drivers/efi/uefi_capsules.c: coalesce and store UEFI capsules

How it approximately works:

(During a normal system run):
1. OS puts a capsule into RAM and calls UpdateCapsule() function of EFI
   runtime
2. If applying the update requires a reboot, EFI implementation creates
   a new CapsuleUpdateData* EFI variable pointing at the beginning of
   capsules description (not data, but description of the data) and does
   a warm reboot leaving capsule data and its description in RAM to be
   picked by firmware on the next boot process

(After DEV_INIT:)
3. Capsules are discovered by checking for CapsuleUpdateData* variables
4. Capsule description in memory and capsule data is validated for
   sanity
5. Capsule data is coalesced into a continuous piece of memory

(On BS_WRITE_TABLES via dasharo_add_capsules_to_bootmem() hook:)
6. Buffer with coalesced capsules is marked as reserved

(On BS_WRITE_TABLES via lb_uefi_capsules() hook:)
7. coreboot table entry is added for each of the discovered capsules

(In UEFI payload:)
8. CapsuleUpdateData* get removed
9. coreboot table is checked for any update capsules which are then
   applied

Change-Id: I162d678ae5c504906084b59c1a8d8c26dadb9433
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83422
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Krystian Hebel <krystian.hebel@3mdeb.com>

4 files changed, 800 insertions, 0 deletions

diff --git a/src/drivers/efi/Kconfig b/src/drivers/efi/Kconfig
index 399443bdaa..07e5f146a6 100644
--- a/src/drivers/efi/Kconfig
+++ b/src/drivers/efi/Kconfig
@@ -38,3 +38,11 @@ config DRIVERS_EFI_MAIN_FW_LSV
 	  32-bit unsigned integer representing lowest firmware version number
 	  that is allowed to replace the current one.  Can be used to forbid
 	  bugged versions.
+
+config DRIVERS_EFI_UPDATE_CAPSULES
+	bool "Include EFI update capsules driver"
+	depends on DRIVERS_EFI_VARIABLE_STORE && SMMSTORE_V2 && DRIVERS_EFI_FW_INFO
+	help
+	  Adds a driver that is able to parse CapsuleUpdateData* EFI variables
+	  to discover firmware updates and expose them for tianocore thorough
+	  CBMEM for execution.  tianocore is responsible for erasing the variables.
diff --git a/src/drivers/efi/Makefile.mk b/src/drivers/efi/Makefile.mk
index 47f0e82990..2c3cf9c3bf 100644
--- a/src/drivers/efi/Makefile.mk
+++ b/src/drivers/efi/Makefile.mk
@@ -3,6 +3,8 @@
 all-$(CONFIG_DRIVERS_EFI_VARIABLE_STORE)	+= efivars.c
 smm-$(CONFIG_DRIVERS_EFI_VARIABLE_STORE)	+= efivars.c
 
+ramstage-$(CONFIG_DRIVERS_EFI_UPDATE_CAPSULES)	+= capsules.c
+
 all-$(CONFIG_USE_UEFI_VARIABLE_STORE)	+= option.c
 smm-$(CONFIG_USE_UEFI_VARIABLE_STORE)	+= option.c
 
diff --git a/src/drivers/efi/capsules.c b/src/drivers/efi/capsules.c
new file mode 100644
index 0000000000..e674e33228
--- /dev/null
+++ b/src/drivers/efi/capsules.c
@@ -0,0 +1,770 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <acpi/acpi.h>
+#include <boot/coreboot_tables.h>
+#include <bootmem.h>
+#include <bootstate.h>
+#include <cbmem.h>
+#include <console/console.h>
+#include <cpu/x86/pae.h>
+#include <drivers/efi/efivars.h>
+#include <drivers/efi/capsules.h>
+#include <memrange.h>
+#include <string.h>
+#include <stdio.h>
+#include <smmstore.h>
+#include <types.h>
+
+#include <Uefi/UefiSpec.h>
+#include <Guid/GlobalVariable.h>
+#include <Guid/FmpCapsule.h>
+#include <IndustryStandard/WindowsUxCapsule.h>
+
+/*
+ * Overview
+ *
+ * SG stands for scatter-gather.  SG list consists of SG blocks that describe a
+ * potentially discontinuous sequence of memory blocks while not necessarily
+ * lying in continuous memory themselves.
