
   partition larger may fail because of the scratch partition.
   If this happens, either fastboot flashall or adb enable-verity can
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 70a54d9..60ce452 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -1005,8 +1005,9 @@
     for (i = 0; i < fstab->num_entries; i++) {
         /* Don't mount entries that are managed by vold or not for the mount mode*/
         if ((fstab->recs[i].fs_mgr_flags & (MF_VOLDMANAGED | MF_RECOVERYONLY)) ||
-             ((mount_mode == MOUNT_MODE_LATE) && !fs_mgr_is_latemount(&fstab->recs[i])) ||
-             ((mount_mode == MOUNT_MODE_EARLY) && fs_mgr_is_latemount(&fstab->recs[i]))) {
+            ((mount_mode == MOUNT_MODE_LATE) && !fs_mgr_is_latemount(&fstab->recs[i])) ||
+            ((mount_mode == MOUNT_MODE_EARLY) && fs_mgr_is_latemount(&fstab->recs[i])) ||
+            fs_mgr_is_first_stage_mount(&fstab->recs[i])) {
             continue;
         }
 
diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/fs_mgr_fstab.cpp
index 31b0944..0fde22e 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/fs_mgr_fstab.cpp
@@ -57,7 +57,7 @@
 
 struct flag_list {
     const char *name;
-    int flag;
+    unsigned int flag;
 };
 
 static struct flag_list mount_flags[] = {
@@ -102,6 +102,7 @@
         {"formattable", MF_FORMATTABLE},
         {"slotselect", MF_SLOTSELECT},
         {"nofail", MF_NOFAIL},
+        {"first_stage_mount", MF_FIRST_STAGE_MOUNT},
         {"latemount", MF_LATEMOUNT},
         {"reservedsize=", MF_RESERVEDSIZE},
         {"quota", MF_QUOTA},
@@ -998,6 +999,10 @@
     return fstab->fs_mgr_flags & MF_NOFAIL;
 }
 
+int fs_mgr_is_first_stage_mount(const struct fstab_rec* fstab) {
+    return fstab->fs_mgr_flags & MF_FIRST_STAGE_MOUNT;
+}
+
 int fs_mgr_is_latemount(const struct fstab_rec* fstab) {
     return fstab->fs_mgr_flags & MF_LATEMOUNT;
 }
diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 57e984d..649c8bf 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -74,7 +74,7 @@
     return false;
 }
 
-bool fs_mgr_overlayfs_mount_all(const std::vector<const fstab_rec*>&) {
+bool fs_mgr_overlayfs_mount_all(const std::vector<fstab_rec*>&) {
     return false;
 }
 
@@ -82,7 +82,7 @@
     return {};
 }
 
-std::vector<std::string> fs_mgr_overlayfs_required_devices(const std::vector<const fstab_rec*>&) {
+std::vector<std::string> fs_mgr_overlayfs_required_devices(const std::vector<fstab_rec*>&) {
     return {};
 }
 
@@ -96,6 +96,10 @@
     return false;
 }
 
+bool fs_mgr_overlayfs_is_setup() {
+    return false;
+}
+
 #else  // ALLOW_ADBD_DISABLE_VERITY == 0
 
 namespace {
@@ -382,8 +386,10 @@
     return SlotNumberForSlotSuffix(fs_mgr_get_slot_suffix());
 }
 
+const auto kPhysicalDevice = "/dev/block/by-name/"s;
+
 std::string fs_mgr_overlayfs_super_device(uint32_t slot_number) {
-    return "/dev/block/by-name/" + fs_mgr_get_super_partition_name(slot_number);
+    return kPhysicalDevice + fs_mgr_get_super_partition_name(slot_number);
 }
 
 bool fs_mgr_overlayfs_has_logical(const fstab* fstab) {
@@ -641,19 +647,50 @@
 std::string fs_mgr_overlayfs_scratch_device() {
     if (!scratch_device_cache.empty()) return scratch_device_cache;
 
-    auto& dm = DeviceMapper::Instance();
-    const auto partition_name = android::base::Basename(kScratchMountPoint);
-    std::string path;
-    if (!dm.GetDmDevicePathByName(partition_name, &path)) return "";
+    // Is this a multiple super device (retrofit)?
+    auto slot_number = fs_mgr_overlayfs_slot_number();
+    auto super_device = fs_mgr_overlayfs_super_device(slot_number);
+    auto path = fs_mgr_overlayfs_super_device(slot_number == 0);
+    if (super_device == path) {
+        // Create from within single super device;
+        auto& dm = DeviceMapper::Instance();
+        const auto partition_name = android::base::Basename(kScratchMountPoint);
+        if (!dm.GetDmDevicePathByName(partition_name, &path)) return "";
+    }
     return scratch_device_cache = path;
 }
 
-// Create and mount kScratchMountPoint storage if we have logical partitions
-bool fs_mgr_overlayfs_setup_scratch(const fstab* fstab, bool* change) {
-    if (fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) return true;
-    auto mnt_type = fs_mgr_overlayfs_scratch_mount_type();
-    auto scratch_device = fs_mgr_overlayfs_scratch_device();
-    auto partition_create = !fs_mgr_rw_access(scratch_device);
+bool fs_mgr_overlayfs_make_scratch(const std::string& scratch_device, const std::string& mnt_type) {
+    // Force mkfs by design for overlay support of adb remount, simplify and
+    // thus do not rely on fsck to correct problems that could creep in.
+    auto command = ""s;
+    if (mnt_type == "f2fs") {
+        command = kMkF2fs + " -w 4096 -f -d1 -l" + android::base::Basename(kScratchMountPoint);
+    } else if (mnt_type == "ext4") {
+        command = kMkExt4 + " -b 4096 -t ext4 -m 0 -O has_journal -M " + kScratchMountPoint;
+    } else {
+        errno = ESRCH;
+        LERROR << mnt_type << " has no mkfs cookbook";
+        return false;
+    }
+    command += " " + scratch_device;
+    auto ret = system(command.c_str());
+    if (ret) {
+        LERROR << "make " << mnt_type << " filesystem on " << scratch_device << " return=" << ret;
+        return false;
+    }
+    return true;
+}
+
+bool fs_mgr_overlayfs_create_scratch(const fstab* fstab, std::string* scratch_device,
+                                     bool* partition_exists, bool* change) {
+    *scratch_device = fs_mgr_overlayfs_scratch_device();
+    *partition_exists = fs_mgr_rw_access(*scratch_device);
+    auto partition_create = !*partition_exists;
+    // Do we need to create a logical "scratch" partition?
+    if (!partition_create && android::base::StartsWith(*scratch_device, kPhysicalDevice)) {
+        return true;
+    }
     auto slot_number = fs_mgr_overlayfs_slot_number();
     auto super_device = fs_mgr_overlayfs_super_device(slot_number);
     if (!fs_mgr_rw_access(super_device)) return false;
@@ -665,9 +702,9 @@
     }
     const auto partition_name = android::base::Basename(kScratchMountPoint);
     auto partition = builder->FindPartition(partition_name);
-    auto partition_exists = partition != nullptr;
+    *partition_exists = partition != nullptr;
     auto changed = false;
-    if (!partition_exists) {
+    if (!*partition_exists) {
         partition = builder->AddPartition(partition_name, LP_PARTITION_ATTR_NONE);
         if (!partition) {
             LERROR << "create " << partition_name;
@@ -703,7 +740,7 @@
                 }
                 if (!partition_create) DestroyLogicalPartition(partition_name, 10s);
                 changed = true;
-                partition_exists = false;
+                *partition_exists = false;
             }
         }
     }
@@ -720,39 +757,36 @@
 
     if (changed || partition_create) {
         if (!CreateLogicalPartition(super_device, slot_number, partition_name, true, 0s,
-                                    &scratch_device))
+                                    scratch_device))
             return false;
 
         if (change) *change = true;
     }
+    return true;
+}
 
+// Create and mount kScratchMountPoint storage if we have logical partitions
+bool fs_mgr_overlayfs_setup_scratch(const fstab* fstab, bool* change) {
+    if (fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) return true;
+
+    std::string scratch_device;
+    bool partition_exists;
+    if (!fs_mgr_overlayfs_create_scratch(fstab, &scratch_device, &partition_exists, change)) {
+        return false;
+    }
+
+    // If the partition exists, assume first that it can be mounted.
+    auto mnt_type = fs_mgr_overlayfs_scratch_mount_type();
     if (partition_exists) {
         if (fs_mgr_overlayfs_mount_scratch(scratch_device, mnt_type)) {
             if (change) *change = true;
             return true;
         }
-        // partition existed, but was not initialized;
+        // partition existed, but was not initialized; fall through to make it.
         errno = 0;
     }
 
