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[PATCH] dwarf2read.c: Check type of linkage name attribute prior to decoding


This is a fix for PR 16822.  Keith Seitz wrote the patch for the fix. I
wrote the test case.

The Texas Instruments compiler uses the encoding for
DW_AT_MIPS_linkage_name for other purposes.  TI uses the encoding,
0x2007, for TI_AT_TI_end_line which, unlike DW_AT_MIPS_linkage_name,
does not have a string-typed value.  Keith's patch simply makes sure
that linkage_name attributes have a string type prior to attempting to
decode them as such.

My test case causes GDB to segfault in an unpatched GDB.  There
will be one PASS in a patched GDB.

Unpatched GDB:

(gdb) file testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name
Reading symbols from testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name...done.
ERROR: Couldn't load testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name into gdb (eof).
ERROR: Couldn't send ptype return_true to GDB.
UNRESOLVED: gdb.dwarf2/dw2-bad-mips-linkage-name.exp: ptype return_true

Patched GDB:

(gdb) file testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name
Reading symbols from /mesquite2/sourceware-git/mesquite-native-5894223/bld/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name...done.
(gdb) ptype return_true
type = bool (void)
(gdb) PASS: gdb.dwarf2/dw2-bad-mips-linkage-name.exp: ptype return_true

gdb/ChangeLog:
    
    	* dwarf2read.c (dwarf2_physname): Verify that the attribute
    	is a string prior to decoding it as such.
    
gdb/testsuite/ChangeLog:
    
    	* gdb.dwarf2/dw2-bad-mips-linkage-name.S: New file.
    	* gdb.dwarf2/dw2-bad-mips-linkage-name.exp: New file.
---
 gdb/dwarf2read.c                                   |   5 +-
 .../gdb.dwarf2/dw2-bad-mips-linkage-name.S         | 207 +++++++++++++++++++++
 .../gdb.dwarf2/dw2-bad-mips-linkage-name.exp       |  36 ++++
 3 files changed, 247 insertions(+), 1 deletion(-)

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 24a4022..9eb7cbc 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -8722,7 +8722,10 @@ dwarf2_physname (const char *name, struct die_info *die, struct dwarf2_cu *cu)
 
   /* DW_AT_linkage_name is missing in some cases - depend on what GDB
      has computed.  */
-  if (attr && DW_STRING (attr))
+  if (attr 
+      && (attr->form == DW_FORM_strp || attr->form == DW_FORM_string
+          || attr->form == DW_FORM_GNU_strp_alt)
+      && DW_STRING (attr))
     {
       char *demangled;
 
