readelf: Handle signedness of DW_FORM_implicit_const and DW_AT_const_value.

We only handles DW_FORM_sdata as a signed form, but DW_FORM_implicit_const
is also signed by default. For DW_AT_const_value we can do a little better.
GCC encodes some const_values with signed forms, even though the type
is unsigned. Lookup the (base) type of the DIE and display the const value
as their (signed) type/size (if we can determine that).

Add a new testcase run-readelf-const-values.sh that shows that.
With the new testcase the const values would come out as follows:

  name                 (string) "i"
  const_value          (implicit_const) 18446744073709551615
  name                 (string) "j"
  const_value          (implicit_const) 18446744073709551615

  name                 (string) "sc"
  const_value          (sdata) -2
  name                 (string) "uc"
  const_value          (sdata) -2
  name                 (string) "ss"
  const_value          (sdata) -16
  name                 (string) "us"
  const_value          (sdata) -16
  name                 (string) "si"
  const_value          (sdata) -3
  name                 (string) "ui"
  const_value          (sdata) -94967296
  name                 (string) "sl"
  const_value          (sdata) -1
  name                 (string) "ul"
  const_value          (sdata) -1

With this patch they show up as:

  name                 (string) "i"
  const_value          (implicit_const) -1
  name                 (string) "j"
  const_value          (implicit_const) -1

  name                 (string) "sc"
  const_value          (sdata) -2
  name                 (string) "uc"
  const_value          (sdata) 254 (-2)
  name                 (string) "ss"
  const_value          (sdata) -16
  name                 (string) "us"
  const_value          (sdata) 65520 (-16)
  name                 (string) "si"
  const_value          (sdata) -3
  name                 (string) "ui"
  const_value          (sdata) 4200000000 (-94967296)
  name                 (string) "sl"
  const_value          (sdata) -1
  name                 (string) "ul"
  const_value          (sdata) 18446744073709551615 (-1)

(for signed/unsigned int char, short and long)