+ *
+ * SG list is basically a linked list of arrays of block descriptors (SG
+ * blocks).  Each of SG blocks can be:
+ *  - a data block, which points to capsule's data
+ *  - a continuation block, which says where other SG blocks are to be found
+ *  - end-of-list block, which indicates there are no more blocks
+ *
+ * Each of the CapsuleUpdateData* EFI variables point to some SG list which
+ * might contain one or more update capsules.  SG blocks never contain data of
+ * more than one of the capsules.  Boundary between capsules in an SG list is
+ * determined by parsing capsule headers and counting amount of data seen so
+ * far.
+ *
+ * There can be multiple CapsuleUpdateData* variables (CapsuleUpdateData,
+ * CapsuleUpdateData1, etc.) in which case their SG lists are chained together
+ * after sanity checks.
+ */
+
+/* This should be more than enough. */
+#define MAX_CAPSULES 32
+
+/* 4 should be enough, but 8 won't hurt. */
+#define CAPSULE_ALIGNMENT 8
+
+/*
+ * A helper structure which bundles physical block address with its data.  It's
+ * necessary because 32-bit code can't easily access anything beyond 4 GiB
+ * boundary and this structure allows reading the data, passing it around and,
+ * if necessary, updating it.
+ *
+ * Usage:
+ *  1) Set .self to physical address
+ *  2) Check block's address with is_good_block()
+ *  3) Use load_block() to fetch or store_block() to update data
+ */
+struct block_descr {
+	/* Where the data comes from. */
+	uint64_t self;
+
+	/*
+	 * Data read from the self address above.  Three cases:
+	 *  - len != 0 && addr != 0  =>  len bytes of capsule data at addr
+	 *                               next block_descr follows this one (self + 16)
+	 *  - len == 0 && addr != 0  =>  no data
+	 *                               next block_descr is at addr
+	 *  - len == 0 && addr == 0  =>  no data
+	 *                               no next block_descr
+	 */
+	uint64_t len;
+	uint64_t addr;
+};
+
+/* For passing data from efi_parse_capsules() to bootmem and CBMEM callbacks. */
+struct memory_range {
+	uint32_t base;
+	uint32_t len;
+};
+
+static const EFI_GUID capsule_vendor_guid = {
+	0x711C703F, 0xC285, 0x4B10, { 0xA3, 0xB0, 0x36, 0xEC, 0xBD, 0x3C, 0x8B, 0xE2 }
+};
+static const EFI_GUID windows_ux_capsule_guid = WINDOWS_UX_CAPSULE_GUID;
+static const EFI_GUID edk2_capsule_on_disk_name_guid = {
+	0x98C80A4F, 0xE16B, 0x4D11, { 0x93, 0x9A, 0xAB, 0xE5, 0x61, 0x26, 0x3, 0x30 }
+};
+static const EFI_GUID efi_fmp_capsule_guid = EFI_FIRMWARE_MANAGEMENT_CAPSULE_ID_GUID;
+
+/* Memory map to keep track of unused or reserved ranges. */
+struct memranges memory_map;
+
+/* Page tables required for pae_map_2M_page(). */
+static char pae_page_tables[20 * KiB] __aligned(4 * KiB);
+
+/* Where all coalesced capsules are located. */
+struct memory_range coalesce_buffer;
+
+/* Where individual coalesced capsules are located and their count. */
+static struct memory_range uefi_capsules[MAX_CAPSULES];
+static int uefi_capsule_count;
+
+static bool is_data_block(const struct block_descr *block)
+{
+	return (block->len != 0);
+}
+
+static bool is_final_block(const struct block_descr *block)
+{
+	return (block->len == 0 && block->addr == 0);
+}
+
+static void *map_range(uint64_t base, uint32_t len)
+{
+	static uint64_t last_mapping_base = UINT64_MAX;
