Set DS to make work on hardware, more failed UEFI attempts

.gitignore

@@ -1,4 +1,6 @@
 *.bin
+*.efi
 *.img
 *.iso
 *.o
+*.so

Makefile

@@ -1,8 +1,5 @@
 .POSIX:
 
--include params.makefile
-
-BITS ?= 32
 IN_EXT ?= .S
 LD ?= ld
 # Use gcc so that the preprocessor will run first.

README.md

@@ -20,16 +20,29 @@ Hello world examples of programs without an OS. A.K.A. bare bones.
 
 ## Getting started
 
-    sudo apt-get install build-essential qemu
+    sudo apt-get install build-essential gnu-efi qemu
     make run
     make run RUN=min
     make run RUN=bios_one_char
 
-Tested on Ubuntu 14.04. TODO: get working on real hardware:
+Tested on Ubuntu 14.04.
+
+Run on real hardware: insert as USB, determine its device (`/dev/sdX`) with:
+
+    sudo lsblk
+    sudo fdisk -l
+
+then run:
 
     sudo dd if=bios_hello_world.img of=/dev/sdX
 
-into an USB did not work.
+Then:
+
+- insert the USB in a computer
+- during boot, hit some special key, usually F12
+- choose to boot from the USB
+
+Tested on: ThinkPad T400.
 
 More assembly info at: <https://github.com/cirosantilli/assembly-cheat>
 

TODO.md

@@ -1,6 +1,5 @@
 # TODO
 
--   make work on real hardware
 -   ACPI
 -   get multiboot working
 -   reboot computer. Would put QEMU into an infinite reboot loop. Awesome.

a.ld

@@ -1,6 +1,10 @@
 SECTIONS
 {
-    /* We could also pass the -Ttext 0x7C00 to as instead of doing this. */
+    /*
+    We could also pass the -Ttext 0x7C00 to as instead of doing this.
+
+    If your program does not have any memory accesses, you can omit this.
+    */
     . = 0x7c00;
     .text :
     {

bios_hello_world.S

@@ -1,6 +1,5 @@
 #include "common.h"
 BEGIN
-    cli
     mov $msg, %si
     mov $0x0e, %ah
 loop:

bios_one_char.S

@@ -2,7 +2,6 @@
 # More minimal than the hello world.
 #include "common.h"
 BEGIN
-cli
 mov $0x40, %al
 mov $0x0e, %ah
 int $0x10

common.h

@@ -1,2 +1,5 @@
-#define BEGIN .code16
+#define BEGIN .code16; \
+    cli; \
+    mov $0x0000, %ax; \
+    mov %ax, %ds
 #define END

min.S

@@ -6,5 +6,19 @@
 /* Don't listen to interrupts. */
 cli
 
+/*
+Zero ds.
+
+This is only needed if we are going to access memory.
+
+The program might work on QEMU without this, but fail on real hardware:
+http://stackoverflow.com/questions/32508919/how-to-produce-a-minimal-bios-hello-world-boot-sector-with-gcc-that-works-from-a
+
+You cannot write immediates direclty to it, must pass through ax:
+http://stackoverflow.com/questions/19074666/8086-why-cant-we-move-an-immediate-data-into-segment-register
+*/
+mov $0x0000, %ax
+mov %ax, %ds
+
 /* Stop the processor. */
 hlt

no-ld-script/main.S

@@ -2,6 +2,8 @@
 .global _start
 _start:
     cli
+    mov $0x0000, %ax
+    mov %ax, %ds
     mov $msg, %si
     mov $0x0e, %ah
 loop:

uefi/Makefile

@@ -1,6 +1,37 @@
 .POSIX:
 
-.PHONY: run
+.PHONY: all clean
 
-run:
-	qemu-system-32 -bios ovmf.fd
+ARCH            = $(shell uname -m | sed s,i[3456789]86,ia32,)
+
+OBJS            = main.o
+TARGET          = hello.efi
+
+EFIINC          = /usr/include/efi
+EFIINCS         = -I$(EFIINC) -I$(EFIINC)/$(ARCH) -I$(EFIINC)/protocol
+LIB             = /usr/lib
+EFILIB          = /usr/lib
+EFI_CRT_OBJS    = $(EFILIB)/crt0-efi-$(ARCH).o
+EFI_LDS         = $(EFILIB)/elf_$(ARCH)_efi.lds
+
+CFLAGS          = $(EFIINCS) -fno-stack-protector -fpic \
+		  -fshort-wchar -mno-red-zone -Wall
+ifeq ($(ARCH),x86_64)
+  CFLAGS += -DEFI_FUNCTION_WRAPPER
+endif
+
+LDFLAGS         = -nostdlib -znocombreloc -T $(EFI_LDS) -shared \
+		  -Bsymbolic -L $(EFILIB) -L $(LIB) $(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) $^ $@
+
+clean:
+	rm -f *.efi *.o *.so

uefi/Makefile.bak

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

uefi/README.md

@@ -4,10 +4,13 @@ Successor for BIOS.
 
 TODO get a hello world program working.
 
+- http://www.rodsbooks.com/efi-programming/hello.html Best source so far: allowed me to compile the hello world! TODO: how to run it now on QEMU and real hardware?
 - http://wiki.osdev.org/UEFI
 - https://fedoraproject.org/wiki/Using_UEFI_with_QEMU
 - https://wiki.ubuntu.com/UEFI/OVMF
 
+Running without image gives the UEFI shell, and a Linux kernel image booted fine with it: http://unix.stackexchange.com/a/228053/32558 , so we just need to generate the image.
+
 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

@@ -1,13 +1,23 @@
 #include <efi.h>
 #include <efilib.h>
- 
-EFI_STATUS efi_main(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
-{
+
+EFI_STATUS
+EFIAPI
+efi_main (EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable) {
+   InitializeLib(ImageHandle, SystemTable);
+   Print(L"Hello, world!\n");
+   return EFI_SUCCESS;
+}
+
+/*
+#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;
-}
+}
+*/