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Diffstat (limited to 'boot_control/libboot_control.cpp')
| -rw-r--r-- | boot_control/libboot_control.cpp | 328 |
1 files changed, 328 insertions, 0 deletions
diff --git a/boot_control/libboot_control.cpp b/boot_control/libboot_control.cpp new file mode 100644 index 000000000..8b44d5d1c --- /dev/null +++ b/boot_control/libboot_control.cpp @@ -0,0 +1,328 @@ +/* + * Copyright (C) 2015 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 <libboot_control/libboot_control.h> + +#include <endian.h> +#include <errno.h> +#include <fcntl.h> +#include <string.h> + +#include <string> + +#include <android-base/file.h> +#include <android-base/logging.h> +#include <android-base/properties.h> +#include <android-base/stringprintf.h> +#include <android-base/unique_fd.h> + +#include <bootloader_message/bootloader_message.h> + +namespace android { +namespace bootable { + +// The number of boot attempts that should be made from a new slot before +// rolling back to the previous slot. +constexpr unsigned int kDefaultBootAttempts = 7; +static_assert(kDefaultBootAttempts < 8, "tries_remaining field only has 3 bits"); + +constexpr unsigned int kMaxNumSlots = + sizeof(bootloader_control::slot_info) / sizeof(bootloader_control::slot_info[0]); +constexpr const char* kSlotSuffixes[kMaxNumSlots] = { "_a", "_b", "_c", "_d" }; +constexpr off_t kBootloaderControlOffset = offsetof(bootloader_message_ab, slot_suffix); + +static uint32_t CRC32(const uint8_t* buf, size_t size) { + static uint32_t crc_table[256]; + + // Compute the CRC-32 table only once. + if (!crc_table[1]) { + for (uint32_t i = 0; i < 256; ++i) { + uint32_t crc = i; + for (uint32_t j = 0; j < 8; ++j) { + uint32_t mask = -(crc & 1); + crc = (crc >> 1) ^ (0xEDB88320 & mask); + } + crc_table[i] = crc; + } + } + + uint32_t ret = -1; + for (size_t i = 0; i < size; ++i) { + ret = (ret >> 8) ^ crc_table[(ret ^ buf[i]) & 0xFF]; + } + + return ~ret; +} + +// Return the little-endian representation of the CRC-32 of the first fields +// in |boot_ctrl| up to the crc32_le field. +uint32_t BootloaderControlLECRC(const bootloader_control* boot_ctrl) { + return htole32( + CRC32(reinterpret_cast<const uint8_t*>(boot_ctrl), offsetof(bootloader_control, crc32_le))); +} + +bool LoadBootloaderControl(const std::string& misc_device, bootloader_control* buffer) { + android::base::unique_fd fd(open(misc_device.c_str(), O_RDONLY)); + if (fd.get() == -1) { + PLOG(ERROR) << "failed to open " << misc_device; + return false; + } + if (lseek(fd, kBootloaderControlOffset, SEEK_SET) != kBootloaderControlOffset) { + PLOG(ERROR) << "failed to lseek " << misc_device; + return false; + } + if (!android::base::ReadFully(fd.get(), buffer, sizeof(bootloader_control))) { + PLOG(ERROR) << "failed to read " << misc_device; + return false; + } + return true; +} + +bool UpdateAndSaveBootloaderControl(const std::string& misc_device, bootloader_control* buffer) { + buffer->crc32_le = BootloaderControlLECRC(buffer); + android::base::unique_fd fd(open(misc_device.c_str(), O_WRONLY | O_SYNC)); + if (fd.get() == -1) { + PLOG(ERROR) << "failed to open " << misc_device; + return false; + } + if (lseek(fd.get(), kBootloaderControlOffset, SEEK_SET) != kBootloaderControlOffset) { + PLOG(ERROR) << "failed to lseek " << misc_device; + return false; + } + if (!android::base::WriteFully(fd.get(), buffer, sizeof(bootloader_control))) { + PLOG(ERROR) << "failed to write " << misc_device; + return false; + } + return true; +} + +void InitDefaultBootloaderControl(BootControl* control, bootloader_control* boot_ctrl) { + memset(boot_ctrl, 0, sizeof(*boot_ctrl)); + + unsigned int current_slot = control->GetCurrentSlot(); + if (current_slot < kMaxNumSlots) { + strlcpy(boot_ctrl->slot_suffix, kSlotSuffixes[current_slot], sizeof(boot_ctrl->slot_suffix)); + } + boot_ctrl->magic = BOOT_CTRL_MAGIC; + boot_ctrl->version = BOOT_CTRL_VERSION; + + // Figure out the number of slots by checking if the partitions exist, + // otherwise assume the maximum supported by the header. + boot_ctrl->nb_slot = kMaxNumSlots; + std::string base_path = control->misc_device(); + size_t last_path_sep = base_path.rfind('/'); + if (last_path_sep != std::string::npos) { + // We test the existence of the "boot" partition on each possible slot, + // which is a partition required by Android Bootloader Requirements. + base_path = base_path.substr(0, last_path_sep + 1) + "boot"; + int last_existing_slot = -1; + int first_missing_slot = -1; + for (unsigned int slot = 0; slot < kMaxNumSlots; ++slot) { + std::string partition_path = base_path + kSlotSuffixes[slot]; + struct stat part_stat; + int err = stat(partition_path.c_str(), &part_stat); + if (!err) { + last_existing_slot = slot; + LOG(INFO) << "Found slot: " << kSlotSuffixes[slot]; + } else if (err < 0 && errno == ENOENT && first_missing_slot == -1) { + first_missing_slot = slot; + } + } + // We only declare that we found the actual number of slots if we found all + // the boot partitions up to the number of slots, and no boot partition + // after that. Not finding any of the boot partitions implies a problem so + // we just leave the number of slots in the maximum value. + if ((last_existing_slot != -1 && last_existing_slot + 1 == first_missing_slot) || + (first_missing_slot == -1 && last_existing_slot + 1 == kMaxNumSlots)) { + boot_ctrl->nb_slot = last_existing_slot + 1; + LOG(INFO) << "Found a system with " << last_existing_slot + 1 << " slots."; + } + } + + for (unsigned int slot = 0; slot < kMaxNumSlots; ++slot) { + slot_metadata entry = {}; + + if (slot < boot_ctrl->nb_slot) { + entry.priority = 7; + entry.tries_remaining = kDefaultBootAttempts; + entry.successful_boot = 0; + } else { + entry.priority = 0; // Unbootable + } + + // When the boot_control stored on disk is invalid, we assume that the + // current slot is successful. The bootloader should repair this situation + // before booting and write a valid boot_control slot, so if we reach this + // stage it means that the misc partition was corrupted since boot. + if (current_slot == slot) { + entry.successful_boot = 1; + } + + boot_ctrl->slot_info[slot] = entry; + } + boot_ctrl->recovery_tries_remaining = 0; + + boot_ctrl->crc32_le = BootloaderControlLECRC(boot_ctrl); +} + +// Return the index of the slot suffix passed or -1 if not a valid slot suffix. +int SlotSuffixToIndex(const char* suffix) { + for (unsigned int slot = 0; slot < kMaxNumSlots; ++slot) { + if (!strcmp(kSlotSuffixes[slot], suffix)) return slot; + } + return -1; +} + +// Initialize the boot_control_private struct with the information from +// the bootloader_message buffer stored in |boot_ctrl|. Returns whether the +// initialization succeeded. +bool BootControl::Init() { + if (initialized_) return true; + + // Initialize the current_slot from the read-only property. If the property + // was not set (from either the command line or the device tree), we can later + // initialize it from the bootloader_control struct. + std::string suffix_prop = android::base::GetProperty("ro.boot.slot_suffix", ""); + current_slot_ = SlotSuffixToIndex(suffix_prop.c_str()); + + std::string err; + std::string device = get_bootloader_message_blk_device(&err); + if (device.empty()) return false; + + bootloader_control boot_ctrl; + if (!LoadBootloaderControl(device.c_str(), &boot_ctrl)) return false; + + // Note that since there isn't a module unload function this memory is leaked. + misc_device_ = strdup(device.c_str()); + initialized_ = true; + + // Validate the loaded data, otherwise we will destroy it and re-initialize it + // with the current information. + uint32_t computed_crc32 = BootloaderControlLECRC(&boot_ctrl); + if (boot_ctrl.crc32_le != computed_crc32) { + LOG(WARNING) << "Invalid boot control found, expected CRC-32 0x" << std::hex << computed_crc32 + << " but found 0x" << std::hex << boot_ctrl.crc32_le << ". Re-initializing."; + InitDefaultBootloaderControl(this, &boot_ctrl); + UpdateAndSaveBootloaderControl(device.c_str(), &boot_ctrl); + } + + num_slots_ = boot_ctrl.nb_slot; + return true; +} + +unsigned int BootControl::GetNumberSlots() { + return num_slots_; +} + +unsigned int BootControl::GetCurrentSlot() { + return current_slot_; +} + +bool BootControl::MarkBootSuccessful() { + bootloader_control bootctrl; + if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false; + + bootctrl.slot_info[current_slot_].successful_boot = 1; + // tries_remaining == 0 means that the slot is not bootable anymore, make + // sure we mark the current slot as bootable if it succeeds in the last + // attempt. + bootctrl.slot_info[current_slot_].tries_remaining = 1; + return UpdateAndSaveBootloaderControl(misc_device_, &bootctrl); +} + +bool BootControl::SetActiveBootSlot(unsigned int slot) { + if (slot >= kMaxNumSlots || slot >= num_slots_) { + // Invalid slot number. + return false; + } + + bootloader_control bootctrl; + if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false; + + // Set every other slot with a lower priority than the new "active" slot. + const unsigned int kActivePriority = 15; + const unsigned int kActiveTries = 6; + for (unsigned int i = 0; i < num_slots_; ++i) { + if (i != slot) { + if (bootctrl.slot_info[i].priority >= kActivePriority) + bootctrl.slot_info[i].priority = kActivePriority - 1; + } + } + + // Note that setting a slot as active doesn't change the successful bit. + // The successful bit will only be changed by setSlotAsUnbootable(). + bootctrl.slot_info[slot].priority = kActivePriority; + bootctrl.slot_info[slot].tries_remaining = kActiveTries; + + // Setting the current slot as active is a way to revert the operation that + // set *another* slot as active at the end of an updater. This is commonly + // used to cancel the pending update. We should only reset the verity_corrpted + // bit when attempting a new slot, otherwise the verity bit on the current + // slot would be flip. + if (slot != current_slot_) bootctrl.slot_info[slot].verity_corrupted = 0; + + return UpdateAndSaveBootloaderControl(misc_device_, &bootctrl); +} + +bool BootControl::SetSlotAsUnbootable(unsigned int slot) { + if (slot >= kMaxNumSlots || slot >= num_slots_) { + // Invalid slot number. + return false; + } + + bootloader_control bootctrl; + if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false; + + // The only way to mark a slot as unbootable, regardless of the priority is to + // set the tries_remaining to 0. + bootctrl.slot_info[slot].successful_boot = 0; + bootctrl.slot_info[slot].tries_remaining = 0; + return UpdateAndSaveBootloaderControl(misc_device_, &bootctrl); +} + +bool BootControl::IsSlotBootable(unsigned int slot) { + if (slot >= kMaxNumSlots || slot >= num_slots_) { + // Invalid slot number. + return false; + } + + bootloader_control bootctrl; + if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false; + + return bootctrl.slot_info[slot].tries_remaining != 0; +} + +bool BootControl::IsSlotMarkedSuccessful(unsigned int slot) { + if (slot >= kMaxNumSlots || slot >= num_slots_) { + // Invalid slot number. + return false; + } + + bootloader_control bootctrl; + if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false; + + return bootctrl.slot_info[slot].successful_boot && bootctrl.slot_info[slot].tries_remaining; +} + +const char* BootControl::GetSuffix(unsigned int slot) { + if (slot >= kMaxNumSlots || slot >= num_slots_) { + return nullptr; + } + return kSlotSuffixes[slot]; +} + +} // namespace bootable +} // namespace android |