Date: Tue, 25 Oct 2016 11:40:38 -0700 From: Mark Millard <markmi@dsl-only.net> To: freebsd-arm <freebsd-arm@freebsd.org>, FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Cc: FreeBSD Toolchain <freebsd-toolchain@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: stable/11 -r307797 on BPi-M3 (cortex-a7): truss gets segmentation fault for handling unknown system call Message-ID: <B6F65857-301A-4584-B66B-CA9794AC014B@dsl-only.net>
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[The following has been reported in: = https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D213778 .] 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=09 385 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=09 389 t->cs.sc =3D sc; (gdb) print *t $2 =3D {entries =3D {le_next =3D 0x0, le_prev =3D 0x20617070}, proc =3D = 0x20617060, tid =3D 100150, in_syscall =3D 1, cs =3D {sc =3D 0x0, name =3D= 0x0, number =3D 580828064, 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 = report: (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 = markmi@FreeBSDx64:/usr/local/src/crochet/work/obj/arm.armv6/usr/src/sys/AL= LWINNER arm armv6 1100505 1100505 =3D=3D=3D Mark Millard markmi at dsl-only.net
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