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.S b/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.S
new file mode 100644
index 0000000..562e708
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.S
@@ -0,0 +1,207 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 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/>.  */
+
+/* This test includes both DW_AT_MIPS_linkage_name and DW_AT_TI_end_line,
+   both of which use the same encoding.  It doesn't matter to us whether
+   GDB do anything useful with DW_AT_TI_end_line; we just don't want it
+   to crash.  */
+
+	.section	.debug_abbrev,"",@progbits
+$Ldebug_abbrev0:
+	.section	.debug_info,"",@progbits
+$Ldebug_info0:
+	.section	.debug_line,"",@progbits
+$Ldebug_line0:
+	.text
+$Ltext0:
+	.globl	_Z11return_truev
+$LFB0 = .
+	.file 1 "dw2-bad-mips-linkage-name.cc"
+_Z11return_truev:
+	.4byte 0xabcdef
+$LFE0:
+	.globl	main
+$LFB1 = .
+main:
+	.4byte 0xfedbca
+$LFE1:
+	.size	main, .-main
+$Letext0:
+	.section	.debug_info
+	.4byte	0x5d	 # Length of Compilation Unit Info
+	.2byte	0x2	 # DWARF version number
+	.4byte	$Ldebug_abbrev0	 # Offset Into Abbrev. Section
+	.byte	0x4	 # Pointer Size (in bytes)
+	.uleb128 0x1	 # (DIE (0xb) DW_TAG_compile_unit)
+	.4byte	$LASF1	 # DW_AT_producer: "GNU C++"
+	.byte	0x4	 # DW_AT_language
+	.4byte	$LASF2	 # DW_AT_name: "dw2-bad-mips-linkage-name.cc"
+	.4byte	$LASF3	 # DW_AT_comp_dir: "/"
+	.4byte	$Ltext0	 # DW_AT_low_pc
+	.4byte	$Letext0	 # DW_AT_high_pc
+	.4byte	$Ldebug_line0	 # DW_AT_stmt_list
+	.uleb128 0x2	 # (DIE (0x25) DW_TAG_subprogram)
+	.byte	0x1	 # DW_AT_external
+	.4byte	$LASF4	 # DW_AT_name: "return_true"
+	.byte	0x1	 # DW_AT_decl_file (dw2-bad-mips-linkage-name.cc)
+	.byte	0x2	 # DW_AT_decl_line
+	.4byte	$LASF5	 # DW_AT_MIPS_linkage_name: "_Z11return_truev"
+	.4byte	0x3d	 # DW_AT_type
+	.4byte	$LFB0	 # DW_AT_low_pc
+	.4byte	$LFE0	 # DW_AT_high_pc
+	.uleb128 0x3	 # (DIE (0x41) DW_TAG_base_type)
+	.byte	0x1	 # DW_AT_byte_size
+	.byte	0x2	 # DW_AT_encoding
+	.4byte	$LASF0	 # DW_AT_name: "bool"
+	.uleb128 0x4	 # (DIE (0x48) DW_TAG_subprogram)
+	.byte	0x1	 # DW_AT_external
+	.4byte	$LASF6	 # DW_AT_name: "main"
+	.byte	0x1	 # DW_AT_decl_file (dw2-bad-mips-linkage-name.cc)
+	.byte	0x8	 # DW_AT_decl_line
+	.byte	0x6      # DW_AT_TI_end_line (which shares same encoding
+	                 # with DW_AT_MIPS_linkage_name)
+	.4byte	0x59	 # DW_AT_type
+	.4byte	$LFB1	 # DW_AT_low_pc
+	.4byte	$LFE1	 # DW_AT_high_pc
+	.uleb128 0x5	 # (DIE (0x60) DW_TAG_base_type)
+	.byte	0x4	 # DW_AT_byte_size
+	.byte	0x5	 # DW_AT_encoding
+	.ascii "int\0"	 # DW_AT_name
+	.byte	0x0	 # end of children of DIE 0xb
+	.section	.debug_abbrev
+	.uleb128 0x1	 # (abbrev code)
+	.uleb128 0x11	 # (TAG: DW_TAG_compile_unit)
+	.byte	0x1	 # DW_children_yes
+	.uleb128 0x25	 # (DW_AT_producer)
+	.uleb128 0xe	 # (DW_FORM_strp)
+	.uleb128 0x13	 # (DW_AT_language)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x3	 # (DW_AT_name)
+	.uleb128 0xe	 # (DW_FORM_strp)
+	.uleb128 0x1b	 # (DW_AT_comp_dir)
+	.uleb128 0xe	 # (DW_FORM_strp)
+	.uleb128 0x11	 # (DW_AT_low_pc)
+	.uleb128 0x1	 # (DW_FORM_addr)
+	.uleb128 0x12	 # (DW_AT_high_pc)
+	.uleb128 0x1	 # (DW_FORM_addr)
+	.uleb128 0x10	 # (DW_AT_stmt_list)
+	.uleb128 0x6	 # (DW_FORM_data4)
+	.byte	0x0
+	.byte	0x0
+	.uleb128 0x2	 # (abbrev code)
+	.uleb128 0x2e	 # (TAG: DW_TAG_subprogram)
+	.byte	0x0	 # DW_children_no
+	.uleb128 0x3f	 # (DW_AT_external)
+	.uleb128 0xc	 # (DW_FORM_flag)
+	.uleb128 0x3	 # (DW_AT_name)
+	.uleb128 0xe	 # (DW_FORM_strp)
+	.uleb128 0x3a	 # (DW_AT_decl_file)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x3b	 # (DW_AT_decl_line)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x2007	 # (DW_AT_MIPS_linkage_name)
