Add C89 Support

23-fixes/Makefile

@@ -4,10 +4,10 @@ HEADERS = $(wildcard kernel/*.h drivers/*.h cpu/*.h libc/*.h)
 OBJ = ${C_SOURCES:.c=.o cpu/interrupt.o} 
 
 # Change this if your cross-compiler is somewhere else
-CC = /usr/local/i386elfgcc/bin/i386-elf-gcc
-GDB = /usr/local/i386elfgcc/bin/i386-elf-gdb
+CC = gcc -m32 -Wall -Wextra -pedantic-errors -std=c89
+GDB = gdb
 # -g: Use debugging symbols in gcc
-CFLAGS = -g -ffreestanding -Wall -Wextra -fno-exceptions -m32
+CFLAGS = -g -ffreestanding -Wall -Wextra -fno-exceptions -m32 -fno-pie
 
 # First rule is run by default
 os-image.bin: boot/bootsect.bin kernel.bin
@@ -16,11 +16,11 @@ os-image.bin: boot/bootsect.bin kernel.bin
 # '--oformat binary' deletes all symbols as a collateral, so we don't need
 # to 'strip' them manually on this case
 kernel.bin: boot/kernel_entry.o ${OBJ}
-	i386-elf-ld -o $@ -Ttext 0x1000 $^ --oformat binary
+	@ld -melf_i386 -o $@ -Ttext 0x1000 $^ --oformat binary
 
 # Used for debugging purposes
 kernel.elf: boot/kernel_entry.o ${OBJ}
-	i386-elf-ld -o $@ -Ttext 0x1000 $^ 
+	ld -melf_i386 -o $@ -Ttext 0x1000 $^
 
 run: os-image.bin
 	qemu-system-i386 -fda os-image.bin

23-fixes/cpu/idt.c

@@ -13,5 +13,5 @@ void set_idt() {
     idt_reg.base = (uint32_t) &idt;
     idt_reg.limit = IDT_ENTRIES * sizeof(idt_gate_t) - 1;
     /* Don't make the mistake of loading &idt -- always load &idt_reg */
-    asm volatile("lidtl (%0)" : : "r" (&idt_reg));
+    __asm__ volatile("lidtl (%0)" : : "r" (&idt_reg));
 }

23-fixes/cpu/isr.c

@@ -44,7 +44,7 @@ void isr_install() {
     set_idt_gate(30, (uint32_t)isr30);
     set_idt_gate(31, (uint32_t)isr31);
 
-    // Remap the PIC
+    /* Remap the PIC */
     port_byte_out(0x20, 0x11);
     port_byte_out(0xA0, 0x11);
     port_byte_out(0x21, 0x20);
@@ -56,7 +56,7 @@ void isr_install() {
     port_byte_out(0x21, 0x0);
     port_byte_out(0xA1, 0x0); 
 
-    // Install the IRQs
+    /* Install the IRQs */
     set_idt_gate(32, (uint32_t)irq0);
     set_idt_gate(33, (uint32_t)irq1);
     set_idt_gate(34, (uint32_t)irq2);
@@ -74,7 +74,7 @@ void isr_install() {
     set_idt_gate(46, (uint32_t)irq14);
     set_idt_gate(47, (uint32_t)irq15);
 
-    set_idt(); // Load with ASM
+    set_idt(); /* Load with ASM */
 }
 
 /* To print the message which defines every exception */
@@ -117,8 +117,8 @@ char *exception_messages[] = {
 };
 
 void isr_handler(registers_t *r) {
-    kprint("received interrupt: ");
     char s[3];
+    kprint("received interrupt: ");
     int_to_ascii(r->int_no, s);
     kprint(s);
     kprint("\n");
@@ -133,19 +133,20 @@ void register_interrupt_handler(uint8_t n, isr_t handler) {
 void irq_handler(registers_t *r) {
     /* After every interrupt we need to send an EOI to the PICs
      * or they will not send another interrupt again */
+    isr_t handler;
     if (r->int_no >= 40) port_byte_out(0xA0, 0x20); /* slave */
     port_byte_out(0x20, 0x20); /* master */
 
     /* Handle the interrupt in a more modular way */
     if (interrupt_handlers[r->int_no] != 0) {
-        isr_t handler = interrupt_handlers[r->int_no];
+        handler = interrupt_handlers[r->int_no];
         handler(r);
     }
 }
 
 void irq_install() {
     /* Enable interruptions */
-    asm volatile("sti");
+    __asm__ volatile("sti");
     /* IRQ0: timer */
     init_timer(50);
     /* IRQ1: keyboard */