+
+	/* Using MMCONF should be safe as long as we don't do any device
+	   initialization during parsing of capsules and don't forget to call
+	   paging_disable_pae() at the end. */
+	_Static_assert(IS_ALIGNED(CONFIG_ECAM_MMCONF_BASE_ADDRESS, 2 * MiB));
+	uintptr_t window_base = CONFIG_ECAM_MMCONF_BASE_ADDRESS;
+	size_t window_size = 2 * MiB;
+
+	printk(BIOS_SPEW, "capsules: mapping %#010x bytes at %#010llx.\n", len, base);
+
+	if (base + len <= 4ULL * GiB &&
+	    (base + len <= window_base || base >= window_base + window_size)) {
+		/* Don't bother with the mapping, the whole range must be
+		   already accessible without it. */
+		printk(BIOS_SPEW, "capsules: no need to map anything.\n");
+		return (void *)(uintptr_t)base;
+	}
+
+	uint64_t aligned_base = ALIGN_DOWN(base, 2 * MiB);
+	if (base - aligned_base + len > 2 * MiB)
+		die("capsules: memory range map request can't be satisfied.\n");
+
+	/* No need to map the same data. */
+	if (aligned_base != last_mapping_base) {
+		printk(BIOS_SPEW, "capsules: mapping from %#010llx.\n", aligned_base);
+		pae_map_2M_page(&pae_page_tables, aligned_base, (void *)window_base);
+		last_mapping_base = aligned_base;
+	}
+
+	return (uint8_t *)window_base + (base - aligned_base);
+}
+
+/*
+ * Alignment requirement on EFI_CAPSULE_BLOCK_DESCRIPTOR seems to be 8 bytes,
+ * which means that it can be cut in half by a mapping.  Could map two 2 MiB
+ * pages instead, but should be easier to simply read those 16 bytes and pass
+ * them around.
+ *
+ * `volatile` is to guard against a hypothetical statement reordering.
+ */
+
+static void load_block(struct block_descr *block)
+{
+	volatile uint64_t *len = map_range(block->self, sizeof(uint64_t));
+	block->len = *len;
+
+	volatile uint64_t *addr = map_range(block->self + sizeof(uint64_t), sizeof(uint64_t));
+	block->addr = *addr;
+}
+
+static void store_block(const struct block_descr *block)
+{
+	volatile uint64_t *len = map_range(block->self, sizeof(uint64_t));
+	*len = block->len;
+
+	volatile uint64_t *addr = map_range(block->self + sizeof(uint64_t), sizeof(uint64_t));
+	*addr = block->addr;
+}
+
+static void advance_block(struct block_descr *block)
+{
+	if (is_final_block(block))
+		die("capsules: attempt to advance beyond final SG block of UEFI capsules.\n");
+
+	if (is_data_block(block)) {
+		/* That was at least part of a capsule. */
+		block->self = block->self + sizeof(EFI_CAPSULE_BLOCK_DESCRIPTOR);
+	} else {
+		/* End of continuous sequence of descriptors, but there are more. */
+		block->self = block->addr;
+	}
+}
+
+static bool is_good_capsule(const EFI_CAPSULE_HEADER *capsule)
+{
+	if (capsule->HeaderSize < sizeof(*capsule)) {
+		printk(BIOS_ERR, "capsules: capsule header size is too small: %#010x.\n",
+		       capsule->HeaderSize);
+		return false;
+	}
+	if (capsule->CapsuleImageSize <= capsule->HeaderSize) {
+		printk(BIOS_ERR, "capsules: capsule image size is too small: %#010x.\n",
+		       capsule->CapsuleImageSize);
+		return false;
+	}
+	if (!(capsule->Flags & CAPSULE_FLAGS_PERSIST_ACROSS_RESET)) {
+		printk(BIOS_ERR,
+		       "capsules: this capsule should not have persisted, flags: %#010x.\n",
+		       capsule->Flags);
+		return false;
+	}
+
+	const EFI_GUID *guid = &capsule->CapsuleGuid;
+	if (memcmp(guid, &windows_ux_capsule_guid, sizeof(*guid)) == 0)
