From 41664b45ab6387184bd0e7512fcf7a72c58744e7 Mon Sep 17 00:00:00 2001 From: Doug Gilmore Date: Wed, 28 Jun 2017 02:54:22 +0100 Subject: [PATCH] Fix PR 21337: segfault when re-reading symbols. Fix issue exposed by commit 3e29f34. The basic issue is that section data referenced through an objfile pointer can also be referenced via the program-space data pointer, although via a separate mapping mechanism, which is set up by update_section_map. Thus once section data attached to an objfile pointer is released, the section map associated with the program-space data pointer must be marked dirty to ensure that update_section_map is called to prevent stale data being referenced. For the matter at hand this marking is being done via a call to objfiles_changed. Before commit 3e29f34 objfiles_changed could be called after all of the objfile pointers were processed in reread_symbols since section data references via the program-space data pointer would not occur in the calls of read_symbols performed by reread_symbols. With commit 3e29f34 MIPS target specific calls to find_pc_section were added to the code for DWARF information processing, which is called via read_symbols. Thus in reread_symbols the call to objfiles_changed needs to be called before calling read_symbols, otherwise stale section data can be referenced. Thanks to Luis Machado for providing text for the main comment associated with the change. gdb/ 2017-06-28 Doug Gilmore PR gdb/21337 * symfile.c (reread_symbols): Call objfiles_changed just before read_symbols. gdb/testsuite/ 2017-06-28 Doug Gilmore PR gdb/21337 * gdb.base/reread-readsym.exp: New file. * gdb.base/reread-readsym.c: New file. --- gdb/ChangeLog | 6 +++ gdb/symfile.c | 23 +++++++-- gdb/testsuite/ChangeLog | 6 +++ gdb/testsuite/gdb.base/reread-readsym.c | 22 ++++++++ gdb/testsuite/gdb.base/reread-readsym.exp | 61 +++++++++++++++++++++++ 5 files changed, 115 insertions(+), 3 deletions(-) create mode 100644 gdb/testsuite/gdb.base/reread-readsym.c create mode 100644 gdb/testsuite/gdb.base/reread-readsym.exp diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 1ce56caa162..ae79dc681df 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2017-06-28 Doug Gilmore + + PR gdb/21337 + * symfile.c (reread_symbols): Call objfiles_changed just before + read_symbols. + 2017-06-27 Pedro Alves * symtab.c (COMPLETION_LIST_ADD_SYMBOL) diff --git a/gdb/symfile.c b/gdb/symfile.c index aa534153617..9cbd6e52138 100644 --- a/gdb/symfile.c +++ b/gdb/symfile.c @@ -2587,6 +2587,9 @@ reread_symbols (void) /* Free the obstacks for non-reusable objfiles. */ psymbol_bcache_free (objfile->psymbol_cache); objfile->psymbol_cache = psymbol_bcache_init (); + + /* NB: after this call to obstack_free, objfiles_changed + will need to be called (see discussion below). */ obstack_free (&objfile->objfile_obstack, 0); objfile->sections = NULL; objfile->compunit_symtabs = NULL; @@ -2639,6 +2642,23 @@ reread_symbols (void) clear_complaints (&symfile_complaints, 1, 1); objfile->flags &= ~OBJF_PSYMTABS_READ; + + /* We are about to read new symbols and potentially also + DWARF information. Some targets may want to pass addresses + read from DWARF DIE's through an adjustment function before + saving them, like MIPS, which may call into + "find_pc_section". When called, that function will make + use of per-objfile program space data. + + Since we discarded our section information above, we have + dangling pointers in the per-objfile program space data + structure. Force GDB to update the section mapping + information by letting it know the objfile has changed, + making the dangling pointers point to correct data + again. */ + + objfiles_changed (); + read_symbols (objfile, 0); if (!objfile_has_symbols (objfile)) @@ -2671,9 +2691,6 @@ reread_symbols (void) if (!new_objfiles.empty ()) { - /* Notify objfiles that we've modified objfile sections. */ - objfiles_changed (); - clear_symtab_users (0); /* clear_objfile_data for each objfile was called before freeing it and diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 253e22908b2..b7462a5cdcb 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2017-06-28 Doug Gilmore + + PR gdb/21337 + * gdb.base/reread-readsym.exp: New file. + * gdb.base/reread-readsym.c: New file. + 2017-06-21 Kevin Buettner * gdb.exp (gdb_test): Using noncapturing parens for the $pattern diff --git a/gdb/testsuite/gdb.base/reread-readsym.c b/gdb/testsuite/gdb.base/reread-readsym.c new file mode 100644 index 00000000000..2fee6961d55 --- /dev/null +++ b/gdb/testsuite/gdb.base/reread-readsym.c @@ -0,0 +1,22 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2017 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) +{ + return 0; +} diff --git a/gdb/testsuite/gdb.base/reread-readsym.exp b/gdb/testsuite/gdb.base/reread-readsym.exp new file mode 100644 index 00000000000..b69eaadaad7 --- /dev/null +++ b/gdb/testsuite/gdb.base/reread-readsym.exp @@ -0,0 +1,61 @@ +# Copyright 2017 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 . + +standard_testfile + +set gdbfile [standard_output_file ${testfile}.gdb] + +# Test rereading executable. See PR gdb/21337. + +proc generate_cmd_file {gdbfile binfile} { + set ofd [open $gdbfile w] + + puts $ofd "file ${binfile}" + puts $ofd "shell sleep 1; touch ${binfile}" + puts $ofd "run" + puts $ofd "file" + puts $ofd "file ${binfile}" + puts $ofd "shell sleep 1; touch ${binfile}" + puts $ofd "run" + puts $ofd "file" + puts $ofd "file ${binfile}" + puts $ofd "shell sleep 1; touch ${binfile}" + puts $ofd "run" + puts $ofd "file" + puts $ofd "p \"source-command-completed\"" + close $ofd +} + +if [use_gdb_stub] { + return 0 +} + +if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} { + return -1 +} + +# Start with a fresh gdb. +clean_restart ${testfile} + +# Using the source command to read commands from a file is important, +# otherwise section data is freed and reallocated using the same +# memory locations and the bug is not exposed. +generate_cmd_file $gdbfile $binfile + +gdb_test "source $gdbfile" ".*source-command-completed.*" \ + "source $testfile.gdb 1" +# Sometimes the failure only occurs on the second invocation. +gdb_test "source $gdbfile" ".*source-command-completed.*" \ + "source $testfile.gdb 2" -- 2.30.2