-    // Force mkfs by design for overlay support of adb remount, simplify and
-    // thus do not rely on fsck to correct problems that could creep in.
-    auto command = ""s;
-    if (mnt_type == "f2fs") {
-        command = kMkF2fs + " -w 4096 -f -d1 -l" + android::base::Basename(kScratchMountPoint);
-    } else if (mnt_type == "ext4") {
-        command = kMkExt4 + " -b 4096 -t ext4 -m 0 -O has_journal -M " + kScratchMountPoint;
-    } else {
-        errno = ESRCH;
-        LERROR << mnt_type << " has no mkfs cookbook";
-        return false;
-    }
-    command += " " + scratch_device;
-    auto ret = system(command.c_str());
-    if (ret) {
-        LERROR << "make " << mnt_type << " filesystem on " << scratch_device << " return=" << ret;
-        return false;
-    }
+    if (!fs_mgr_overlayfs_make_scratch(scratch_device, mnt_type)) return false;
 
     if (change) *change = true;
 
@@ -762,6 +796,7 @@
 bool fs_mgr_overlayfs_scratch_can_be_mounted(const std::string& scratch_device) {
     if (scratch_device.empty()) return false;
     if (fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) return false;
+    if (android::base::StartsWith(scratch_device, kPhysicalDevice)) return true;
     if (fs_mgr_rw_access(scratch_device)) return true;
     auto slot_number = fs_mgr_overlayfs_slot_number();
     auto super_device = fs_mgr_overlayfs_super_device(slot_number);
@@ -805,7 +840,7 @@
     return ret;
 }
 
-bool fs_mgr_overlayfs_mount_all(const std::vector<const fstab_rec*>& fsrecs) {
+bool fs_mgr_overlayfs_mount_all(const std::vector<fstab_rec*>& fsrecs) {
     std::vector<fstab_rec> recs;
     for (const auto& rec : fsrecs) recs.push_back(*rec);
     fstab fstab = {static_cast<int>(fsrecs.size()), &recs[0]};
@@ -828,8 +863,7 @@
     return {};
 }
 
-std::vector<std::string> fs_mgr_overlayfs_required_devices(
-        const std::vector<const fstab_rec*>& fsrecs) {
+std::vector<std::string> fs_mgr_overlayfs_required_devices(const std::vector<fstab_rec*>& fsrecs) {
     std::vector<fstab_rec> recs;
     for (const auto& rec : fsrecs) recs.push_back(*rec);
     fstab fstab = {static_cast<int>(fsrecs.size()), &recs[0]};
@@ -924,6 +958,17 @@
     return ret;
 }
 
+bool fs_mgr_overlayfs_is_setup() {
+    if (fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) return true;
+    std::unique_ptr<fstab, decltype(&fs_mgr_free_fstab)> fstab(fs_mgr_read_fstab_default(),
+                                                               fs_mgr_free_fstab);
+    if (fs_mgr_overlayfs_invalid(fstab.get())) return false;
+    for (const auto& mount_point : fs_mgr_candidate_list(fstab.get())) {
+        if (fs_mgr_overlayfs_already_mounted(mount_point)) return true;
+    }
+    return false;
+}
+
 #endif  // ALLOW_ADBD_DISABLE_VERITY != 0
 
 bool fs_mgr_has_shared_blocks(const std::string& mount_point, const std::string& dev) {
diff --git a/fs_mgr/fs_mgr_priv.h b/fs_mgr/fs_mgr_priv.h
index 84e4ce5..faef34b 100644
--- a/fs_mgr/fs_mgr_priv.h
+++ b/fs_mgr/fs_mgr_priv.h
@@ -118,6 +118,8 @@
 #define MF_LOGICAL        0x10000000
 #define MF_CHECKPOINT_BLK 0x20000000
 #define MF_CHECKPOINT_FS  0x40000000
+#define MF_FIRST_STAGE_MOUNT \
+                          0x80000000
 // clang-format on
 
 #define DM_BUF_SIZE 4096
diff --git a/fs_mgr/include/fs_mgr_overlayfs.h b/fs_mgr/include/fs_mgr_overlayfs.h
index deaf4cb..0dd9121 100644
--- a/fs_mgr/include/fs_mgr_overlayfs.h
+++ b/fs_mgr/include/fs_mgr_overlayfs.h
@@ -22,13 +22,13 @@
 #include <vector>
 
 bool fs_mgr_overlayfs_mount_all(fstab* fstab);
-bool fs_mgr_overlayfs_mount_all(const std::vector<const fstab_rec*>& fstab);
+bool fs_mgr_overlayfs_mount_all(const std::vector<fstab_rec*>& fstab);
 std::vector<std::string> fs_mgr_overlayfs_required_devices(fstab* fstab);
-std::vector<std::string> fs_mgr_overlayfs_required_devices(
-        const std::vector<const fstab_rec*>& fstab);
+std::vector<std::string> fs_mgr_overlayfs_required_devices(const std::vector<fstab_rec*>& fstab);
 bool fs_mgr_overlayfs_setup(const char* backing = nullptr, const char* mount_point = nullptr,
                             bool* change = nullptr);
 bool fs_mgr_overlayfs_teardown(const char* mount_point = nullptr, bool* change = nullptr);
+bool fs_mgr_overlayfs_is_setup();
 bool fs_mgr_has_shared_blocks(const std::string& mount_point, const std::string& dev);
 std::string fs_mgr_get_context(const std::string& mount_point);
 
