From fb12bc1e8e7c5246e4eabcebdb4644c43bc7e6b9 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Mon, 17 Apr 2023 18:09:32 +0200 Subject: [PATCH] [gdb/symtab] Handle empty file name in .debug_line section 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. Reviewed-By: Tom Tromey PR symtab/30357 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30357 --- gdb/dwarf2/line-header.c | 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 diff --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 . + +# 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] } -- 2.30.2