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I noticed that gdb.multi/multi-arch.exp wasn't passing with extended-remote GDBserver with my pending multi-process+multi-arch series anymore on current mainline, while it used to pass before: (gdb) run Starting program: /home/pedro/gdb/mygit/build/gdb/testsuite/gdb.multi/ma-hangout Process /home/pedro/gdb/mygit/build/gdb/testsuite/gdb.multi/ma-hangout created; pid = 32067 Warning: Cannot insert breakpoint 2. Error accessing memory address 0x4005c2: Unknown error -1. Cannot insert breakpoint -1. Temporarily disabling shared library breakpoints: breakpoint #-1 (gdb) FAIL: gdb.multi/multi-arch.exp: starting inferior 2 Investigating manually, I found an easy way to reproduce. You just need breakpoints on distinct inferiors, and a way to have GDB install them in one go: (gdb) set breakpoint always-inserted on (gdb) info breakpoints Num Type Disp Enb Address What 2 breakpoint del n <MULTIPLE> 2.1 y 0x00000000004005c2 in main at ../../../src/gdb/testsuite/gdb.multi/hello.c:40 inf 1 2.2 y 0x08048475 in main at ../../../src/gdb/testsuite/gdb.multi/hangout.c:22 inf 2 (gdb) enable 2 Warning: Cannot insert breakpoint 2. Error accessing memory address 0x4005c2: Unknown error -1. And turning on remote debugging, we see: (gdb) set debug remote 1 (gdb) disable 2 (gdb) enable 2 Sending packet: $Z0,4005c2,1#71...Packet received: E01 Sending packet: $Z0,8048475,1#87...Packet received: OK Warning: Cannot insert breakpoint 2. Error accessing memory address 0x4005c2: Unknown error -1. Notice that each of those Z0 breakpoints should be set in different processes. However, no Hg packet to select a process has been sent in between, so GDBserver tries to plant both on the same process that happens to be current. The first Z0 then not so surprisingly fails. IOW, the blame is on GDB, for telling GDBserver to plant both breakpoints in the same process. remote.c has a lazy scheme where it keeps a local cache of the remote's selected general thread, and delays updating it on the remote side until necessary (memory/register reads/writes, etc.). This is done to reduce RSP traffic. The bug is that the Zx breakpoint insert/remove methods weren't committing the selected thread/process back to the remote side: Breakpoint 3, remote_insert_breakpoint (gdbarch=0x1383ae0, bp_tgt=0x140c2b0) at ../../src/gdb/remote.c:8148 8148 if (remote_protocol_packets[PACKET_Z0].support != PACKET_DISABLE) (top-gdb) p inferior_ptid $3 = {pid = 3670, lwp = 0, tid = 3670} (top-gdb) p general_thread $4 = {pid = 3671, lwp = 0, tid = 3671} IOW, a call to set_general_process is missing. I did some auditing over remote.c, and added calls to all places I found missing it. This only used to work by chance before. breakpoint.c switches to a thread of the target process before installing a breakpoint location. That calls switch_to_thread. Before: 2012-07-27 Yao Qi <yao@codesourcery.com> * thread.c (switch_to_thread): Don't call registers_changed. that caused the register caches to all be flushed and refetched before installing the breakpoint location. Given fetching registers commits the remote general thread (with Hg), masking out the latent bug. Tested on x86_64 Fedora 17 with GDBserver. gdb/ 2013-05-29 Pedro Alves <palves@redhat.com> * remote.c (remote_insert_breakpoint, remote_remove_breakpoint) (remote_insert_watchpoint, remote_remove_watchpoint) (remote_insert_hw_breakpoint, remote_remove_hw_breakpoint) (remote_verify_memory, compare_sections_command) (remote_search_memory): Set the general process/thread on the remote side. |
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bfd | ||
binutils | ||
config | ||
cpu | ||
elfcpp | ||
etc | ||
gas | ||
gdb | ||
gold | ||
gprof | ||
include | ||
intl | ||
ld | ||
libdecnumber | ||
libiberty | ||
opcodes | ||
readline | ||
sim | ||
texinfo | ||
.cvsignore | ||
.gitignore | ||
ChangeLog | ||
compile | ||
config-ml.in | ||
config.guess | ||
config.rpath | ||
config.sub | ||
configure | ||
configure.ac | ||
COPYING | ||
COPYING3 | ||
COPYING3.LIB | ||
COPYING.LIB | ||
COPYING.LIBGLOSS | ||
COPYING.NEWLIB | ||
depcomp | ||
djunpack.bat | ||
install-sh | ||
libtool.m4 | ||
lt~obsolete.m4 | ||
ltgcc.m4 | ||
ltmain.sh | ||
ltoptions.m4 | ||
ltsugar.m4 | ||
ltversion.m4 | ||
MAINTAINERS | ||
Makefile.def | ||
Makefile.in | ||
Makefile.tpl | ||
makefile.vms | ||
missing | ||
mkdep | ||
mkinstalldirs | ||
move-if-change | ||
README | ||
README-maintainer-mode | ||
setup.com | ||
src-release | ||
symlink-tree | ||
ylwrap |
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.