+		return true;
+	if (memcmp(guid, &edk2_capsule_on_disk_name_guid, sizeof(*guid)) == 0)
+		return true;
+	if (memcmp(guid, &efi_fmp_capsule_guid, sizeof(*guid)) == 0)
+		return true;
+
+	printk(BIOS_ERR, "capsules: unrecognized capsule GUID.\n");
+	return false;
+}
+
+static bool is_in_unused_ram(uint64_t base, uint64_t len)
+{
+	if (len == 0) {
+		die("capsules: %s() was passed an empty range: %#010llx:%#010llx.\n",
+		    __func__, base, len);
+	}
+	if (base + len < base) {
+		die("capsules: %s() was passed an invalid range: %#010llx:%#010llx.\n",
+		    __func__, base, len);
+	}
+
+	const struct range_entry *r;
+	memranges_each_entry(r, &memory_map) {
+		if (range_entry_tag(r) != BM_MEM_RAM)
+			continue;
+
+		if (base >= range_entry_base(r) && base + len <= range_entry_end(r))
+			return true;
+	}
+
+	return false;
+}
+
+static bool is_good_block(struct block_descr *block)
+{
+	if (!IS_ALIGNED(block->self, sizeof(uint64_t))) {
+		printk(BIOS_ERR, "capsules: misaligned SG block at %#010llx.\n", block->self);
+		return false;
+	}
+
+	if (!is_in_unused_ram(block->self, sizeof(*block))) {
+		printk(BIOS_ERR, "capsules: SG block is not in unused memory.\n");
+		return false;
+	}
+
+	return true;
+}
+
+static bool is_good_capsule_head(struct block_descr *block)
+{
+	if (!is_data_block(block)) {
+		printk(BIOS_ERR, "capsules: first capsule SG block is not a data block.\n");
+		return false;
+	}
+
+	if (block->len < sizeof(EFI_CAPSULE_HEADER)) {
+		printk(BIOS_ERR, "capsules: first SG block of a capsule is too small.\n");
+		return false;
+	}
+
+	if (!is_in_unused_ram(block->addr, block->len)) {
+		printk(BIOS_ERR, "capsules: capsule header is not in unused memory.\n");
+		return false;
+	}
+
+	return true;
+}
+
+static bool is_good_capsule_block(struct block_descr *block, uint32_t size_left)
+{
+	if (is_final_block(block)) {
+		printk(BIOS_ERR, "capsules: not enough SG blocks to cover a capsule.\n");
+		return false;
+	}
+
+	if (!is_data_block(block)) {
+		printk(BIOS_ERR, "capsules: capsule SG block is not a data block.\n");
+		return false;
+	}
+
+	if (block->len > size_left) {
+		printk(BIOS_ERR, "capsules: SG blocks reach beyond a capsule.\n");
+		return false;
+	}
+
+	if (!is_in_unused_ram(block->addr, block->len)) {
+		printk(BIOS_ERR, "capsules: capsule data is not in unused memory.\n");
+		return false;
+	}
+
+	return true;
+}
+
+/* Checks a single SG list for sanity.  Returns its end-of-list descriptor or
+   an empty one on error. */
+static struct block_descr check_capsule_block(struct block_descr first_block,
+					      uint64_t *total_data_size)
+{
+	struct block_descr block = first_block;
+	if (!is_good_block(&block)) {
+		printk(BIOS_ERR, "capsules: bad capsule block start.\n");
+		goto error;
+	}
+
+	load_block(&block);
+
+	uint64_t data_size = 0;
+	while (!is_final_block(&block)) {
+		/*
+		 * This results in dropping of this capsule block if any of
+		 * contained capsule headers looks weird.  An alternative is to
+		 * cut the capsule block upon finding a bad header.  Maybe
+		 * could even jump over a broken capsule, temporarily trusting
+		 * size field in its header because invalid value should not
+		 * break parsing anyway, and then cut it out of the sequence of
+		 * blocks.  EDK doesn't bother, so only noting the possibility.
