160 lines
4.8 KiB
Diff
160 lines
4.8 KiB
Diff
From 8f53ac47d3f9c3800c8429d9187961ba81707d8b Mon Sep 17 00:00:00 2001
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From: Tom de Vries <tdevries@suse.de>
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Date: Wed, 16 Aug 2023 23:43:25 +0200
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Subject: [PATCH 1/2] [gdb/symtab] Handle self-reference DIE
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While working on a dwarf assembly test-case I accidentally created the
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following pathological dwarf:
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...
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<1><be>: Abbrev Number: 3 (DW_TAG_class_type)
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<bf> DW_AT_name : c1
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<c2> DW_AT_specification: <0xbe>
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...
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and noticed gdb segfaulting during cooked index creating due to running out of
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stack. This is a regression from gdb-12, where gdb just hung.
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Fix this by inhibiting the scan_attributes self-recursion for self-references.
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The same test-case with -readnow makes gdb hang, so also fix this in
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dwarf2_attr and follow_die_ref.
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Note that this doesn't fix the same problems for the more complicated case of:
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...
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<1><be>: Abbrev Number: 3 (DW_TAG_class_type)
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<bf> DW_AT_name : c1
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<c2> DW_AT_specification: <0xc6>
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<1><c6>: Abbrev Number: 4 (DW_TAG_class_type)
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<c7> DW_AT_name : c2
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<ca> DW_AT_specification: <0xbe>
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...
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but the approach for deciding whether to fix pathological dwarf cases is as
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per PR27981 comment 3:
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...
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yes if it is cheap/obvious, and no if it is something complicated or expensive.
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...
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and at this point I'm not sure whether fixing this will fall in the first
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category.
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Tested on x86_64-linux.
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Approved-By: Tom Tromey <tom@tromey.com>
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---
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gdb/dwarf2/read.c | 22 +++++++++--
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gdb/testsuite/gdb.dwarf2/self-spec.exp | 54 ++++++++++++++++++++++++++
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2 files changed, 73 insertions(+), 3 deletions(-)
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create mode 100644 gdb/testsuite/gdb.dwarf2/self-spec.exp
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diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
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index 61f4bd75013..1be5f381432 100644
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--- a/gdb/dwarf2/read.c
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+++ b/gdb/dwarf2/read.c
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@@ -18289,9 +18289,15 @@ cooked_indexer::scan_attributes (dwarf2_per_cu_data *scanning_per_cu,
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new_info_ptr,
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&bytes_read);
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new_info_ptr += bytes_read;
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- scan_attributes (scanning_per_cu, new_reader, new_info_ptr, new_info_ptr,
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- new_abbrev, name, linkage_name, flags, nullptr,
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- parent_entry, maybe_defer, true);
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+
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+ if (new_reader->cu == reader->cu && new_info_ptr == watermark_ptr)
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+ {
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+ /* Self-reference, we're done. */
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+ }
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+ else
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+ scan_attributes (scanning_per_cu, new_reader, new_info_ptr,
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+ new_info_ptr, new_abbrev, name, linkage_name,
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+ flags, nullptr, parent_entry, maybe_defer, true);
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}
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}
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@@ -19783,7 +19789,11 @@ dwarf2_attr (struct die_info *die, unsigned int name, struct dwarf2_cu *cu)
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if (!spec)
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break;
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+ struct die_info *prev_die = die;
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die = follow_die_ref (die, spec, &cu);
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+ if (die == prev_die)
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+ /* Self-reference, we're done. */
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+ break;
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}
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return NULL;
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@@ -22521,6 +22531,12 @@ follow_die_ref (struct die_info *src_die, const struct attribute *attr,
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struct dwarf2_cu *cu = *ref_cu;
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struct die_info *die;
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+ if (attr->form != DW_FORM_GNU_ref_alt && src_die->sect_off == sect_off)
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+ {
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+ /* Self-reference, we're done. */
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+ return src_die;
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+ }
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+
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die = follow_die_offset (sect_off,
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(attr->form == DW_FORM_GNU_ref_alt
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|| cu->per_cu->is_dwz),
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diff --git a/gdb/testsuite/gdb.dwarf2/self-spec.exp b/gdb/testsuite/gdb.dwarf2/self-spec.exp
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new file mode 100644
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index 00000000000..77e92549fd1
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--- /dev/null
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+++ b/gdb/testsuite/gdb.dwarf2/self-spec.exp
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@@ -0,0 +1,54 @@
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+# Copyright 2023 Free Software Foundation, Inc.
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+
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+# This program is free software; you can redistribute it and/or modify
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+# it under the terms of the GNU General Public License as published by
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+# the Free Software Foundation; either version 3 of the License, or
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+# (at your option) any later version.
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+#
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+# This program is distributed in the hope that it will be useful,
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+# but WITHOUT ANY WARRANTY; without even the implied warranty of
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+# GNU General Public License for more details.
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+#
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+# You should have received a copy of the GNU General Public License
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+# along with this program. If not, see <http://www.gnu.org/licenses/>.
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+
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+# Check that gdb doesn't hang or segfault on reading a DIE with a
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+# specification reference to itself.
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+
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+load_lib dwarf.exp
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+
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+if {![dwarf2_support]} {
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+ return 0
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+}
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+
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+standard_testfile main.c .S
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+
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+# Create the DWARF.
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+set asm_file [standard_output_file $srcfile2]
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+Dwarf::assemble $asm_file {
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+ cu {} {
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+ compile_unit {{language @DW_LANG_C_plus_plus}} {
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+ declare_labels c1
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+ c1: class_type {
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+ {name c1}
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+ {specification :$c1}
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+ }
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+ }
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+ }
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+}
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+
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+if [prepare_for_testing "failed to prepare" $testfile "${asm_file} ${srcfile}" {}] {
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+ return -1
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+}
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+
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+set index [have_index $binfile]
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+if { ![string eq $index ""] } {
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+ return 0
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+}
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+
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+if { [readnow] } {
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+ return 0
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+}
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+
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+gdb_test "maint expand-symtabs"
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base-commit: 6c9e159dbd1a35aafa134fcd52982174236a8dd9
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--
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2.35.3
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