Calling global constructors

5 files changed, 72 insertions, 16 deletions

diff --git a/Makefile b/Makefile
index 56ffd05..0a86795 100644
--- a/Makefile
+++ b/Makefile
@@ -1,27 +1,49 @@
-SOURCE_DIR=src
-BUILD_DIR=build
-ISO_DIR=isodir
+CC = i686-elf-gcc
+AS = i686-elf-as
+CFLAGS = 
 
+MKDIR = mkdir -p
+RM = rm -rf
+CP = cp
+
+SOURCE_DIR = src
+BUILD_DIR = build
+ISO_DIR = isodir
+
+AS_SOURCE = boot.s
+C_SOURCE = kernel.c
+
+OBJ_FILES = boot.o kernel.o
+CRTBEGIN_OBJ:=$(shell $(CC) -print-file-name=crtbegin.o)
+CRTEND_OBJ:=$(shell $(CC) -print-file-name=crtend.o)
+
+OBJ = $(BUILD_DIR)/crti.o $(CRTBEGIN_OBJ) $(patsubst %,$(BUILD_DIR)/%,$(OBJ_FILES)) $(CRTEND_OBJ) $(BUILD_DIR)/crtn.o
+
+# Creating iso file
 .PHONY: all
 all: $(BUILD_DIR)/myos.bin
 	grub-file --is-x86-multiboot $(BUILD_DIR)/myos.bin
 	mkdir -p $(ISO_DIR)/boot/grub
-	cp $(BUILD_DIR)/myos.bin $(ISO_DIR)/boot/myos.bin
-	cp $(SOURCE_DIR)/grub.cfg $(ISO_DIR)/boot/grub/grub.cfg
+	$(CP) $(BUILD_DIR)/myos.bin $(ISO_DIR)/boot/myos.bin
+	$(CP) $(SOURCE_DIR)/grub.cfg $(ISO_DIR)/boot/grub/grub.cfg
 	grub-mkrescue -o myos.iso $(ISO_DIR)
 
-$(BUILD_DIR)/boot.o: $(SOURCE_DIR)/boot.s
-	mkdir -p $(BUILD_DIR)
-	i686-elf-as $(SOURCE_DIR)/boot.s -o $(BUILD_DIR)/boot.o
+# Linking object files
+$(BUILD_DIR)/myos.bin: $(OBJ)
+	$(MKDIR) $(BUILD_DIR)
+	$(CC) -T $(SOURCE_DIR)/linker.ld -o $(BUILD_DIR)/myos.bin -ffreestanding -O2 -nostdlib $(OBJ) -lgcc
 
-$(BUILD_DIR)/kernel.o: $(SOURCE_DIR)/kernel.c
-	mkdir -p $(BUILD_DIR)
-	i686-elf-gcc -c $(SOURCE_DIR)/kernel.c -o $(BUILD_DIR)/kernel.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra
+# Compiling as sources
+$(BUILD_DIR)/%.o: $(SOURCE_DIR)/%.s
+	$(MKDIR) $(BUILD_DIR)
+	$(AS) $< -o $@
 
-$(BUILD_DIR)/myos.bin: $(BUILD_DIR)/kernel.o $(BUILD_DIR)/boot.o
-	mkdir -p $(BUILD_DIR)
-	i686-elf-gcc -T $(SOURCE_DIR)/linker.ld -o $(BUILD_DIR)/myos.bin -ffreestanding -O2 -nostdlib $(BUILD_DIR)/boot.o $(BUILD_DIR)/kernel.o -lgcc
+# Compiling C sources
+$(BUILD_DIR)/%.o: $(SOURCE_DIR)/%.c
+	$(MKDIR) $(BUILD_DIR)
+	$(CC) -c $< -o $@ -std=gnu99 -ffreestanding -O2 -Wall -Wextra
 
+# Cleaning
 .PHONY: clean
 clean:
-	rm -rf $(BUILD_DIR) $(ISO_DIR) myos.iso
+	$(RM) $(BUILD_DIR) $(ISO_DIR) myos.iso
diff --git a/src/boot.s b/src/boot.s
index 172fd14..a043012 100644
--- a/src/boot.s
+++ b/src/boot.s
@@ -84,6 +84,7 @@ _start:
 	stack since (pushed 0 bytes so far), so the alignment has thus been
 	preserved and the call is well defined.
 	*/
+	call _init
 	call kernel_main
  
 	/*
diff --git a/src/crti.s b/src/crti.s
new file mode 100644
index 0000000..30dd4ea
--- /dev/null
+++ b/src/crti.s
@@ -0,0 +1,16 @@
+/* x86 crti.s */
+.section .init
+.global _init
+.type _init, @function
+_init:
+	push %ebp
+	movl %esp, %ebp
+	/* gcc will nicely put the contents of crtbegin.o's .init section here. */
+
+.section .fini
+.global _fini
+.type _fini, @function
+_fini:
+	push %ebp
+	movl %esp, %ebp
+	/* gcc will nicely put the contents of crtbegin.o's .fini section here. */
diff --git a/src/crtn.s b/src/crtn.s
new file mode 100644
index 0000000..1da795d
--- /dev/null
+++ b/src/crtn.s
@@ -0,0 +1,10 @@
+/* x86 crtn.s */
+.section .init
+	/* gcc will nicely put the contents of crtend.o's .init section here. */
+	popl %ebp
+	ret
+
+.section .fini
+	/* gcc will nicely put the contents of crtend.o's .fini section here. */
+	popl %ebp
+	ret
diff --git a/src/kernel.c b/src/kernel.c
index dd81d33..2c71ba4 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -111,14 +111,21 @@ void terminal_writestring(const char* data)
 {
     terminal_write(data, strlen(data));
 }
+
+char *rec;
+__attribute__ ((constructor)) void foo(void)
+{
+    rec="aleksa";
+}
  
 void kernel_main(void) 
 {
     terminal_initialize();
 
-    for(size_t i=0;i<80;i++)
+    for(size_t i=0;i<50;i++)
     {
 	for(size_t j=0;j<i;j++) terminal_writestring("#");
 	terminal_writestring("Hello, kernel World!\n");
     }
+    terminal_writestring(rec);
 }