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Fix gdb segv when objfile can't be opened

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This fixes PR 16577.

This patch changes gdb_bfd_map_section to issue a warning rather than an error
if it is unable to read the object file, and sets the size of the section/frame
that it attempted to read to 0 on error.

The description of gdb_bfd_map_section states that it will try to read or map
the contents of the section SECT, and if successful, the section data is
returned and *SIZE is set to the size of the section data.  This function was
throwing an error and leaving *SIZE as-is.  Setting the section size to 0
indicates to dwarf2_build_frame_info that there is no data to read, otherwise
it will try to read from an invalid frame pointer.

Changing the error to a warning allows this to be handled gracefully.
Additionally, the error was clobbering the breakpoint output indicating the
current frame (function name, arguments, source file, and line number).  E.g.

Thread 3 "foo" hit Breakpoint 1, BFD: reopening /tmp/jna-1013829440/jna2973250704389291330.tmp: No such file or directory
BFD: reopening /tmp/jna-1013829440/jna2973250704389291330.tmp: No such file or directory
(gdb)

While the "BFD: reopening ..." messages will still appear interspersed in the
breakpoint output, the current frame info is now displayed:

Thread 3 "foo" hit Breakpoint 1, BFD: reopening /tmp/jna-1013829440/jna1875755897659885075.tmp: No such file or directory
BFD: reopening /tmp/jna-1013829440/jna1875755897659885075.tmp: No such file or directory
warning: Can't read data for section '.eh_frame' in file '/tmp/jna-1013829440/jna1875755897659885075.tmp'
do_something () at file.cpp:80
80	{
(gdb)
This commit is contained in:
Mike Gulick 2017-10-30 18:13:44 -04:00 • committed by Simon Marchi
parent 4d9b86e175
commit 4166753056
8 changed files with 261 additions and 12 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
gdb/ChangeLog
View file

@ -1,3 +1,11 @@
2017-10-30 Mike Gulick <mgulick@mathworks.com>
PR gdb/16577
* gdb_bfd.c (gdb_bfd_map_section): If unable to read object file, issue
a warning instead of throwing an error, set section size to 0 and return
NULL.
* gdb_bfd.h (gdb_bfd_map_section): Update description.
2018-01-17 Simon Marchi <simon.marchi@ericsson.com>
* nat/linux-ptrace.h (linux_ptrace_attach_fail_reason): Return

8
gdb/gdb_bfd.c
View file

@ -702,9 +702,15 @@ gdb_bfd_map_section (asection *sectp, bfd_size_type *size)
data = NULL;
if (!bfd_get_full_section_contents (abfd, sectp, &data))
error (_("Can't read data for section '%s' in file '%s'"),
{
warning (_("Can't read data for section '%s' in file '%s'"),
bfd_get_section_name (abfd, sectp),
bfd_get_filename (abfd));
/* Set size to 0 to prevent further attempts to read the invalid
section. */
*size = 0;
return (const gdb_byte *) NULL;
}
descriptor->data = data;
done:

17
gdb/gdb_bfd.h
View file

@ -115,15 +115,14 @@ void gdb_bfd_mark_parent (bfd *child, bfd *parent);
void gdb_bfd_record_inclusion (bfd *includer, bfd *includee);
/* Try to read or map the contents of the section SECT. If
successful, the section data is returned and *SIZE is set to the
size of the section data; this may not be the same as the size
according to bfd_get_section_size if the section was compressed.
The returned section data is associated with the BFD and will be
destroyed when the BFD is destroyed. There is no other way to free
it; for temporary uses of section data, see
bfd_malloc_and_get_section. SECT may not have relocations. This
function will throw on error. */
/* Try to read or map the contents of the section SECT. If successful, the
section data is returned and *SIZE is set to the size of the section data;
this may not be the same as the size according to bfd_get_section_size if the
section was compressed. The returned section data is associated with the BFD
and will be destroyed when the BFD is destroyed. There is no other way to
free it; for temporary uses of section data, see bfd_malloc_and_get_section.
SECT may not have relocations. If there is an error reading the section,
this issues a warning, sets *SIZE to 0, and returns NULL. */
const gdb_byte *gdb_bfd_map_section (asection *section, bfd_size_type *size);

8
gdb/testsuite/ChangeLog
View file

@ -1,3 +1,11 @@
2017-10-30 Mike Gulick <mgulick@mathworks.com>
PR gdb/16577
* gdb.base/solib-vanish.exp: New.
* gdb.base/solib-vanish-main.c: New.
* gdb.base/solib-vanish-lib1.c: New.
* gdb.base/solib-vanish-lib2.c: New.
2018-01-17 Yao Qi <yao.qi@linaro.org>
* gdb.compile/compile.exp: Match the address printed for

24
gdb/testsuite/gdb.base/solib-vanish-lib1.c Normal file
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@ -0,0 +1,24 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2017-2018 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
extern int bar (int);
int
foo (int x)
{
return bar (x);
}

