From 92ff191c3dfc8fac74a88f6dc24ce345dce54f4e Mon Sep 17 00:00:00 2001
From: Carlos <carlos.fenollosa@gmail.com>
Date: Tue, 18 Aug 2015 10:14:06 +0200
Subject: [PATCH] lesson 23, steps 1 and 2

---
 23-fixes/Makefile              |  3 +--
 23-fixes/README.md             | 46 ++++++++++++++++++++++++++++++++++
 23-fixes/boot/kernel_entry.asm |  9 ++++---
 23-fixes/kernel/kernel.c       |  2 +-
 4 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/23-fixes/Makefile b/23-fixes/Makefile
index 1478294..6b679a7 100644
--- a/23-fixes/Makefile
+++ b/23-fixes/Makefile
@@ -7,8 +7,7 @@ OBJ = ${C_SOURCES:.c=.o cpu/interrupt.o}
 CC = /usr/local/i386elfgcc/bin/i386-elf-gcc
 GDB = /usr/local/i386elfgcc/bin/i386-elf-gdb
 # -g: Use debugging symbols in gcc
-CFLAGS = -g -m32 -nostdlib -nostdinc -fno-builtin -fno-stack-protector -nostartfiles -nodefaultlibs \
-		 -Wall -Wextra -Werror
+CFLAGS = -g -ffreestanding -Wall -Wextra -fno-exceptions
 
 # First rule is run by default
 os-image.bin: boot/bootsect.bin kernel.bin
diff --git a/23-fixes/README.md b/23-fixes/README.md
index 4c29f36..c27f74d 100644
--- a/23-fixes/README.md
+++ b/23-fixes/README.md
@@ -7,4 +7,50 @@ JamesM's tutorial](http://wiki.osdev.org/James_Molloy%27s_Tutorial_Known_Bugs).
 Since we followed his tutorial for lessons 18-22 (interrupts through malloc), we'll
 need to make sure we fix any of the issues before moving on.
 
+1. Wrong CFLAGS
+---------------
+
+We add  `-ffreestanding` when compiling `.o` files, which includes `kernel_entry.o` and thus
+`kernel.bin` and `os-image.bin`.
+
+Before, we disabled libgcc (not libc) through the use of `-nostdlib` and we didn't re-enable
+it for linking. Since this is tricky, we'll delete `-nostdlib`
+
+
+2. Not setting a stack
+----------------------
+
+
+
+3. kernel.c `main()` function
+-----------------------------
+
+Modify `kernel/kernel.c` and change `main()` to `kernel_main()` since gcc recognizes "main" as 
+a special keyword and we don't want to mess with that.
+
+Change `boot/kernel_entry.asm` to point to the new name accordingly.
+
+To fix the `i386-elf-ld: warning: cannot find entry symbol _start; defaulting to 0000000000001000`
+warning message, add a `global _start;` and define the `_start:` label in `boot/kernel_entry.asm`.
+
+4. Reinvented datatypes
+-----------------------
+<stddef.h> to provide size\_t
+
+
+
+5. Missing functions
+--------------------
+
+6. Interrupt handlers
+---------------------
+- also cli, sti in interrupt handlers
+
+
+7. Structs and attributes
+-------------------------
+
+8. Improperly aligned `kmalloc`
+-------------------------------
+
 
diff --git a/23-fixes/boot/kernel_entry.asm b/23-fixes/boot/kernel_entry.asm
index 6728303..4148566 100644
--- a/23-fixes/boot/kernel_entry.asm
+++ b/23-fixes/boot/kernel_entry.asm
@@ -1,4 +1,7 @@
+global _start;
 [bits 32]
-[extern main] ; Define calling point. Must have same name as kernel.c 'main' function
-call main ; Calls the C function. The linker will know where it is placed in memory
-jmp $
+
+_start:
+    [extern kernel_main] ; Define calling point. Must have same name as kernel.c 'main' function
+    call kernel_main ; Calls the C function. The linker will know where it is placed in memory
+    jmp $
diff --git a/23-fixes/kernel/kernel.c b/23-fixes/kernel/kernel.c
index ecd034c..064b87a 100644
--- a/23-fixes/kernel/kernel.c
+++ b/23-fixes/kernel/kernel.c
@@ -4,7 +4,7 @@
 #include "../libc/string.h"
 #include "../libc/mem.h"
 
-void main() {
+void kernel_main() {
     isr_install();
     irq_install();