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=213778 .] 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 = sysdecode_syscallname(t->proc->abi->abi, t->cs.number); 381 if (t->cs.name == NULL) (gdb) 382 fprintf(info->outfile, "-- UNKNOWN %s SYSCALL %d --\n", 383 t->proc->abi->type, t->cs.number); 384 385 sc = get_syscall(t->cs.name, narg); 386 t->cs.nargs = sc->nargs; 387 assert(sc->nargs <= nitems(t->cs.s_args)); 388 389 t->cs.sc = sc; (gdb) print *t $2 = {entries = {le_next = 0x0, le_prev = 0x20617070}, proc = 0x20617060, tid = 100150, in_syscall = 1, cs = {sc = 0x0, name = 0x0, number = 580828064, args = 0x2061b0c0, nargs = 0, s_args = 0x2061b0ec}, before = {tv_sec = 1477418265, tv_nsec = 492342263}, after = {tv_sec = 1477418265, tv_nsec = 492496630}} (gdb) print sc $3 = (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 = 0x10166 "FreeBSD ELF32" (gdb) print t->cs.number $5 = 580828064 (gdb) print narg $6 = 0 (that last is for context for the get_syscall arguments). FYI: 580828064 = 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/ALLWINNER arm armv6 1100505 1100505 === Mark Millard markmi at dsl-only.net
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