Date: Tue, 19 Apr 2016 22:49:15 +0530 From: Aijaz Baig <aijazbaig1@gmail.com> To: cem@freebsd.org Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org>, freebsd-stable@freebsd.org Subject: Re: Toggling between remote KGDB and local DDB within a debugging session Message-ID: <CAHB2L%2BftX2ih%2B39774GvUvNk5_cGO6rZ6WO=P5Lo2q1X7PnFBA@mail.gmail.com> In-Reply-To: <CAG6CVpXXOhP4PHu-bgVjFsawUiydDBwVAnL%2BwBBTtgtRacMujg@mail.gmail.com> References: <CAHB2L%2Bde=Bxn4G2uEDdN%2BSPY=SREN9REGShV=gnRombjqStYzw@mail.gmail.com> <CAG6CVpV_P2eCERSjQ3cwAMvNkuO8d919Td3DxkQJR1SGHSvLag@mail.gmail.com> <CAHB2L%2BfKTSDk-Ke6UWubE_X4gaxaHLULgWKu_Je8tNUddht5tw@mail.gmail.com> <CAG6CVpXXOhP4PHu-bgVjFsawUiydDBwVAnL%2BwBBTtgtRacMujg@mail.gmail.com>
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On Tue, Apr 19, 2016 at 10:17 PM, Conrad Meyer <cem@freebsd.org> wrote: > On Tue, Apr 19, 2016 at 9:35 AM, Aijaz Baig <aijazbaig1@gmail.com> wrote: >> On Tue, Apr 19, 2016 at 9:08 PM, Conrad Meyer <cem@freebsd.org> wrote: >>> On Tue, Apr 19, 2016 at 5:49 AM, Aijaz Baig <aijazbaig1@gmail.com> wrote: >>>> I would like to know if there is indeed a way to toggle between gdb >>>> and ddb while debugging a remote kernel. I am already at the gdb (or >>>> rather kgdb) prompt. From here how do I switch to local ddb on the >>>> debugged machine?? >>> >>> Ctrl-c on the serial console. >> For me I merely see 'Quit' being spat out when I do a ctrl-c > > Ctrl-C on the serial console, not in GDB. It looks like this: Yes I tried ctrl-c on the serial console (in-fact it even says so at the ddb promp) but it doesn't work I find the control still with the kgdb Has it got anything to do with the fact that I am on a VM? Has anyone been successful in doing this with VMs? > > # sysctl debug.kdb.enter=1 > debug.kdb.enter:KDB: enter: sysctl debug.kdb.enter > [ thread pid 21907 tid 102340 ] > Stopped at kdb_sysctl_enter+0x87: movq $0,kdb_why > db> gdb > (ctrl-c will return control to ddb) > Switching to gdb back-end > Received ^C; trying to switch back to ddb. > using longjmp, hope it works! > KDB: reentering > KDB: stack backtrace: > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffea79d0e6140 > kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffea79d0e61f0 > kdb_reenter() at kdb_reenter+0x33/frame 0xfffffea79d0e6200 > gdb_tx_end() at gdb_tx_end+0x28a/frame 0xfffffea79d0e6240 > gdb_trap() at gdb_trap+0x1f9/frame 0xfffffea79d0e6390 > kdb_trap() at kdb_trap+0x169/frame 0xfffffea79d0e63f0 > trap() at trap+0x71d/frame 0xfffffea79d0e6600 > calltrap() at calltrap+0x8/frame 0xfffffea79d0e6600 > --- trap 0x3, rip = 0xffffffff8058f177, rsp = 0xfffffea79d0e66c0, rbp > = 0xfffffea79d0e66f0 --- > kdb_sysctl_enter() at kdb_sysctl_enter+0x87/frame 0xfffffea79d0e66f0 > sysctl_root() at sysctl_root+0x24a/frame 0xfffffea79d0e6740 > userland_sysctl() at userland_sysctl+0x1d2/frame 0xfffffea79d0e67f0 > sys___sysctl() at sys___sysctl+0x74/frame 0xfffffea79d0e68a0 > amd64_syscall() at amd64_syscall+0x397/frame 0xfffffea79d0e6ab0 > Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffea79d0e6ab0 > --- syscall (202, FreeBSD ELF64, sys___sysctl), rip = 0x80095ed4a, rsp > = 0x7fffffffc948, rbp = 0x7fffffffc980 --- > gdb_trap bailing, hopefully back to ddb! > Switching to ddb back-end > [ thread pid 21907 tid 102340 ] > Stopped at kdb_sysctl_enter+0x87: movq $0,kdb_why > db> c > 0 -> 0 > > Best, > Conrad -- Best Regards, Aijaz Baig
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