23-fixes/cpu/ports.c

@@ -13,7 +13,7 @@ uint8_t port_byte_in (uint16_t port) {
      *
      * Inputs and outputs are separated by colons
      */
-    asm("in %%dx, %%al" : "=a" (result) : "d" (port));
+    __asm__ volatile("in %%dx, %%al" : "=a" (result) : "d" (port));
     return result;
 }
 
@@ -23,15 +23,15 @@ void port_byte_out (uint16_t port, uint8_t data) {
      * However we see a comma since there are two variables in the input area
      * and none in the 'return' area
      */
-    asm volatile("out %%al, %%dx" : : "a" (data), "d" (port));
+    __asm__ volatile("out %%al, %%dx" : : "a" (data), "d" (port));
 }
 
 uint16_t port_word_in (uint16_t port) {
     uint16_t result;
-    asm("in %%dx, %%ax" : "=a" (result) : "d" (port));
+    __asm__ volatile("in %%dx, %%ax" : "=a" (result) : "d" (port));
     return result;
 }
 
 void port_word_out (uint16_t port, uint16_t data) {
-    asm volatile("out %%ax, %%dx" : : "a" (data), "d" (port));
+    __asm__ volatile("out %%ax, %%dx" : : "a" (data), "d" (port));
 }

23-fixes/cpu/timer.c

@@ -11,13 +11,14 @@ static void timer_callback(registers_t *regs) {
 }
 
 void init_timer(uint32_t freq) {
-    /* Install the function we just wrote */
-    register_interrupt_handler(IRQ0, timer_callback);
-
     /* Get the PIT value: hardware clock at 1193180 Hz */
     uint32_t divisor = 1193180 / freq;
     uint8_t low  = (uint8_t)(divisor & 0xFF);
     uint8_t high = (uint8_t)( (divisor >> 8) & 0xFF);
+
+    /* Install the function we just wrote */
+    register_interrupt_handler(IRQ0, timer_callback);
+
     /* Send the command */
     port_byte_out(0x43, 0x36); /* Command port */
     port_byte_out(0x40, low);

23-fixes/drivers/keyboard.c

@@ -28,7 +28,8 @@ const char sc_ascii[] = { '?', '?', '1', '2', '3', '4', '5', '6',
 static void keyboard_callback(registers_t *regs) {
     /* The PIC leaves us the scancode in port 0x60 */
     uint8_t scancode = port_byte_in(0x60);
-    
+    char letter;
+    char str[2];
     if (scancode > SC_MAX) return;
     if (scancode == BACKSPACE) {
         backspace(key_buffer);
@@ -38,9 +39,10 @@ static void keyboard_callback(registers_t *regs) {
         user_input(key_buffer); /* kernel-controlled function */
         key_buffer[0] = '\0';
     } else {
-        char letter = sc_ascii[(int)scancode];
+        letter = sc_ascii[(int)scancode];
         /* Remember that kprint only accepts char[] */
-        char str[2] = {letter, '\0'};
+        str[0] = letter;
+        str[1] = '\0';
         append(key_buffer, letter);
         kprint(str);
     }

23-fixes/drivers/screen.c

@@ -21,7 +21,7 @@ int get_offset_col(int offset);
  */
 void kprint_at(char *message, int col, int row) {
     /* Set cursor if col/row are negative */
-    int offset;
+    int offset, i = 0;
     if (col >= 0 && row >= 0)
         offset = get_offset(col, row);
     else {
@@ -31,7 +31,6 @@ void kprint_at(char *message, int col, int row) {
     }
 
     /* Loop through message and print it */
-    int i = 0;
     while (message[i] != 0) {
         offset = print_char(message[i++], col, row, WHITE_ON_BLACK);
         /* Compute row/col for next iteration */
@@ -67,6 +66,9 @@ void kprint_backspace() {
  */
 int print_char(char c, int col, int row, char attr) {
     uint8_t *vidmem = (uint8_t*) VIDEO_ADDRESS;
+    int offset;
+    int i;
+    char *last_line;
     if (!attr) attr = WHITE_ON_BLACK;
 
     /* Error control: print a red 'E' if the coords aren't right */
@@ -76,7 +78,6 @@ int print_char(char c, int col, int row, char attr) {
         return get_offset(col, row);
     }
 
