File correct-bounds-check-when-working-around-gas-dwarf-5.patch of Package gdb
From c91de4aa70627bd3c33788d90597c1b787c8d905 Mon Sep 17 00:00:00 2001
From: Keith Seitz <keiths@redhat.com>
Date: Fri, 19 Sep 2025 09:50:46 -0700
Subject: [PATCH 02/25] Correct bounds check when working around GAS DWARF 5
directory table bug
Recent Go toolchains are causing GDB to crash on a relatively recent
workaround for a GAS bug:
commit a833790a626d9620319d0ca6aee23daa584d445c
Date: Wed Nov 1 00:33:12 2023 +0100
[gdb/symtab] Work around gas PR28629
In the original GAS bug, the first directory table entry did not contain
the current directory of the compilation. So the above commit added a
workaround fix to prepend the second directory table entry.
However recent Go toolchain compilations (specifically on aarch64)
only output a single directory table entry. Looking at the workaround:
if (lh->version == 5 && lh->is_valid_file_index (1))
{
std::string dir = lh->include_dir_at (1);
fnd.set_comp_dir (std::move (dir));
}
`lh->is_valid_file_index (1)' is true, but since the directory table only
has one entry, `include_dir_at (1)' returns nullptr. Consequently the
std::string ctor will segfault. Since there are no guarantees that the file
and directory tables are the same size, a better bounds check is to simply
rely on `include_dir_at' to ensure a valid directory table entry.
I have updated the workaround commit's test, gdb.dwarf2/dw2-gas-workaround.exp
and tested on x86_64 and aarch64 RHEL 9 and Fedora 41.
Approved-By: Andrew Burgess <aburgess@redhat.com>
---
gdb/dwarf2/read.c | 2 +-
.../gdb.dwarf2/dw2-gas-workaround.exp | 92 ++++++++++++-------
2 files changed, 58 insertions(+), 36 deletions(-)
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 5fe92c24559..19a46425f84 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -7520,7 +7520,7 @@ read_file_scope (struct die_info *die, struct dwarf2_cu *cu)
sect_offset line_offset = (sect_offset) attr->as_unsigned ();
line_header_up lh = dwarf_decode_line_header (line_offset, cu,
fnd.get_comp_dir ());
- if (lh->version == 5 && lh->is_valid_file_index (1))
+ if (lh->version == 5 && lh->include_dir_at (1) != nullptr)
{
std::string dir = lh->include_dir_at (1);
fnd.set_comp_dir (std::move (dir));
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-gas-workaround.exp b/gdb/testsuite/gdb.dwarf2/dw2-gas-workaround.exp
index 5d6e13a9ae0..4155358f50e 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-gas-workaround.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-gas-workaround.exp
@@ -20,7 +20,7 @@ load_lib dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
require dwarf2_support
-standard_testfile dw2-lines.c -dw2.S
+standard_testfile dw2-lines.c -dw2.S -dw2-one-diridx.S
with_shared_gdb {
set func_info_vars [get_func_info bar]
@@ -33,49 +33,61 @@ proc line_for { l } {
return [expr $line + 1]
}
-set asm_file [standard_output_file $srcfile2]
-Dwarf::assemble $asm_file {
- declare_labels Llines
- global srcdir subdir srcfile objdir
- global func_info_vars
- foreach var $func_info_vars {
- global $var
- }
+# A helper proc to create the DWARF assembly for the test.
+# If ONE_DIRIDX is true, then the directory table will be limited
+# to one entry.
+proc create_dwarf_assembly {source_file one_diridx} {
+ set asm_file [standard_output_file $source_file]
+ Dwarf::assemble $asm_file {
+ declare_labels Llines
+ global srcdir subdir srcfile objdir
+ global func_info_vars
+ upvar one_diridx one_diridx
+ foreach var $func_info_vars {
+ global $var
+ }
- cu { version 5 } {
- compile_unit {
- {language @DW_LANG_Mips_Assembler}
- {name $srcfile}
- {comp_dir $objdir}
- {stmt_list $Llines DW_FORM_sec_offset}
- {producer "GNU AS 2.35.2"}
- } {
- subprogram {
- {external 1 flag}
- {name bar}
- {low_pc $bar_start addr}
- {high_pc "$bar_start + $bar_len" addr}
+ cu { version 5 } {
+ compile_unit {
+ {DW_AT_language @DW_LANG_Mips_Assembler}
+ {DW_AT_name $srcfile}
+ {DW_AT_comp_dir $objdir}
+ {DW_AT_stmt_list $Llines DW_FORM_sec_offset}
+ {DW_AT_producer "GNU AS 2.35.2"}
+ } {
+ subprogram {
+ {DW_AT_external 1 flag}
+ {DW_AT_name bar}
+ {DW_AT_low_pc $bar_start addr}
+ {DW_AT_high_pc "$bar_start + $bar_len" addr}
+ }
}
}
- }
- lines [list version 5] Llines {
- set diridx1 [include_dir "${srcdir}/${subdir}"]
- set diridx2 [include_dir "${srcdir}/${subdir}"]
- file_name "$srcfile" $diridx1
- file_name "$srcfile" $diridx2
-
- program {
- DW_LNE_set_address bar_label
- line [line_for bar_label]
- DW_LNS_copy
+ lines [list version 5] Llines {
+ set diridx1 [include_dir "${srcdir}/${subdir}"]
+ file_name "$srcfile" $diridx1
+ if {!$one_diridx} {
+ set diridx2 [include_dir "${srcdir}/${subdir}"]
+ file_name "$srcfile" $diridx2
+ } else {
+ file_name "$srcfile" $diridx1
+ }
+ program {
+ DW_LNE_set_address bar_label
+ line [line_for bar_label]
+ DW_LNS_copy
- DW_LNE_set_address $bar_end
- DW_LNE_end_sequence
+ DW_LNE_set_address $bar_end
+ DW_LNE_end_sequence
+ }
}
}
+
+ return $asm_file
}
+set asm_file [create_dwarf_assembly $srcfile2 false]
if { [prepare_for_testing "failed to prepare" ${testfile} \
[list $srcfile $asm_file] {nodebug}] } {
return -1
@@ -90,3 +102,13 @@ gdb_test_multiple "ptype bar" "" {
pass $gdb_test_name
}
}
+
+# Test whether gdb crashes in the case where the number of
+# directory indexes is only one.
+set asm_file [create_dwarf_assembly $srcfile3 true]
+if {[prepare_for_testing "failed to prepare" ${testfile}-one-diridx \
+ [list $srcfile $asm_file] {nodebug}] } {
+ return -1
+}
+
+gdb_test "ptype bar" ".*" "do not crash with only one directory table entry"
--
2.51.0
