+A UEFI images is basically a windows EXE without symbol tables. There are three
+types of UEFI images; we use the EFI application, which has subsystem `10`. It
+is an x68-64 image, which has value `0x8664`.
+
+UEFI applications use [Microsoft's 64-bit calling
+convention](https://en.wikipedia.org/wiki/X86_calling_conventions#Microsoft_x64_calling_convention)
+for x68-64 functions. See the linked article for a full description. Here is
+the short version:
+
+- Integer or pointer arguments are given in RCX, RDX, R8 and R9.
+- Additional arguments are pushed onto the stack from right to left.
+- Integer or pointer values are returned in RAX.
+- An integer-sized struct is passed directly; non-integer-sized structs are passed as pointers.
+- The caller must allocate 32 bytes of "shadow space" on the stack immediately
+ before calling the function, regardless of the number of parameters used, and
+ the caller is responsible for popping the stack afterwards.
+- The following registers are volatile (caller-saved): RAX, RCX, RDX, R8, R9, R10, R11
+- The following registers are nonvolatile (callee-saved): RBX, RBP, RDI, RSI, RSP, R12, R13, R14, R15
+
+When the application is loaded, RCX contains a firmware allocated `EFI_HANDLE`
+for the UEFI image, RDX contains a `EFI_SYSTEM_TABLE*` pointer to the EFI system
+table and RSP contains the return address. For more infromation about how a UEFI
+application is entered, see "4 - EFI System Table" in [the latest UEFI
+specification as of March 2020 (PDF)](https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_A_Feb14.pdf).
+
+**Sources:**
+
+- [UEFI applications in detail - OSDev Wiki](https://wiki.osdev.org/UEFI#UEFI_applications_in_detail)
+- [Microsoft x64 calling convention](https://en.wikipedia.org/wiki/X86_calling_conventions#Microsoft_x64_calling_convention)
+- [UEFI Specifications](https://uefi.org/specifications)
+
+### UEFI with FASM
+
+We might want to consider using something like this: https://wiki.osdev.org/Uefi.inc)
+
+FASM can generate UEFI application binaries by default. Use the following
+template to output a 64-bit UEFI application:
+
+ format pe64 dll efi
+ entry main
+
+ section '.text' code executable readable
+
+ main:
+ ;; ...
+ ret
+
+ section '.data' data readable writable
+
+ ;; ...
+
+Use `objdump -x` to inspect the assembled application binary.
+
+### UEFI documentation
+
+- [Latest specification as of March 2020 (PDF)](https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_A_Feb14.pdf)
+
+Notable sections:
+
+- 2\. Overview (14)
+- 4\. EFI System Table (89)
+- 7\. Services - Boot Services (140)
+- 8\. Services - Runtime Services (228)
+- 12\. Protocols - Console Support (429)
+- 13\. Protocols - Media Access (493)
+- Appendix B - Console (2201)
+- Appendix D - Status Codes (2211)