+	.uleb128 0xe	 # (DW_FORM_strp)
+	.uleb128 0x49	 # (DW_AT_type)
+	.uleb128 0x13	 # (DW_FORM_ref4)
+	.uleb128 0x11	 # (DW_AT_low_pc)
+	.uleb128 0x1	 # (DW_FORM_addr)
+	.uleb128 0x12	 # (DW_AT_high_pc)
+	.uleb128 0x1	 # (DW_FORM_addr)
+	.byte	0x0
+	.byte	0x0
+	.uleb128 0x3	 # (abbrev code)
+	.uleb128 0x24	 # (TAG: DW_TAG_base_type)
+	.byte	0x0	 # DW_children_no
+	.uleb128 0xb	 # (DW_AT_byte_size)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x3e	 # (DW_AT_encoding)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x3	 # (DW_AT_name)
+	.uleb128 0xe	 # (DW_FORM_strp)
+	.byte	0x0
+	.byte	0x0
+	.uleb128 0x4	 # (abbrev code)
+	.uleb128 0x2e	 # (TAG: DW_TAG_subprogram)
+	.byte	0x0	 # DW_children_no
+	.uleb128 0x3f	 # (DW_AT_external)
+	.uleb128 0xc	 # (DW_FORM_flag)
+	.uleb128 0x3	 # (DW_AT_name)
+	.uleb128 0xe	 # (DW_FORM_strp)
+	.uleb128 0x3a	 # (DW_AT_decl_file)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x3b	 # (DW_AT_decl_line)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x2007  # (DW_AT_TI_end_line / DW_AT_MIPS_linkage_name)
+	.uleb128 0xb     # (DW_FORM_data1)
+	.uleb128 0x49	 # (DW_AT_type)
+	.uleb128 0x13	 # (DW_FORM_ref4)
+	.uleb128 0x11	 # (DW_AT_low_pc)
+	.uleb128 0x1	 # (DW_FORM_addr)
+	.uleb128 0x12	 # (DW_AT_high_pc)
+	.uleb128 0x1	 # (DW_FORM_addr)
+	.byte	0x0
+	.byte	0x0
+	.uleb128 0x5	 # (abbrev code)
+	.uleb128 0x24	 # (TAG: DW_TAG_base_type)
+	.byte	0x0	 # DW_children_no
+	.uleb128 0xb	 # (DW_AT_byte_size)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x3e	 # (DW_AT_encoding)
+	.uleb128 0xb	 # (DW_FORM_data1)
+	.uleb128 0x3	 # (DW_AT_name)
+	.uleb128 0x8	 # (DW_FORM_string)
+	.byte	0x0
+	.byte	0x0
+	.byte	0x0
+	.section	.debug_pubnames,"",@progbits
+	.4byte	0x27	 # Length of Public Names Info
+	.2byte	0x2	 # DWARF Version
+	.4byte	$Ldebug_info0	 # Offset of Compilation Unit Info
+	.4byte	0x68	 # Compilation Unit Length
+	.4byte	0x25	 # DIE offset
+	.ascii "return_true\0"	 # external name
+	.4byte	0x40	 # DIE offset
+	.ascii "main\0"	 # external name
+	.4byte	0x0
+	.section	.debug_aranges,"",@progbits
+	.4byte	0x1c	 # Length of Address Ranges Info
+	.2byte	0x2	 # DWARF Version
+	.4byte	$Ldebug_info0	 # Offset of Compilation Unit Info
+	.byte	0x4	 # Size of Address
+	.byte	0x0	 # Size of Segment Descriptor
+	.2byte	0x0	 # Pad to 8 byte boundary
+	.2byte	0x0
+	.4byte	$Ltext0	 # Address
+	.4byte	$Letext0-$Ltext0	 # Length
+	.4byte	0x0
+	.4byte	0x0
+	.section	.debug_str,"MS",@progbits,1
+$LASF2:
+	.ascii	"dw2-bad-mips-linkage-name.cc\000"
+$LASF0:
+	.ascii	"bool\000"
+$LASF5:
+	.ascii	"_Z11return_truev\000"
+$LASF1:
+	.ascii	"GNU C++"
+$LASF4:
+	.ascii	"return_true\000"
+$LASF3:
+	.ascii	"/\000"
+$LASF6:
+	.ascii	"main\000"
+
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.exp b/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.exp
new file mode 100644
index 0000000..91c640a
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-mips-linkage-name.exp
@@ -0,0 +1,36 @@
+# Copyright 2015 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/>.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0  
+}
+
+# This testfile has reproducibility only with cc-with-index.sh.
+
+standard_testfile .S
+
+if [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] {
+    return -1
+}
+
+# A successful run will have just one PASS.  An unsuccessful run will
+# likely show errors out before getting to this point due to a
+# segfault in GDB.
+
+gdb_test "ptype return_true" " = bool \\(void\\)"
+


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