The GNU GDB Debugger and NetBSD (Part 4)


September 10, 2020 posted by Kamil Rytarowski

The NetBSD team of developers maintains two copies of GDB:
  • One in the base-system with a stack of local patches.
  • One in pkgsrc with mostly build fix patches.

The base-system version of GDB (GPLv3) still relies on a set of local patches. I set a goal to reduce the local patches to bare minimum, ideally reaching no local modifications at all.

GDB changes

Over the past month I worked on gdbserver for NetBSD/amd64 and finally upstreamed it to the GDB mainline, just in time for GDB 10.

What is gdbserver? Let's quote the official GDB documentation:

gdbserver is a control program for Unix-like systems, which allows you to connect your program with a remote GDB via target remote or target extended-but without linking in the usual debugging stub.

gdbserver is not a complete replacement for the debugging stubs, because it requires essentially the same operating-system facilities that GDB itself does. In fact, a system that can run gdbserver to connect to a remote GDB could also run GDB locally! gdbserver is sometimes useful nevertheless, because it is a much smaller program than GDB itself. It is also easier to port than all of GDB, so you may be able to get started more quickly on a new system by using gdbserver. Finally, if you develop code for real-time systems, you may find that the tradeoffs involved in real-time operation make it more convenient to do as much development work as possible on another system, for example by cross-compiling. You can use gdbserver to make a similar choice for debugging.

GDB and gdbserver communicate via either a serial line or a TCP connection, using the standard GDB remote serial protocol. remote

This illustrated that gdbserver is especially useful for debugging applications on embedded and thin devices, connected to a controlling computer equipped with full distribution sources, toolchain, debugging information etc. Eventually, this approach of gdb and gdbserver can replace the native gdb plugin entirely and spawn all connections debugging sessions using this protocol. This design decision was already introduced into LLDB, where remote process plugin is the only supported program on Linux, NetBSD and highly recommended for other kernels.

I've picked amd64 as the first target as it's the easiest to develop and test.

An example debugging session looks like this:

$ uname -rms
NetBSD 9.99.72 amd64
$ LC_ALL=C date
Thu Sep 10 22:43:10 CEST 2020
$ ./gdbserver/gdbserver --version                
GNU gdbserver (GDB) 10.0.50.20200910-git
Copyright (C) 2020 Free Software Foundation, Inc.
gdbserver is free software, covered by the GNU General Public License.
This gdbserver was configured as "x86_64-unknown-netbsd9.99"
$ ./gdbserver/gdbserver localhost:1234 /usr/bin/nslookup
Process /usr/bin/nslookup created; pid = 26383
Listening on port 1234

Then on the other terminal:

$ ./gdb/gdb 
GNU gdb (GDB) 10.0.50.20200910-git
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-unknown-netbsd9.99".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
.
Find the GDB manual and other documentation resources online at:
--Type  for more, q to quit, c to continue without paging--
    .

