GNU_RELRO support broken on mips64e[bl] (Was: "security/sudo" gets SIGBUS on Lemote Yeeloong (LOONGSON))

On 9 Sep 2016 16:58 John D. Baker wrote:
> A freshly-built "security/sudo" from pkgsrc-HEAD (20160909) dies with
> "Bus error" prior to any authentication attempt.  Rebuilding with
> debugging enabled and using 'su' to become root and run it under 'gdb'
> reveals:

I observed the same error on ERLITE (evbmips64-eb) with kernel and
userland from current (20160908). However, I tried this again with
yesterday's current, then "Bus error" turned into "Memory fault":

   $ sudo
   trap: pid 28935(sudo): sig 11: cause=0x4 epc=0x7876fe60 va=0x78785321
   registers:
   [ 0]=00000000 [ 1]=00000000 [ 2]=78780000 [ 3]=00000001
   [ 4]=00000003 [ 5]=7fff6cc0 [ 6]=00000000 [ 7]=00000000
   [ 8]=00000000 [ 9]=00000000 [10]=00099960 [11]=0001eb79
   [12]=00000001 [13]=00000062 [14]=787cd000 [15]=787fc4c0
   [16]=787629a4 [17]=787d0000 [18]=787f4794 [19]=00000001
   [20]=787ca480 [21]=ffffffffff7fffff [22]=00800000 [23]=7fff6cc0
   [24]=00162000 [25]=7876fe30 [26]=00000000 [27]=00000000
   [28]=7878d100 [29]=7fff6c10 [30]=00000000 [31]=787629c8
   pid 28935 (sudo), uid 0: exited on signal 11 (core not dumped, err = 1
   Memory fault
   $

Diffs between two kernels are followings:

   -     $NetBSD: trap.c,v 1.241 2016/07/11 18:54:32 skrll Exp $
   +     $NetBSD: trap.c,v 1.243 2016/09/10 13:42:11 skrll Exp $
   -     $NetBSD: netbsd32_netbsd.c,v 1.200 2016/05/13 16:54:36 christos Exp $
   +     $NetBSD: netbsd32_netbsd.c,v 1.202 2016/09/10 08:21:26 skrll Exp $
   -     $NetBSD: netbsd32_socket.c,v 1.42 2015/07/22 14:25:39 maxv Exp $
   +     $NetBSD: netbsd32_socket.c,v 1.43 2016/09/08 18:54:03 martin Exp $
   -     $NetBSD: netbsd32_sysent.c,v 1.121 2015/12/03 10:39:50 pgoyette Exp $
   +     $NetBSD: netbsd32_sysent.c,v 1.122 2016/09/10 08:19:58 skrll Exp $

I found that this failure occurs with binaries compiled with -Wl,-z,relro:

   $ cc hello.c && ./a.out
   Hello, World!
   $ cc -Wl,-z,relro hello.c && ./a.out
   pid 2526(a.out): sig 11: cause=0x80000004
   (snip)
   pid 2526 (a.out), uid 501: exited on signal 11 (core dumped)
   Memory fault
   $

Memory fault does not occur with sudo compiled without that option. Something
is wrong withGNU_RELRO support. Actually, this failure can be avoided when
ld.elf_so is compiled without -DGNU_RELRO option.

Thanks,
Rin