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68901c4d43
When we find out that a breakpoint is set on top of a program
breakpoint, we mark it as "permanent". E.g.,:
...
if (bp_loc_is_permanent (loc))
{
loc->inserted = 1;
loc->permanent = 1;
}
...
Note we didn't fill in the breakpoint's shadow (shadow_len remains 0).
In case the target claims support for evaluating breakpoint
conditions, GDB sometimes reinserts breakpoints that are already
inserted (to update the conditions on the target side). Since GDB
doesn't know whether the target supports evaluating conditions _of_
software breakpoints (vs hardware breakpoints, etc.) until it actually
tries it, if the target doesn't actually support z0 breakpoints, GDB
ends up reinserting a GDB-managed software/memory breakpoint
(mem-break.c).
And that is the case that is buggy: breakpoints that are marked
inserted contribute their shadows (if any) to the memory returned by
target_read_memory, to mask out breakpoints. Permanent breakpoints
are always marked as inserted. So if the permanent breakpoint doesn't
have a shadow yet in its shadow buffer, but we set shadow_len before
calling target_read_memory, then the still clear shadow_contents
buffer will be used by the breakpoint masking code... And then from
there on, the permanent breakpoint has a broken shadow buffer, and
thus any memory read out of that address will read bogus code, and
many random bad things fall out from that.
The fix is just to set shadow_len at the same time shadow_contents is
set, not one before and another after...
Fixes all gdb.base/bp-permanent.exp FAILs on PPC64 GNU/Linux gdbserver
and probably any other gdbserver port that doesn't do z0 breakpoints.
gdb/ChangeLog:
2015-03-05 Pedro Alves <palves@redhat.com>
PR gdb/18002
* mem-break.c (default_memory_insert_breakpoint): Set shadow_len
after reading the breakpoint's shadow memory.
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| config | ||
| cpu | ||
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| gdb | ||
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| include | ||
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| ld | ||
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| missing | ||
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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.