dasharo/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 entries are added for each of the discovered capsules

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

Change-Id: I162d678ae5c504906084b59c1a8d8c26dadb9433
Signed-off-by: Sergii Dmytruk <[email protected]>

src/drivers/efi/Kconfig

@@ -6,3 +6,11 @@ config DRIVERS_EFI_VARIABLE_STORE
 	help
 	  Adds a driver that is able to read and write an EFI formatted
 	  VariableStore as used by tianocore.
+
+config DRIVERS_EFI_UPDATE_CAPSULES
+	bool "Include EFI update capsules driver"
+	depends on DRIVERS_EFI_VARIABLE_STORE && SMMSTORE_V2
+	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.

src/drivers/efi/Makefile.mk

@@ -3,5 +3,7 @@
 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