diff --git a/fs_mgr/include_fstab/fstab/fstab.h b/fs_mgr/include_fstab/fstab/fstab.h
index 80bdb87..4706028 100644
--- a/fs_mgr/include_fstab/fstab/fstab.h
+++ b/fs_mgr/include_fstab/fstab/fstab.h
@@ -84,6 +84,7 @@
 int fs_mgr_is_formattable(const struct fstab_rec* fstab);
 int fs_mgr_is_slotselect(const struct fstab_rec* fstab);
 int fs_mgr_is_nofail(const struct fstab_rec* fstab);
+int fs_mgr_is_first_stage_mount(const struct fstab_rec* fstab);
 int fs_mgr_is_latemount(const struct fstab_rec* fstab);
 int fs_mgr_is_quota(const struct fstab_rec* fstab);
 int fs_mgr_is_logical(const struct fstab_rec* fstab);
diff --git a/fs_mgr/tests/adb-remount-test.sh b/fs_mgr/tests/adb-remount-test.sh
index c7c86eb..561debb 100755
--- a/fs_mgr/tests/adb-remount-test.sh
+++ b/fs_mgr/tests/adb-remount-test.sh
@@ -378,6 +378,11 @@
 M=`adb_sh cat /proc/mounts | sed -n 's@\([^ ]*\) /mnt/scratch \([^ ]*\) .*@\2 on \1@p'`
 [ -n "${M}" ] &&
   echo "${BLUE}[     INFO ]${NORMAL} scratch filesystem ${M}"
+uses_dynamic_scratch=true
+if [ "${M}" != "${M##*/dev/block/by-name/}" ]; then
+  uses_dynamic_scratch=false
+  scratch_partition="${M##*/dev/block/by-name/}"
+fi
 scratch_size=`adb_sh df -k /mnt/scratch </dev/null 2>/dev/null |
               while read device kblocks used available use mounted on; do
                 if [ "/mnt/scratch" = "\${mounted}" ]; then
@@ -453,16 +458,30 @@
   fastboot flash vendor ||
   ( fastboot reboot && false) ||
   die "fastboot flash vendor"
-# check ${scratch_partition} via fastboot
-fastboot_getvar partition-type:${scratch_partition} raw &&
-  fastboot_getvar has-slot:${scratch_partition} no &&
-  fastboot_getvar is-logical:${scratch_partition} yes ||
+fastboot_getvar partition-type:${scratch_partition} raw ||
   ( fastboot reboot && false) ||
   die "fastboot can not see ${scratch_partition} parameters"
-echo "${BLUE}[     INFO ]${NORMAL} expect fastboot erase ${scratch_partition} to fail" >&2
-fastboot erase ${scratch_partition} &&
-  ( fastboot reboot || true) &&
-  die "fastboot can erase ${scratch_partition}"
+if ${uses_dynamic_scratch}; then
+  # check ${scratch_partition} via fastboot
+  fastboot_getvar has-slot:${scratch_partition} no &&
+    fastboot_getvar is-logical:${scratch_partition} yes ||
+    ( fastboot reboot && false) ||
+    die "fastboot can not see ${scratch_partition} parameters"
+else
+  fastboot_getvar is-logical:${scratch_partition} no ||
+    ( fastboot reboot && false) ||
+    die "fastboot can not see ${scratch_partition} parameters"
+fi
+if ! ${uses_dynamic_scratch}; then
+  fastboot reboot-bootloader ||
+    die "Reboot into fastboot"
+fi
+if ${uses_dynamic_scratch}; then
+  echo "${BLUE}[     INFO ]${NORMAL} expect fastboot erase ${scratch_partition} to fail" >&2
+  fastboot erase ${scratch_partition} &&
+    ( fastboot reboot || true) &&
+    die "fastboot can erase ${scratch_partition}"
+fi
 echo "${BLUE}[     INFO ]${NORMAL} expect fastboot format ${scratch_partition} to fail" >&2
 fastboot format ${scratch_partition} &&
   ( fastboot reboot || true) &&
@@ -507,12 +526,13 @@
 
 echo "${GREEN}[ RUN      ]${NORMAL} test fastboot flash to ${scratch_partition}" >&2
 
-adb reboot-fastboot &&
-  dd if=/dev/zero of=/tmp/adb-remount-test.img bs=4096 count=16 2>/dev/null &&
+adb reboot-fastboot ||
+  die "Reboot into fastbootd"
+dd if=/dev/zero of=/tmp/adb-remount-test.img bs=4096 count=16 2>/dev/null &&
   fastboot_wait 2m ||
   ( rm /tmp/adb-remount-test.img && false) ||
   die "reboot into fastboot"
-fastboot flash ${scratch_partition} /tmp/adb-remount-test.img
+fastboot flash --force ${scratch_partition} /tmp/adb-remount-test.img
 err=${?}
 rm /tmp/adb-remount-test.img
 fastboot reboot ||
diff --git a/init/Android.bp b/init/Android.bp
index ea66ac6..e7b8516 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -19,6 +19,7 @@
     cpp_std: "experimental",
     sanitize: {
         misc_undefined: ["signed-integer-overflow"],
+        address: false,  // TODO(b/120561310): Fix ASAN to work without /proc mounted and re-enable.
     },
     cflags: [
         "-DLOG_UEVENTS=0",
diff --git a/init/Android.mk b/init/Android.mk
index 0e6ee0b..bdd0301 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -104,7 +104,6 @@
 LOCAL_REQUIRED_MODULES := \
    init_second_stage \
 
-LOCAL_POST_INSTALL_CMD := ln -sf /system/bin/init $(TARGET_ROOT_OUT)/init
 include $(BUILD_PHONY_PACKAGE)
 
 include $(CLEAR_VARS)
diff --git a/init/first_stage_mount.cpp b/init/first_stage_mount.cpp
index 2f7f79d..c124656 100644
--- a/init/first_stage_mount.cpp
+++ b/init/first_stage_mount.cpp
@@ -84,7 +84,7 @@
 
     bool need_dm_verity_;
 
-    std::unique_ptr<fstab, decltype(&fs_mgr_free_fstab)> device_tree_fstab_;
+    std::unique_ptr<fstab, decltype(&fs_mgr_free_fstab)> fstab_;
     std::string lp_metadata_partition_;
     std::vector<fstab_rec*> mount_fstab_recs_;
     std::set<std::string> required_devices_partition_names_;
@@ -132,15 +132,27 @@
 // Class Definitions
 // -----------------
 FirstStageMount::FirstStageMount()
-    : need_dm_verity_(false), device_tree_fstab_(fs_mgr_read_fstab_dt(), fs_mgr_free_fstab) {
-    if (device_tree_fstab_) {
-        // Stores device_tree_fstab_->recs[] into mount_fstab_recs_ (vector<fstab_rec*>)
-        // for easier manipulation later, e.g., range-base for loop.
-        for (int i = 0; i < device_tree_fstab_->num_entries; i++) {
-            mount_fstab_recs_.push_back(&device_tree_fstab_->recs[i]);
+    : need_dm_verity_(false), fstab_(fs_mgr_read_fstab_dt(), fs_mgr_free_fstab) {
+    // Stores fstab_->recs[] into mount_fstab_recs_ (vector<fstab_rec*>)
+    // for easier manipulation later, e.g., range-base for loop.
+    if (fstab_) {
+        // DT Fstab predated having a first_stage_mount fs_mgr flag, so if it exists, we use it.
+        for (int i = 0; i < fstab_->num_entries; i++) {
+            mount_fstab_recs_.push_back(&fstab_->recs[i]);
         }
     } else {
-        LOG(INFO) << "Failed to read fstab from device tree";
+        // Fstab found in first stage ramdisk, which should be a copy of the normal fstab.
+        // Mounts intended for first stage are explicitly flagged as such.
+        fstab_.reset(fs_mgr_read_fstab_default());
+        if (fstab_) {
+            for (int i = 0; i < fstab_->num_entries; i++) {
+                if (fs_mgr_is_first_stage_mount(&fstab_->recs[i])) {
+                    mount_fstab_recs_.push_back(&fstab_->recs[i]);
+                }
+            }
+        } else {
+            LOG(INFO) << "Failed to read fstab from device tree";
+        }
     }
 
     auto boot_devices = fs_mgr_get_boot_devices();
@@ -412,7 +424,7 @@
     }
 
     // heads up for instantiating required device(s) for overlayfs logic
-    const auto devices = fs_mgr_overlayfs_required_devices(device_tree_fstab_.get());
+    const auto devices = fs_mgr_overlayfs_required_devices(mount_fstab_recs_);
     for (auto const& device : devices) {
         if (android::base::StartsWith(device, "/dev/block/by-name/")) {
             required_devices_partition_names_.emplace(basename(device.c_str()));
@@ -424,7 +436,7 @@
         }
     }
 
-    fs_mgr_overlayfs_mount_all(device_tree_fstab_.get());
+    fs_mgr_overlayfs_mount_all(mount_fstab_recs_);
 
     return true;
 }
diff --git a/libprocinfo/include/procinfo/process_map.h b/libprocinfo/include/procinfo/process_map.h
index 0fc4201..981241e 100644
--- a/libprocinfo/include/procinfo/process_map.h
+++ b/libprocinfo/include/procinfo/process_map.h
@@ -17,6 +17,7 @@
 #pragma once
 