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

1 files changed, 230 insertions, 0 deletions

diff --git a/tests/run-readelf-const-values.sh b/tests/run-readelf-const-values.sh
new file mode 100755
index 00000000..0a6356f1
--- /dev/null
+++ b/tests/run-readelf-const-values.sh
@@ -0,0 +1,230 @@
+#! /bin/sh
+# Test for displaying DW_AT_const_types with the "correct" sign.
+# Copyright (C) 2018 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
+
+# = s.c
+#
+# int s()
+# {
+#   int i = -1;
+#   int j = -1;
+#
+#   return i - j;
+# }
+#
+# = m.c
+#
+# extern int s();
+#
+# int
+# main ()
+# {
+#   const signed char sc = -2;
+#   const unsigned char uc = 254;
+#
+#   const signed short ss = -16;
+#   const unsigned short us = 65520;
+#
+#   const signed int si = -3;
+#   const unsigned int ui = 4200000000;
+#
+#   signed long sl = -1;
+#   unsigned long ul = 0xffffffffffffffffUL;
+#
+#   return s ();
+# }
+#
+# gcc -gdwarf-5 -O2 -c s.c
+# gcc -gdwarf-4 -O2 -c m.c
+# gcc -o testfile-const-values s.o m.o
+# eu-strip -g -f testfile-const-values.debug testfile-const-values
+
+testfiles testfile-const-values.debug
+
+testrun_compare ${abs_top_builddir}/src/readelf --debug-dump=info testfile-const-values.debug << EOF
+
+DWARF section [28] '.debug_info' at offset 0x2e0:
+ [Offset]
+ Compilation unit at offset 0:
+ Version: 5, Abbreviation section offset: 0, Address size: 8, Offset size: 4
+ Unit type: compile (1)
+ [     c]  compile_unit         abbrev: 2
+           producer             (strp) "GNU C11 7.3.1 20180303 (Red Hat 7.3.1-5) -mtune=generic -march=x86-64 -gdwarf-5 -O2"
+           language             (data1) C11 (29)
+           name                 (string) "s.c"
+           comp_dir             (strp) "/home/mark/build/elfutils-obj"
+           low_pc               (addr) 0x00000000004004d0
+           high_pc              (data8) 3 (0x00000000004004d3)
+           stmt_list            (sec_offset) 0
+ [    2e]    subprogram           abbrev: 3
+             external             (flag_present) yes
+             name                 (string) "s"
+             decl_file            (data1) s.c (1)
+             decl_line            (data1) 1
+             type                 (ref4) [    5e]
+             low_pc               (addr) 0x00000000004004d0
+             high_pc              (data8) 3 (0x00000000004004d3)
+             frame_base           (exprloc) 
+              [ 0] call_frame_cfa
+             call_all_calls       (flag_present) yes
+             sibling              (ref4) [    5e]
+ [    4d]      variable             abbrev: 1
+               name                 (string) "i"
+               decl_file            (implicit_const) s.c (1)
+               decl_line            (data1) 3
+               type                 (ref4) [    5e]
+               const_value          (implicit_const) -1
+ [    55]      variable             abbrev: 1
+               name                 (string) "j"
+               decl_file            (implicit_const) s.c (1)
+               decl_line            (data1) 4
+               type                 (ref4) [    5e]
+               const_value          (implicit_const) -1
+ [    5e]    base_type            abbrev: 4
+             byte_size            (data1) 4
+             encoding             (data1) signed (5)
+             name                 (string) "int"
+ Compilation unit at offset 102:
+ Version: 4, Abbreviation section offset: 73, Address size: 8, Offset size: 4
+ [    71]  compile_unit         abbrev: 1
+           producer             (strp) "GNU C11 7.3.1 20180303 (Red Hat 7.3.1-5) -mtune=generic -march=x86-64 -gdwarf-4 -O2"
+           language             (data1) C99 (12)
+           name                 (string) "m.c"
+           comp_dir             (strp) "/home/mark/build/elfutils-obj"
+           ranges               (sec_offset) range list [     0]
+           low_pc               (addr) 000000000000000000
+           stmt_list            (sec_offset) 54
+ [    8f]    subprogram           abbrev: 2
+             external             (flag_present) yes
+             name                 (strp) "main"
+             decl_file            (data1) m.c (1)
+             decl_line            (data1) 4
+             type                 (ref4) [   119]
+             low_pc               (addr) 0x00000000004003e0
+             high_pc              (data8) 7 (0x00000000004003e7)
+             frame_base           (exprloc) 
+              [ 0] call_frame_cfa
+             GNU_all_call_sites   (flag_present) yes
+             sibling              (ref4) [   119]
+ [    b0]      variable             abbrev: 3
+               name                 (string) "sc"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 6
+               type                 (ref4) [   12c]
+               const_value          (sdata) -2
+ [    bb]      variable             abbrev: 3
+               name                 (string) "uc"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 7
+               type                 (ref4) [   138]
+               const_value          (sdata) 254 (-2)
+ [    c6]      variable             abbrev: 3
+               name                 (string) "ss"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 9
+               type                 (ref4) [   144]
+               const_value          (sdata) -16
+ [    d1]      variable             abbrev: 3
+               name                 (string) "us"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 10
+               type                 (ref4) [   150]
+               const_value          (sdata) 65520 (-16)
+ [    dc]      variable             abbrev: 3
+               name                 (string) "si"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 12
+               type                 (ref4) [   120]
+               const_value          (sdata) -3
+ [    e7]      variable             abbrev: 3
+               name                 (string) "ui"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 13
+               type                 (ref4) [   15c]
+               const_value          (sdata) 4200000000 (-94967296)
+ [    f5]      variable             abbrev: 3
+               name                 (string) "sl"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 15
+               type                 (ref4) [   161]
+               const_value          (sdata) -1
+ [   100]      variable             abbrev: 3
+               name                 (string) "ul"
+               decl_file            (data1) m.c (1)
+               decl_line            (data1) 16
+               type                 (ref4) [   168]
+               const_value          (sdata) 18446744073709551615 (-1)
+ [   10b]      GNU_call_site        abbrev: 4
+               low_pc               (addr) 0x00000000004003e7
+               GNU_tail_call        (flag_present) yes
+               abstract_origin      (ref4) [   16f]
+ [   119]    base_type            abbrev: 5
+             byte_size            (data1) 4
+             encoding             (data1) signed (5)
+             name                 (string) "int"
+ [   120]    const_type           abbrev: 6
+             type                 (ref4) [   119]
+ [   125]    base_type            abbrev: 7
+             byte_size            (data1) 1
+             encoding             (data1) signed_char (6)
+             name                 (strp) "signed char"
+ [   12c]    const_type           abbrev: 6
+             type                 (ref4) [   125]
+ [   131]    base_type            abbrev: 7
+             byte_size            (data1) 1
+             encoding             (data1) unsigned_char (8)
+             name                 (strp) "unsigned char"
+ [   138]    const_type           abbrev: 6
+             type                 (ref4) [   131]
+ [   13d]    base_type            abbrev: 7
+             byte_size            (data1) 2
+             encoding             (data1) signed (5)
+             name                 (strp) "short int"
+ [   144]    const_type           abbrev: 6
+             type                 (ref4) [   13d]
+ [   149]    base_type            abbrev: 7
+             byte_size            (data1) 2
+             encoding             (data1) unsigned (7)
+             name                 (strp) "short unsigned int"
+ [   150]    const_type           abbrev: 6
+             type                 (ref4) [   149]
+ [   155]    base_type            abbrev: 7
+             byte_size            (data1) 4
+             encoding             (data1) unsigned (7)
+             name                 (strp) "unsigned int"
+ [   15c]    const_type           abbrev: 6
+             type                 (ref4) [   155]
+ [   161]    base_type            abbrev: 7
+             byte_size            (data1) 8
+             encoding             (data1) signed (5)
+             name                 (strp) "long int"
+ [   168]    base_type            abbrev: 7
+             byte_size            (data1) 8
+             encoding             (data1) unsigned (7)
+             name                 (strp) "long unsigned int"
+ [   16f]    subprogram           abbrev: 8
+             external             (flag_present) yes
+             declaration          (flag_present) yes
+             linkage_name         (string) "s"
+             name                 (string) "s"
+             decl_file            (data1) m.c (1)
+             decl_line            (data1) 1
+EOF
+
+exit 0