b2e586e850
Using this simple test:
static void
break_here ()
{
}
int
main (int argc, char *argv[])
{
fork ();
break_here();
return 0;
}
compiled as a PIE:
$ gcc test.c -g3 -O0 -o test -pie
and running this:
$ ./gdb -nx -q --data-directory=data-directory ./test -ex "b break_here" -ex "set detach-on-fork off" -ex r
gives:
Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0x64a
Note that GDB might get stopped by SIGTTOU because of this issue:
https://sourceware.org/bugzilla/show_bug.cgi?id=23020
In that case, just use "fg" to continue.
This issue happens only with position-independent executables. Adding
the main objfile for the new inferior (the fork child) causes GDB to try
to reset the breakpoints. However, that new objfile has not been
relocated yet. So the breakpoint on "break_here" resolves to an
unrelocated address, from which we are trying to read/write to set a
breakpoint. Passing SYMFILE_DEFER_BP_RESET avoids that problem. The
executable is relocated just after, in the follow_fork_inferior
function.
The buildbot seems happy with this patch. I don't think it's necessary
to add a new test. Just changing this made many tests go from FAIL to
PASS on my machine, where gcc produces PIE executables by default. If
anything, I think we would need to add a board file that produces
position-independent executables, so that we can run all the tests with
PIE, even on machines where that is not the default.
gdb/ChangeLog:
* progspace.c (clone_program_space): Pass SYMFILE_DEFER_BP_RESET
to symbol_file_add_main.
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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.