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-rw-r--r--src/boot/efi/part-discovery.c298
1 files changed, 298 insertions, 0 deletions
diff --git a/src/boot/efi/part-discovery.c b/src/boot/efi/part-discovery.c
new file mode 100644
index 0000000..f5b1573
--- /dev/null
+++ b/src/boot/efi/part-discovery.c
@@ -0,0 +1,298 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "device-path-util.h"
+#include "part-discovery.h"
+#include "proto/block-io.h"
+#include "proto/device-path.h"
+#include "util.h"
+
+typedef struct {
+ EFI_GUID PartitionTypeGUID;
+ EFI_GUID UniquePartitionGUID;
+ EFI_LBA StartingLBA;
+ EFI_LBA EndingLBA;
+ uint64_t Attributes;
+ char16_t PartitionName[36];
+} EFI_PARTITION_ENTRY;
+
+typedef struct {
+ EFI_TABLE_HEADER Header;
+ EFI_LBA MyLBA;
+ EFI_LBA AlternateLBA;
+ EFI_LBA FirstUsableLBA;
+ EFI_LBA LastUsableLBA;
+ EFI_GUID DiskGUID;
+ EFI_LBA PartitionEntryLBA;
+ uint32_t NumberOfPartitionEntries;
+ uint32_t SizeOfPartitionEntry;
+ uint32_t PartitionEntryArrayCRC32;
+ uint8_t _pad[420];
+} _packed_ GptHeader;
+assert_cc(sizeof(GptHeader) == 512);
+
+static bool verify_gpt(/*const*/ GptHeader *h, EFI_LBA lba_expected) {
+ uint32_t crc32, crc32_saved;
+ EFI_STATUS err;
+
+ assert(h);
+
+ /* 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(h, 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 > SIZE_MAX / h->NumberOfPartitionEntries)
+ return false;
+
+ return true;
+}
+
+static EFI_STATUS try_gpt(
+ const EFI_GUID *type,
+ 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;
+ GptHeader gpt;
+ EFI_STATUS err;
+ uint32_t crc32;
+ size_t 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.AlternateLBA;
+
+ if (!verify_gpt(&gpt, lba))
+ return EFI_NOT_FOUND;
+
+ /* Now load the GPT entry table */
+ size = ALIGN_TO((size_t) gpt.SizeOfPartitionEntry * (size_t) gpt.NumberOfPartitionEntries, 512);
+ entries = xmalloc(size);
+
+ err = block_io->ReadBlocks(
+ block_io,
+ block_io->Media->MediaId,
+ gpt.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.PartitionEntryArrayCRC32)
+ return EFI_CRC_ERROR;
+
+ /* Now we can finally look for xbootloader partitions. */
+ for (size_t i = 0; i < gpt.NumberOfPartitionEntries; i++) {
+ EFI_PARTITION_ENTRY *entry =
+ (EFI_PARTITION_ENTRY *) ((uint8_t *) entries + gpt.SizeOfPartitionEntry * i);
+
+ if (!efi_guid_equal(&entry->PartitionTypeGUID, type))
+ continue;
+
+ if (entry->EndingLBA < entry->StartingLBA) /* Bogus? */
+ continue;
+
+ *ret_hd = (HARDDRIVE_DEVICE_PATH) {
+ .Header = {
+ .Type = MEDIA_DEVICE_PATH,
+ .SubType = MEDIA_HARDDRIVE_DP,
+ .Length = sizeof(HARDDRIVE_DEVICE_PATH),
+ },
+ .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));
+
+ 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(const EFI_GUID *type, 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, MAKE_GUID_PTR(EFI_DEVICE_PATH_PROTOCOL), (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; !device_path_is_end(node);
+ node = device_path_next_node(node)) {
+ if (node->Type != MEDIA_DEVICE_PATH || node->SubType != 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 = device_path_replace_node(partition_path, part_node, NULL);
+
+ EFI_HANDLE disk_handle;
+ EFI_BLOCK_IO_PROTOCOL *block_io;
+ err = BS->LocateDevicePath(MAKE_GUID_PTR(EFI_BLOCK_IO_PROTOCOL), &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, MAKE_GUID_PTR(EFI_BLOCK_IO_PROTOCOL), (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 (size_t 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(type, 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 = device_path_replace_node(partition_path, part_node, (EFI_DEVICE_PATH *) &hd);
+ return EFI_SUCCESS;
+ }
+
+ /* No xbootloader partition found */
+ return EFI_NOT_FOUND;
+}
+
+EFI_STATUS partition_open(const EFI_GUID *type, 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(type);
+ assert(device);
+ assert(ret_root_dir);
+
+ err = find_device(type, device, &partition_path);
+ if (err != EFI_SUCCESS)
+ return err;
+
+ EFI_DEVICE_PATH *dp = partition_path;
+ err = BS->LocateDevicePath(MAKE_GUID_PTR(EFI_BLOCK_IO_PROTOCOL), &dp, &new_device);
+ if (err != EFI_SUCCESS)
+ return err;
+
+ err = open_volume(new_device, &root_dir);
+ if (err != EFI_SUCCESS)
+ return err;
+
+ if (ret_device)
+ *ret_device = new_device;
+ *ret_root_dir = root_dir;
+ return EFI_SUCCESS;
+}
+
+char16_t *disk_get_part_uuid(EFI_HANDLE *handle) {
+ EFI_STATUS err;
+ EFI_DEVICE_PATH *dp;
+
+ /* export the device path this image is started from */
+
+ if (!handle)
+ return NULL;
+
+ err = BS->HandleProtocol(handle, MAKE_GUID_PTR(EFI_DEVICE_PATH_PROTOCOL), (void **) &dp);
+ if (err != EFI_SUCCESS)
+ return NULL;
+
+ for (; !device_path_is_end(dp); dp = device_path_next_node(dp)) {
+ if (dp->Type != MEDIA_DEVICE_PATH || dp->SubType != MEDIA_HARDDRIVE_DP)
+ continue;
+
+ HARDDRIVE_DEVICE_PATH *hd = (HARDDRIVE_DEVICE_PATH *) dp;
+ if (hd->SignatureType != SIGNATURE_TYPE_GUID)
+ continue;
+
+ return xasprintf(GUID_FORMAT_STR, GUID_FORMAT_VAL(hd->SignatureGuid));
+ }
+
+ return NULL;
+}
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