From: Tom de Vries <tdevries@suse.de>
To: gdb-patches@sourceware.org
Cc: Tom Tromey <tom@tromey.com>
Subject: [PATCH] [gdb/symtab] Handle empty file name in .debug_line section
Date: Mon, 17 Apr 2023 11:17:28 +0200 [thread overview]
Message-ID: <20230417091728.26004-1-tdevries@suse.de> (raw)
With DWARF 5, it's possible to produce an empty file name in the File Name
Table of the .debug_line section:
...
The File Name Table (offset 0x112, lines 1, columns 2):
Entry Dir Name
0 1 (indirect line string, offset: 0x2d):
...
Currently, when gdb reads an exec containing such debug info, it segfaults:
...
Thread 1 "gdb" received signal SIGSEGV, Segmentation fault.
0x000000000072cd38 in dwarf2_start_subfile (cu=0x2badc50, fe=..., lh=...) at \
gdb/dwarf2/read.c:18716
18716 if (!IS_ABSOLUTE_PATH (filename) && dirname != NULL)
...
because read_direct_string transforms "" into a nullptr, and we end up
dereferencing the nullptr.
Note that the behaviour of read_direct_string has been present since repo
creation.
Fix this in read_formatted_entries, by transforming nullptr filenames in to ""
filenames.
Tested on x86_64-linux.
PR symtab/30357
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30357
---
| 4 ++
.../gdb.dwarf2/dw2-empty-file-name.exp | 66 +++++++++++++++++++
2 files changed, 70 insertions(+)
create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-empty-file-name.exp
--git a/gdb/dwarf2/line-header.c b/gdb/dwarf2/line-header.c
index 9d74c8fe75b..d072a91bac9 100644
--- a/gdb/dwarf2/line-header.c
+++ b/gdb/dwarf2/line-header.c
@@ -215,6 +215,10 @@ read_formatted_entries (dwarf2_per_objfile *per_objfile, bfd *abfd,
break;
}
+ /* Normalize nullptr string. */
+ if (string.has_value () && *string == nullptr)
+ string.emplace ("");
+
switch (content_type)
{
case DW_LNCT_path:
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-empty-file-name.exp b/gdb/testsuite/gdb.dwarf2/dw2-empty-file-name.exp
new file mode 100644
index 00000000000..6030e4a0579
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-empty-file-name.exp
@@ -0,0 +1,66 @@
+# Copyright 2023 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/>.
+
+# Check that an empty file name in the .debug_line section doesn't cause
+# problems.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+require dwarf2_support
+
+# The .c files use __attribute__.
+require is_c_compiler_gcc
+
+standard_testfile main.c -dw.S
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ declare_labels Llines
+ global srcdir subdir srcfile
+
+ cu { version 5 } {
+ compile_unit {
+ {language @DW_LANG_C}
+ {name $srcfile}
+ {stmt_list $Llines DW_FORM_sec_offset}
+ } {
+ subprogram {
+ {external 1 flag}
+ {MACRO_AT_func {main}}
+ }
+ }
+ }
+
+ lines {version 5} Llines {
+ include_dir "${srcdir}/${subdir}"
+ file_name "" 1
+ }
+}
+
+if { [build_executable "failed to prepare" ${testfile} \
+ [list $srcfile $asm_file] {nodebug}] } {
+ return -1
+}
+
+clean_restart
+
+# If there's an ERROR during gdb_load, the assert will produce an UNRESOLVED
+# rather than a FAIL.
+gdb_assert { [gdb_load $binfile] == 0 }
+
+# But this will produce an actual FAIL, which is more visible than
+# ERROR/UNRESOLVED.
+gdb_assert { [info exists gdb_spawn_id] }
base-commit: 55003828f4d81a3d857ccfdfe4841704004a6468
--
2.35.3
next reply other threads:[~2023-04-17 9:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-17 9:17 Tom de Vries [this message]
2023-04-17 14:56 ` Tom Tromey
2023-04-17 16:14 ` Tom de Vries
2023-04-17 16:33 ` Tom de Vries
2023-04-17 16:59 ` Tom Tromey
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