[gdb/symtab] Fix zero address complaint for shlib

In PR28004 the following warning / Internal error is reported:
...
$ gdb -q -batch \
    -iex "set sysroot $(pwd -P)/repro" \
    ./repro/gdb \
    ./repro/core \
    -ex bt
  ...
 Program terminated with signal SIGABRT, Aborted.
 #0  0x00007ff8fe8e5d22 in raise () from repro/usr/lib/libc.so.6
 [Current thread is 1 (LWP 1762498)]
 #1  0x00007ff8fe8cf862 in abort () from repro/usr/lib/libc.so.6
 warning: (Internal error: pc 0x7ff8feb2c21d in read in psymtab, \
           but not in symtab.)
 warning: (Internal error: pc 0x7ff8feb2c218 in read in psymtab, \
           but not in symtab.)
  ...
 #2  0x00007ff8feb2c21e in __gnu_debug::_Error_formatter::_M_error() const \
   [clone .cold] (warning: (Internal error: pc 0x7ff8feb2c21d in read in \
   psymtab, but not in symtab.)

) from repro/usr/lib/libstdc++.so.6
...

The warning is about the following:
- in find_pc_sect_compunit_symtab we try to find the address
  (0x7ff8feb2c218 / 0x7ff8feb2c21d) in the symtabs.
- that fails, so we try again in the partial symtabs.
- we find a matching partial symtab
- however, the partial symtab has a full symtab, so
  we should have found a matching symtab in the first step.

The addresses are:
...
(gdb) info sym 0x7ff8feb2c218
__gnu_debug::_Error_formatter::_M_error() const [clone .cold] in \
  section .text of repro/usr/lib/libstdc++.so.6
(gdb) info sym 0x7ff8feb2c21d
__gnu_debug::_Error_formatter::_M_error() const [clone .cold] + 5 in \
  section .text of repro/usr/lib/libstdc++.so.6
...
which correspond to unrelocated addresses 0x9c218 and 0x9c21d:
...
$ nm -C  repro/usr/lib/libstdc++.so.6.0.29 | grep 000000000009c218
000000000009c218 t __gnu_debug::_Error_formatter::_M_error() const \
  [clone .cold]
...
which belong to function __gnu_debug::_Error_formatter::_M_error() in
/build/gcc/src/gcc/libstdc++-v3/src/c++11/debug.cc.

The partial symtab that is found for the addresses is instead the one for
/build/gcc/src/gcc/libstdc++-v3/src/c++98/bitmap_allocator.cc, which is
incorrect.

This happens as follows.

The bitmap_allocator.cc CU has DW_AT_ranges at .debug_rnglist offset 0x4b50:
...
    00004b50 0000000000000000 0000000000000056
    00004b5a 00000000000a4790 00000000000a479c
    00004b64 00000000000a47a0 00000000000a47ac
...

When reading the first range 0x0..0x56, it doesn't trigger the "start address
of zero" complaint here:
...
      /* A not-uncommon case of bad debug info.
         Don't pollute the addrmap with bad data.  */
      if (range_beginning + baseaddr == 0
          && !per_objfile->per_bfd->has_section_at_zero)
        {
          complaint (_(".debug_rnglists entry has start address of zero"
                       " [in module %s]"), objfile_name (objfile));
          continue;
        }
...
because baseaddr != 0, which seems incorrect given that when loading the
shared library individually in gdb (and consequently baseaddr == 0), we do see
the complaint.

Consequently, we run into this case in dwarf2_get_pc_bounds:
...
  if (low == 0 && !per_objfile->per_bfd->has_section_at_zero)
    return PC_BOUNDS_INVALID;
...
which then results in this code in process_psymtab_comp_unit_reader being
called with cu_bounds_kind == PC_BOUNDS_INVALID, which sets the set_addrmap
argument to 1:
...
      scan_partial_symbols (first_die, &lowpc, &highpc,
                            cu_bounds_kind <= PC_BOUNDS_INVALID, cu);
...
and consequently, the CU addrmap gets build using address info from the
functions.