+		 */
+		if (!is_good_capsule_head(&block)) {
+			printk(BIOS_ERR, "capsules: bad capsule header @ %#010llx.\n",
+			       block.addr);
+			goto error;
+		}
+
+		const EFI_CAPSULE_HEADER *capsule_hdr =
+			map_range(block.addr, sizeof(*capsule_hdr));
+		if (!is_good_capsule(capsule_hdr)) {
+			printk(BIOS_ERR, "capsules: bad capsule header @ %#010llx.\n",
+			       block.addr);
+			goto error;
+		}
+
+		data_size += ALIGN_UP(capsule_hdr->CapsuleImageSize, CAPSULE_ALIGNMENT);
+
+		uint32_t size_left = capsule_hdr->CapsuleImageSize;
+		while (size_left != 0) {
+			/* is_good_block() holds here whether it's the first iteration or
+			   not. */
+
+			if (!is_good_capsule_block(&block, size_left))
+				goto error;
+
+			size_left -= block.len;
+
+			advance_block(&block);
+			if (!is_good_block(&block)) {
+				printk(BIOS_ERR, "capsules: capsule body has a bad block.\n");
+				goto error;
+			}
+
+			load_block(&block);
+			if (!is_final_block(&block) && !is_data_block(&block)) {
+				/* Advance to the next page of block descriptors. */
+				advance_block(&block);
+				if (!is_good_block(&block)) {
+					printk(BIOS_ERR, "capsules: bad SG continuation.\n");
+					goto error;
+				}
+
+				load_block(&block);
+				/* Not expecting a continuation to be followed by another
+				   continuation or an end-of-list. */
+				if (!is_data_block(&block)) {
+					printk(BIOS_ERR,
+					       "capsules: chained SG continuations.\n");
+					goto error;
+				}
+			}
+		}
+	}
+
+	/* Increase the size only on successful parsing of the capsule block. */
+	*total_data_size += data_size;
+
+	return block;
+
+error:
+	return (struct block_descr){ .self = 0 };
+}
+
+/* Fills an array with pointers to capsule blocks.  Returns number of
+   discovered capsule blocks or -1 on error. */
+static int discover_capsule_blocks(struct region_device *rdev,
+				   struct block_descr *blocks,
+				   int max_blocks)
+{
+	int block_count = 0;
+	for (int i = 0; block_count < max_blocks; ++i) {
+		char var_name[32];
+		if (i == 0)
+			strcpy(var_name, "CapsuleUpdateData");
+		else
+			snprintf(var_name, sizeof(var_name), "CapsuleUpdateData%d", i);
+
+		struct block_descr block;
+		uint32_t size = sizeof(block.self);
+		enum cb_err ret = efi_fv_get_option(rdev, &capsule_vendor_guid, var_name,
+						    &block.self, &size);
+		if (ret != CB_SUCCESS) {
+			/* No more variables. */
+			break;
+		}
+		if (size != sizeof(block.self)) {
+			printk(BIOS_ERR, "capsules: unexpected capsule data size (%d).\n",
+			       size);
+			return -1;
+		}
+
+		/*
+		 * EDK2 checks for duplicates probably because we'll get into
+		 * trouble with chaining if there are any, so do the check.
+		 *
+		 * This, however, won't handle all possible situations which
+		 * lead to loops or processing the same capsule more than once.
+		 */
+		int j;
+		for (j = 0; j < block_count; ++j) {
+			if (blocks[j].self == block.self)
+				break;
+		}
+		if (j < block_count) {
+			printk(BIOS_INFO, "capsules: skipping duplicated %s.\n", var_name);
+			continue;
+		}
+
+		printk(BIOS_INFO, "capsules: capsule block #%d at %#010llx.\n",
+		       block_count, block.self);
+		blocks[block_count++] = block;
+	}
+
+	return block_count;
+}
+
+/*
+ * This function connects tail of one block of descriptors with the head of the
+ * next one and returns pointer to the head of the whole chain.  While at it:
+ *  - validate structures and pointers for sanity
+ *  - compute total amount of memory needed for coalesced capsules
+ *
+ * Returns block that starts at 0 on error.
