hi,linux-mips,
This patch does:
1.As Mr. Atsushi Nemoto has pointed out,the newest unaligned.c leave out several jb in
the sw/sh emulation code.It will lead to oops if someone use unaligned addresses as syscall
arguments to be stored to.Because the fixup code won't return to emulate_load_store_insn then.
2.when search_exception_table does find a fixup in emulate_load_store_insn,I think we should
skip compute_return_epc(regs) in do_ade then.Or it will jump to wrong fixup position later.
ltp failed the getsockname syscall test in this way:
getsockname(fd,&sock,(int *)1) 1 is used at the position of &sinlen.
then,kernel will finally call get_user to fetch the user provided len and
cause a AdeL exception:
get_user(len,ulen)
(a fixup installed for the lw)
---->exception
---> do_ade
------>emulate_load_store_insn
emulate fail
--->exception
<---fixup
search_exception_table find the handler
installed by get_user and change
regs->cp0_epc to the fixup position
<-------return
compute_return_epc(regs) ADD another 4 to epc!
<----------------
execution continues from fixup + 4,this omit the code to load -EFAULT to return
value of get_user,may lead to further failures
so i propose watch epc during emulate_load_store_insn,if it changes,then skip compute_return
_epc
3.(optional,implemented)it may be better for search_exception_table & fixup_exception
to use PC instead of regs->cp0_epc as arguments. PC points to the actual load/store
instruction anyway, although this is for kernel code so it is almost impossible for
user space accessing code to put load/store in a branch delay.
4.(optional,unimplemented) Will it be more efficient to put use emulation code of lw/lh/sw/sh
before other impossible conditions?
Am i missing something?
BTW:
Could somebody be so kind to explain the use of save_static_function?I know they build
a pseudo function with a return, so call sys_sigsuspend will fall through to _sys_sigsuspend
but what's the use? Nobody calls _sys_sigsuspend.
Regards
Zhang Fuxin
fxzhang@ict.ac.cn
unaligned.c.patch
