diff options
Diffstat (limited to 'src/boot/efi/xbootldr.c')
| -rw-r--r-- | src/boot/efi/xbootldr.c | 285 |
1 files changed, 285 insertions, 0 deletions
diff --git a/src/boot/efi/xbootldr.c b/src/boot/efi/xbootldr.c new file mode 100644 index 0000000..7fef909 --- /dev/null +++ b/src/boot/efi/xbootldr.c @@ -0,0 +1,285 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <efi.h> +#include <efigpt.h> +#include <efilib.h> + +#include "util.h" +#include "xbootldr.h" + +union GptHeaderBuffer { + EFI_PARTITION_TABLE_HEADER gpt_header; + uint8_t space[CONST_ALIGN_TO(sizeof(EFI_PARTITION_TABLE_HEADER), 512)]; +}; + +static EFI_DEVICE_PATH *path_replace_hd( + const EFI_DEVICE_PATH *path, + const EFI_DEVICE_PATH *node, + const HARDDRIVE_DEVICE_PATH *new_node) { + + /* Create a new device path as a copy of path, while chopping off the remainder starting at the given + * node. If new_node is provided, it is appended at the end of the new path. */ + + assert(path); + assert(node); + + size_t len = (uint8_t *) node - (uint8_t *) path, new_node_len = 0; + if (new_node) + new_node_len = DevicePathNodeLength(&new_node->Header); + + EFI_DEVICE_PATH *ret = xmalloc(len + new_node_len + END_DEVICE_PATH_LENGTH); + EFI_DEVICE_PATH *end = mempcpy(ret, path, len); + + if (new_node) + end = mempcpy(end, new_node, new_node_len); + + SetDevicePathEndNode(end); + return ret; +} + +static bool verify_gpt(union GptHeaderBuffer *gpt_header_buffer, EFI_LBA lba_expected) { + EFI_PARTITION_TABLE_HEADER *h; + uint32_t crc32, crc32_saved; + EFI_STATUS err; + + assert(gpt_header_buffer); + + h = &gpt_header_buffer->gpt_header; + + /* Some superficial validation of the GPT header */ + if (memcmp(&h->Header.Signature, "EFI PART", sizeof(h->Header.Signature)) != 0) + return false; + + if (h->Header.HeaderSize < 92 || h->Header.HeaderSize > 512) + return false; + + if (h->Header.Revision != 0x00010000U) + return false; + + /* Calculate CRC check */ + crc32_saved = h->Header.CRC32; + h->Header.CRC32 = 0; + err = BS->CalculateCrc32(gpt_header_buffer, h->Header.HeaderSize, &crc32); + h->Header.CRC32 = crc32_saved; + if (err != EFI_SUCCESS || crc32 != crc32_saved) + return false; + + if (h->MyLBA != lba_expected) + return false; + + if ((h->SizeOfPartitionEntry % sizeof(EFI_PARTITION_ENTRY)) != 0) + return false; + + if (h->NumberOfPartitionEntries <= 0 || h->NumberOfPartitionEntries > 1024) + return false; + + /* overflow check */ + if (h->SizeOfPartitionEntry > UINTN_MAX / h->NumberOfPartitionEntries) + return false; + + return true; +} + +static EFI_STATUS try_gpt( + EFI_BLOCK_IO_PROTOCOL *block_io, + EFI_LBA lba, + EFI_LBA *ret_backup_lba, /* May be changed even on error! */ + HARDDRIVE_DEVICE_PATH *ret_hd) { + + _cleanup_free_ EFI_PARTITION_ENTRY *entries = NULL; + union GptHeaderBuffer gpt; + EFI_STATUS err; + uint32_t crc32; + UINTN size; + + assert(block_io); + assert(ret_hd); + + /* Read the GPT header */ + err = block_io->ReadBlocks( + block_io, + block_io->Media->MediaId, + lba, + sizeof(gpt), &gpt); + if (err != EFI_SUCCESS) + return err; + + /* Indicate the location of backup LBA even if the rest of the header is corrupt. */ + if (ret_backup_lba) + *ret_backup_lba = gpt.gpt_header.AlternateLBA; + + if (!verify_gpt(&gpt, lba)) + return EFI_NOT_FOUND; + + /* Now load the GPT entry table */ + size = ALIGN_TO((UINTN) gpt.gpt_header.SizeOfPartitionEntry * (UINTN) gpt.gpt_header.NumberOfPartitionEntries, 512); + entries = xmalloc(size); + + err = block_io->ReadBlocks( + block_io, + block_io->Media->MediaId, + gpt.gpt_header.PartitionEntryLBA, + size, entries); + if (err != EFI_SUCCESS) + return err; + + /* Calculate CRC of entries array, too */ + err = BS->CalculateCrc32(entries, size, &crc32); + if (err != EFI_SUCCESS || crc32 != gpt.gpt_header.PartitionEntryArrayCRC32) + return EFI_CRC_ERROR; + + /* Now we can finally look for xbootloader partitions. */ + for (UINTN i = 0; i < gpt.gpt_header.NumberOfPartitionEntries; i++) { + EFI_PARTITION_ENTRY *entry = + (EFI_PARTITION_ENTRY *) ((uint8_t *) entries + gpt.gpt_header.SizeOfPartitionEntry * i); + + if (memcmp(&entry->PartitionTypeGUID, XBOOTLDR_GUID, sizeof(entry->PartitionTypeGUID)) != 0) + continue; + + if (entry->EndingLBA < entry->StartingLBA) /* Bogus? */ + continue; + + *ret_hd = (HARDDRIVE_DEVICE_PATH) { + .Header = { + .Type = MEDIA_DEVICE_PATH, + .SubType = MEDIA_HARDDRIVE_DP, + }, + .PartitionNumber = i + 1, + .PartitionStart = entry->StartingLBA, + .PartitionSize = entry->EndingLBA - entry->StartingLBA + 1, + .MBRType = MBR_TYPE_EFI_PARTITION_TABLE_HEADER, + .SignatureType = SIGNATURE_TYPE_GUID, + }; + memcpy(ret_hd->Signature, &entry->UniquePartitionGUID, sizeof(ret_hd->Signature)); + + /* HARDDRIVE_DEVICE_PATH has padding, which at least OVMF does not like. */ + SetDevicePathNodeLength( + &ret_hd->Header, + offsetof(HARDDRIVE_DEVICE_PATH, SignatureType) + sizeof(ret_hd->SignatureType)); + + return EFI_SUCCESS; + } + + /* This GPT was fully valid, but we didn't find what we are looking for. This + * means there's no reason to check the second copy of the GPT header */ + return EFI_NOT_FOUND; +} + +static EFI_STATUS find_device(EFI_HANDLE *device, EFI_DEVICE_PATH **ret_device_path) { + EFI_STATUS err; + + assert(device); + assert(ret_device_path); + + EFI_DEVICE_PATH *partition_path; + err = BS->HandleProtocol(device, &DevicePathProtocol, (void **) &partition_path); + if (err != EFI_SUCCESS) + return err; + + /* Find the (last) partition node itself. */ + EFI_DEVICE_PATH *part_node = NULL; + for (EFI_DEVICE_PATH *node = partition_path; !IsDevicePathEnd(node); node = NextDevicePathNode(node)) { + if (DevicePathType(node) != MEDIA_DEVICE_PATH) + continue; + + if (DevicePathSubType(node) != MEDIA_HARDDRIVE_DP) + continue; + + part_node = node; + } + + if (!part_node) + return EFI_NOT_FOUND; + + /* Chop off the partition part, leaving us with the full path to the disk itself. */ + _cleanup_free_ EFI_DEVICE_PATH *disk_path = NULL; + EFI_DEVICE_PATH *p = disk_path = path_replace_hd(partition_path, part_node, NULL); + + EFI_HANDLE disk_handle; + EFI_BLOCK_IO_PROTOCOL *block_io; + err = BS->LocateDevicePath(&BlockIoProtocol, &p, &disk_handle); + if (err != EFI_SUCCESS) + return err; + + /* The drivers for other partitions on this drive may not be initialized on fastboot firmware, so we + * have to ask the firmware to do just that. */ + (void) BS->ConnectController(disk_handle, NULL, NULL, true); + + err = BS->HandleProtocol(disk_handle, &BlockIoProtocol, (void **)&block_io); + if (err != EFI_SUCCESS) + return err; + + /* Filter out some block devices early. (We only care about block devices that aren't + * partitions themselves — we look for GPT partition tables to parse after all —, and only + * those which contain a medium and have at least 2 blocks.) */ + if (block_io->Media->LogicalPartition || + !block_io->Media->MediaPresent || + block_io->Media->LastBlock <= 1) + return EFI_NOT_FOUND; + + /* Try several copies of the GPT header, in case one is corrupted */ + EFI_LBA backup_lba = 0; + for (UINTN nr = 0; nr < 3; nr++) { + EFI_LBA lba; + + /* Read the first copy at LBA 1 and then try the backup GPT header pointed + * to by the first header if that one was corrupted. As a last resort, + * try the very last LBA of this block device. */ + if (nr == 0) + lba = 1; + else if (nr == 1 && backup_lba != 0) + lba = backup_lba; + else if (nr == 2 && backup_lba != block_io->Media->LastBlock) + lba = block_io->Media->LastBlock; + else + continue; + + HARDDRIVE_DEVICE_PATH hd; + err = try_gpt( + block_io, lba, + nr == 0 ? &backup_lba : NULL, /* Only get backup LBA location from first GPT header. */ + &hd); + if (err != EFI_SUCCESS) { + /* GPT was valid but no XBOOT loader partition found. */ + if (err == EFI_NOT_FOUND) + break; + /* Bad GPT, try next one. */ + continue; + } + + /* Patch in the data we found */ + *ret_device_path = path_replace_hd(partition_path, part_node, &hd); + return EFI_SUCCESS; + } + + /* No xbootloader partition found */ + return EFI_NOT_FOUND; +} + +EFI_STATUS xbootldr_open(EFI_HANDLE *device, EFI_HANDLE *ret_device, EFI_FILE **ret_root_dir) { + _cleanup_free_ EFI_DEVICE_PATH *partition_path = NULL; + EFI_HANDLE new_device; + EFI_FILE *root_dir; + EFI_STATUS err; + + assert(device); + assert(ret_device); + assert(ret_root_dir); + + err = find_device(device, &partition_path); + if (err != EFI_SUCCESS) + return err; + + EFI_DEVICE_PATH *dp = partition_path; + err = BS->LocateDevicePath(&BlockIoProtocol, &dp, &new_device); + if (err != EFI_SUCCESS) + return err; + + err = open_volume(new_device, &root_dir); + if (err != EFI_SUCCESS) + return err; + + *ret_device = new_device; + *ret_root_dir = root_dir; + return EFI_SUCCESS; +} |