+ */
+static struct block_descr verify_and_chain_blocks(struct block_descr *blocks,
+						  int block_count,
+						  uint64_t *total_data_size)
+{
+	/* This won't be blocks[0] if there is something wrong with the first capsule block. */
+	struct block_descr head = {0};
+
+	/* End-of-list descriptor of the last chained block. */
+	struct block_descr tail = {0};
+
+	*total_data_size = 0;
+
+	for (int i = 0; i < block_count; ++i) {
+		struct block_descr last_block = check_capsule_block(blocks[i], total_data_size);
+		if (last_block.self == 0) {
+			/* Fail hard instead?  EDK just keeps going, as if capsule
+			   blocks are always independent. */
+			printk(BIOS_WARNING,
+			       "capsules: skipping damaged capsule block #%d @ %#010llx.\n",
+			       i, blocks[i].self);
+			continue;
+		}
+
+		if (head.self == 0) {
+			head = blocks[i];
+		} else {
+			tail.addr = blocks[i].self;
+			store_block(&tail);
+		}
+
+		tail = last_block;
+	}
+
+	return head;
+}
+
+/* Marks structures and data of SG lists as BM_MEM_RESERVED so we don't step on
+   them when looking for usable memory. */
+static void reserve_capsules(struct block_descr block_chain)
+{
+	struct block_descr block = block_chain;
+
+	/* This is the first block of a continuous sequence of blocks. */
+	struct block_descr seq_start = {0};
+
+	/* The code reserves sequences of blocks to avoid invoking
+	   memranges_insert() on each of a bunch of adjacent 16-byte blocks. */
+
+	load_block(&block);
+	for (; !is_final_block(&block); advance_block(&block), load_block(&block)) {
+		if (seq_start.self == 0)
+			seq_start = block;
+
+		if (is_data_block(&block)) {
+			/* Reserve capsule data. */
+			memranges_insert(&memory_map, block.addr, block.len, BM_MEM_RESERVED);
+		} else {
+			/* This isn't the final or a data block, so it must be the
+			   last block of a continuous sequence.  Reserve the whole
+			   sequence. */
+			memranges_insert(&memory_map,
+					 seq_start.self,
+					 block.self - seq_start.self +
+					 sizeof(EFI_CAPSULE_BLOCK_DESCRIPTOR),
+					 BM_MEM_RESERVED);
+
+			/* Will be set on the next iteration if there is one. */
+			seq_start.self = 0;
+		}
+	}
+
+	/* If continuations never show up in a row as checked by
+	   check_capsule_block(), seq_start must be non-NULL here. */
+	memranges_insert(&memory_map,
+			 seq_start.self,
+			 block.self - seq_start.self + sizeof(EFI_CAPSULE_BLOCK_DESCRIPTOR),
+			 BM_MEM_RESERVED);
+}
+
+/*
+ * Find a buffer below 4 GiB for coalesced capsules.
+ *
+ * Keeping it simple and allocating a single buffer.  However, there is
+ * no requirement to put all the capsules together, only that each of
+ * them is continuous in memory.  So if this is bad for some reason,
+ * can allocate a separate block for each.
+ *
+ * Returns buffer that starts at 0 on error.
+ */
+static struct memory_range pick_buffer(uint64_t total_data_size)
+{
+	struct memory_range buffer = {0};
+
+	/* 4 * KiB is the alignment set by memranges_init(). */
+	total_data_size = ALIGN_UP(total_data_size, 4 * KiB);
+
+	const struct range_entry *r;
+	memranges_each_entry(r, &memory_map) {
+		if (range_entry_tag(r) != BM_MEM_RAM)
+			continue;
+
+		resource_t base = range_entry_base(r);
+		if (base >= 4ULL * GiB)
+			break;
+
+		/* Possibly reduce size to not deal with ranges that cross 4 GiB boundary. */
+		resource_t size = range_entry_size(r);
+		if (base + size > 4ULL * GiB)
+			size -= base + size - 4ULL * GiB;
+
+		if (size >= total_data_size) {
+			/*
+			 * To not create troubles for payloads prefer higher addresses:
