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Jan Kratochvil bb805577d2 PR gdb/20609 - attach of JIT-debug-enabled inf 7.11.1 regression
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.

136613ef0c 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.
2016-09-29 17:39:39 +02:00
bfd Automatic date update in version.in 2016-09-29 00:00:22 +00:00
binutils Frame info dump: Fix bad register marks. 2016-09-29 16:34:57 +02:00
config
cpu
elfcpp
etc
gas Add .cfi_val_offset GAS command. 2016-09-29 16:33:25 +02:00
gdb PR gdb/20609 - attach of JIT-debug-enabled inf 7.11.1 regression 2016-09-29 17:39:39 +02:00
gold Don't treat as separate symbols if unversioned symbol is undefined. 2016-09-27 12:08:28 -07:00
gprof When building target binaries, ensure that the warning flags selected for the command line match the target compiler. 2016-09-26 16:36:08 +01:00
include Disallow 3-operand cmp[l][i] for ppc64 2016-09-29 15:12:47 +09:30
intl
ld [ARM] PR ld/20608 Relocation truncated to fit: R_ARM_THM_JUMP24 for relocation to PLT entry 2016-09-28 01:41:00 +02:00
libdecnumber
libiberty
opcodes Disallow 3-operand cmp[l][i] for ppc64 2016-09-29 15:12:47 +09:30
readline Improve MinGW support in Readline 2016-09-17 11:50:37 +03:00
sim
texinfo
zlib
.cvsignore
.gitattributes
.gitignore Add archives and make stamps to the .gitignore file. 2016-09-27 15:10:42 +01:00
ChangeLog Add archives and make stamps to the .gitignore file. 2016-09-27 15:10:42 +01:00
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		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
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If you are receiving this as part of a GDB release, see the file gdb/README.
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	make

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