Regression: gdb --pid $(pidof qemu-system-x86_64) stopped working with gdb 7.11.1 https://sourceware.org/bugzilla/show_bug.cgi?id=20609 It was reported for qemu-system-x86_64 but it happens for any multithreaded inferior with a JIT debugging hook. 136613ef0c6850427317e57be1b644080ff6decb is the first bad commit Author: Pedro Alves <palves@redhat.com> Fix PR gdb/19828: gdb -p <process from a container>: internal error Message-ID: <cbdf2e04-4fa8-872a-2a23-08c9c1b26e00@redhat.com> https://sourceware.org/ml/gdb-patches/2016-05/msg00450.html jit_breakpoint_re_set() is specific by trying to insert a breakpoint into the main executable, not into a shared library. During attachment GDB thinks it needs to use 'breakpoint always-inserted' from breakpoints_should_be_inserted_now() as a newly attached thread is 'thread_info->executing' due to 'lwp_info->must_set_ptrace_flags' enabled and the task not yet stopped. This did not happen before the 'bad commit' above which adds tracking of such thread. GDB then fails to insert the breakpoints to invalid address as PIE executable gets properly relocated during later phase of attachment. One can see in the backtraces below: -> jit_breakpoint_re_set_internal() later: -> svr4_exec_displacement() One can suppress the initial breakpoint_re_set() call as there will be another breakpoint_re_set() done from the final post_create_inferior() call in setup_inferior(). BTW additionally 'threads_executing' cache bool is somehow stale (somewhere is missing update_threads_executing()). I was trying to deal with that in my first/second attempt below but in my final third attempt (attached) I have left it as it is. First attempt trying not to falsely require 'breakpoint always-inserted': https://people.redhat.com/jkratoch/rhbz1375553-fix1.patch Reduced first attempt: https://people.redhat.com/jkratoch/rhbz1375553-fix2.patch The third attempt suppresses breakpoint insertion until PIE executable gets relocated by svr4_exec_displacement(). Applied. gdb/ChangeLog 2016-09-29 Jan Kratochvil <jan.kratochvil@redhat.com> PR gdb/20609 - attach of JIT-debug-enabled inf 7.11.1 regression * exec.c (exec_file_locate_attach): Add parameter defer_bp_reset. Use it. * gdbcore.h (exec_file_locate_attach): Add parameter defer_bp_reset. * infcmd.c (setup_inferior): Update caller. * remote.c (remote_add_inferior): Likewise. gdb/testsuite/ChangeLog 2016-09-29 Jan Kratochvil <jan.kratochvil@redhat.com> PR gdb/20609 - attach of JIT-debug-enabled inf 7.11.1 regression * gdb.base/jit-attach-pie.c: New file. * gdb.base/jit-attach-pie.exp: New file. |
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README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.