 #include <stdlib.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <sys/types.h>
 
diff --git a/libstats/include/stats_event_list.h b/libstats/include/stats_event_list.h
index a9832db..41ca79b 100644
--- a/libstats/include/stats_event_list.h
+++ b/libstats/include/stats_event_list.h
@@ -26,7 +26,7 @@
 int write_to_logger(android_log_context context, log_id_t id);
 void note_log_drop();
 void stats_log_close();
-
+int android_log_write_char_array(android_log_context ctx, const char* value, size_t len);
 #ifdef __cplusplus
 }
 #endif
@@ -244,6 +244,14 @@
         return ret >= 0;
     }
 
+    bool AppendCharArray(const char* value, size_t len) {
+        int retval = android_log_write_char_array(ctx, value, len);
+        if (retval < 0) {
+            ret = retval;
+        }
+        return ret >= 0;
+    }
+
     android_log_list_element read() { return android_log_read_next(ctx); }
     android_log_list_element peek() { return android_log_peek_next(ctx); }
 };
diff --git a/libstats/stats_event_list.c b/libstats/stats_event_list.c
index 72770d4..f4a7e94 100644
--- a/libstats/stats_event_list.c
+++ b/libstats/stats_event_list.c
@@ -193,3 +193,47 @@
     errno = save_errno;
     return ret;
 }
+
+static inline void copy4LE(uint8_t* buf, uint32_t val) {
+    buf[0] = val & 0xFF;
+    buf[1] = (val >> 8) & 0xFF;
+    buf[2] = (val >> 16) & 0xFF;
+    buf[3] = (val >> 24) & 0xFF;
+}
+
+// Note: this function differs from android_log_write_string8_len in that the length passed in
+// should be treated as actual length and not max length.
+int android_log_write_char_array(android_log_context ctx, const char* value, size_t actual_len) {
+    size_t needed;
+    ssize_t len = actual_len;
+    android_log_context_internal* context;
+
+    context = (android_log_context_internal*)ctx;
+    if (!context || (kAndroidLoggerWrite != context->read_write_flag)) {
+        return -EBADF;
+    }
+    if (context->overflow) {
+        return -EIO;
+    }
+    if (!value) {
+        value = "";
+        len = 0;
+    }
+    needed = sizeof(uint8_t) + sizeof(int32_t) + len;
+    if ((context->pos + needed) > MAX_EVENT_PAYLOAD) {
+        /* Truncate string for delivery */
+        len = MAX_EVENT_PAYLOAD - context->pos - 1 - sizeof(int32_t);
+        if (len <= 0) {
+            context->overflow = true;
+            return -EIO;
+        }
+    }
+    context->count[context->list_nest_depth]++;
+    context->storage[context->pos + 0] = EVENT_TYPE_STRING;
+    copy4LE(&context->storage[context->pos + 1], len);
+    if (len) {
+        memcpy(&context->storage[context->pos + 5], value, len);
+    }
+    context->pos += needed;
+    return len;
+}
diff --git a/libsysutils/Android.bp b/libsysutils/Android.bp
index 29d23c8..da5d86c 100644
--- a/libsysutils/Android.bp
+++ b/libsysutils/Android.bp
@@ -1,4 +1,4 @@
-cc_library_shared {
+cc_library {
     name: "libsysutils",
     vendor_available: true,
     vndk: {
diff --git a/libunwindstack/Elf.cpp b/libunwindstack/Elf.cpp
index 4d72ead..5b586a2 100644
--- a/libunwindstack/Elf.cpp
+++ b/libunwindstack/Elf.cpp
@@ -140,6 +140,10 @@
   return true;
 }
 
+bool Elf::GetBuildID(std::string* build_id) {
+  return valid_ && interface_->GetBuildID(build_id);
+}
+
 void Elf::GetLastError(ErrorData* data) {
   if (valid_) {
     *data = interface_->last_error();
diff --git a/libunwindstack/ElfInterface.cpp b/libunwindstack/ElfInterface.cpp
index f59a472..d0af94a 100644
--- a/libunwindstack/ElfInterface.cpp
+++ b/libunwindstack/ElfInterface.cpp
@@ -237,6 +237,56 @@
   }
 }
 
+template <typename NhdrType>
+bool ElfInterface::ReadBuildID(std::string* build_id) {
+  // Ensure there is no overflow in any of the calulations below.
+  uint64_t tmp;
+  if (__builtin_add_overflow(gnu_build_id_offset_, gnu_build_id_size_, &tmp)) {
+    return false;
+  }
+
+  uint64_t offset = 0;
+  while (offset < gnu_build_id_size_) {
+    if (gnu_build_id_size_ - offset < sizeof(NhdrType)) {
+      return false;
+    }
+    NhdrType hdr;
+    if (!memory_->ReadFully(gnu_build_id_offset_ + offset, &hdr, sizeof(hdr))) {
+      return false;
+    }
+    offset += sizeof(hdr);
+
+    if (gnu_build_id_size_ - offset < hdr.n_namesz) {
+      return false;
+    }
+    if (hdr.n_namesz > 0) {
+      std::string name(hdr.n_namesz, '\0');
+      if (!memory_->ReadFully(gnu_build_id_offset_ + offset, &(name[0]), hdr.n_namesz)) {
+        return false;
+      }
+
+      // Trim trailing \0 as GNU is stored as a C string in the ELF file.
+      if (name.back() == '\0')
+        name.resize(name.size() - 1);
+
+      // Align hdr.n_namesz to next power multiple of 4. See man 5 elf.
+      offset += (hdr.n_namesz + 3) & ~3;
+
+      if (name == "GNU" && hdr.n_type == NT_GNU_BUILD_ID) {
+        if (gnu_build_id_size_ - offset < hdr.n_descsz) {
+          return false;
+        }
+        build_id->resize(hdr.n_descsz);
+        return memory_->ReadFully(gnu_build_id_offset_ + offset, &(*build_id)[0],
+                                  hdr.n_descsz);
+      }
+    }
+    // Align hdr.n_descsz to next power multiple of 4. See man 5 elf.
+    offset += (hdr.n_descsz + 3) & ~3;
+  }
+  return false;
+}
+
 template <typename EhdrType, typename ShdrType>
 void ElfInterface::ReadSectionHeaders(const EhdrType& ehdr) {
   uint64_t offset = ehdr.e_shoff;
@@ -308,6 +358,15 @@
       // In order to read soname, keep track of address to offset mapping.
       strtabs_.push_back(std::make_pair<uint64_t, uint64_t>(static_cast<uint64_t>(shdr.sh_addr),
                                                             static_cast<uint64_t>(shdr.sh_offset)));
+    } else if (shdr.sh_type == SHT_NOTE) {
+      if (shdr.sh_name < sec_size) {
+        std::string name;
+        if (memory_->ReadString(sec_offset + shdr.sh_name, &name) &&
+            name == ".note.gnu.build-id") {
+          gnu_build_id_offset_ = shdr.sh_offset;
+          gnu_build_id_size_ = shdr.sh_size;
+        }
+      }
     }
   }
 }
@@ -492,6 +551,9 @@
 template void ElfInterface::ReadSectionHeaders<Elf32_Ehdr, Elf32_Shdr>(const Elf32_Ehdr&);
 template void ElfInterface::ReadSectionHeaders<Elf64_Ehdr, Elf64_Shdr>(const Elf64_Ehdr&);
 
+template bool ElfInterface::ReadBuildID<Elf32_Nhdr>(std::string*);
+template bool ElfInterface::ReadBuildID<Elf64_Nhdr>(std::string*);
+
 template bool ElfInterface::GetSonameWithTemplate<Elf32_Dyn>(std::string*);
 template bool ElfInterface::GetSonameWithTemplate<Elf64_Dyn>(std::string*);
 
diff --git a/libunwindstack/Global.cpp b/libunwindstack/Global.cpp
index 7a3de01..fdfd705 100644
--- a/libunwindstack/Global.cpp
+++ b/libunwindstack/Global.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 #include <sys/mman.h>
 