For help, type "help".
Type "apropos word" to search for commands related to "word".
(gdb) target remote localhost:1234
Remote debugging using localhost:1234
Reading /usr/bin/nslookup from remote target...
warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
Reading /usr/bin/nslookup from remote target...
Reading symbols from target:/usr/bin/nslookup...
Reading /usr/bin/nslookup.debug from remote target...
Reading /usr/bin/.debug/nslookup.debug from remote target...
Reading /usr/libdata/debug//usr/bin/nslookup.debug from remote target...
Reading /usr/libdata/debug//usr/bin/nslookup.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/bin/nslookup.debug...
process 28353 is executing new program: /usr/bin/nslookup
Reading /usr/bin/nslookup from remote target...
Reading /usr/bin/nslookup from remote target...
Reading /usr/bin/nslookup.debug from remote target...
Reading /usr/bin/.debug/nslookup.debug from remote target...
Reading /usr/libdata/debug//usr/bin/nslookup.debug from remote target...
Reading /usr/libdata/debug//usr/bin/nslookup.debug from remote target...
Reading /usr/libexec/ld.elf_so from remote target...
Reading /usr/libexec/ld.elf_so from remote target...
Reading /usr/libexec/ld.elf_so.debug from remote target...
Reading /usr/libexec/.debug/ld.elf_so.debug from remote target...
Reading /usr/libdata/debug//usr/libexec/ld.elf_so.debug from remote target...
Reading /usr/libdata/debug//usr/libexec/ld.elf_so.debug from remote target...
warning: Invalid remote reply: timeout [kamil: repeated multiple times...]
Reading /usr/lib/libbind9.so.15 from remote target...
Reading /usr/lib/libisccfg.so.15 from remote target...
Reading /usr/lib/libdns.so.15 from remote target...
Reading /usr/lib/libns.so.15 from remote target...
Reading /usr/lib/libirs.so.15 from remote target...
Reading /usr/lib/libisccc.so.15 from remote target...
Reading /usr/lib/libisc.so.15 from remote target...
Reading /usr/lib/libkvm.so.6 from remote target...
Reading /usr/lib/libz.so.1 from remote target...
Reading /usr/lib/libblocklist.so.0 from remote target...
Reading /usr/lib/libpthread.so.1 from remote target...
Reading /usr/lib/libpthread.so.1.4.debug from remote target...
Reading /usr/lib/.debug/libpthread.so.1.4.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libpthread.so.1.4.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libpthread.so.1.4.debug from remote target...
Reading /usr/lib/libgssapi.so.11 from remote target...
Reading /usr/lib/libheimntlm.so.5 from remote target...
Reading /usr/lib/libkrb5.so.27 from remote target...
Reading /usr/lib/libcom_err.so.8 from remote target...
Reading /usr/lib/libhx509.so.6 from remote target...
Reading /usr/lib/libcrypto.so.14 from remote target...
Reading /usr/lib/libasn1.so.10 from remote target...
Reading /usr/lib/libwind.so.1 from remote target...
Reading /usr/lib/libheimbase.so.2 from remote target...
Reading /usr/lib/libroken.so.20 from remote target...
Reading /usr/lib/libsqlite3.so.1 from remote target...
Reading /usr/lib/libcrypt.so.1 from remote target...
Reading /usr/lib/libutil.so.7 from remote target...
Reading /usr/lib/libedit.so.3 from remote target...
Reading /usr/lib/libterminfo.so.2 from remote target...
Reading /usr/lib/libc.so.12 from remote target...
Reading /usr/lib/libgcc_s.so.1 from remote target...
Reading symbols from target:/usr/lib/libbind9.so.15...
Reading /usr/lib/libbind9.so.15.0.debug from remote target...
Reading /usr/lib/.debug/libbind9.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libbind9.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libbind9.so.15.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libbind9.so.15.0.debug...
Reading symbols from target:/usr/lib/libisccfg.so.15...
Reading /usr/lib/libisccfg.so.15.0.debug from remote target...
Reading /usr/lib/.debug/libisccfg.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libisccfg.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libisccfg.so.15.0.debug from remote target...
--Type  for more, q to quit, c to continue without paging--
Reading symbols from target:/usr/libdata/debug//usr/lib/libisccfg.so.15.0.debug...
Reading symbols from target:/usr/lib/libdns.so.15...
Reading /usr/lib/libdns.so.15.0.debug from remote target...
Reading /usr/lib/.debug/libdns.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libdns.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libdns.so.15.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libdns.so.15.0.debug...
Reading symbols from target:/usr/lib/libns.so.15...
Reading /usr/lib/libns.so.15.0.debug from remote target...
Reading /usr/lib/.debug/libns.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libns.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libns.so.15.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libns.so.15.0.debug...
Reading symbols from target:/usr/lib/libirs.so.15...
Reading /usr/lib/libirs.so.15.0.debug from remote target...
Reading /usr/lib/.debug/libirs.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libirs.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libirs.so.15.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libirs.so.15.0.debug...
Reading symbols from target:/usr/lib/libisccc.so.15...
Reading /usr/lib/libisccc.so.15.0.debug from remote target...
Reading /usr/lib/.debug/libisccc.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libisccc.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libisccc.so.15.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libisccc.so.15.0.debug...
Reading symbols from target:/usr/lib/libisc.so.15...
Reading /usr/lib/libisc.so.15.0.debug from remote target...
Reading /usr/lib/.debug/libisc.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libisc.so.15.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libisc.so.15.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libisc.so.15.0.debug...
Reading symbols from target:/usr/lib/libkvm.so.6...
Reading /usr/lib/libkvm.so.6.0.debug from remote target...
Reading /usr/lib/.debug/libkvm.so.6.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libkvm.so.6.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libkvm.so.6.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libkvm.so.6.0.debug...
Reading symbols from target:/usr/lib/libz.so.1...
Reading /usr/lib/libz.so.1.0.debug from remote target...
Reading /usr/lib/.debug/libz.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libz.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libz.so.1.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libz.so.1.0.debug...
Reading symbols from target:/usr/lib/libblocklist.so.0...
Reading /usr/lib/libblocklist.so.0.0.debug from remote target...
