+ stc
+ ret
+
+
+ # detect extended memory using BIOS call 15h/e801
+detect_mem_e801:
+ mov $boot_mem_map, %esi
+ mov boot_mem_map_size, %ebp
+ movl $0, (%ebp)
+
+ xor %cx, %cx
+ xor %dx, %dx
+ mov $0xe801, %ax
+ int $0x15
+ jc e801_fail
+
+ cmp $0, %cx
+ jnz 0f
+ cmp $0, %ax
+ jz e801_fail
+ mov %ax, %cx
+ mov %bx, %dx
+
+0: movl $0x100000, (%esi)
+ movzx %cx, %eax
+ # first size is in KB, convert to bytes
+ shl $10, %eax
+ jnc 0f
+ # overflow means it's >4GB, clamp to 4GB
+ mov $0xffffffff, %eax
+0: mov %eax, 4(%esi)
+ incl boot_mem_map_size
+ cmp $0, %dx
+ jz e801_done
+ movl $0x1000000, 8(%esi)
+ movzx %dx, %eax
+ # second size is in 64kb blocks, convert to bytes
+ shl $16, %eax
+ jnc 0f
+ # overflow means it's >4GB, clamp to 4GB
+ mov $0xffffffff, %eax
+0: mov %eax, 12(%esi)
+ incl boot_mem_map_size
+e801_done:
+ clc
+ ret
+e801_fail:
+ stc
+ ret
+
+detect_mem_88:
+ # reportedly some BIOS implementations fail to clear CF on success
+ clc
+ mov $0x88, %ah
+ int $0x15
+ jc x88_fail
+
+ cmp $0, %ax
+ jz x88_fail
+
+ # ax has size in KB, convert to bytes in eax
+ and $0xffff, %eax
+ shl $10, %eax
+
+ mov $boot_mem_map, %esi
+ movl $0x100000, (%esi)
+ mov %eax, 4(%esi)
+
+ movl $1, boot_mem_map_size
+ clc
+ ret
+
+x88_fail:
+ stc
+ ret