 #include <string>
diff --git a/libunwindstack/Maps.cpp b/libunwindstack/Maps.cpp
index 8729871..a9fb859 100644
--- a/libunwindstack/Maps.cpp
+++ b/libunwindstack/Maps.cpp
@@ -19,6 +19,7 @@
 #include <inttypes.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <unistd.h>
diff --git a/libunwindstack/Memory.cpp b/libunwindstack/Memory.cpp
index a30d65e..9904fef 100644
--- a/libunwindstack/Memory.cpp
+++ b/libunwindstack/Memory.cpp
@@ -16,6 +16,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <sys/ptrace.h>
 #include <sys/stat.h>
diff --git a/libunwindstack/RegsArm.cpp b/libunwindstack/RegsArm.cpp
index de22bde..885dc94 100644
--- a/libunwindstack/RegsArm.cpp
+++ b/libunwindstack/RegsArm.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 
 #include <functional>
 
diff --git a/libunwindstack/RegsArm64.cpp b/libunwindstack/RegsArm64.cpp
index a68f6e0..e9787aa 100644
--- a/libunwindstack/RegsArm64.cpp
+++ b/libunwindstack/RegsArm64.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 
 #include <functional>
 
diff --git a/libunwindstack/RegsMips.cpp b/libunwindstack/RegsMips.cpp
index 2e6908c..14a4e31 100644
--- a/libunwindstack/RegsMips.cpp
+++ b/libunwindstack/RegsMips.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 
 #include <functional>
 
diff --git a/libunwindstack/RegsMips64.cpp b/libunwindstack/RegsMips64.cpp
index 0b835a1..3f67d92 100644
--- a/libunwindstack/RegsMips64.cpp
+++ b/libunwindstack/RegsMips64.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 
 #include <functional>
 
diff --git a/libunwindstack/RegsX86_64.cpp b/libunwindstack/RegsX86_64.cpp
index ebad3f4..74cd1cb 100644
--- a/libunwindstack/RegsX86_64.cpp
+++ b/libunwindstack/RegsX86_64.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 
 #include <functional>
 
diff --git a/libunwindstack/Symbols.cpp b/libunwindstack/Symbols.cpp
index 14ebdbb..e3c15a2 100644
--- a/libunwindstack/Symbols.cpp
+++ b/libunwindstack/Symbols.cpp
@@ -17,6 +17,7 @@
 #include <elf.h>
 #include <stdint.h>
 
+#include <algorithm>
 #include <string>
 
 #include <unwindstack/Memory.h>
diff --git a/libunwindstack/include/unwindstack/Elf.h b/libunwindstack/include/unwindstack/Elf.h
index e5b0a89..27f7201 100644
--- a/libunwindstack/include/unwindstack/Elf.h
+++ b/libunwindstack/include/unwindstack/Elf.h
@@ -65,6 +65,8 @@
 
   bool GetGlobalVariable(const std::string& name, uint64_t* memory_address);
 
+  bool GetBuildID(std::string* build_id);
+
   uint64_t GetRelPc(uint64_t pc, const MapInfo* map_info);
 
   bool Step(uint64_t rel_pc, uint64_t adjusted_rel_pc, Regs* regs, Memory* process_memory,
diff --git a/libunwindstack/include/unwindstack/ElfInterface.h b/libunwindstack/include/unwindstack/ElfInterface.h
index a45eba8..52992d9 100644
--- a/libunwindstack/include/unwindstack/ElfInterface.h
+++ b/libunwindstack/include/unwindstack/ElfInterface.h
@@ -62,6 +62,8 @@
 
   virtual bool GetGlobalVariable(const std::string& name, uint64_t* memory_address) = 0;
 
+  virtual bool GetBuildID(std::string* build_id) = 0;
+
   virtual bool Step(uint64_t rel_pc, Regs* regs, Memory* process_memory, bool* finished);
 
   virtual bool IsValidPc(uint64_t pc);
@@ -85,6 +87,8 @@
   uint64_t debug_frame_size() { return debug_frame_size_; }
   uint64_t gnu_debugdata_offset() { return gnu_debugdata_offset_; }
   uint64_t gnu_debugdata_size() { return gnu_debugdata_size_; }
+  uint64_t gnu_build_id_offset() { return gnu_build_id_offset_; }
+  uint64_t gnu_build_id_size() { return gnu_build_id_size_; }
 
   DwarfSection* eh_frame() { return eh_frame_.get(); }
   DwarfSection* debug_frame() { return debug_frame_.get(); }
@@ -123,6 +127,9 @@
   template <typename EhdrType>
   static void GetMaxSizeWithTemplate(Memory* memory, uint64_t* size);
 
+  template <typename NhdrType>
+  bool ReadBuildID(std::string* build_id);
+
   Memory* memory_;
   std::unordered_map<uint64_t, LoadInfo> pt_loads_;
 
@@ -143,6 +150,9 @@
   uint64_t gnu_debugdata_offset_ = 0;
   uint64_t gnu_debugdata_size_ = 0;
 
+  uint64_t gnu_build_id_offset_ = 0;
+  uint64_t gnu_build_id_size_ = 0;
+
   uint8_t soname_type_ = SONAME_UNKNOWN;
   std::string soname_;
 
@@ -182,6 +192,10 @@
     return ElfInterface::GetGlobalVariableWithTemplate<Elf32_Sym>(name, memory_address);
   }
 
+  bool GetBuildID(std::string* build_id) {
+    return ElfInterface::ReadBuildID<Elf32_Nhdr>(build_id);
+  }
+
   static void GetMaxSize(Memory* memory, uint64_t* size) {
     GetMaxSizeWithTemplate<Elf32_Ehdr>(memory, size);
   }
@@ -212,6 +226,10 @@
     return ElfInterface::GetGlobalVariableWithTemplate<Elf64_Sym>(name, memory_address);
   }
 
+  bool GetBuildID(std::string* build_id) {
+    return ElfInterface::ReadBuildID<Elf64_Nhdr>(build_id);
+  }
+
   static void GetMaxSize(Memory* memory, uint64_t* size) {
     GetMaxSizeWithTemplate<Elf64_Ehdr>(memory, size);
   }
diff --git a/libunwindstack/tests/ElfFake.h b/libunwindstack/tests/ElfFake.h
index a3bf5ce..c2bd0f6 100644
--- a/libunwindstack/tests/ElfFake.h
+++ b/libunwindstack/tests/ElfFake.h
@@ -72,6 +72,9 @@
 
   bool GetFunctionName(uint64_t, std::string*, uint64_t*) override;
   bool GetGlobalVariable(const std::string&, uint64_t*) override;
+  bool GetBuildID(std::string*) override {
+    return false;
+  }
 
   bool Step(uint64_t, Regs*, Memory*, bool*) override;
 
diff --git a/libunwindstack/tests/ElfInterfaceTest.cpp b/libunwindstack/tests/ElfInterfaceTest.cpp
index 9326bff..6023dc4 100644
--- a/libunwindstack/tests/ElfInterfaceTest.cpp
+++ b/libunwindstack/tests/ElfInterfaceTest.cpp
@@ -116,6 +116,21 @@
   void InitSym(uint64_t offset, uint32_t value, uint32_t size, uint32_t name_offset,
                uint64_t sym_offset, const char* name);
 
+  template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+  void BuildID();
+
+  template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+  void BuildIDTwoNotes();
+
+  template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+  void BuildIDSectionTooSmallForName();
+
+  template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+  void BuildIDSectionTooSmallForDesc();
+
+  template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+  void BuildIDSectionTooSmallForHeader();
+
   MemoryFake memory_;
 };
 
