/*
* 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
