handle an unspecified return address column

Debugging PR 16155 further, I found that the DWARF unwinder found the
function in question, but thought it had no registers saved
(fs->regs.num_regs == 0).

It seems to me that if a frame does not specify the return address
column, or if the return address column is explicitly marked as
DWARF2_FRAME_REG_UNSPECIFIED, then we should set the
"undefined_retaddr" flag and let the DWARF unwinder gracefully stop.

This patch implements that idea.

With this patch the backtrace works properly:

    (gdb) bt
    #0  0x0000007fb7ed485c in nanosleep () from /lib64/libc.so.6
    #1  0x0000007fb7ed4508 in sleep () from /lib64/libc.so.6
    #2  0x00000000004008bc in thread_function (arg=0x4) at threadapply.c:73
    #3  0x0000007fb7fad950 in start_thread () from /lib64/libpthread.so.0
    #4  0x0000007fb7f0956c in clone () from /lib64/libc.so.6

2013-11-22  Tom Tromey  <tromey@redhat.com>

	PR backtrace/16155:
	* dwarf2-frame.c (dwarf2_frame_cache): Set undefined_retaddr if
	the return address column is unspecified.

2013-11-22  Tom Tromey  <tromey@redhat.com>

	* gdb.dwarf2/dw2-bad-cfi.c: New file.
	* gdb.dwarf2/dw2-bad-cfi.exp: New file.
	* gdb.dwarf2/dw2-bad-cfi.S: New file.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1260b5c23531d0812ea6e0ae1b2b94580412ca0f..0b8683dc5d8d4a7f6dc69d31c2909b09f2bb0851 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2013-11-22  Tom Tromey  <tromey@redhat.com>
+
+       PR backtrace/16155:
+       * dwarf2-frame.c (dwarf2_frame_cache): Set undefined_retaddr if
+       the return address column is unspecified.
+
 2013-11-22  Tom Tromey  <tromey@redhat.com>
            Pedro Alves  <palves@redhat.com>
 

diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index c4f87715c1779853c5aba0c0e31ea11d66085d3c..f185ca6e8c19b7ab829447eace006b34322bd79f 100644 (file)
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -1245,6 +1245,10 @@ incomplete CFI data; unspecified registers (e.g., %s) at %s"),
   if (fs->retaddr_column < fs->regs.num_regs
       && fs->regs.reg[fs->retaddr_column].how == DWARF2_FRAME_REG_UNDEFINED)
     cache->undefined_retaddr = 1;
+  else if (fs->retaddr_column >= fs->regs.num_regs
+         || (fs->regs.reg[fs->retaddr_column].how
+             == DWARF2_FRAME_REG_UNSPECIFIED))
+    cache->undefined_retaddr = 1;
 
   do_cleanups (old_chain);
   discard_cleanups (reset_cache_cleanup);

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 0135ece2379f43d78c7e800c4e09039a018ffbb1..74a1e06219d211e0e6ae83261583d543b36d6aa6 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2013-11-22  Tom Tromey  <tromey@redhat.com>
+
+       * gdb.dwarf2/dw2-bad-cfi.c: New file.
+       * gdb.dwarf2/dw2-bad-cfi.exp: New file.
+       * gdb.dwarf2/dw2-bad-cfi.S: New file.
+
 2013-11-22  Pedro Alves  <palves@redhat.com>
 