Reading /usr/lib/.debug/libblocklist.so.0.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libblocklist.so.0.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libblocklist.so.0.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libblocklist.so.0.0.debug...
Reading symbols from target:/usr/lib/libgssapi.so.11...
Reading /usr/lib/libgssapi.so.11.0.debug from remote target...
Reading /usr/lib/.debug/libgssapi.so.11.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libgssapi.so.11.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libgssapi.so.11.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libgssapi.so.11.0.debug...
Reading symbols from target:/usr/lib/libheimntlm.so.5...
Reading /usr/lib/libheimntlm.so.5.0.debug from remote target...
Reading /usr/lib/.debug/libheimntlm.so.5.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libheimntlm.so.5.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libheimntlm.so.5.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libheimntlm.so.5.0.debug...
Reading symbols from target:/usr/lib/libkrb5.so.27...
Reading /usr/lib/libkrb5.so.27.0.debug from remote target...
Reading /usr/lib/.debug/libkrb5.so.27.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libkrb5.so.27.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libkrb5.so.27.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libkrb5.so.27.0.debug...
Reading symbols from target:/usr/lib/libcom_err.so.8...
Reading /usr/lib/libcom_err.so.8.0.debug from remote target...
Reading /usr/lib/.debug/libcom_err.so.8.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libcom_err.so.8.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libcom_err.so.8.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libcom_err.so.8.0.debug...
Reading symbols from target:/usr/lib/libhx509.so.6...
Reading /usr/lib/libhx509.so.6.0.debug from remote target...
Reading /usr/lib/.debug/libhx509.so.6.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libhx509.so.6.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libhx509.so.6.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libhx509.so.6.0.debug...
Reading symbols from target:/usr/lib/libcrypto.so.14...
Reading /usr/lib/libcrypto.so.14.0.debug from remote target...
Reading /usr/lib/.debug/libcrypto.so.14.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libcrypto.so.14.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libcrypto.so.14.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libcrypto.so.14.0.debug...
Reading symbols from target:/usr/lib/libasn1.so.10...
Reading /usr/lib/libasn1.so.10.0.debug from remote target...
Reading /usr/lib/.debug/libasn1.so.10.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libasn1.so.10.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libasn1.so.10.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libasn1.so.10.0.debug...
Reading symbols from target:/usr/lib/libwind.so.1...
Reading /usr/lib/libwind.so.1.0.debug from remote target...
Reading /usr/lib/.debug/libwind.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libwind.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libwind.so.1.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libwind.so.1.0.debug...
Reading symbols from target:/usr/lib/libheimbase.so.2...
Reading /usr/lib/libheimbase.so.2.0.debug from remote target...
Reading /usr/lib/.debug/libheimbase.so.2.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libheimbase.so.2.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libheimbase.so.2.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libheimbase.so.2.0.debug...
Reading symbols from target:/usr/lib/libroken.so.20...
Reading /usr/lib/libroken.so.20.0.debug from remote target...
Reading /usr/lib/.debug/libroken.so.20.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libroken.so.20.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libroken.so.20.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libroken.so.20.0.debug...
Reading symbols from target:/usr/lib/libsqlite3.so.1...
Reading /usr/lib/libsqlite3.so.1.4.debug from remote target...
Reading /usr/lib/.debug/libsqlite3.so.1.4.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libsqlite3.so.1.4.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libsqlite3.so.1.4.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libsqlite3.so.1.4.debug...
Reading symbols from target:/usr/lib/libcrypt.so.1...
Reading /usr/lib/libcrypt.so.1.0.debug from remote target...
Reading /usr/lib/.debug/libcrypt.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libcrypt.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libcrypt.so.1.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libcrypt.so.1.0.debug...
Reading symbols from target:/usr/lib/libutil.so.7...
Reading /usr/lib/libutil.so.7.24.debug from remote target...
Reading /usr/lib/.debug/libutil.so.7.24.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libutil.so.7.24.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libutil.so.7.24.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libutil.so.7.24.debug...
Reading symbols from target:/usr/lib/libedit.so.3...
Reading /usr/lib/libedit.so.3.1.debug from remote target...
Reading /usr/lib/.debug/libedit.so.3.1.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libedit.so.3.1.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libedit.so.3.1.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libedit.so.3.1.debug...
Reading symbols from target:/usr/lib/libterminfo.so.2...
Reading /usr/lib/libterminfo.so.2.0.debug from remote target...
Reading /usr/lib/.debug/libterminfo.so.2.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libterminfo.so.2.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libterminfo.so.2.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libterminfo.so.2.0.debug...
Reading symbols from target:/usr/lib/libc.so.12...
Reading /usr/lib/libc.so.12.217.debug from remote target...
Reading /usr/lib/.debug/libc.so.12.217.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libc.so.12.217.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libc.so.12.217.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libc.so.12.217.debug...
Reading symbols from target:/usr/lib/libgcc_s.so.1...
Reading /usr/lib/libgcc_s.so.1.0.debug from remote target...
Reading /usr/lib/.debug/libgcc_s.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libgcc_s.so.1.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/libgcc_s.so.1.0.debug from remote target...
Reading symbols from target:/usr/libdata/debug//usr/lib/libgcc_s.so.1.0.debug...
Reading /usr/libexec/ld.elf_so from remote target...
_rtld_debug_state () at /usr/src/libexec/ld.elf_so/rtld.c:1577
1577            __insn_barrier();
(gdb) b main
Breakpoint 1 at 0x211c00: file /usr/src/external/mpl/bind/bin/nslookup/../../dist/bin/dig/nslookup.c, line 990.
(gdb) c
Continuing.