During that process, addrmap_set_empty is called with a range that includes
0x9c218 and 0x9c21d:
...
(gdb) p /x start
$7 = 0x9989c
(gdb) p /x end_inclusive
$8 = 0xb200d
...
but it's called for a function at DIE 0x54153 with DW_AT_ranges at 0x40ae:
...
    000040ae 00000000000b1ee0 00000000000b200e
    000040b9 000000000009989c 00000000000998c4
    000040c3 <End of list>
...
and neither range includes 0x9c218 and 0x9c21d.

This is caused by this code in partial_die_info::read:
...
            if (dwarf2_ranges_read (ranges_offset, &lowpc, &highpc, cu,
                                    nullptr, tag))
             has_pc_info = 1;
...
which pretends that the function is located at addresses 0x9989c..0xb200d,
which is indeed not the case.

This patch fixes the first problem encountered: fix the "start address of
zero" complaint warning by removing the baseaddr part from the condition.
Same for dwarf2_ranges_process.

The effect is that:
- the complaint is triggered, and
- the warning / Internal error is no longer triggered.

This does not fix the observed problem in partial_die_info::read, which is
filed as PR28200.

Tested on x86_64-linux.

Co-Authored-By: Simon Marchi <simon.marchi@polymtl.ca>
gdb/ChangeLog:

2021-08-06  Simon Marchi  <simon.marchi@polymtl.ca>
	    Tom de Vries  <tdevries@suse.de>

	PR symtab/28004
	* dwarf2/read.c (dwarf2_rnglists_process, dwarf2_ranges_process):
	Fix zero address complaint.

gdb/testsuite/ChangeLog:

2021-08-06  Simon Marchi  <simon.marchi@polymtl.ca>
	    Tom de Vries  <tdevries@suse.de>

	PR symtab/28004
	* gdb.dwarf2/dw2-zero-range-shlib.c: New test.
	* gdb.dwarf2/dw2-zero-range.c: New test.
	* gdb.dwarf2/dw2-zero-range.exp: New file.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b8f06a7878f174ceafffe515c7a2eea18cc04117..fdc8a1d0085ca01b1b7b5bd178750af9f4c648c2 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2021-08-06  Simon Marchi  <simon.marchi@polymtl.ca>
+           Tom de Vries  <tdevries@suse.de>
+
+       PR symtab/28004
+       * dwarf2/read.c (dwarf2_rnglists_process, dwarf2_ranges_process):
+       Fix zero address complaint.
+
 2021-08-02  Tom Tromey  <tromey@adacore.com>
 
        PR varobj/28131

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 2b054f56e09f35cd4d1d5dbd3b877674dd901f91..a9af00559c69f9c6e145d65f48031dd20e7aad07 100644 (file)
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -13608,7 +13608,6 @@ dwarf2_rnglists_process (unsigned offset, struct dwarf2_cu *cu,
   /* Base address selection entry.  */
   gdb::optional<CORE_ADDR> base;
   const gdb_byte *buffer;
-  CORE_ADDR baseaddr;
   bool overflow = false;
   ULONGEST addr_index;
   struct dwarf2_section_info *rnglists_section;
@@ -13625,8 +13624,6 @@ dwarf2_rnglists_process (unsigned offset, struct dwarf2_cu *cu,
     }
   buffer = rnglists_section->buffer + offset;
 
-  baseaddr = objfile->text_section_offset ();
-
   while (1)
     {
       /* Initialize it due to a false compiler warning.  */
@@ -13768,7 +13765,7 @@ dwarf2_rnglists_process (unsigned offset, struct dwarf2_cu *cu,
 
