From df931e3b4bc07ac752ab92075dfffc32bde5f50e Mon Sep 17 00:00:00 2001
From: Regia König
Date: Tue, 16 Aug 2022 12:56:08 +0200
Subject: Minimal working example with GNU-efi

---
 documentation/GNU-efi | 111 +++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 106 insertions(+), 5 deletions(-)

(limited to 'documentation')

diff --git a/documentation/GNU-efi b/documentation/GNU-efi
index 7fb0f1f..8dddc4a 100644
--- a/documentation/GNU-efi
+++ b/documentation/GNU-efi
@@ -1,5 +1,106 @@
-##################################################################
-##								##
-##		BUILDING HELLOWORLD.EFI WIH GNU-EFI		##	
-##								##
-##################################################################
+##################################################################################
+##										##
+##		BUILDING HELLOWORLD.EFI WIH GNU-EFI				##	
+##										##
+##################################################################################
+
+#################################################################################
+#				SUMMARY						#
+#################################################################################
+
+Minimal working example:
+
+	hello.c
+---------------------------------------------------------------------------------
+#include <efi.h>
+#include <efilib.h>
+
+EFI_STATUS
+EFIAPI
+efi_main (EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable) {
+
+    InitializeLib(ImageHandle, SystemTable);
+    Print(L"Hello, world!\n");
+
+    return EFI_SUCCESS;
+}
+
+
+Makefile
+--------------------------------------------------------------------------------
+ARCH        = $(shell uname -m | sed s,i[3456789]86,ia32,)
+
+OBJS        = hello.o
+TARGET        = hello.efi
+
+EFIINC        = /usr/include/efi
+EFFINCS        = -I$(EFIINC) -I$(EFIINC)/$(ARCH) -I$(EFIINC)/protocol
+EFILIB        = /usr/lib
+EFI_CRT_OBJS    = $(EFILIB)/crt0-efi-$(ARCH).o
+EFI_LDS        = $(EFILIB)/elf_$(ARCH)_efi.lds
+
+CFLAGS        = $(EFFINCS) -fno-stack-protector -fpic \
+            -fshort-wchar -mno-red-zone -Wall
+
+ifeq ($(ARCH),x86_64)
+    CFLAGS += -DEFI_FUNCTION_WRAPPER
+endif
+
+LDFLAGS        = -nostdlib -znocombreloc -T $(EFI_LDS) -shared \
+            -Bsymbolic -L $(EFILIB) $(EFI_CRT_OBJS)
+
+all: $(TARGET)
+
+hello.so: $(OBJS)
+    ld $(LDFLAGS) $(OBJS) -o $@ -lefi -lgnuefi
+
+%.efi: %.so
+    objcopy -j .text -j .sdata -j .data -j .dynamic \
+    -j .dynsym -j .rel -j .rela -j .reloc \
+    --target=efi-app-$(ARCH) $^ $@
+
+
+
+
+#################################################################################
+#		https://wiki.osdev.org/GNU-EFI					# 
+#################################################################################
+
+GNU-EFI is a very lightweight developing environment to create UEFI applications.
+It is a set of libraries and headers for compiling UEFI applications with a
+system's native GCC.
+
+You can use host native compiler, then convert resulting ELF into UEFI-compatible
+PE.
+	OR
+Use GCC Cross-Compiler generating PE directly.
+
+*********************************************************************************
+* $ git clone https://git.code.sf.net/p/gnu-efi/code gnu-efi			*
+* $ cd gnu-efi									*
+* $ make									*
+*********************************************************************************
+
+This should create
+* crt0-efi-x86_64.o:
+	A CRT0 (C runtime initialization code) that will call the 
+	"efi_main" function
+
+* libgnuefi.a:
+	A library containing a single function (_relocate)
+	that is used by the CRT0
+
+* (optional) libefi.a:
+	A library containing convenience functions like CRC computation, string
+	length calculation, and easy text printing
+
+HEADERS can be used from:
+* /usr/include/efi   (updated to the latest)
+* from EDK2 package
+* Or from gnu-efi/inc
+
+LINKER SCRIPT:
+* gnu-efi/gnuefi/elf_x86_64_efi.lds
+	OR
+* /usr/lib/elf_x86_64_efi.lds
+
-- 
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