binutils-gdb modified for the FreeChainXenon project
43968415b0
We noticed the following error on ppc-lynx178, using just about
any program:
(gdb) tar remote mytarget:4444
Remote debugging using mytarget:4444
0x000100c8 in _start ()
(gdb) b try
Breakpoint 1 at 0x10844: file try.adb, line 11.
(gdb) cont
Continuing.
!!!-> Cannot remove breakpoints because program is no longer writable.
!!!-> Further execution is probably impossible.
Breakpoint 1, try () at try.adb:11
11 Local : Integer := 18;
And, of course, trying to continue yielded the expected outcome:
(gdb) c
Continuing.
warning: Error removing breakpoint 1
Cannot remove breakpoints because program is no longer writable.
Further execution is probably impossible.
It turns out that the problem is caused by an intentional test
against a variable with an undefined value. After GDB receives
notification of the inferior stopping, it tries to remove the
breakpoint by sending a memory-write packet ("X10844,4:9 ").
This leads us to lynx_write_memory, where it tries to split
the memory-write into chunks of 4 bytes. And, in order to handle
writes which are not aligned on word boundaries, we have the
following code:
if (skip > 0 || truncate > 0)
/* We need to read the memory at this address in order to preserve
the data that we are not overwriting. */
lynx_read_memory (addr, (unsigned char *) &buf, xfer_size);
if (errno)
return errno;
(the comment explains what the code is about).
Unfortunately, the not-so-glaring error that we've made here is
that we're checking ERRNO regardless of whether we've called
lynx_read_memory. In our case, because we are writing 4 bytes
aligned on a word boundary, we do not call lynx_read_memory and
therefore test an ERRNO with an undefined value.
gdb/gdbserver/ChangeLog:
* lynx-low.c (lynx_write_memory): Put lynx_read_memory and
corresponding ERRNO check in same block.
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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.