        PR 16155

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.S b/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.S
new file mode 100644 (file)
index 0000000..9a97889
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.S
@@ -0,0 +1,216 @@
+# This file was created by running dw2-bad-cfi.c
+# through 'gcc -g -dA -S', and then hand-editing
+# the CFI in "callee" to suit.
+
+       .file   "dw2-bad-cfi.c"
+       .text
+.Ltext0:
+       .globl  callee
+       .type   callee, @function
+callee:
+.LFB0:
+       .file 1 "dw2-bad-cfi.c"
+       # dw2-bad-cfi.c:20
+       .loc 1 20 0
+       .cfi_startproc
+# BLOCK 2 seq:0
+# PRED: ENTRY (fallthru)
+       pushq   %rbp
+/*
+       .cfi_def_cfa_offset 16
+       .cfi_offset 6, -16
+*/
+       movq    %rsp, %rbp
+/*     .cfi_def_cfa_register 6 */
+       # dw2-bad-cfi.c:21
+       .loc 1 21 0
+       popq    %rbp
+/*     .cfi_def_cfa 7, 8 */
+       # Our little lies.
+       .cfi_undefined 6
+       .cfi_return_column 6
+# SUCC: EXIT [100.0%] 
+       ret
+       .cfi_endproc
+.LFE0:
+       .size   callee, .-callee
+       .globl  main
+       .type   main, @function
+main:
+.LFB1:
+       # dw2-bad-cfi.c:25
+       .loc 1 25 0
+       .cfi_startproc
+# BLOCK 2 seq:0
+# PRED: ENTRY (fallthru)
+       pushq   %rbp
+       .cfi_def_cfa_offset 16
+       .cfi_offset 6, -16
+       movq    %rsp, %rbp
+       .cfi_def_cfa_register 6
+       # dw2-bad-cfi.c:26
+       .loc 1 26 0
+       call    callee
+       # dw2-bad-cfi.c:27
+       .loc 1 27 0
+       movl    $0, %eax
+       # dw2-bad-cfi.c:28
+       .loc 1 28 0
+       popq    %rbp
+       .cfi_def_cfa 7, 8
+# SUCC: EXIT [100.0%] 
+       ret
+       .cfi_endproc
+.LFE1:
+       .size   main, .-main
+.Letext0:
+       .section        .debug_info,"",@progbits
+.Ldebug_info0:
+       .long   0x67    # Length of Compilation Unit Info
+       .value  0x4     # DWARF version number
+       .long   .Ldebug_abbrev0 # Offset Into Abbrev. Section
+       .byte   0x8     # Pointer Size (in bytes)
+       .uleb128 0x1    # (DIE (0xb) DW_TAG_compile_unit)
+       .long   .LASF0  # DW_AT_producer: "GNU C 4.7.2 20121109 (Red Hat 4.7.2-8) -mtune=generic -march=x86-64 -g"
+       .byte   0x1     # DW_AT_language
+       .long   .LASF1  # DW_AT_name: "dw2-bad-cfi.c"
+       .long   .LASF2  # DW_AT_comp_dir: "/home/tromey/gnu/gdb/devel/binutils-gdb/gdb/testsuite/gdb.dwarf2"
+       .quad   .Ltext0 # DW_AT_low_pc
+       .quad   .Letext0        # DW_AT_high_pc
+       .long   .Ldebug_line0   # DW_AT_stmt_list
+       .uleb128 0x2    # (DIE (0x2d) DW_TAG_subprogram)
+                       # DW_AT_external
+       .long   .LASF3  # DW_AT_name: "callee"
+       .byte   0x1     # DW_AT_decl_file (dw2-bad-cfi.c)
+       .byte   0x13    # DW_AT_decl_line
+                       # DW_AT_prototyped
+       .quad   .LFB0   # DW_AT_low_pc
+       .quad   .LFE0   # DW_AT_high_pc
+       .uleb128 0x1    # DW_AT_frame_base
+       .byte   0x9c    # DW_OP_call_frame_cfa
+                       # DW_AT_GNU_all_call_sites
+       .uleb128 0x3    # (DIE (0x46) DW_TAG_subprogram)
+                       # DW_AT_external
+       .long   .LASF4  # DW_AT_name: "main"
+       .byte   0x1     # DW_AT_decl_file (dw2-bad-cfi.c)
+       .byte   0x18    # DW_AT_decl_line
+                       # DW_AT_prototyped
+       .long   0x63    # DW_AT_type
+       .quad   .LFB1   # DW_AT_low_pc
+       .quad   .LFE1   # DW_AT_high_pc
+       .uleb128 0x1    # DW_AT_frame_base
+       .byte   0x9c    # DW_OP_call_frame_cfa
+                       # DW_AT_GNU_all_tail_call_sites
+       .uleb128 0x4    # (DIE (0x63) DW_TAG_base_type)
+       .byte   0x4     # DW_AT_byte_size
+       .byte   0x5     # DW_AT_encoding
+       .ascii "int\0"  # DW_AT_name
+       .byte   0       # end of children of DIE 0xb
+       .section        .debug_abbrev,"",@progbits
+.Ldebug_abbrev0:
+       .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 0x17   # (DW_FORM_sec_offset)
