refacto(utils: macro): add BIT macro to generate nth bit

Changes:
* Renamed old BIT macro to BIT_READ
* Create new BIT macro to generate nth BIT (1 << n)

kernel/arch/i686/src/devices/pic.c

@@ -99,7 +99,7 @@ static DEFINE_INTERRUPT_HANDLER(irq_keyboard)
     const u8 scan_code = inb(0x60);
 
     // If not key release;  write character
-    if (!BIT(scan_code, 7) && ascii[scan_code])
+    if (!BIT_READ(scan_code, 7) && ascii[scan_code])
         tty_putchar(ascii[scan_code]);
 
     pic_eoi(IRQ_KEYBOARD);

kernel/arch/i686/src/devices/uart.c

@@ -73,7 +73,7 @@ void uart_reset()
 int uart_putc(const char c)
 {
     /* Wait until transfer buffer is empty */
-    WAIT_FOR(BIT(inb(UART_REG(LSR)), 5));
+    WAIT_FOR(BIT_READ(inb(UART_REG(LSR)), 5));
 
     outb(UART_REG(THR), c);
     return 0;
@@ -89,7 +89,7 @@ int uart_write(const char *buf, size_t length)
 char uart_getc()
 {
     /* Wait until data is available to be read */
-    WAIT_FOR(BIT(inb(UART_REG(LSR)), 0));
+    WAIT_FOR(BIT_READ(inb(UART_REG(LSR)), 0));
 
     return inb(UART_REG(THR));
 }

kernel/arch/i686/src/gdt.c

@@ -33,6 +33,8 @@ void gdt_init(void)
      *
      * To perform this operation, we assume that we are in protected mode,
      * and that we are using a falt model (which is the case if using GRUB).
+     *
+     * FIXME: Should not use a fixed address
      */
     static gdtr gdtr = {.size = GDT_SIZE - 1, .offset = GDT_BASE_ADDRESS};
     ASM("lgdt (%0)" : : "m"(gdtr) : "memory");

kernel/arch/i686/src/interrupts.c

@@ -78,9 +78,7 @@ static const char *interrupt_names[] = {
 };
 
 // IDT entry flag: gate is present
-#define IDT_PRESENT 0x80
-
-// TODO: Find a way to inline this ...
+#define IDT_PRESENT BIT(7)
 
 const char *interrupts_to_str(u8 nr)
 {

kernel/include/kernel/pmm.h

@@ -16,6 +16,7 @@
 
 #include <kernel/memory.h>
 
+#include <utils/macro.h>
 #include <utils/types.h>
 
 #include <multiboot.h>
@@ -45,7 +46,7 @@
 
 /// The pageframe should be located inside the kernel's physical address space.
 #define PMM_MAP_KERNEL_BIT 0x1
-#define PMM_MAP_KERNEL (1 << PMM_MAP_KERNEL_BIT) // TODO: BIT macro
+#define PMM_MAP_KERNEL BIT(PMM_MAP_KERNEL_BIT)
 
 /// @}
 

kernel/include/utils/macro.h

@@ -1,14 +1,17 @@
 #ifndef UTILS_MACRO_H
 #define UTILS_MACRO_H
 
+/* Generate the nth power of 2 (nth bit set) */
+#define BIT(_n) (1 << (_n))
+
 /* Clear the nth bit */
-#define BIT_MASK(_x, _n) ((_x) & ~(1 << (_n)))
+#define BIT_MASK(_x, _n) ((_x) & ~BIT((_n)))
 
 /* Set the nth bit */
-#define BIT_SET(_x, _n) ((_x) | (1 << (_n)))
+#define BIT_SET(_x, _n) ((_x) | BIT((_n)))
 
 /* Read the nth bit */
-#define BIT(_x, _n) ((_x) & (1 << (_n)))
+#define BIT_READ(_x, _n) ((_x)&BIT((_n)))
 
 /* Most/Less significant byte from 16bit integer */
 #define MSB(_x) ((_x) >> 8)

kernel/src/memory/pmm.c

@@ -70,13 +70,13 @@ static inline void pmm_bitmap_set(u32 page, u8 availability)
 /// @return a pageframe's state according to the allocator's bitmap
 static inline int pmm_bitmap_read(u32 page)
 {
-    return BIT(g_pmm_free_bitmap[BITMAP_INDEX(page)], page % 32);
+    return BIT_READ(g_pmm_free_bitmap[BITMAP_INDEX(page)], page % 32);
 }
 
 static bool pmm_initialize_bitmap(struct multiboot_info *mbt)
 {
     // If bit 6 in the flags uint16_t is set, then the mmap_* fields are valid
-    if (!BIT(mbt->flags, 6)) {
+    if (!BIT_READ(mbt->flags, 6)) {
         log_err("PMM", "Multiboot structure does not support memory map.");
         return false;
     }
@@ -189,7 +189,7 @@ bool pmm_init(struct multiboot_info *mbt)
 
 u32 pmm_allocate(int flags)
 {
-    pmm_frame_allocator *allocator = BIT(flags, PMM_MAP_KERNEL_BIT)
+    pmm_frame_allocator *allocator = BIT_READ(flags, PMM_MAP_KERNEL_BIT)
                                        ? &g_pmm_kernel_allocator
                                        : &g_pmm_user_allocator;