From c6882778696fe40b799887d35ec3f4b48792abaf Mon Sep 17 00:00:00 2001
From: Carlos Maiolino <cem@toxiclabs.cc>
Date: Sun, 20 Jul 2025 14:38:22 +0200
Subject: Add kernel.c

Create the kernel.c file and its initial start_kernel(), and
jump to it from the ASM.

Also setup the build system to actually build it

Signed-off-by: Carlos Maiolino <cem@toxiclabs.cc>
---
 Makefile             | 20 ++++++++++++++++----
 src/include/kernel.h |  6 ++++++
 src/kernel.asm       |  3 +++
 src/kernel.c         |  6 ++++++
 4 files changed, 31 insertions(+), 4 deletions(-)
 create mode 100644 src/include/kernel.h
 create mode 100644 src/kernel.c

diff --git a/Makefile b/Makefile
index c43d848..eccede7 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,12 @@
-FILLES = ./build/kernel.asm.o
+FILLES = ./build/kernel.asm.o ./build/kernel.o
+INCLUDES= -I./src/include
+FLAGS= -g -ffreestanding -falign-jumps -falign-functions	\
+	-falign-labels -falign-loops -fstrength-reduce		\
+	-fomit-frame-pointer -finline-functions			\
+	-Wno-unused-function -fno-builtin -Werror		\
+	-Wno-unused-label -Wno-cpp -Wno-unused-parameter	\
+	-nostdlib -nostartfiles -nodefaultlibs -Wall -O0 -Iinc	\
+
 
 BOOTLOADER=./src/boot/bootloader.asm
 TARGET=./bin/boot.bin
@@ -8,9 +16,9 @@ all: ./bin/boot.bin ./bin/kernel.bin
 	dd if=./bin/boot.bin >> ./bin/os.bin
 	dd if=./bin/kernel.bin >> ./bin/os.bin
 	dd if=/dev/zero bs=512 count=100 >> ./bin/os.bin
-./bin/kernel.bin: ./build/kernel.asm.o
-	i686-elf-ld -g -relocatable ./build/kernel.asm.o -o ./build/cemOS.o
-	i686-elf-gcc -T ./src/linker.ld -o ./bin/kernel.bin -ffreestanding -O0 -nostdlib ./build/cemOS.o
+./bin/kernel.bin: ./build/kernel.asm.o ./build/kernel.o
+	i686-elf-ld -g -relocatable ./build/kernel.asm.o ./build/kernel.o -o ./build/cemOS.o
+	i686-elf-gcc $(FLAGS) -T ./src/linker.ld -o ./bin/kernel.bin -ffreestanding -O0 -nostdlib ./build/cemOS.o
 
 ./bin/boot.bin: ./src/boot/bootloader.asm
 	nasm -f bin $(BOOTLOADER) -o $(TARGET)
@@ -18,9 +26,13 @@ all: ./bin/boot.bin ./bin/kernel.bin
 ./build/kernel.asm.o: ./src/kernel.asm
 	nasm -f elf -g ./src/kernel.asm -o ./build/kernel.asm.o
 
+./build/kernel.o: ./src/kernel.c
+	i686-elf-gcc $(INCLUDES) $(FLAGS) -std=gnu99 -c ./src/kernel.c -o ./build/kernel.o
+
 clean:
 	rm -f $(TARGET)
 	rm -f bin/kernel.bin
 	rm -f build/cemOS.o
 	rm -f build/kernel.asm.o
+	rm -f build/kernel.o
 	rm -f bin/os.bin
diff --git a/src/include/kernel.h b/src/include/kernel.h
new file mode 100644
index 0000000..2007693
--- /dev/null
+++ b/src/include/kernel.h
@@ -0,0 +1,6 @@
+#ifndef KERNEL_H
+#define KERNEL_H
+
+void kernel_main();
+
+#endif /* KERNEL_H */
diff --git a/src/kernel.asm b/src/kernel.asm
index 6d2779a..252fd7b 100644
--- a/src/kernel.asm
+++ b/src/kernel.asm
@@ -1,5 +1,6 @@
 [BITS 32]
 global _start
+extern start_kernel
 
 CODE_SEG equ 0x08
 DATA_SEG equ 0x10
@@ -23,6 +24,8 @@ _start:
 	or al, 2
 	out 0x92, al
 
+	; Jump to C code
+	call start_kernel
 	jmp $
 
 ; Hack to align the source code at 16bytes (because 512 is a multiple of 16)
diff --git a/src/kernel.c b/src/kernel.c
new file mode 100644
index 0000000..d39aac5
--- /dev/null
+++ b/src/kernel.c
@@ -0,0 +1,6 @@
+#include <kernel.h>
+
+void start_kernel()
+
+{
+}
-- 
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