add code for data abort and prefetch abort errors

simple implementation just to dump the registers's
value, will add more features later

Signed-off-by: Le Min <lemin9538@gmail.com>
fs/vfs.c getdent, 4 bytes aligin when get the string

Signed-off-by: Le Min <lemin9538@gmail.com>
add lock and bitmap for tty allocation in case of race

Signed-off-by: Le Min <lemin9538@gmail.com>
workaround the slab free issue

when release a slab, if the usage of the page
which the slab belongs is 0, then the page will
automaticlly freed, but since there may slab list
to the slab plist and they are not deleted at the
same time. it will cause problems when get a same
size's slab

from these issue, it can be found that there are
lots issue of memory manergment system. we need
a new and strong MM system. will try to improve
it later

Signed-off-by: Le Min <lemin9538@gmail.com>
remove unused char in panic function

Signed-off-by: Le Min <lemin9538@gmail.com>
remove some unused function of mm and slab

Signed-off-by: Le Min <lemin9538@gmail.com>