@@ -898,7 +913,7 @@
 
   Ehdr ehdr = {};
   ehdr.e_shoff = offset;
-  ehdr.e_shnum = 6;
+  ehdr.e_shnum = 7;
   ehdr.e_shentsize = sizeof(Shdr);
   ehdr.e_shstrndx = 2;
   memory_.SetMemory(0, &ehdr, sizeof(ehdr));
@@ -958,10 +973,19 @@
   memory_.SetMemory(offset, &shdr, sizeof(shdr));
   offset += ehdr.e_shentsize;
 
+  memset(&shdr, 0, sizeof(shdr));
+  shdr.sh_type = SHT_NOTE;
+  shdr.sh_name = 0x500;
+  shdr.sh_offset = 0xb000;
+  shdr.sh_size = 0xf00;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
   memory_.SetMemory(0xf100, ".debug_frame", sizeof(".debug_frame"));
   memory_.SetMemory(0xf200, ".gnu_debugdata", sizeof(".gnu_debugdata"));
   memory_.SetMemory(0xf300, ".eh_frame", sizeof(".eh_frame"));
   memory_.SetMemory(0xf400, ".eh_frame_hdr", sizeof(".eh_frame_hdr"));
+  memory_.SetMemory(0xf500, ".note.gnu.build-id", sizeof(".note.gnu.build-id"));
 
   uint64_t load_bias = 0;
   ASSERT_TRUE(elf->Init(&load_bias));
@@ -974,6 +998,8 @@
   EXPECT_EQ(0x800U, elf->eh_frame_size());
   EXPECT_EQ(0xa000U, elf->eh_frame_hdr_offset());
   EXPECT_EQ(0xf00U, elf->eh_frame_hdr_size());
+  EXPECT_EQ(0xb000U, elf->gnu_build_id_offset());
+  EXPECT_EQ(0xf00U, elf->gnu_build_id_size());
 }
 
 TEST_F(ElfInterfaceTest, init_section_headers_offsets32) {
@@ -1153,4 +1179,321 @@
   EXPECT_FALSE(elf->IsValidPc(0x2a00));
 }
 
