From 757e686afb4ac97bcf9333b10a6a0880bdd310f8 Mon Sep 17 00:00:00 2001 From: John Baldwin Date: Thu, 29 Jul 2021 13:16:28 -0700 Subject: [PATCH] Don't compile x86 debug register support on OpenBSD. Simon Marchi tried gdb on OpenBSD, and it immediately segfaults when running a program. Simon tracked down the problem to x86_dr_low.get_status being nullptr at this point: (lldb) print x86_dr_low.get_status (unsigned long (*)()) $0 = 0x0000000000000000 (lldb) bt * thread #1, stop reason = step over * frame #0: 0x0000033b64b764aa gdb`x86_dr_stopped_data_address(state=0x0000033d7162a310, addr_p=0x00007f7ffffc5688) at x86-dregs.c:645:12 frame #1: 0x0000033b64b766de gdb`x86_dr_stopped_by_watchpoint(state=0x0000033d7162a310) at x86-dregs.c:687:10 frame #2: 0x0000033b64ea5f72 gdb`x86_stopped_by_watchpoint() at x86-nat.c:206:10 frame #3: 0x0000033b64637fbb gdb`x86_nat_target::stopped_by_watchpoint(this=0x0000033b65252820) at x86-nat.h:100:12 frame #4: 0x0000033b64d3ff11 gdb`target_stopped_by_watchpoint() at target.c:468:46 frame #5: 0x0000033b6469b001 gdb`watchpoints_triggered(ws=0x00007f7ffffc61c8) at breakpoint.c:4790:32 frame #6: 0x0000033b64a8bb8b gdb`handle_signal_stop(ecs=0x00007f7ffffc61a0) at infrun.c:6072:29 frame #7: 0x0000033b64a7e3a7 gdb`handle_inferior_event(ecs=0x00007f7ffffc61a0) at infrun.c:5694:7 frame #8: 0x0000033b64a7c1a0 gdb`fetch_inferior_event() at infrun.c:4090:5 frame #9: 0x0000033b64a51921 gdb`inferior_event_handler(event_type=INF_REG_EVENT) at inf-loop.c:41:7 frame #10: 0x0000033b64a827c9 gdb`infrun_async_inferior_event_handler(data=0x0000000000000000) at infrun.c:9384:3 frame #11: 0x0000033b6465bd4f gdb`check_async_event_handlers() at async-event.c:335:4 frame #12: 0x0000033b65070917 gdb`gdb_do_one_event() at event-loop.cc:216:10 frame #13: 0x0000033b64af0db1 gdb`start_event_loop() at main.c:421:13 frame #14: 0x0000033b64aefe9a gdb`captured_command_loop() at main.c:481:3 frame #15: 0x0000033b64aed5c2 gdb`captured_main(data=0x00007f7ffffc6470) at main.c:1353:4 frame #16: 0x0000033b64aed4f2 gdb`gdb_main(args=0x00007f7ffffc6470) at main.c:1368:7 frame #17: 0x0000033b6459d787 gdb`main(argc=5, argv=0x00007f7ffffc6518) at gdb.c:32:10 frame #18: 0x0000033b6459d521 gdb`___start + 321 On BSDs, get_status is set in _initialize_x86_bsd_nat, but only if HAVE_PT_GETDBREGS is defined. PT_GETDBREGS doesn't exist on OpenBSD, so get_status (and the other fields of x86_dr_low) are left as nullptr. OpenBSD doesn't support getting or setting the x86 debug registers, so fix by omitting debug register support entirely on OpenBSD: - Change x86bsd_nat_target to only inherit from x86_nat_target if PT_GETDBREGS is supported. - Don't include x86-nat.o and nat/x86-dregs.o for OpenBSD/amd64. They were already omitted for OpenBSD/i386. --- gdb/configure.nat | 5 ++--- gdb/x86-bsd-nat.h | 9 +++++++-- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/gdb/configure.nat b/gdb/configure.nat index e34cccffd98..655c75dd1ab 100644 --- a/gdb/configure.nat +++ b/gdb/configure.nat @@ -451,9 +451,8 @@ case ${gdb_host} in case ${gdb_host_cpu} in i386) # Host: OpenBSD/amd64 - NATDEPFILES="${NATDEPFILES} obsd-nat.o amd64-nat.o x86-nat.o \ - x86-bsd-nat.o amd64-bsd-nat.o amd64-obsd-nat.o bsd-kvm.o \ - nat/x86-dregs.o" + NATDEPFILES="${NATDEPFILES} obsd-nat.o amd64-nat.o \ + x86-bsd-nat.o amd64-bsd-nat.o amd64-obsd-nat.o bsd-kvm.o" LOADLIBES='-lkvm' ;; mips) diff --git a/gdb/x86-bsd-nat.h b/gdb/x86-bsd-nat.h index 02d61c20b0b..caf62e38df6 100644 --- a/gdb/x86-bsd-nat.h +++ b/gdb/x86-bsd-nat.h @@ -27,18 +27,23 @@ extern size_t x86bsd_xsave_len; /* A prototype *BSD/x86 target. */ +#ifdef HAVE_PT_GETDBREGS template class x86bsd_nat_target : public x86_nat_target { using base_class = x86_nat_target; public: -#ifdef HAVE_PT_GETDBREGS void mourn_inferior () override { x86_cleanup_dregs (); base_class::mourn_inferior (); } -#endif /* HAVE_PT_GETDBREGS */ }; +#else /* !HAVE_PT_GETDBREGS */ +template +class x86bsd_nat_target : public BaseTarget +{ +}; +#endif /* HAVE_PT_GETDBREGS */ #endif /* x86-bsd-nat.h */ -- 2.30.2