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I ended up debugging a malformed ELF where a section containing executable code was not correctly marked as allocatable. Before realising the ELF was corrupted I tried to place a breakpoint on a symbol in the non-allocatable, executable section, and GDB crashed. Though trying to debug such an ELF clearly isn't going to go well I would prefer, as far as possible, that any input, no matter how corrupted, not crash GDB. The crash occurs when trying to set a breakpoint on the name of a function from the corrupted section. GDB converts the symbol to a symtab_and_line, and looks up a suitable section for this. The problem is that the section is actually an obj_section, which is stored in the table within the objfile, and we only initialise this table for allocatable sections (see add_to_objfile_sections_full in objfiles.c). So, if the symbol is in a non-allocatable section then we end up referencing an uninitialised obj_section. Later we call get_sal_arch on the symtab_and_line, which calls get_objfile_arch, which uses the objfile from the uninitialised obj_section, which will be nullptr, at which point GDB crashes. The fix I propose here is that when we setup the section references on msymbols, we should check if the bfd_section being referenced is allocatable or not. If it is not then we should set the section reference back to the default 0 section (see how MSYMBOL_OBJ_SECTION and SYMBOL_OBJ_SECTION treat the 0 section index). With this fix in place GDB no longer crashes. Instead GDB creates the breakpoint at the non-allocated address, and then fails, with an error, when it tries to insert the breakpoint. gdb/ChangeLog: * elfread.c (record_minimal_symbol): Set section index to 0 for non-allocatable sections. gdb/testsuite/ChangeLog: * gdb.dwarf2/dw2-bad-elf-other.S: New file. * gdb.dwarf2/dw2-bad-elf.c: New file. * gdb.dwarf2/dw2-bad-elf.exp: New file. Change-Id: Ie05436ab4c6a71440304d20ee639dfb021223f8b
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.