OSDev.org

Code: Select all

static inline void _read_sect_lba(
	unsigned char *sbuff, uint32_t lba_address, size_t sectors)
{
	/*
	 * steps
	 *
	 * 1 - before any operation on the hd, we wait disk rdy
	 * 2 - setup address and issue read
	 * 3 - wait for DRQ bit to be set
	 * 4 - read (bochs-multi)sector data
	 *
	 * NOTE: bochs here allows to read whole multisector data
	 *       while virtualbox, more picky, want you wait DRQ for
	 *       each sector (loop to 3).
	 * 
	 * Functions stay modified for all emulators to work.
	 *
	 *
	 */
	__asm__ __volatile__ (
		"	and	$0xfffffff, %%rax	\n"
		"	mov	%%rax, %%rbx		\n"
		"	_d_rdy				\n"
		"	mov	$0x1f6, %%dx		\n"
		"	shr	$24, %%eax		\n"
		"	or	$0xe0, %%al		\n"
		"	out	%%al, %%dx		\n"
		"	mov	$0x1f2, %%dx		\n"
		"	mov	%%cl, %%al		\n"
		"	out	%%al, %%dx		\n"
		"	inc	%%dx			\n"
		"	mov	%%rbx, %%rax		\n"
		"	out	%%al, %%dx		\n"
		"	inc	%%dx			\n"
		"	mov	%%rbx, %%rax		\n"
		"	shr	$8, %%rax		\n"
		"	out	%%al, %%dx		\n"
		"	inc	%%dx			\n"
		"	mov	%%rbx, %%rax		\n"
		"	shr	$16, %%rax		\n"
		"	out	%%al, %%dx		\n"
		"	mov	$0x1f7, %%dx		\n"
		"	mov	$0x20, %%al		\n"
		"	out	%%al, %%dx		\n"
		"	mov	%%rcx, %%r8		\n"
		"check:					\n"
		"	_b_rdy				\n"
		"	mov	$256, %%rcx		\n"
		"	mov	$0x1f0, %%dx		\n"
		"	rep	insw			\n"
		"	dec	%%r8			\n"
		"	cmp	$0, %%r8		\n"
		"	jne	check			\n"
		:
		: "c"(sectors), "a"(lba_address), "D"(sbuff)
		: "%rdx"
	);
}