From 49fa1332a69bc4b09d2cc7db587e27ea30f2a29d Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Mon, 29 Nov 2021 16:19:16 +0100 Subject: [gdb/symtab] Fix segfault in search_one_symtab PR28539 describes a segfault in lambda function search_one_symtab due to psymbol_functions::expand_symtabs_matching calling expansion_notify with a nullptr symtab: ... struct compunit_symtab *symtab = psymtab_to_symtab (objfile, ps); if (expansion_notify != NULL) if (!expansion_notify (symtab)) return false; ... This happens as follows. The partial symtab ps is a dwarf2_include_psymtab for some header file: ... (gdb) p ps.filename $5 = 0x64fcf80 "/usr/include/c++/11/bits/stl_construct.h" ... The includer of ps is a shared symtab for a partial unit, with as user: ... (gdb) p ps.includer().user.filename $11 = 0x64fc9f0 \ "/usr/src/debug/llvm13-13.0.0-1.2.x86_64/tools/clang/lib/AST/Decl.cpp" ... The call to psymtab_to_symtab expands the Decl.cpp symtab (and consequently the shared symtab), but returns nullptr because: ... struct dwarf2_include_psymtab : public partial_symtab { ... compunit_symtab *get_compunit_symtab (struct objfile *objfile) const override { return nullptr; } ... Fix this by returning the Decl.cpp symtab instead, which fixes the segfault in the PR. Tested on x86_64-linux. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28539 --- gdb/dwarf2/read.c | 5 +- gdb/psymtab.c | 2 + .../gdb.dwarf2/dw2-symtab-includes-lookup.exp | 99 ++++++++++++++++++++++ 3 files changed, 105 insertions(+), 1 deletion(-) create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-symtab-includes-lookup.exp diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index a513cc4..737d8a4 100644 --- a/gdb/dwarf2/read.c +++ b/gdb/dwarf2/read.c @@ -5787,7 +5787,10 @@ struct dwarf2_include_psymtab : public partial_symtab compunit_symtab *get_compunit_symtab (struct objfile *objfile) const override { - return nullptr; + compunit_symtab *cust = includer ()->get_compunit_symtab (objfile); + while (cust != nullptr && cust->user != nullptr) + cust = cust->user; + return cust; } private: diff --git a/gdb/psymtab.c b/gdb/psymtab.c index 7ffb743..e09537d 100644 --- a/gdb/psymtab.c +++ b/gdb/psymtab.c @@ -1152,6 +1152,8 @@ psymbol_functions::expand_symtabs_matching struct compunit_symtab *symtab = psymtab_to_symtab (objfile, ps); + gdb_assert (symtab != nullptr); + if (expansion_notify != NULL) if (!expansion_notify (symtab)) return false; diff --git a/gdb/testsuite/gdb.dwarf2/dw2-symtab-includes-lookup.exp b/gdb/testsuite/gdb.dwarf2/dw2-symtab-includes-lookup.exp new file mode 100644 index 0000000..ec3371d --- /dev/null +++ b/gdb/testsuite/gdb.dwarf2/dw2-symtab-includes-lookup.exp @@ -0,0 +1,99 @@ +# Copyright 2021 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 . + +# Lookup a type in a partial unit with DW_AT_stmt_list. +# +# The test-case is setup such that the partial symtab expansion route is +# .h partial symtab -> shared partial symtab -> toplevel symtab. +# +# That is, the partial symtabs (as displayed by maint print objfiles) are: +# +# ../sysdeps/x86_64/crtn.S at 0x3d944e0^M +# elf-init.c at 0x3d94440^M +# dw2-symtab-includes.h at 0x3d7c7a0^M +# at 0x31ef870^M +# bla.c at 0x33985f0^M +# ../sysdeps/x86_64/crti.S at 0x33e9a00^M +# init.c at 0x33fa600^M +# ../sysdeps/x86_64/start.S at 0x33f3fd0^M +# +# and the expansion of dw2-symtab-includes.h triggers the expansion of its +# includer , which triggers expansion of user bla.c. +# +# The problem in PR28539 was that after expansion of dw2-symtab-includes.h +# the expansion_notify function in psymbol_functions::expand_symtabs_matching +# should be called with the bla.c symtab, but instead it got called with +# nullptr, which caused a segfault. + +load_lib dwarf.exp + +# This test can only be run on targets which support DWARF-2 and use gas. +require dwarf2_support 1 + +standard_testfile main.c .S + +# Create the DWARF. +set asm_file [standard_output_file $srcfile2] +Dwarf::assemble $asm_file { + declare_labels partial_label lines_label + global srcdir subdir srcfile + + cu {} { + partial_label: partial_unit { + {stmt_list ${lines_label} DW_FORM_sec_offset} + } { + DW_TAG_base_type { + {DW_AT_byte_size 4 DW_FORM_sdata} + {DW_AT_encoding @DW_ATE_signed} + {DW_AT_name myint} + } + } + } + + cu {} { + compile_unit { + {language @DW_LANG_C} + {DW_AT_name bla.c} + } { + imported_unit { + {import $partial_label ref_addr} + } + } + } + + lines {version 2} lines_label { + include_dir "${srcdir}/${subdir}" + file_name "dw2-symtab-includes.h" 1 + program { + {DW_LNS_advance_line 1} + } + } +} + +if { [prepare_for_testing "failed to prepare" $testfile \ + "${asm_file} ${srcfile}" {}] } { + return -1 +} + +# Check that no symtabs are expanded. +set test "no symtabs expanded" +if { [readnow] } { + unsupported $test +} else { + gdb_test_no_output "maint info symtabs" $test +} + +# Lookup myint. Regression test for PR28539. +gdb_test "ptype myint" "type = myint" -- cgit v1.1