+template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+void ElfInterfaceTest::BuildID() {
+  std::unique_ptr<ElfInterfaceType> elf(new ElfInterfaceType(&memory_));
+
+  uint64_t offset = 0x2000;
+
+  Ehdr ehdr = {};
+  ehdr.e_shoff = offset;
+  ehdr.e_shnum = 3;
+  ehdr.e_shentsize = sizeof(Shdr);
+  ehdr.e_shstrndx = 2;
+  memory_.SetMemory(0, &ehdr, sizeof(ehdr));
+
+  offset += ehdr.e_shentsize;
+
+  char note_section[128];
+  Nhdr note_header = {};
+  note_header.n_namesz = 4;  // "GNU"
+  note_header.n_descsz = 8; // "BUILDID"
+  note_header.n_type = NT_GNU_BUILD_ID;
+  memcpy(&note_section, &note_header, sizeof(note_header));
+  size_t note_offset = sizeof(note_header);
+  memcpy(&note_section[note_offset], "GNU", sizeof("GNU"));
+  note_offset += sizeof("GNU");
+  memcpy(&note_section[note_offset], "BUILDID", sizeof("BUILDID"));
+  note_offset += sizeof("BUILDID");
+
+  Shdr shdr = {};
+  shdr.sh_type = SHT_NOTE;
+  shdr.sh_name = 0x500;
+  shdr.sh_offset = 0xb000;
+  shdr.sh_size = sizeof(note_section);
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  // The string data for section header names.
+  memset(&shdr, 0, sizeof(shdr));
+  shdr.sh_type = SHT_STRTAB;
+  shdr.sh_name = 0x20000;
+  shdr.sh_offset = 0xf000;
+  shdr.sh_size = 0x1000;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  memory_.SetMemory(0xf500, ".note.gnu.build-id", sizeof(".note.gnu.build-id"));
+  memory_.SetMemory(0xb000, note_section, sizeof(note_section));
+
+  uint64_t load_bias = 0;
+  ASSERT_TRUE(elf->Init(&load_bias));
+  std::string build_id;
+  ASSERT_TRUE(elf->GetBuildID(&build_id));
+  EXPECT_STREQ(build_id.c_str(), "BUILDID");
+}
+
+template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+void ElfInterfaceTest::BuildIDTwoNotes() {
+  std::unique_ptr<ElfInterfaceType> elf(new ElfInterfaceType(&memory_));
+
+  uint64_t offset = 0x2000;
+
+  Ehdr ehdr = {};
+  ehdr.e_shoff = offset;
+  ehdr.e_shnum = 3;
+  ehdr.e_shentsize = sizeof(Shdr);
+  ehdr.e_shstrndx = 2;
+  memory_.SetMemory(0, &ehdr, sizeof(ehdr));
+
+  offset += ehdr.e_shentsize;
+
+  char note_section[128];
+  Nhdr note_header = {};
+  note_header.n_namesz = 8;  // "WRONG" aligned to 4
+  note_header.n_descsz = 8; // "BUILDID"
+  note_header.n_type = NT_GNU_BUILD_ID;
+  memcpy(&note_section, &note_header, sizeof(note_header));
+  size_t note_offset = sizeof(note_header);
+  memcpy(&note_section[note_offset], "WRONG", sizeof("WRONG"));
+  note_offset += 8;
+  memcpy(&note_section[note_offset], "BUILDID", sizeof("BUILDID"));
+  note_offset += sizeof("BUILDID");
+
+  note_header.n_namesz = 4;  // "GNU"
+  note_header.n_descsz = 8; // "BUILDID"
+  note_header.n_type = NT_GNU_BUILD_ID;
+  memcpy(&note_section[note_offset], &note_header, sizeof(note_header));
+  note_offset += sizeof(note_header);
+  memcpy(&note_section[note_offset], "GNU", sizeof("GNU"));
+  note_offset += sizeof("GNU");
+  memcpy(&note_section[note_offset], "BUILDID", sizeof("BUILDID"));
+  note_offset += sizeof("BUILDID");
+
+  Shdr shdr = {};
+  shdr.sh_type = SHT_NOTE;
+  shdr.sh_name = 0x500;
+  shdr.sh_offset = 0xb000;
+  shdr.sh_size = sizeof(note_section);
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  // The string data for section header names.
+  memset(&shdr, 0, sizeof(shdr));
+  shdr.sh_type = SHT_STRTAB;
+  shdr.sh_name = 0x20000;
+  shdr.sh_offset = 0xf000;
+  shdr.sh_size = 0x1000;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  memory_.SetMemory(0xf500, ".note.gnu.build-id", sizeof(".note.gnu.build-id"));
+  memory_.SetMemory(0xb000, note_section, sizeof(note_section));
+
+  uint64_t load_bias = 0;
+  ASSERT_TRUE(elf->Init(&load_bias));
+  std::string build_id;
+  ASSERT_TRUE(elf->GetBuildID(&build_id));
+  EXPECT_STREQ(build_id.c_str(), "BUILDID");
+}
+
+template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+void ElfInterfaceTest::BuildIDSectionTooSmallForName () {
+  std::unique_ptr<ElfInterfaceType> elf(new ElfInterfaceType(&memory_));
+
+  uint64_t offset = 0x2000;
+
+  Ehdr ehdr = {};
+  ehdr.e_shoff = offset;
+  ehdr.e_shnum = 3;
+  ehdr.e_shentsize = sizeof(Shdr);
+  ehdr.e_shstrndx = 2;
+  memory_.SetMemory(0, &ehdr, sizeof(ehdr));
+
+  offset += ehdr.e_shentsize;
+
+  char note_section[128];
+  Nhdr note_header = {};
+  note_header.n_namesz = 4;  // "GNU"
+  note_header.n_descsz = 8; // "BUILDID"
+  note_header.n_type = NT_GNU_BUILD_ID;
+  memcpy(&note_section, &note_header, sizeof(note_header));
+  size_t note_offset = sizeof(note_header);
+  memcpy(&note_section[note_offset], "GNU", sizeof("GNU"));
+  note_offset += sizeof("GNU");
+  memcpy(&note_section[note_offset], "BUILDID", sizeof("BUILDID"));
+  note_offset += sizeof("BUILDID");
+
+  Shdr shdr = {};
+  shdr.sh_type = SHT_NOTE;
+  shdr.sh_name = 0x500;
+  shdr.sh_offset = 0xb000;
+  shdr.sh_size = sizeof(note_header) + 1;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  // The string data for section header names.
+  memset(&shdr, 0, sizeof(shdr));
+  shdr.sh_type = SHT_STRTAB;
+  shdr.sh_name = 0x20000;
+  shdr.sh_offset = 0xf000;
+  shdr.sh_size = 0x1000;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  memory_.SetMemory(0xf500, ".note.gnu.build-id", sizeof(".note.gnu.build-id"));
+  memory_.SetMemory(0xb000, note_section, sizeof(note_section));
+
+  uint64_t load_bias = 0;
+  ASSERT_TRUE(elf->Init(&load_bias));
+  std::string build_id;
+  ASSERT_FALSE(elf->GetBuildID(&build_id));
+}
+
+template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+void ElfInterfaceTest::BuildIDSectionTooSmallForDesc () {
+  std::unique_ptr<ElfInterfaceType> elf(new ElfInterfaceType(&memory_));
+
+  uint64_t offset = 0x2000;
+
+  Ehdr ehdr = {};
+  ehdr.e_shoff = offset;
+  ehdr.e_shnum = 3;
+  ehdr.e_shentsize = sizeof(Shdr);
+  ehdr.e_shstrndx = 2;
+  memory_.SetMemory(0, &ehdr, sizeof(ehdr));
+
+  offset += ehdr.e_shentsize;
+
+  char note_section[128];
+  Nhdr note_header = {};
+  note_header.n_namesz = 4;  // "GNU"
+  note_header.n_descsz = 8; // "BUILDID"
+  note_header.n_type = NT_GNU_BUILD_ID;
+  memcpy(&note_section, &note_header, sizeof(note_header));
+  size_t note_offset = sizeof(note_header);
+  memcpy(&note_section[note_offset], "GNU", sizeof("GNU"));
+  note_offset += sizeof("GNU");
+  memcpy(&note_section[note_offset], "BUILDID", sizeof("BUILDID"));
+  note_offset += sizeof("BUILDID");
+
+  Shdr shdr = {};
+  shdr.sh_type = SHT_NOTE;
+  shdr.sh_name = 0x500;
+  shdr.sh_offset = 0xb000;
+  shdr.sh_size = sizeof(note_header) + sizeof("GNU") + 1;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  // The string data for section header names.
+  memset(&shdr, 0, sizeof(shdr));
+  shdr.sh_type = SHT_STRTAB;
+  shdr.sh_name = 0x20000;
+  shdr.sh_offset = 0xf000;
+  shdr.sh_size = 0x1000;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  memory_.SetMemory(0xf500, ".note.gnu.build-id", sizeof(".note.gnu.build-id"));
+  memory_.SetMemory(0xb000, note_section, sizeof(note_section));
+
+  uint64_t load_bias = 0;
+  ASSERT_TRUE(elf->Init(&load_bias));
+  std::string build_id;
+  ASSERT_FALSE(elf->GetBuildID(&build_id));
+}
+
+template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
+void ElfInterfaceTest::BuildIDSectionTooSmallForHeader () {
+  std::unique_ptr<ElfInterfaceType> elf(new ElfInterfaceType(&memory_));
+
+  uint64_t offset = 0x2000;
+
+  Ehdr ehdr = {};
+  ehdr.e_shoff = offset;
+  ehdr.e_shnum = 3;
+  ehdr.e_shentsize = sizeof(Shdr);
+  ehdr.e_shstrndx = 2;
+  memory_.SetMemory(0, &ehdr, sizeof(ehdr));
+
+  offset += ehdr.e_shentsize;
+
+  char note_section[128];
+  Nhdr note_header = {};
+  note_header.n_namesz = 4;  // "GNU"
+  note_header.n_descsz = 8; // "BUILDID"
+  note_header.n_type = NT_GNU_BUILD_ID;
+  memcpy(&note_section, &note_header, sizeof(note_header));
+  size_t note_offset = sizeof(note_header);
+  memcpy(&note_section[note_offset], "GNU", sizeof("GNU"));
+  note_offset += sizeof("GNU");
+  memcpy(&note_section[note_offset], "BUILDID", sizeof("BUILDID"));
+  note_offset += sizeof("BUILDID");
+
+  Shdr shdr = {};
+  shdr.sh_type = SHT_NOTE;
+  shdr.sh_name = 0x500;
+  shdr.sh_offset = 0xb000;
+  shdr.sh_size = sizeof(note_header) - 1;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  // The string data for section header names.
+  memset(&shdr, 0, sizeof(shdr));
+  shdr.sh_type = SHT_STRTAB;
+  shdr.sh_name = 0x20000;
+  shdr.sh_offset = 0xf000;
+  shdr.sh_size = 0x1000;
+  memory_.SetMemory(offset, &shdr, sizeof(shdr));
+  offset += ehdr.e_shentsize;
+
+  memory_.SetMemory(0xf500, ".note.gnu.build-id", sizeof(".note.gnu.build-id"));
+  memory_.SetMemory(0xb000, note_section, sizeof(note_section));
+
+  uint64_t load_bias = 0;
+  ASSERT_TRUE(elf->Init(&load_bias));
+  std::string build_id;
+  ASSERT_FALSE(elf->GetBuildID(&build_id));
+}
+
+TEST_F(ElfInterfaceTest, build_id32) {
+  BuildID<Elf32_Ehdr, Elf32_Shdr, Elf32_Nhdr, ElfInterface32>();
+}
+
+TEST_F(ElfInterfaceTest, build_id64) {
+  BuildID<Elf64_Ehdr, Elf64_Shdr, Elf64_Nhdr, ElfInterface64>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_two_notes32) {
+  BuildIDTwoNotes<Elf32_Ehdr, Elf32_Shdr, Elf32_Nhdr, ElfInterface32>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_two_notes64) {
+  BuildIDTwoNotes<Elf64_Ehdr, Elf64_Shdr, Elf64_Nhdr, ElfInterface64>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_section_too_small_for_name32) {
+  BuildIDSectionTooSmallForName<Elf32_Ehdr, Elf32_Shdr, Elf32_Nhdr, ElfInterface32>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_section_too_small_for_name64) {
+  BuildIDSectionTooSmallForName<Elf64_Ehdr, Elf64_Shdr, Elf64_Nhdr, ElfInterface64>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_section_too_small_for_desc32) {
+  BuildIDSectionTooSmallForDesc<Elf32_Ehdr, Elf32_Shdr, Elf32_Nhdr, ElfInterface32>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_section_too_small_for_desc64) {
+  BuildIDSectionTooSmallForDesc<Elf64_Ehdr, Elf64_Shdr, Elf64_Nhdr, ElfInterface64>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_section_too_small_for_header32) {
+  BuildIDSectionTooSmallForHeader<Elf32_Ehdr, Elf32_Shdr, Elf32_Nhdr, ElfInterface32>();
+}
+
+TEST_F(ElfInterfaceTest, build_id_section_too_small_for_header64) {
+  BuildIDSectionTooSmallForHeader<Elf64_Ehdr, Elf64_Shdr, Elf64_Nhdr, ElfInterface64>();
+}
+
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/ElfTest.cpp b/libunwindstack/tests/ElfTest.cpp
index ccf8927..7766218 100644
--- a/libunwindstack/tests/ElfTest.cpp
+++ b/libunwindstack/tests/ElfTest.cpp
@@ -311,6 +311,7 @@
   void InitHeaders(uint64_t) override {}
   bool GetSoname(std::string*) override { return false; }
   bool GetFunctionName(uint64_t, std::string*, uint64_t*) override { return false; }
+  bool GetBuildID(std::string*) override { return false; }
 
