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Date:      Tue, 25 Oct 2016 18:38:24 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-bugs@FreeBSD.org
Subject:   [Bug 213778] stable/11 -r307797 on BPi-M3 (cortex-a7): truss gets segmentation fault for handling SIGSYS
Message-ID:  <bug-213778-8@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D213778

            Bug ID: 213778
           Summary: stable/11 -r307797 on BPi-M3 (cortex-a7): truss gets
                    segmentation fault for handling SIGSYS
           Product: Base System
           Version: 11.0-STABLE
          Hardware: arm
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: bin
          Assignee: freebsd-bugs@FreeBSD.org
          Reporter: markmi@dsl-only.net

In trying to build lang/gcc6 xgcc's cc1 got some SIGSYS examples. In trying=
 to
track things down I ran into truss getting a SIGSEGV when it tries to handle
the situation. . .

In truss's enter_syscall there is (from a live gdb on truss, after the
segmentation fault):

380             t->cs.name =3D sysdecode_syscallname(t->proc->abi->abi,
t->cs.number);
381             if (t->cs.name =3D=3D NULL)
(gdb)=20
382                     fprintf(info->outfile, "-- UNKNOWN %s SYSCALL %d --=
\n",
383                         t->proc->abi->type, t->cs.number);
384=20=20=20=20=20
385             sc =3D get_syscall(t->cs.name, narg);
386             t->cs.nargs =3D sc->nargs;
387             assert(sc->nargs <=3D nitems(t->cs.s_args));
388=20=20=20=20=20
389             t->cs.sc =3D sc;

(gdb) print *t
$2 =3D {entries =3D {le_next =3D 0x0, le_prev =3D 0x20617070}, proc =3D 0x2=
0617060, tid =3D
100150, in_syscall =3D 1, cs =3D {sc =3D 0x0, name =3D 0x0, number =3D 5808=
28064, args =3D
0x2061b0c0, nargs =3D 0,=20
    s_args =3D 0x2061b0ec}, before =3D {tv_sec =3D 1477418265, tv_nsec =3D =
492342263},
after =3D {tv_sec =3D 1477418265, tv_nsec =3D 492496630}}

(gdb) print sc
$3 =3D (struct syscall *) 0x0

So line 386 listed above gets a segmentation fault for sc->nargs when
t->cs.name is a NULL pointer: sc ends up NULL.

Looking at the two things that the fprintf on lines 382 and 383 would repor=
t:

(gdb) print t->proc->abi->type
$4 =3D 0x10166 "FreeBSD ELF32"

(gdb) print t->cs.number
$5 =3D 580828064

(gdb) print narg
$6 =3D 0

(that last is for context for the get_syscall arguments).

FYI: 580828064 =3D 0x229EBBA0


Context:

root@bananapi-m3:/usr/ports # uname -apKU
FreeBSD bananapi-m3 11.0-STABLE FreeBSD 11.0-STABLE #0 r307797M: Mon Oct 24
00:41:16 PDT 2016=20=20=20=20
markmi@FreeBSDx64:/usr/local/src/crochet/work/obj/arm.armv6/usr/src/sys/ALL=
WINNER
 arm armv6 1100505 1100505

--=20
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