+       .byte   0
+       .byte   0
+       .uleb128 0x2    # (abbrev code)
+       .uleb128 0x2e   # (TAG: DW_TAG_subprogram)
+       .byte   0       # DW_children_no
+       .uleb128 0x3f   # (DW_AT_external)
+       .uleb128 0x19   # (DW_FORM_flag_present)
+       .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 0x27   # (DW_AT_prototyped)
+       .uleb128 0x19   # (DW_FORM_flag_present)
+       .uleb128 0x11   # (DW_AT_low_pc)
+       .uleb128 0x1    # (DW_FORM_addr)
+       .uleb128 0x12   # (DW_AT_high_pc)
+       .uleb128 0x1    # (DW_FORM_addr)
+       .uleb128 0x40   # (DW_AT_frame_base)
+       .uleb128 0x18   # (DW_FORM_exprloc)
+       .uleb128 0x2117 # (DW_AT_GNU_all_call_sites)
+       .uleb128 0x19   # (DW_FORM_flag_present)
+       .byte   0
+       .byte   0
+       .uleb128 0x3    # (abbrev code)
+       .uleb128 0x2e   # (TAG: DW_TAG_subprogram)
+       .byte   0       # DW_children_no
+       .uleb128 0x3f   # (DW_AT_external)
+       .uleb128 0x19   # (DW_FORM_flag_present)
+       .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 0x27   # (DW_AT_prototyped)
+       .uleb128 0x19   # (DW_FORM_flag_present)
+       .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)
+       .uleb128 0x40   # (DW_AT_frame_base)
+       .uleb128 0x18   # (DW_FORM_exprloc)
+       .uleb128 0x2116 # (DW_AT_GNU_all_tail_call_sites)
+       .uleb128 0x19   # (DW_FORM_flag_present)
+       .byte   0
+       .byte   0
+       .uleb128 0x4    # (abbrev code)
+       .uleb128 0x24   # (TAG: DW_TAG_base_type)
+       .byte   0       # 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   0
+       .byte   0
+       .byte   0
+       .section        .debug_aranges,"",@progbits
+       .long   0x2c    # Length of Address Ranges Info
+       .value  0x2     # DWARF Version
+       .long   .Ldebug_info0   # Offset of Compilation Unit Info
+       .byte   0x8     # Size of Address
+       .byte   0       # Size of Segment Descriptor
+       .value  0       # Pad to 16 byte boundary
+       .value  0
+       .quad   .Ltext0 # Address
+       .quad   .Letext0-.Ltext0        # Length
+       .quad   0
+       .quad   0
+       .section        .debug_line,"",@progbits
+.Ldebug_line0:
+       .section        .debug_str,"MS",@progbits,1
+.LASF3:
+       .string "callee"
+.LASF1:
+       .string "dw2-bad-cfi.c"
+.LASF2:
+       .string "/home/tromey/gnu/gdb/devel/binutils-gdb/gdb/testsuite/gdb.dwarf2"
+.LASF4:
+       .string "main"
+.LASF0:
+       .string "GNU C 4.7.2 20121109 (Red Hat 4.7.2-8) -mtune=generic -march=x86-64 -g"
+       .ident  "GCC: (GNU) 4.7.2 20121109 (Red Hat 4.7.2-8)"
+       .section        .note.GNU-stack,"",@progbits

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.c b/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.c
new file mode 100644 (file)
index 0000000..f5b415b
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.c
@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2013 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
+callee (void)
+{
+}
+
+int
+main(void)
+{
+  callee ();
+  return 0;
+}

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.exp b/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.exp
new file mode 100644 (file)
index 0000000..12b1275
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-cfi.exp
@@ -0,0 +1,42 @@
+# Copyright 2013 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
+
+standard_testfile .S
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if ![dwarf2_support] {
+    return 0  
+}
+
+# This test can only be run on x86-64 targets.
+if {![istarget x86_64-*] || ![is_lp64_target]} {
+    return 0
+}
+
+if {[prepare_for_testing "$testfile.exp" "$testfile" $srcfile {nodebug}]} {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_breakpoint "callee"
+gdb_continue_to_breakpoint "callee"
+
+# This test ensures that the backtrace does not go past "callee".
+gdb_test "bt" ".*callee .. at [file rootname $srcfile]\\.c:\[0-9\]*"