-    int offset;
     if (col >= 0 && row >= 0) offset = get_offset(col, row);
     else offset = get_cursor_offset();
 
@@ -94,14 +95,13 @@ int print_char(char c, int col, int row, char attr) {
 
     /* Check if the offset is over screen size and scroll */
     if (offset >= MAX_ROWS * MAX_COLS * 2) {
-        int i;
-        for (i = 1; i < MAX_ROWS; i++) 
+        for (i = 1; i < MAX_ROWS; i++)
             memory_copy((uint8_t*)(get_offset(0, i) + VIDEO_ADDRESS),
                         (uint8_t*)(get_offset(0, i-1) + VIDEO_ADDRESS),
                         MAX_COLS * 2);
 
         /* Blank last line */
-        char *last_line = (char*) (get_offset(0, MAX_ROWS-1) + (uint8_t*) VIDEO_ADDRESS);
+        last_line = (char*) (get_offset(0, MAX_ROWS-1) + (uint8_t*) VIDEO_ADDRESS);
         for (i = 0; i < MAX_COLS * 2; i++) last_line[i] = 0;
 
         offset -= 2 * MAX_COLS;
@@ -116,8 +116,9 @@ int get_cursor_offset() {
      * 1. Ask for high byte of the cursor offset (data 14)
      * 2. Ask for low byte (data 15)
      */
+    int offset;
     port_byte_out(REG_SCREEN_CTRL, 14);
-    int offset = port_byte_in(REG_SCREEN_DATA) << 8; /* High byte: << 8 */
+    offset = port_byte_in(REG_SCREEN_DATA) << 8; /* High byte: << 8 */
     port_byte_out(REG_SCREEN_CTRL, 15);
     offset += port_byte_in(REG_SCREEN_DATA);
     return offset * 2; /* Position * size of character cell */

23-fixes/kernel/kernel.c

@@ -9,24 +9,25 @@ void kernel_main() {
     isr_install();
     irq_install();
 
-    asm("int $2");
-    asm("int $3");
+    __asm__ volatile("int $2");
+    __asm__ volatile("int $3");
 
     kprint("Type something, it will go through the kernel\n"
         "Type END to halt the CPU or PAGE to request a kmalloc()\n> ");
 }
 
 void user_input(char *input) {
+    char page_str[16] = "";
+    char phys_str[16] = "";
+    uint32_t phys_addr;
+    uint32_t page;
     if (strcmp(input, "END") == 0) {
         kprint("Stopping the CPU. Bye!\n");
-        asm volatile("hlt");
+        __asm__ volatile("hlt");
     } else if (strcmp(input, "PAGE") == 0) {
         /* Lesson 22: Code to test kmalloc, the rest is unchanged */
-        uint32_t phys_addr;
-        uint32_t page = kmalloc(1000, 1, &phys_addr);
-        char page_str[16] = "";
+        page = kmalloc(1000, 1, &phys_addr);
         hex_to_ascii(page, page_str);
-        char phys_str[16] = "";
         hex_to_ascii(phys_addr, phys_str);
         kprint("Page: ");
         kprint(page_str);

23-fixes/libc/mem.c

@@ -19,6 +19,7 @@ uint32_t free_mem_addr = 0x10000;
 /* Implementation is just a pointer to some free memory which
  * keeps growing */
 uint32_t kmalloc(size_t size, int align, uint32_t *phys_addr) {
+    uint32_t ret;
     /* Pages are aligned to 4K, or 0x1000 */
     if (align == 1 && (free_mem_addr & 0xFFFFF000)) {
         free_mem_addr &= 0xFFFFF000;
@@ -27,7 +28,7 @@ uint32_t kmalloc(size_t size, int align, uint32_t *phys_addr) {
     /* Save also the physical address */
     if (phys_addr) *phys_addr = free_mem_addr;
 
-    uint32_t ret = free_mem_addr;
+    ret = free_mem_addr;
     free_mem_addr += size; /* Remember to increment the pointer */
     return ret;
 }

23-fixes/libc/string.c

@@ -19,12 +19,12 @@ void int_to_ascii(int n, char str[]) {
 }
 
 void hex_to_ascii(int n, char str[]) {
-    append(str, '0');
-    append(str, 'x');
     char zeros = 0;
 
     int32_t tmp;
     int i;
+    append(str, '0');
+    append(str, 'x');
     for (i = 28; i > 0; i -= 4) {
         tmp = (n >> i) & 0xF;
         if (tmp == 0 && zeros == 0) continue;