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5fae2a2c66
Consider the following test-case small.c:
...
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main (void) {
int *p = (int *)malloc (sizeof(int) * 4);
memset (p, 0, sizeof(p));
printf ("p[0] = %d; p[3] = %d\n", p[0], p[3]);
return 0;
}
...
On Ubuntu 20.04, we get:
...
$ gcc -O0 -g small.c
$ gdb -batch a.out -ex start -ex step
Temporary breakpoint 1, main () at small.c:6
6 int *p = (int *) malloc(sizeof(int) * 4);
p[0] = 0; p[3] = 0
[Inferior 1 (process $dec) exited normally]
...
but after switching off the on-by-default fcf-protection, we get the desired
behaviour:
...
$ gcc -O0 -g small.c -fcf-protection=none
$ gdb -batch a.out -ex start -ex step
Temporary breakpoint 1, main () at small.c:6
6 int *p = (int *) malloc(sizeof(int) * 4);
7 memset (p, 0, sizeof(p));
...
Using "set debug infrun 1", the first observable difference between the two
debug sessions is that with -fcf-protection=none we get:
...
[infrun] process_event_stop_test: stepped into dynsym resolve code
...
In this case, "in_solib_dynsym_resolve_code (malloc@plt)" returns true because
"in_plt_section (malloc@plt)" returns true.
With -fcf-protection=full, "in_solib_dynsym_resolve_code (malloc@plt)" returns
false because "in_plt_section (malloc@plt)" returns false, because the section
name for malloc@plt is .plt.sec instead of .plt, which is not handled in
in_plt_section:
...
static inline int
in_plt_section (CORE_ADDR pc)
{
return pc_in_section (pc, ".plt");
}
...
Fix this by handling .plt.sec in in_plt_section.
Tested on x86_64-linux.
[ Another requirement to be able to reproduce this is to have a dynamic linker
with a "malloc" minimal symbol, which causes find_solib_trampoline_target to
find it, such that skip_language_trampoline returns the address for the
dynamic linkers malloc. This causes the step machinery to set a breakpoint
there, and to continue, expecting to hit it. Obviously, we execute glibc's
malloc instead, so the breakpoint is not hit and we continue to program
completion. ]
gdb/ChangeLog:
2021-01-14 Tom de Vries <tdevries@suse.de>
PR breakpoints/27151
* objfiles.h (in_plt_section): Handle .plt.sec.
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.