libdw: Add support for DWZ multifile forms DW_FORM_GNU_ref_alt/strp_alt.

DWZ multifile forms http://www.dwarfstd.org/ShowIssue.php?issue=120604.1
DW_FORM_GNU_ref_alt and DW_FORM_GNU_strp_alt reference an alternative
debuginfo file.  dwarf_begin and dwarf_begin_elf will try to use this
automatically.  There are no user visible changes to the libdw interface.

dwarf_formref_die, dwarf_formstring and dwarf_formudata can now return
a Dwarf_Die which comes from a CU in the alternative Dwarf descriptor.

__libdw_read_offset was adjusted to take an alternative Dwarf descriptor
into account.

Signed-off-by: Mark Wielaard <[email protected]>

1 files changed, 156 insertions, 0 deletions

diff --git a/tests/run-readelf-dwz-multi.sh b/tests/run-readelf-dwz-multi.sh
new file mode 100755
index 00000000..42e6aa4c
--- /dev/null
+++ b/tests/run-readelf-dwz-multi.sh
@@ -0,0 +1,156 @@
+#! /bin/sh
+# Copyright (C) 2012 Red Hat, Inc.
+# This file is part of elfutils.
+#
+# This file 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.
+#
+# elfutils 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/>.
+
+. $srcdir/test-subr.sh
+
+# common.h
+#
+# #include <stdio.h>
+#
+# struct foobar
+# {
+#   int foo;
+#   struct foobar *bar;
+# };
+#
+# extern int call_foo(struct foobar *foobar_struct_ptr);
+
+# main.c
+#
+# #include "common.h"
+#
+# int main(int argc, char ** argv)
+# {
+#   struct foobar b;
+#   b.foo = 42;
+#   b.bar = &b;
+#
+#   return call_foo(b.bar);
+# }
+
+# shared.c
+#
+# #include "common.h"
+#
+# int call_foo(struct foobar *fb)
+# {
+#   return fb->bar->foo - 42;
+# }
+
+# gcc -fPIC -g -c -Wall shared.c
+# gcc -shared -o libtestfile_multi_shared.so shared.o
+# gcc -g -o testfile_multi_main -L. -ltestfile_multi_shared main.c -Wl,-rpath,.
+# dwz -m testfile_multi.dwz testfile_multi_main libtestfile_multi_shared.so
+
+testfiles libtestfile_multi_shared.so testfile_multi_main testfile_multi.dwz
+
+testrun_compare ../src/readelf --debug-dump=info testfile_multi_main <<\EOF
+
+DWARF section [28] '.debug_info' at offset 0x1078:
+ [Offset]
+ Compilation unit at offset 0:
+ Version: 4, Abbreviation section offset: 0, Address size: 8, Offset size: 4
+ [     b]  compile_unit
+           producer             (strp) "GNU C 4.7.0 20120507 (Red Hat 4.7.0-5) -mtune=generic -march=x86-64 -g"
+           language             (data1) ISO C89 (1)
+           name                 (strp) "main.c"
+           comp_dir             (GNU_strp_alt) "/home/mark/src/tests/dwz"
+           low_pc               (addr) 0x00000000004006ac <main>
+           high_pc              (udata) 44
+           stmt_list            (sec_offset) 0
+ [    26]    imported_unit
+             import               (GNU_ref_alt) [     b]
+ [    2b]    pointer_type
+             byte_size            (data1) 8
+             type                 (GNU_ref_alt) [    53]
+ [    31]    subprogram
+             external             (flag_present) 
+             name                 (strp) "main"
+             decl_file            (data1) 1
+             decl_line            (data1) 3
+             prototyped           (flag_present) 
+             type                 (GNU_ref_alt) [    3e]
+             low_pc               (addr) 0x00000000004006ac <main>
+             high_pc              (udata) 44
+             frame_base           (exprloc) 
+              [   0] call_frame_cfa
+             GNU_all_tail_call_sites (flag_present) 
+             sibling              (ref_udata) [    6e]
+ [    48]      formal_parameter
+               name                 (strp) "argc"
+               decl_file            (data1) 1
+               decl_line            (data1) 3
+               type                 (GNU_ref_alt) [    3e]
+               location             (exprloc) 
+                [   0] fbreg -36
+ [    56]      formal_parameter
+               name                 (strp) "argv"
+               decl_file            (data1) 1
+               decl_line            (data1) 3
+               type                 (ref_udata) [    6e]
+               location             (exprloc) 
+                [   0] fbreg -48
+ [    61]      variable
+               name                 (string) "b"
+               decl_file            (data1) 1
+               decl_line            (data1) 5
+               type                 (GNU_ref_alt) [    5a]
+               location             (exprloc) 
+                [   0] fbreg -32
+ [    6e]    pointer_type
+             byte_size            (data1) 8
+             type                 (ref_udata) [    2b]
+EOF
+
+testrun_compare ../src/readelf --debug-dump=info libtestfile_multi_shared.so <<\EOF
+
+DWARF section [25] '.debug_info' at offset 0x106c:
+ [Offset]
+ Compilation unit at offset 0:
+ Version: 4, Abbreviation section offset: 0, Address size: 8, Offset size: 4
+ [     b]  compile_unit
+           producer             (strp) "GNU C 4.7.0 20120507 (Red Hat 4.7.0-5) -fpreprocessed -mtune=generic -march=x86-64 -g -fPIC"
+           language             (data1) ISO C89 (1)
+           name                 (strp) "shared.c"
+           comp_dir             (GNU_strp_alt) "/home/mark/src/tests/dwz"
+           low_pc               (addr) +0x0000000000000670 <call_foo>
+           high_pc              (udata) 23
+           stmt_list            (sec_offset) 0
+ [    26]    imported_unit
+             import               (GNU_ref_alt) [     b]
+ [    2b]    subprogram
+             external             (flag_present) 
+             name                 (strp) "call_foo"
+             decl_file            (data1) 1
+             decl_line            (data1) 3
+             prototyped           (flag_present) 
+             type                 (GNU_ref_alt) [    3e]
+             low_pc               (addr) +0x0000000000000670 <call_foo>
+             high_pc              (udata) 23
+             frame_base           (exprloc) 
+              [   0] call_frame_cfa
+             GNU_all_call_sites   (flag_present) 
+ [    41]      formal_parameter
+               name                 (string) "fb"
+               decl_file            (data1) 1
+               decl_line            (data1) 3
+               type                 (GNU_ref_alt) [    76]
+               location             (exprloc) 
+                [   0] fbreg -24
+EOF
+
+exit 0