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diff --git a/Documentation/util/smmstoretool/index.md b/Documentation/util/smmstoretool/index.md new file mode 100644 index 0000000000..f7af60579d --- /dev/null +++ b/Documentation/util/smmstoretool/index.md @@ -0,0 +1,126 @@ +# smmstoretool + +Offline SMMSTORE variable modification tool. + +## Operation + +### Storage initialization + +If SMMSTORE presence isn't detected and an update operation is requested, the +store spanning the whole file is created automatically. Size of the store file +must be a multiple of 64 KiB (block size in version 2 of SMMSTORE protocol), +the variable storage itself will be 64 KiB in size. That's the way EDK2 makes +use of it. + +Unlike online editing which mostly appends new variable entries each storage +update with this tool drops all deleted or incomplete entries. + +### Unicode + +There is no actual support for it. ASCII bytes (or UTF-8 bytes if that was +passed in) is just extended to 16 bits. And Unicode chars that are larger than +8 bit are turned into `?`. Need UTF-8 to/from UTF-16 conversion functions for +proper support. + +## Help + +Start with: + +``` +$ smmstoretool -h +Usage: smmstoretool smm-store-file sub-command + smmstoretool -h|--help + +Sub-commands: + * get - display current value of a variable + * guids - show GUID to alias mapping + * help - provide built-in help + * list - list variables present in the store + * remove - remove a variable from the store + * set - add or updates a variable in the store +``` + +Then run `smmstoretool rom help sub-command-name` to get more details. + +## Data types + +EFI variables in the storage don't have an associated data type and it needs to +be specified on reading/writing variables. Several basic types that correspond +to typical configuration values are supported: + + * `bool` (`true`, `false`) + * `uint8` (0-255) + * `uint16` (0-65535) + * `uint32` (0-4294967295) + * `ascii` (NUL-terminated) + * `unicode` (widened and NUL-terminated) + * `raw` (output only; raw bytes on output) + +## Examples + +`SMMSTORE` is the name of a file containing SMMSTORE data. + +### Variable listing + +``` +$ smmstoretool SMMSTORE list +dasharo :NetworkBoot (1 byte) +c076ec0c-7028-4399-a07271ee5c448b9f:CustomMode (1 byte) +d9bee56e-75dc-49d9-b4d7b534210f637a:certdb (4 bytes) +9073e4e0-60ec-4b6e-99034c223c260f3c:VendorKeysNv (1 byte) +6339d487-26ba-424b-9a5d687e25d740bc:TCG2_DEVICE_DETECTION (1 byte) +6339d487-26ba-424b-9a5d687e25d740bc:TCG2_CONFIGURATION (1 byte) +6339d487-26ba-424b-9a5d687e25d740bc:TCG2_VERSION (16 bytes) +global :Boot0000 (66 bytes) +global :Timeout (2 bytes) +global :PlatformLang (3 bytes) +global :Lang (4 bytes) +global :Key0000 (14 bytes) +global :Boot0001 (102 bytes) +global :Key0001 (14 bytes) +04b37fe8-f6ae-480b-bdd537d98c5e89aa:VarErrorFlag (1 byte) +dasharo :Type1UUID (16 bytes) +dasharo :Type2SN (10 bytes) +global :Boot0002 (90 bytes) +global :BootOrder (8 bytes) +global :Boot0003 (76 bytes) +... +``` + +### Variable reading + +``` +$ smmstoretool SMMSTORE get -g dasharo -n UsbDriverStack -t bool +false +``` + +### Variable writing + +``` +$ smmstoretool SMMSTORE set -g dasharo -n UsbDriverStack -t bool -v true +``` + +### Variable deletion + +``` +$ smmstoretool SMMSTORE remove -g dasharo -n NetworkBoot +``` + +### Real-world usage + +If one edits a newly generated Dasharo `coreboot.rom`: + +```bash +cbfstool coreboot.rom read -r SMMSTORE -f SMMSTORE +smmstoretool SMMSTORE set -g dasharo -n NetworkBoot -t bool -v true +cbfstool coreboot.rom write -r SMMSTORE -f SMMSTORE +``` + +On the first boot, "Network Boot" setting will already be enabled. + +Can also read SMMSTORE from a flash and examine some of its contents for +debugging purposes without adding new logging code or powering on the hardware: + +```bash +smmstoretool SMMSTORE get -g global -n BootOrder -t raw | hexdump -C +``` |