       /* A not-uncommon case of bad debug info.
         Don't pollute the addrmap with bad data.  */
-      if (range_beginning + baseaddr == 0
+      if (range_beginning == 0
          && !per_objfile->per_bfd->has_section_at_zero)
        {
          complaint (_(".debug_rnglists entry has start address of zero"
@@ -13810,7 +13807,6 @@ dwarf2_ranges_process (unsigned offset, struct dwarf2_cu *cu, dwarf_tag tag,
   gdb::optional<CORE_ADDR> base;
   unsigned int dummy;
   const gdb_byte *buffer;
-  CORE_ADDR baseaddr;
 
   if (cu_header->version >= 5)
     return dwarf2_rnglists_process (offset, cu, tag, callback);
@@ -13826,8 +13822,6 @@ dwarf2_ranges_process (unsigned offset, struct dwarf2_cu *cu, dwarf_tag tag,
     }
   buffer = per_objfile->per_bfd->ranges.buffer + offset;
 
-  baseaddr = objfile->text_section_offset ();
-
   while (1)
     {
       CORE_ADDR range_beginning, range_end;
@@ -13878,7 +13872,7 @@ dwarf2_ranges_process (unsigned offset, struct dwarf2_cu *cu, dwarf_tag tag,
 
       /* A not-uncommon case of bad debug info.
         Don't pollute the addrmap with bad data.  */
-      if (range_beginning + baseaddr == 0
+      if (range_beginning == 0
          && !per_objfile->per_bfd->has_section_at_zero)
        {
          complaint (_(".debug_ranges entry has start address of zero"

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index b0fc59256333cb95e0b41ea5fdd9d092130ba4b7..05fe58a3e6da0d284d089e720cab44e170ccbef5 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2021-08-06  Simon Marchi  <simon.marchi@polymtl.ca>
+           Tom de Vries  <tdevries@suse.de>
+
+       PR symtab/28004
+       * gdb.dwarf2/dw2-zero-range-shlib.c: New test.
+       * gdb.dwarf2/dw2-zero-range.c: New test.
+       * gdb.dwarf2/dw2-zero-range.exp: New file.
+
 2021-08-02  Tom Tromey  <tromey@adacore.com>
 
        PR varobj/28131

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-zero-range-shlib.c b/gdb/testsuite/gdb.dwarf2/dw2-zero-range-shlib.c
new file mode 100644 (file)
index 0000000..1ddc8d6
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-zero-range-shlib.c
@@ -0,0 +1,21 @@
+/*
+   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 <http://www.gnu.org/licenses/>.  */
+
+void
+foo (void)
+{
+  asm ("foo_label: .globl foo_label");
+}

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-zero-range.c b/gdb/testsuite/gdb.dwarf2/dw2-zero-range.c
new file mode 100644 (file)
index 0000000..894a04d
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-zero-range.c
@@ -0,0 +1,24 @@
+/*
+   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 <http://www.gnu.org/licenses/>.  */
+
+extern void foo (void);
+
+int
+main (void)
+{
+  asm ("main_label: .globl main_label");
+  foo ();
+}