   MOCK_METHOD4(Step, bool(uint64_t, Regs*, Memory*, bool*));
   MOCK_METHOD2(GetGlobalVariable, bool(const std::string&, uint64_t*));
diff --git a/libunwindstack/tools/unwind_info.cpp b/libunwindstack/tools/unwind_info.cpp
index aebeb95..3f2dfb0 100644
--- a/libunwindstack/tools/unwind_info.cpp
+++ b/libunwindstack/tools/unwind_info.cpp
@@ -123,6 +123,15 @@
     printf("Soname: %s\n", soname.c_str());
   }
 
+  std::string build_id;
+  if (elf.GetBuildID(&build_id)) {
+    printf("Build ID: ");
+    for (size_t i = 0; i < build_id.size(); ++i) {
+      printf("%02hhx", build_id[i]);
+    }
+    printf("\n");
+  }
+
   ElfInterface* interface = elf.interface();
   if (elf.machine_type() == EM_ARM) {
     DumpArm(&elf, reinterpret_cast<ElfInterfaceArm*>(interface));
diff --git a/rootdir/Android.mk b/rootdir/Android.mk
index aad00ad..f88f6b9 100644
--- a/rootdir/Android.mk
+++ b/rootdir/Android.mk
@@ -9,6 +9,10 @@
 LOCAL_MODULE_CLASS := ETC
 LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT)
 
+# The init symlink must be a post install command of a file that is to TARGET_ROOT_OUT.
+# Since init.rc is required for init and satisfies that requirement, we hijack it to create the symlink.
+LOCAL_POST_INSTALL_CMD := ln -sf /system/bin/init $(TARGET_ROOT_OUT)/init
+
 include $(BUILD_PREBUILT)
 
 #######################################
diff --git a/shell_and_utilities/README.md b/shell_and_utilities/README.md
index d8cf867..ffda3a5 100644
--- a/shell_and_utilities/README.md
+++ b/shell_and_utilities/README.md
@@ -1,5 +1,4 @@
-Android's shell and utilities
-=============================
+# Android's shell and utilities
 
 Since IceCreamSandwich Android has used
 [mksh](https://www.mirbsd.org/mksh.htm) as its shell. Before then it used
@@ -34,8 +33,7 @@
 full list for a release by running `toybox` directly.
 
 
-Android 2.3 (Gingerbread)
--------------------------
+## Android 2.3 (Gingerbread)
 
 BSD: cat dd newfs\_msdos
 
@@ -46,8 +44,7 @@
 umount uptime vmstat watchprops wipe
 
 
-Android 4.0 (IceCreamSandwich)
-------------------------------
+## Android 4.0 (IceCreamSandwich)
 
 BSD: cat dd newfs\_msdos
 
@@ -58,8 +55,7 @@
 touch umount uptime vmstat watchprops wipe
 
 
-Android 4.1-4.3 (JellyBean)
----------------------------
+## Android 4.1-4.3 (JellyBean)
 
 BSD: cat cp dd du grep newfs\_msdos
 
@@ -71,8 +67,7 @@
 sync top touch umount uptime vmstat watchprops wipe
 
 
-Android 4.4 (KitKat)
---------------------
+## Android 4.4 (KitKat)
 
 BSD: cat cp dd du grep newfs\_msdos
 
@@ -84,8 +79,7 @@
 stop swapoff swapon sync top touch umount uptime vmstat watchprops wipe
 
 
-Android 5.0 (Lollipop)
-----------------------
+## Android 5.0 (Lollipop)
 
 BSD: cat chown cp dd du grep kill ln mv printenv rm rmdir sleep sync
 
@@ -97,8 +91,7 @@
 top touch umount uptime vmstat watchprops wipe
 
 
-Android 6.0 (Marshmallow)
--------------------------
+## Android 6.0 (Marshmallow)
 
 BSD: dd du grep
 
@@ -118,8 +111,7 @@
 vmstat wc which whoami xargs yes
 
 
-Android 7.0 (Nougat)
---------------------
+## Android 7.0 (Nougat)
 
 BSD: dd grep
 
@@ -140,8 +132,7 @@
 uptime usleep vmstat wc which whoami xargs xxd yes
 
 
-Android 8.0 (Oreo)
-------------------
+## Android 8.0 (Oreo)
 
 BSD: dd grep
 
@@ -164,8 +155,8 @@
 tty ulimit umount uname uniq unix2dos uptime usleep uudecode uuencode
 vmstat wc which whoami xargs xxd yes zcat
 
-Android P
----------
+
+## Android 9.0 (Pie)
 
 BSD: dd grep
 
@@ -190,8 +181,8 @@
 umount uname uniq unix2dos uptime usleep uudecode uuencode vmstat wc
 which whoami xargs xxd yes zcat
 
-Android Q
----------
+
+## Android Q
 
 BSD: grep fsck\_msdos newfs\_msdos
 
@@ -201,17 +192,22 @@
 
 toolbox: getevent getprop
 
-toybox: acpi base64 basename blockdev cal cat chcon chgrp chmod chown
-chroot chrt cksum clear cmp comm cp cpio cut date dd df diff dirname
-dmesg dos2unix du echo env expand expr fallocate false file find flock
-fmt free getenforce groups gunzip gzip head hostname hwclock id ifconfig
-inotifyd insmod ionice iorenice kill killall ln load\_policy log logname
-losetup ls lsmod lsof lspci lsusb md5sum microcom mkdir mkfifo mknod
-mkswap mktemp modinfo modprobe more mount mountpoint mv nc netcat netstat
-nice nl nohup nsenter od paste patch pgrep pidof pkill pmap printenv
-printf ps pwd readlink realpath renice restorecon rm rmdir rmmod runcon
-sed sendevent seq setenforce setprop setsid sha1sum sha224sum sha256sum
-sha384sum sha512sum sleep sort split start stat stop strings stty swapoff
-swapon sync sysctl tac tail tar taskset tee time timeout top touch tr
-true truncate tty ulimit umount uname uniq unix2dos unshare uptime usleep
-uudecode uuencode vmstat wc which whoami xargs xxd yes zcat
+toybox: acpi base64 basename bc blkid blockdev cal cat chattr chcon chgrp
+chmod chown chroot chrt cksum clear cmp comm cp cpio cut date dd df
+diff dirname dmesg dos2unix du echo egrep env expand expr fallocate
+false fgrep file find flock fmt free freeramdisk fsfreeze getconf
+getenforce getfattr grep groups gunzip gzip head help hostname hwclock
+i2cdetect i2cdump i2cget i2cset iconv id ifconfig inotifyd insmod
+install ionice iorenice iotop kill killall ln load\_policy log logname
+losetup ls lsattr lsmod lsof lspci lsusb makedevs md5sum microcom
+mkdir mkfifo mknod mkswap mktemp modinfo modprobe more mount mountpoint
+mv nbd-client nc netcat netstat nice nl nohup nproc nsenter od partprobe
+paste patch pgrep pidof ping ping6 pivot\_root pkill pmap printenv
+printf prlimit ps pwd pwdx readlink realpath renice restorecon rev
+rfkill rm rmdir rmmod runcon sed sendevent seq setenforce setfattr
+setprop setsid sha1sum sha224sum sha256sum sha384sum sha512sum sleep
+sort split start stat stop strings stty swapoff swapon sync sysctl
+tac tail tar taskset tee time timeout top touch tr traceroute traceroute6
+true truncate tty tunctl ulimit umount uname uniq unix2dos unlink
+unshare uptime usleep uudecode uuencode uuidgen vconfig vmstat watch
+wc which whoami xargs xxd yes zcat