Breakpoint 1, main (argc=1, argv=0x7f7fffffe768)
    at /usr/src/external/mpl/bind/bin/nslookup/../../dist/bin/dig/nslookup.c:990
990     main(int argc, char **argv) {
(gdb) bt
#0  main (argc=1, argv=0x7f7fffffe768)
    at /usr/src/external/mpl/bind/bin/nslookup/../../dist/bin/dig/nslookup.c:990
(gdb) info threads 
  Id   Target Id          Frame 
* 1    Thread 28353.28353 main (argc=1, argv=0x7f7fffffe768)
    at /usr/src/external/mpl/bind/bin/nslookup/../../dist/bin/dig/nslookup.c:990
(gdb) b pthread_setname_np
Breakpoint 2 at 0x7f7ff4e0c9e4: file /usr/src/lib/libpthread/pthread.c, line 792.
(gdb) c
Continuing.
[New Thread 28353.27773]

Thread 1 hit Breakpoint 2, pthread_setname_np (thread=0x7f7ff7e41000, 
    name=name@entry=0x7f7fffffe610 "work-0", arg=arg@entry=0x0)
    at /usr/src/lib/libpthread/pthread.c:792
792     {
(gdb) info threads
  Id   Target Id          Frame 
* 1    Thread 28353.28353 pthread_setname_np (thread=0x7f7ff7e41000, 
    name=name@entry=0x7f7fffffe610 "work-0", arg=arg@entry=0x0)
    at /usr/src/lib/libpthread/pthread.c:792
  2    Thread 28353.27773 0x00007f7ff0aa623a in ___lwp_park60 () from target:/usr/lib/libc.so.12
(gdb) n
796             pthread__error(EINVAL, "Invalid thread",
(gdb) n
799             if (pthread__find(thread) != 0)
(gdb) 
802             namelen = snprintf(newname, sizeof(newname), name, arg);
(gdb) 
803             if (namelen >= PTHREAD_MAX_NAMELEN_NP)
(gdb) 
806             cp = strdup(newname);
(gdb) 
807             if (cp == NULL)
(gdb) 
810             pthread_mutex_lock(&thread->pt_lock);
(gdb) 
811             oldname = thread->pt_name;
(gdb) 
812             thread->pt_name = cp;
(gdb) 
813             (void)_lwp_setname(thread->pt_lid, cp);
(gdb) 
814             pthread_mutex_unlock(&thread->pt_lock);
(gdb) n
816             if (oldname != NULL)
(gdb) n
isc_taskmgr_create (mctx=, workers=workers@entry=1, default_quantum=, 
    default_quantum@entry=0, nm=nm@entry=0x0, managerp=managerp@entry=0x418638 )
    at /usr/src/external/mpl/bind/lib/libisc/../../dist/lib/isc/task.c:1431
1431            for (i = 0; i < workers; i++) {
(gdb) info threads
  Id   Target Id                   Frame 
* 1    Thread 28353.28353          isc_taskmgr_create (mctx=, workers=workers@entry=1, 
    default_quantum=, default_quantum@entry=0, nm=nm@entry=0x0, 
    managerp=managerp@entry=0x418638 )
    at /usr/src/external/mpl/bind/lib/libisc/../../dist/lib/isc/task.c:1431
  2    Thread 28353.27773 "work-0" 0x00007f7ff0aa623a in ___lwp_park60 ()
   from target:/usr/lib/libc.so.12
(gdb) dis 1
(gdb) b exit
Breakpoint 3 at 0x7f7ff0b530e0: exit. (2 locations)
(gdb) c
Continuing.

