Magic bytes on ld scrpit working. Failed UEFI attempt.

README.md

@@ -5,11 +5,13 @@ Hello world examples of programs without an OS. A.K.A. bare bones.
 1.  Examples
     1.  [printf](printf/)
     1.  [min](min.S)
+    1.  [no-ld-script](no-ld-script/)
     1.  [bios_one_char](bios_one_char.S)
     1.  [bios_hello_world](bios_hello_world.S)
     1.  [shutdown_apm](shutdown_apm.S)
     1.  TODO not working
         1. [multiboot-c/](multiboot-c/)
+        1. [UEFI](uefi/)
         1. [hajji](hajji)
     1.  [nasm](nasm/)
 1.  [BIOS](bios.md)

TODO.md

@@ -3,8 +3,7 @@
 -   make work on real hardware
 -   ACPI
 -   get multiboot working
--   UEFI
--   reboot computer
+-   reboot computer. Would put QEMU into an infinite reboot loop. Awesome.
 -   multithreading: http://stackoverflow.com/questions/7308391/how-is-concurrency-done-in-intel-x86-assembly || http://stackoverflow.com/questions/980999/what-does-multicore-assembly-language-look-like || http://stackoverflow.com/questions/714905/threads-in-x86-assembler-using-the-gnu-assember-as
 -   transition to protected mode
     - test the paging circuit

a.ld

@@ -9,14 +9,8 @@ SECTIONS
         Magic bytes. 0x1FE == 510.
 
         We could add this on each Gas file.
-
-        TODO make them work here. Mentioned at: http://stackoverflow.com/a/9604338/895245
-
-        Another interesting example shows AT: http://dc0d32.blogspot.fr/2010/06/real-mode-in-c-with-gcc-writing.html
         */
-        /*
         . = 0x1FE;
-        SHORT(0xAA55);
-        */
+        SHORT(0xAA55)
     }
 }

common.h

@@ -1,3 +1,2 @@
 #define BEGIN .code16
-#define END .org 510;\
-            .word 0xaa55
+#define END

min.S

@@ -8,7 +8,3 @@ cli
 
 /* Stop the processor. */
 hlt
-
-/* Mandatory magic bytes 511 and 512. */
-.org 510
-.word 0xaa55

no-ld-script/Makefile

@@ -0,0 +1,15 @@
+.POSIX:
+
+MAIN := main.img
+
+.PHONY: clean run
+
+$(MAIN): main.S
+	as -o main.o '$<'
+	ld --oformat binary -o '$@' -Ttext 0x7C00 main.o
+
+clean:
+	rm -f '$(MAIN)'
+
+run: $(MAIN)
+	qemu-system-i386 -hda '$(MAIN)'

no-ld-script/README.md

@@ -0,0 +1,9 @@
+# No ld script
+
+Hello world using the default `ld` script, no explicit one set with `-T`. Uses:
+
+- `-tText`
+- `.org` inside each assembly file
+- `_start` must be present to avoid a warning, since the default linker script expects it
+
+Less convenient, but a little less code if you are using a single file.

no-ld-script/main.S

@@ -0,0 +1,18 @@
+.code16
+.global _start
+_start:
+    cli
+    mov $msg, %si
+    mov $0x0e, %ah
+loop:
+    lodsb
+    or %al, %al
+    jz halt
+    int $0x10
+    jmp loop
+halt:
+    hlt
+msg:
+    .asciz "hello world"
+.org 510
+.word 0xaa55

uefi/Makefile

@@ -0,0 +1,6 @@
+.POSIX:
+
+.PHONY: run
+
+run:
+	qemu-system-32 -bios ovmf.fd

uefi/README.md

@@ -0,0 +1,13 @@
+# UEFI
+
+Successor for BIOS.
+
+TODO get a hello world program working.
+
+- http://wiki.osdev.org/UEFI
+- https://fedoraproject.org/wiki/Using_UEFI_with_QEMU
+- https://wiki.ubuntu.com/UEFI/OVMF
+
+OVMF.fd IA32 r15214 downloaded from: https://sourceforge.net/projects/edk2/files/OVMF/OVMF-IA32-r15214.zip/download
+
+Included in-source for convenience, even though it is ugly.

uefi/main.c

@@ -0,0 +1,13 @@
+#include <efi.h>
+#include <efilib.h>
+ 
+EFI_STATUS efi_main(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
+{
+  SIMPLE_TEXT_OUTPUT_INTERFACE *conout;
+  InitializeLib(ImageHandle, SystemTable);
+  conout = SystemTable->ConOut;
+ 
+  uefi_call_wrapper(conout->OutputString, 2, conout, (CHAR16 *)L"Hello World\n\r");
+ 
+  return EFI_SUCCESS;
+}