+			 *  - use the top part of a suitable range
+			 *  - exit the loop only after hitting 4 GiB boundary or end of the list
+			 */
+			buffer.base = base + size - total_data_size;
+			buffer.len = total_data_size;
+		}
+	}
+
+	return buffer;
+}
+
+/* Puts capsules into continuous physical memory. */
+static void coalesce_capsules(struct block_descr block_chain, uint8_t *target)
+{
+	struct block_descr block = block_chain;
+	uint8_t *capsule_start = NULL;
+	uint32_t size_left = 0;
+
+	/* No safety checks in this function, as all of them were done earlier. */
+
+	load_block(&block);
+	for (; !is_final_block(&block); advance_block(&block), load_block(&block)) {
+		/* Advance over a continuation. */
+		if (!is_data_block(&block))
+			continue;
+
+		/* This must be the first block of a capsule. */
+		if (size_left == 0) {
+			const EFI_CAPSULE_HEADER *capsule_hdr =
+				map_range(block.addr, sizeof(*capsule_hdr));
+			size_left = capsule_hdr->CapsuleImageSize;
+			capsule_start = target;
+		}
+
+		uint64_t addr = block.addr;
+		uint64_t data_left = block.len;
+		while (data_left != 0) {
+			uint64_t piece_len = MIN(data_left, 2 * MiB - (addr % 2 * MiB));
+			void *data = map_range(addr, piece_len);
+
+			memcpy(target, data, piece_len);
+
+			target += piece_len;
+			addr += piece_len;
+			data_left -= piece_len;
+		}
+
+		size_left -= block.len;
+
+		/* This must be the last block of a capsule, record it. */
+		if (size_left == 0) {
+			/* If we can just ignore corrupted capsules, then we can simply
+			   drop those which don't fit. */
+			if (uefi_capsule_count == MAX_CAPSULES) {
+				printk(BIOS_WARNING,
+				       "capsules: ignoring all capsules after #%d.\n",
+				       MAX_CAPSULES);
+				break;
+			}
+
+			uefi_capsules[uefi_capsule_count].base = (uintptr_t)capsule_start;
+			uefi_capsules[uefi_capsule_count].len = block.len;
+			uefi_capsule_count++;
+
+			/* This is to align start of the next capsule (assumes that
+			   initial value of target was suitably aligned). */
+			if (!IS_ALIGNED(block.len, CAPSULE_ALIGNMENT))
+				target += ALIGN_UP(block.len, CAPSULE_ALIGNMENT) - block.len;
+		}
+	}
+
+	printk(BIOS_INFO, "capsules: found %d capsule(s).\n", uefi_capsule_count);
+}
+
+void efi_parse_capsules(void)
+{
+	/* EDK2 starts with 20 items and then grows the list, but it's unlikely
+	   to be necessary in practice. */
+	enum { MAX_CAPSULE_BLOCKS = MAX_CAPSULES };
+
+	struct region_device rdev;
+	if (smmstore_lookup_region(&rdev)) {
+		printk(BIOS_INFO, "capsules: no SMMSTORE region, no update capsules.\n");
+		return;
+	}
+
+	memranges_init(&memory_map, IORESOURCE_MEM | IORESOURCE_FIXED | IORESOURCE_STORED |
+		       IORESOURCE_ASSIGNED | IORESOURCE_CACHEABLE, IORESOURCE_MEM |
+		       IORESOURCE_FIXED | IORESOURCE_STORED | IORESOURCE_ASSIGNED |
+		       IORESOURCE_CACHEABLE, BM_MEM_RAM);
+
+	init_pae_pagetables(&pae_page_tables);
+
+	/* Blocks are collected here when traversing CapsuleUpdateData*
+	   variables, duplicates are skipped. */
+	struct block_descr blocks[MAX_CAPSULE_BLOCKS];
+	int block_count = discover_capsule_blocks(&rdev, blocks, ARRAY_SIZE(blocks));
+	if (block_count <= 0) {
+		if (block_count == 0)
+			printk(BIOS_INFO, "capsules: no UEFI capsules were discovered.\n");
+		goto exit;
+	}
+
+	printk(BIOS_INFO, "capsules: processing %d capsule block(s).\n", block_count);
+
+	/* Broken capsules are ignored, ignore those which didn't fit as well. */
+	if (block_count == ARRAY_SIZE(blocks)) {
+		printk(BIOS_WARNING,
+		       "capsules: hit limit on capsule blocks, some might be ignored.\n");
+	}
+
