From db72737006fc383cb8838bf7f3dc8e641e60c38f Mon Sep 17 00:00:00 2001 From: Jozef Lawrynowicz Date: Tue, 11 Sep 2018 22:56:36 +0100 Subject: [PATCH] Fix PR gdb/20948: --write option to GDB causes segmentation fault When opening a BFD for update, as gdb --write does, modifications to anything but the contents of sections is restricted. Do not try to write back any ELF headers in this case. bfd/ChangeLog 2018-09-24 Jozef Lawrynowicz PR gdb/20948 * elf.c (_bfd_elf_write_object_contents): Return from function early if abfd->direction == both_direction. gdb/testsuite/ChangeLog 2018-09-24 Jozef Lawrynowicz PR gdb/20948 * gdb.base/write_mem.exp: New test. * gdb.base/write_mem.c: Likewise. --- bfd/ChangeLog | 6 ++++ bfd/elf.c | 12 +++++++ gdb/testsuite/ChangeLog | 6 ++++ gdb/testsuite/gdb.base/write_mem.c | 20 ++++++++++++ gdb/testsuite/gdb.base/write_mem.exp | 47 ++++++++++++++++++++++++++++ 5 files changed, 91 insertions(+) create mode 100644 gdb/testsuite/gdb.base/write_mem.c create mode 100644 gdb/testsuite/gdb.base/write_mem.exp diff --git a/bfd/ChangeLog b/bfd/ChangeLog index a5c857ad71..382df33b36 100644 --- a/bfd/ChangeLog +++ b/bfd/ChangeLog @@ -1,3 +1,9 @@ +2018-09-24 Jozef Lawrynowicz + + PR gdb/20948 + * elf.c (_bfd_elf_write_object_contents): Return from function + early if abfd->direction == both_direction. + 2018-09-21 Simon Marchi * configure.ac: Check for fls. diff --git a/bfd/elf.c b/bfd/elf.c index 02d605c19c..5320ae2237 100644 --- a/bfd/elf.c +++ b/bfd/elf.c @@ -6391,6 +6391,18 @@ _bfd_elf_write_object_contents (bfd *abfd) if (! abfd->output_has_begun && ! _bfd_elf_compute_section_file_positions (abfd, NULL)) return FALSE; + /* Do not rewrite ELF data when the BFD has been opened for update. + abfd->output_has_begun was set to TRUE on opening, so creation of new + sections, and modification of existing section sizes was restricted. + This means the ELF header, program headers and section headers can't have + changed. + If the contents of any sections has been modified, then those changes have + already been written to the BFD. */ + else if (abfd->direction == both_direction) + { + BFD_ASSERT (abfd->output_has_begun); + return TRUE; + } i_shdrp = elf_elfsections (abfd); diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 877edc0cb5..d15fcff17b 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2018-09-24 Jozef Lawrynowicz + + PR gdb/20948 + * gdb.base/write_mem.exp: New test. + * gdb.base/write_mem.c: Likewise. + 2018-09-23 Tom Tromey PR python/18852: diff --git a/gdb/testsuite/gdb.base/write_mem.c b/gdb/testsuite/gdb.base/write_mem.c new file mode 100644 index 0000000000..82d8c41251 --- /dev/null +++ b/gdb/testsuite/gdb.base/write_mem.c @@ -0,0 +1,20 @@ +/* Copyright (C) 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 . */ + +int main (void) +{ + while (1); + return 0; +} diff --git a/gdb/testsuite/gdb.base/write_mem.exp b/gdb/testsuite/gdb.base/write_mem.exp new file mode 100644 index 0000000000..db476e7ea1 --- /dev/null +++ b/gdb/testsuite/gdb.base/write_mem.exp @@ -0,0 +1,47 @@ +# Copyright (C) 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 . + +# Contributed by Jozef Lawrynowicz (jozef.l@mittosystems.com) + +# Test for PR gdb/20948 +# Verify that invoking gdb with the --write argument works as expected + +global GDBFLAGS +standard_testfile + +if {[build_executable $testfile.exp $testfile \ + $srcfile [list debug nowarnings] ] == -1} { + untested $testfile.exp + return -1 +} + +set old_gdbflags $GDBFLAGS + +# Expect a failure before --write has been added to the command line +set GDBFLAGS "$old_gdbflags $binfile" +clean_restart +test_print_reject "set {int}main = 0x4242" "Cannot access memory at address" + +# Setting memory should now work correctly after adding --write +set GDBFLAGS "$old_gdbflags --write $binfile" +clean_restart +gdb_test_no_output "set {int}main = 0x4242" + +# Check that memory write persists after quitting GDB +gdb_exit +gdb_start +gdb_test "x /xh main" "
:.*4242" + +set GDBFLAGS $old_gdbflags -- 2.34.1