22
gdb/testsuite/gdb.base/solib-vanish-lib2.c Normal file
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@ -0,0 +1,22 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2017-2018 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
int
bar (int y)
{
return y + 1; /* break here */
}

75
gdb/testsuite/gdb.base/solib-vanish-main.c Normal file
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@ -0,0 +1,75 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2017-2018 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <dlfcn.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main ()
{
void *handle;
int (*foo) (int);
char *error;
char *dest = VANISH_LIB ".renamed";
/* Open library. */
handle = dlopen (VANISH_LIB, RTLD_NOW);
if (!handle)
{
fprintf (stderr, "%s\n", dlerror ());
exit (EXIT_FAILURE);
}
/* Clear any existing error */
dlerror ();
/* Simulate deleting file by renaming it. */
if (rename (VANISH_LIB, dest) == -1)
{
error = strerror (errno);
fprintf (stderr, "rename %s -> %s: %s\n", VANISH_LIB, dest, error);
exit (EXIT_FAILURE);
}
/* Get function pointer. */
foo = dlsym (handle, "foo");
error = dlerror ();
if (error != NULL)
{
fprintf (stderr, "%s\n", error);
exit (EXIT_FAILURE);
}
/* Call function. */
(*foo) (1);
/* Close and exit. */
dlclose (handle);
/* Put VANISH_LIB back where we found it. */
if (rename (dest, VANISH_LIB) == -1)
{
error = strerror (errno);
fprintf (stderr, "rename %s -> %s: %s\n", dest, VANISH_LIB, error);
exit (EXIT_FAILURE);
}
exit (EXIT_SUCCESS);
}

107
gdb/testsuite/gdb.base/solib-vanish.exp Normal file
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@ -0,0 +1,107 @@
# Copyright 2017-2018 Free Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# This test case verifies that GDB gracefully handles a shared library file
# vanishing after being dlopen'ed. This consists of three nested function calls:
#
# main() -> foo() -> bar()
#
# where:
# - foo exists in solib-vanish-lib1.so, which is dlopen'ed by main()
# - bar exists in solib-vanish-lib2.so, which is dynamically linked into
# solib-vanish-lib1.so
#
# Immediately after dlopen'ing solib-vanish-lib1.so, the so file is moved aside
# by renaming. The main executable and solib-vanish-lib2.so are still
# accessible.
#
# If a breakpoint is set on bar(), gdb throws an error when this breakpoint is
# hit:
#
# (gdb) r
# Starting program: /local/gdb/git/pr_16577_repro/simple/solib-vanish-main
#
# Breakpoint 1, BFD: reopening ./solib-vanish-lib1.so: No such file or directory
#
# BFD: reopening ./solib-vanish-lib1.so: No such file or directory
#
# (gdb)
#
# Notice that this does not print the current frame, i.e.:
# bar (y=1) at solib-vanish-lib2.c:19
# 19 return y + 1; /* break here */
# (gdb)
#
# The current gdb git tip segfaults if we then try to step:
# (gdb) n
# Segmentation fault
# This test verifies that:
# 1) GDB does not segfault when stepping
# 2) The stack frame is printed
if { [skip_shlib_tests] } {
return 0
}
# Library 2
set lib2name "solib-vanish-lib2"
set srcfile_lib2 ${srcdir}/${subdir}/${lib2name}.c
set binfile_lib2 [standard_output_file ${lib2name}.so]
set lib2_flags {debug}
# Library 1
set lib1name "solib-vanish-lib1"
set srcfile_lib1 ${srcdir}/${subdir}/${lib1name}.c
set binfile_lib1 [standard_output_file ${lib1name}.so]
set lib1_flags [list debug shlib=${binfile_lib2}]
# Main program
set testfile "solib-vanish-main"
set srcfile ${srcdir}/${subdir}/${testfile}.c
set executable ${testfile}
set binfile [standard_output_file ${executable}]
set bin_flags [list debug shlib_load additional_flags=-DVANISH_LIB=\"${binfile_lib1}\"]
if { [gdb_compile_shlib ${srcfile_lib2} ${binfile_lib2} $lib2_flags] != ""
|| [gdb_compile_shlib ${srcfile_lib1} ${binfile_lib1} $lib1_flags] != ""
|| [gdb_compile ${srcfile} ${binfile} executable $bin_flags] != "" } {
untested "failed to compile"
return -1
}
clean_restart $testfile
if { ![runto_main] } {
fail "can't run to main"
return
}
delete_breakpoints
set lib2_lineno [gdb_get_line_number "break here" ${srcfile_lib2}]
gdb_breakpoint "${lib2name}.c:${lib2_lineno}" {allow-pending}
# Verify that both the location and source code are displayed
gdb_continue_to_breakpoint "bar" \
".*/${lib2name}.c:${lib2_lineno}.*break here.*"
# This should not segfault
gdb_test "next" \
"" \
"next succeeds"