+	/* Chaining is done to not pass around and update an array of pointers. */
+	uint64_t total_data_size;
+	struct block_descr block_chain =
+		verify_and_chain_blocks(blocks, block_count, &total_data_size);
+	if (block_chain.self == 0) {
+		printk(BIOS_ERR, "capsules: no valid capsules to process.\n");
+		goto exit;
+	}
+
+	printk(BIOS_DEBUG, "capsules: chained capsule blocks.\n");
+
+	/* Reserve all blocks and the data they point to to avoid checking for
+	   overlaps when looking for a buffer. */
+	reserve_capsules(block_chain);
+
+	printk(BIOS_DEBUG, "capsules: reserved capsule blocks.\n");
+
+	/* Also reserve memory range for cbmem.  Since it will still grow in
+	   size by an unknown amount, try to account for that by reserving at
+	   least 4 MiB more. */
+	void *cbmem_current;
+	size_t cbmem_size;
+	cbmem_get_region(&cbmem_current, &cbmem_size);
+	uintptr_t cbmem_future_base = ALIGN_DOWN((uintptr_t)cbmem_current - 4 * MiB, MiB);
+	memranges_insert(&memory_map,
+			 cbmem_future_base,
+			 (uintptr_t)cbmem_current + cbmem_size - cbmem_future_base,
+			 BM_MEM_RESERVED);
+
+	coalesce_buffer = pick_buffer(total_data_size);
+	if (coalesce_buffer.base == 0) {
+		printk(BIOS_ERR,
+		       "capsules: failed to find a buffer (%#llx bytes) for coalesced UEFI capsules.\n",
+		       total_data_size);
+	} else {
+		printk(BIOS_DEBUG, "capsules: coalescing capsules data @ %#010x.\n",
+		       coalesce_buffer.base);
+		coalesce_capsules(block_chain, (void *)(uintptr_t)coalesce_buffer.base);
+	}
+
+exit:
+	paging_disable_pae();
+	memranges_teardown(&memory_map);
+}
+
+void lb_efi_capsules(struct lb_header *header)
+{
+	int i;
+	for (i = 0; i < uefi_capsule_count; ++i) {
+		struct lb_range *capsule = (void *)lb_new_record(header);
+
+		printk(BIOS_INFO, "capsules: publishing a capsule @ %#010x.\n",
+		       uefi_capsules[i].base);
+
+		capsule->tag = LB_TAG_CAPSULE;
+		capsule->size = sizeof(*capsule);
+		capsule->range_start = uefi_capsules[i].base;
+		capsule->range_size = uefi_capsules[i].len;
+	}
+}
+
+void efi_add_capsules_to_bootmem(void)
+{
+	if (coalesce_buffer.len != 0) {
+		printk(BIOS_INFO, "capsules: reserving capsules data @ %#010x.\n",
+		       coalesce_buffer.base);
+		bootmem_add_range(coalesce_buffer.base, coalesce_buffer.len, BM_MEM_RESERVED);
+	}
+}
+
+/*
+ * The code from this unit is typically executed by clear_memory() which is run
+ * after DEV_INIT.  However, clear_memory() might not be compiled in in which
+ * case we still want to process capsules.
+ *
+ * State machine doesn't enforce any particular ordering for callbacks and
+ * running before DEV_INIT is too early due to MTTRs not being initialized.
+ * Hence invoking code is in two different places that should be mutually
+ * exclusive (can't set a "done" flag due to unknown ordering).
+ */
+#if !CONFIG(PLATFORM_HAS_DRAM_CLEAR)
+
+static void parse_capsules(void *unused)
+{
+	if (!acpi_is_wakeup_s3())
+		efi_parse_capsules();
+}
+
+BOOT_STATE_INIT_ENTRY(BS_DEV_INIT, BS_ON_EXIT, parse_capsules, NULL);
+
+#endif
diff --git a/src/drivers/efi/capsules.h b/src/drivers/efi/capsules.h
new file mode 100644
index 0000000000..608ce3400f
--- /dev/null
+++ b/src/drivers/efi/capsules.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _EDK2_CAPSULES_H_
+#define _EDK2_CAPSULES_H_
+
+#if CONFIG(DRIVERS_EFI_UPDATE_CAPSULES)
+
+void efi_parse_capsules(void);
+
+void efi_add_capsules_to_bootmem(void);
+
+#else
+
+static inline void efi_parse_capsules(void) { }
+
+static inline void efi_add_capsules_to_bootmem(void) { }
+
+#endif
+
+#endif /* _EDK2_CAPSULES_H_ */