Thread 1 hit Breakpoint 2, pthread_setname_np (thread=0x7f7ff7e42c00, 
    name=name@entry=0x7f7ff5e6324e "isc-timer", arg=arg@entry=0x0)
    at /usr/src/lib/libpthread/pthread.c:792
792     {
(gdb) dis 2
(gdb) c
Continuing.
Reading /usr/lib/i18n/libUTF8.so.5.0 from remote target...
Reading /usr/lib/i18n/libUTF8.so.5.0.debug from remote target...
Reading /usr/lib/i18n/.debug/libUTF8.so.5.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/i18n/libUTF8.so.5.0.debug from remote target...
Reading /usr/libdata/debug//usr/lib/i18n/libUTF8.so.5.0.debug from remote target...

Then, back to the first terminal:

> netbsd.org
Server:         62.179.1.62
Address:        62.179.1.62#53

Non-authoritative answer:
Name:   netbsd.org
Address: 199.233.217.205
Name:   netbsd.org
Address: 2001:470:a085:999::80
> exit

Thread 1 hit Breakpoint 3, exit (status=1) at /usr/src/lib/libc/stdlib/exit.c:55
55      {
(gdb) info threads 
  Id   Target Id          Frame 
* 1    Thread 28353.28353 exit (status=1) at /usr/src/lib/libc/stdlib/exit.c:55
(gdb) bt
#0  exit (status=1) at /usr/src/lib/libc/stdlib/exit.c:55
#1  0x0000000000206122 in ___start ()
#2  0x00007f7ff7c0c840 in ?? () from target:/usr/libexec/ld.elf_so
#3  0x0000000000000001 in ?? ()
#4  0x00007f7fffffed20 in ?? ()
#5  0x0000000000000000 in ?? ()
(gdb) kill
Kill the program being debugged? (y or n) y
[Inferior 1 (process 28353) killed]

It worked!

In order to get this functionality operational I had to implement multiple GDB functions, in particular: create_inferior, post_create_inferior, attach, kill, detach, mourn, join, thread_alive, resume, wait, fetch_registers, store_registers, read_memory, write_memory, request_interrupt, supports_read_auxv, read_auxv, supports_hardware_single_step, sw_breakpoint_from_kind, supports_z_point_type, insert_point, remove_point, stopped_by_sw_breakpoint, supports_qxfer_siginfo, qxfer_siginfo, supports_stopped_by_sw_breakpoint, supports_non_stop, supports_multi_process, supports_fork_events, supports_vfork_events, supports_exec_events, supports_disable_randomization, supports_qxfer_libraries_svr4, qxfer_libraries_svr4, supports_pid_to_exec_file, pid_to_exec_file, thread_name, supports_catch_syscall.

NetBSD is the first BSD and actually the first Open Source UNIX-like OS besides Linux to grow support for gdbserver.

Plan for the next milestone

Introduce AArch64 support for GDB/NetBSD. [1 comment]

 



Comments:

This is awesome, thanks!

Posted by pin on September 11, 2020 at 04:38 AM UTC #

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