No description
6598661d14
Debugging an x32 process with an x32 gdbserver always results in:
(gdb) c
Continuing.
Program received signal SIGSEGV, Segmentation fault.
0xf7de9600 in _dl_debug_state () from target:/libx32/ld-linux-x32.so.2
(gdb)
Looking at the remote debug logs reveals the problem, here:
Packet received: T05swbreak:;06:a0d4ffff00000000;07:b8d3ffff00000000;10:0096def701000000;thread:p7d7a.7d7a;core:1;
^^^^^^^^^^^^^^^^
The underlined value is the expedited value of RIP (in little endian).
But notice that 01 in 0x01f7de9600, while gdb says the program stopped
at 0xf7de9600. 0x01ffffffff is over 32 bits, which indicates that
something wen't wrong somewhere in gdbserver.
The problem turns out to be in gdbserver's x86_get_pc / x86_set_pc
routines, where "unsigned long" is used assuming that it can fit a
64-bit value, while unsigned long is actually 32-bit on x32. The
result is that collect_register_by_name / supply_register_by_name end
up reading/writing random bytes off the stack.
Fix this by using explicit uint64_t instead of unsigned long.
For consistency, use uint32_t instead of unsigned int in the 32-bit
paths.
gdb/gdbserver/ChangeLog:
2016-07-26 Pedro Alves <palves@redhat.com>
PR server/20414
* linux-x86-low.c (x86_get_pc, x86_set_pc): Use uint64_t instead
of unsigned long for 64-bit registers and use uint32_t instead of
unsigned int for 32-bit registers.
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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.