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-zero-range.exp b/gdb/testsuite/gdb.dwarf2/dw2-zero-range.exp
new file mode 100644 (file)
index 0000000..4f2ac0f
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-zero-range.exp
@@ -0,0 +1,185 @@
+# 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 <http://www.gnu.org/licenses/>.
+
+# Check that the ".debug_ranges entry has start address of zero" complaint
+# is triggered for a loaded shared lib.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    verbose "Skipping $gdb_test_file_name."
+    return 0
+}
+
+if {[skip_shlib_tests]} {
+    return 0
+}
+
+standard_testfile .c -shlib.c -dw.S
+
+# Test with both a .debug_ranges section (DWARF 4) and a .debug_rnglists
+# section (DWARF 5).
+
+foreach_with_prefix ranges_sect {ranges rnglists} {
+    set asm_file [standard_output_file ${ranges_sect}-$srcfile3]
+
+    if { $ranges_sect == "ranges" } {
+       Dwarf::assemble $asm_file {
+           global srcdir subdir srcfile2
+           declare_labels ranges_label
+
+           cu {} {
+               compile_unit {
+                   {language @DW_LANG_C}
+                   {name $srcfile2}
+                   {ranges ${ranges_label} DW_FORM_sec_offset}
+               } {
+                   subprogram {
+                       {external 1 flag}
+                       {name foo}
+                   }
+               }
+           }
+
+           ranges {is_64 [is_64_target]} {
+               ranges_label: sequence {
+                   base 0
+                   range 0 1
+               }
+           }
+       }
+    } elseif { $ranges_sect == "rnglists" } {
+       Dwarf::assemble $asm_file {
+           global srcdir subdir srcfile2
+           declare_labels rnglists_label
+
+           cu {
+               version 5
+           } {
+               compile_unit {
+                   {language @DW_LANG_C}
+                   {name $srcfile2}
+                   {ranges ${rnglists_label} DW_FORM_sec_offset}
+               } {
+                   subprogram {
+                       {external 1 flag}
+                       {name foo}
+                   }
+               }
+           }
+
+           rnglists {
+               table {
+                   rnglists_label: list_ {
+                       start_end 0 1
+                   }
+               }
+           }
+       }
+    } else {
+       error "invalid ranges section kind"
+    }
+
+    set lib1 [standard_output_file shr1.sl]
+    set lib_opts "nodebug"
+
+    set sources [list ${srcdir}/${subdir}/$srcfile2 $asm_file]
+    if { [gdb_compile_shlib $sources ${lib1} $lib_opts] != "" } {
+       untested "failed to compile"
+       return -1
+    }
+
+    set exec_opts [list debug shlib=${lib1}]
+    set sources ${srcdir}/${subdir}/${srcfile}
+    if { [gdb_compile $sources  ${binfile} executable \
+             $exec_opts] != ""} {
+       untested "failed to compile"
+       return -1
+    }
+
+    clean_restart $binfile
+
+    set readnow_p [readnow]
+
+    # Don't load the symbols for $lib1 during runto_main.
+    # Instead, we do this afterwards using "sharedlibrary $lib1".
+    gdb_test_no_output "set auto-solib-add off"
+
+    if { ![runto_main] } {
+       fail "cannot run to main."
+       return -1
+    }
+
+    set complaint_re ".debug_${ranges_sect} entry has start address of zero"
+    set re \
+       "During symbol reading: $complaint_re \\\[in module \[^\r\n\]*\\\]"
+
+    # Test for presence of complaint, with lib1 relocated.
+    with_complaints 1 {
+       set test "Zero address complaint - relocated - psymtab"
+       set have_complaint 0
+       gdb_test_multiple "sharedlibrary $lib1" $test {
+           -re -wrap $re {
+               set have_complaint 1
+           }
+           -re -wrap "" {
+           }
+       }
+
+       if { $have_complaint } {
+           pass $test
+       } else {
+           set index [have_index $lib1]
+           if { $index == "gdb_index" } {
+               kfail symtab/28159 $test
+           } else {
+               fail $test
+           }
+       }
+    }
+
+    if { ! $readnow_p } {
+       with_complaints 1 {
+           gdb_test "maint expand-symtabs $srcfile2" $re \
+               "Zero address complaint - relocated - symtab"
+       }
+    }
+
+    clean_restart
+    # Test for presence of complaint, with lib1 unrelocated.
+    with_complaints 1 {
+       gdb_load $lib1
+       set test "Zero address complaint - unrelocated - psymtab"
+       set have_complaint [regexp $re.* $gdb_file_cmd_msg]
+       if { $have_complaint } {
+           pass $test
+       } else {
+           set index [have_index $lib1]
+           if { $index == "gdb_index" } {
+               kfail symtab/28159 $test
+           } else {
+               fail $test
+           }
+       }
+    }
+
+    if { ! $readnow_p } {
+       with_complaints 1 {
+           gdb_test "maint expand-symtabs $srcfile2" $re \
+               "Zero address complaint - unrelocated - symtab"
+       }
+    }
+}