Re: Debugging issue with gdbserver and a daemon on the target
Laszlo Papp <[email protected]>
| Newsgroups | gmane.comp.gdb.devel |
|---|---|
| Message-ID | <CAOMwXhOQkPH-6By+C0zcu3RAQMhWypC18ZsFrLK+ncdAcq3b0Q@mail.gmail.com> |
On Tue, Aug 19, 2014 at 5:12 PM, Pedro Alves <[email protected]> wrote: > On 08/19/2014 05:02 PM, Laszlo Papp wrote: >> On Tue, Aug 19, 2014 at 4:58 PM, Pedro Alves <[email protected]> wrote: >>> On 08/19/2014 04:44 PM, Laszlo Papp wrote: >>> >>>> >>>> gdbserver --attach 192.168.0.32:2345 pid-of-my-daemon >>>> >>> >>>> (gdb) bt >>>> #0 0x44ad26ec in select () at ../sysdeps/unix/syscall-template.S:81 >>>> #1 0x0002ac08 in bar (timeout=10, name=0x42f30 <yy_ec+56> "foo") at >>>> src/socket.c:906 >>>> #2 0x0003284c in main (argc=0, argv=0x0) at src/bar.c:679 >>>> (gdb) >>>> >>>> >>>> ... And then I do some communication with the daemon where the foo >>>> function is executed based on the logs, but the breakpoint is not hit. >>>> I wished to try hardware breakpoints, but they are not presented on my >>>> hardware. >>>> >>>> Furthermore, if I use the same workflow on a binary that is >>>> "one-shot", i.e. not running continuously as a daemon, the debugging >>>> workflow for stopping at main works with exactly the aforementioned >>>> software breakpoint issue. >>>> >>>> I am completely clueless at this point. Do you know how I can debug a >>>> daemon with gdbserver? >>> >>> "daemon" and "select" makes me think "fork". If the daemon is handling >>> requests by forking a child, and then it's the child that calls 'foo', >>> then this is expected, as GDBserver doesn't know how to follow forks >>> currently. It's WIP, patches have been posted. Meanwhile, the usual >>> thing to do it to attach to the child process the daemon spawns instead >>> of the main daemon pid. You'll usually do that by adding a busyloop in >>> the child somewhere, like: >>> >>> volatile int gdb_here; >>> >>> while (!gdb_here) >>> sleep (1); >>> >>> and after attaching to the child, do "print gdb_here = 1; continue". >>> >>> Thanks, >>> Pedro Alves >> >> Thanks Pedro for the prompt reply. Unfortunately, I am already >> attaching to the child right after the fork. I wonder if this can >> happen if some source file was missing? > > It shouldn't. Source files are only used for display. Where to > place a breakpoint is derived from the debug info in the binary. > > I'd suggest just trying to step through the code instead of > putting a break at "foo", and see if that much works. On an > arm system, stepping is actually implemented with magic > breakpoints behind the scenes. > >> Btw: >> >> gdbserver --version >> GNU gdbserver (GDB) 7.5.1 >> >> arm-polatis-linux-gnueabi-gdb --version >> GNU gdb (GDB) 7.5.1 >> > > Knee-jerk reaction is to suggest a more recent GDB/GDBserver. Note > building these isn't very hard. There aren't that many > dependencies. > > Thanks, > Pedro Alves Hmm, it seems that the stripped binary on the target and the one on the host were out-of-sync. This is really strange since I have not changed the source code. Seems different compilations still can get out-of-sync for the same code so that when I rebuild the same source code, I always need to update the binary on the target, too? Anyway, now I only have problems with finding the sources file to view them in cgdb. I do not know why it is wrong, but it seems to be. As you can see the paths are set up for dwarf correctly: readelf --debug-dump ./tmp/work/foo-foo-linux-gnueabi/foo-core-image-dbg/1.0-r0/rootfs/usr/bin/.debug/foo | grep DW_AT_comp_dir <35> DW_AT_comp_dir : /usr/src/debug///////////////////////////////////////////////////////////////////////////////////eglibc/2.17-r3/eglibc-2.17/libc/csu <df> DW_AT_comp_dir : (indirect string, offset: 0x31): /usr/src/debug/eglibc/2.17-r3/eglibc-2.17/libc/csu <183> DW_AT_comp_dir : /usr/src/debug///////////////////////////////////////////////////////////////////////////////////eglibc/2.17-r3/eglibc-2.17/libc/csu <22d> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <102f> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <2e98> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <3e34> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <471a> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <4c5f> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <55b9> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <84b8> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <94d1> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <a1e9> DW_AT_comp_dir : (indirect string, offset: 0x749): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/bar <af53> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <c382> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <c952> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <d281> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <dcc0> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <e093> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <e953> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <efd6> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <fb07> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <10cd9> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <127e6> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <132ab> DW_AT_comp_dir : (indirect string, offset: 0x3874): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/baz <13bf3> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <1556d> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <162d4> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <17481> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <17900> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <18481> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <1903f> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <19432> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <19524> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <19fe1> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <1d2b4> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <1dc34> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <1f2c1> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <1fa4f> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <1fe13> DW_AT_comp_dir : (indirect string, offset: 0x585a): /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh <203e4> DW_AT_comp_dir : (indirect string, offset: 0x7cfa): /usr/src/debug/flex/2.5.35-r3/flex-2.5.35 <2042a> DW_AT_comp_dir : (indirect string, offset: 0x31): /usr/src/debug/eglibc/2.17-r3/eglibc-2.17/libc/csu <2056c> DW_AT_comp_dir : (indirect string, offset: 0x7de0): /usr/src/debug/eglibc/2.17-r3/eglibc-2.17/libc/io <20833> DW_AT_comp_dir : /usr/src/debug///////////////////////////////////////////////////////////////////////////////////eglibc/2.17-r3/eglibc-2.17/libc/csu DW_AT_comp_dir DW_FORM_string DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_string DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_strp DW_AT_comp_dir DW_FORM_string ... yet, gdb says src/bar.c cannot be found even though it should be in the aforementioned /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh path, provided my sysroot setting is good above, but if that was not good, it would not load the binaries anyway, right? So, if I set that path one line above with the "-d" option to gdb, then the source file can be viewed. What may be going on here? Thanks in advance. I am so desperately lost. :(