Re: [CRIS] dwarf2 frame sniffer problem?

[Orjan Friberg <orjan.friberg@axis.com>]

[-- Attachment #1: Type: text/plain, Size: 1192 bytes --]

Daniel Jacobowitz wrote:
> 
> The beauty of using the CFI data is that it _is_ supposed to work in
> the prologue.  It sounds like the CFI is wrong.  Could you post both
> assembly and CFI data for the same testcase?  I don't know CRIS
> assembly but I imagine I can interpret it well enough to see what's
> going on.

I have attached the test program, dissassembly (objdump -d -S) and the 
dwarf2 info (readelf -w).  (Crash course in CRIS assembly, if at all 
needed: r8 holds the frame pointer and srp holds the return address, 
pushed only in non-leaf functions.)

> It also sounds like your DWARF2_REG_TO_REGNUM may need work, if the
> unwinder thinks r16 is the return address column and GDB thinks it's an
> 8-bit register.

Ugh, I had totally missed that (i.e. I don't even have a CRIS-specific 
DWARF2_REG_TO_REGNUM).  Looking at the other targets' implementations I 
don't understand where they got the dwarf2 register mapping from (though 
amd64-tdep.c mentions System V psABI), and the dwarf2 spec says in 
"2.4.2 Register Name Operators" it should be in the architecture's ABI 
spec.  I'll go bug my compiler guy, or go look in gcc myself.

-- 
Orjan Friberg
Axis Communications


[-- Attachment #2: test.c --]
[-- Type: text/x-csrc, Size: 84 bytes --]

void bar(void) {}
void foo(void) 
{
  bar();
}
int main ()
{
  foo();
  return 0;
}

[-- Attachment #3: disassembly --]
[-- Type: text/plain, Size: 1102 bytes --]


test:     file format elf32-cris

Disassembly of section .text:

00080074 <bar>:
void bar(void) {}
   80074:	fce1 ee8f           	push $r8
   80078:	6e86                	move.d $sp,$r8
   8007a:	68e6                	move.d $r8,$sp
   8007c:	7fb6                	ret 
   8007e:	6e8e                	pop $r8

00080080 <foo>:
void foo(void) 
{
   80080:	fce1 7ebe           	push $srp
   80084:	fce1 ee8f           	push $r8
   80088:	6e86                	move.d $sp,$r8
  bar();
   8008a:	3fbd 7400 0800      	jsr 80074 <bar>
}
   80090:	68e6                	move.d $r8,$sp
   80092:	6e8e                	pop $r8
   80094:	3e0d                	jump [$sp+]

00080096 <main>:
int main ()
{
   80096:	fce1 7ebe           	push $srp
   8009a:	fce1 ee8f           	push $r8
   8009e:	6e86                	move.d $sp,$r8
  foo();
   800a0:	3fbd 8000 0800      	jsr 80080 <foo>
  return 0;
   800a6:	7986                	clear.d $r9
}
   800a8:	69a6                	move.d $r9,$r10
   800aa:	68e6                	move.d $r8,$sp
   800ac:	6e8e                	pop $r8
   800ae:	3e0d                	jump [$sp+]

[-- Attachment #4: dwarf2info --]
[-- Type: text/plain, Size: 5843 bytes --]

The section .debug_aranges contains:

  Length:                   28
  Version:                  2
  Offset into .debug_info:  0
  Pointer Size:             4
  Segment Size:             0

    Address  Length
    00080074 60

Contents of the .debug_pubnames section:

  Length:                              39
  Version:                             2
  Offset into .debug_info section:     0
  Size of area in .debug_info section: 105

    Offset	Name
    37		bar
    56		foo
    75		main

The section .debug_info contains:

  Compilation Unit @ 0:
   Length:        101
   Version:       2
   Abbrev Offset: 0
   Pointer Size:  4
 <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
     DW_AT_stmt_list   : 0	
     DW_AT_high_pc     : 0x800b0 524464	
     DW_AT_low_pc      : 0x80074 524404	
     DW_AT_name        : (indirect string, offset: 0x34): test.c	
     DW_AT_comp_dir    : (indirect string, offset: 0x0): /home/orjanf	
     DW_AT_producer    : (indirect string, offset: 0xd): GNU C 3.2.1 Axis release R55/1.55	
     DW_AT_language    : 1	(ANSI C)
 <1><25>: Abbrev Number: 2 (DW_TAG_subprogram)
     DW_AT_external    : 1	
     DW_AT_name        : bar	
     DW_AT_decl_file   : 1	
     DW_AT_decl_line   : 1	
     DW_AT_prototyped  : 1	
     DW_AT_low_pc      : 0x80074 524404	
     DW_AT_high_pc     : 0x80080 524416	
     DW_AT_frame_base  : 1 byte block: 58 	(DW_OP_reg8; )
 <1><38>: Abbrev Number: 2 (DW_TAG_subprogram)
     DW_AT_external    : 1	
     DW_AT_name        : foo	
     DW_AT_decl_file   : 1	
     DW_AT_decl_line   : 3	
     DW_AT_prototyped  : 1	
     DW_AT_low_pc      : 0x80080 524416	
     DW_AT_high_pc     : 0x80096 524438	
     DW_AT_frame_base  : 1 byte block: 58 	(DW_OP_reg8; )
 <1><4b>: Abbrev Number: 3 (DW_TAG_subprogram)
     DW_AT_external    : 1	
     DW_AT_name        : (indirect string, offset: 0x2f): main	
     DW_AT_decl_file   : 1	
     DW_AT_decl_line   : 7	
     DW_AT_type        : <61>	
     DW_AT_low_pc      : 0x80096 524438	
     DW_AT_high_pc     : 0x800b0 524464	
     DW_AT_frame_base  : 1 byte block: 58 	(DW_OP_reg8; )
 <1><61>: Abbrev Number: 4 (DW_TAG_base_type)
     DW_AT_name        : int	
     DW_AT_byte_size   : 4	
     DW_AT_encoding    : 5	(signed)

Contents of the .debug_abbrev section:

  Number TAG
   1      DW_TAG_compile_unit    [has children]
    DW_AT_stmt_list    DW_FORM_data4
    DW_AT_high_pc      DW_FORM_addr
    DW_AT_low_pc       DW_FORM_addr
    DW_AT_name         DW_FORM_strp
    DW_AT_comp_dir     DW_FORM_strp
    DW_AT_producer     DW_FORM_strp
    DW_AT_language     DW_FORM_data1
   2      DW_TAG_subprogram    [no children]
    DW_AT_external     DW_FORM_flag
    DW_AT_name         DW_FORM_string
    DW_AT_decl_file    DW_FORM_data1
    DW_AT_decl_line    DW_FORM_data1
    DW_AT_prototyped   DW_FORM_flag
    DW_AT_low_pc       DW_FORM_addr
    DW_AT_high_pc      DW_FORM_addr
    DW_AT_frame_base   DW_FORM_block1
   3      DW_TAG_subprogram    [no children]
    DW_AT_external     DW_FORM_flag
    DW_AT_name         DW_FORM_strp
    DW_AT_decl_file    DW_FORM_data1
    DW_AT_decl_line    DW_FORM_data1
    DW_AT_type         DW_FORM_ref4
    DW_AT_low_pc       DW_FORM_addr
    DW_AT_high_pc      DW_FORM_addr
    DW_AT_frame_base   DW_FORM_block1
   4      DW_TAG_base_type    [no children]
    DW_AT_name         DW_FORM_string
    DW_AT_byte_size    DW_FORM_data1
    DW_AT_encoding     DW_FORM_data1


Dump of debug contents of section .debug_line:

  Length:                      52
  DWARF Version:               2
  Prologue Length:             26
  Minimum Instruction Length:  2
  Initial value of 'is_stmt':  1
  Line Base:                   -5
  Line Range:                  14
  Opcode Base:                 10

 Opcodes:
  Opcode 1 has 0 args
  Opcode 2 has 1 args
  Opcode 3 has 1 args
  Opcode 4 has 1 args
  Opcode 5 has 1 args
  Opcode 6 has 0 args
  Opcode 7 has 0 args
  Opcode 8 has 0 args
  Opcode 9 has 1 args

 The Directory Table is empty.

 The File Name Table:
  Entry	Dir	Time	Size	Name
  1	0	0	0	test.c

 Line Number Statements:
  Extended opcode 2: set Address to 0x80074
  Special opcode 5: advance Address by 0 to 0x80074 and Line by 0 to 1
  Special opcode 91: advance Address by 12 to 0x80080 and Line by 2 to 3
  Special opcode 76: advance Address by 10 to 0x8008a and Line by 1 to 4
  Special opcode 48: advance Address by 6 to 0x80090 and Line by 1 to 5
  Special opcode 49: advance Address by 6 to 0x80096 and Line by 2 to 7
  Special opcode 76: advance Address by 10 to 0x800a0 and Line by 1 to 8
  Special opcode 48: advance Address by 6 to 0x800a6 and Line by 1 to 9
  Special opcode 20: advance Address by 2 to 0x800a8 and Line by 1 to 10
  Advance PC by 8 to 800b0
  Extended opcode 1: End of Sequence


The section .debug_frame contains:

00000000 0000000c ffffffff CIE
  Version:               1
  Augmentation:          ""
  Code alignment factor: 1
  Data alignment factor: -1
  Return address column: 16

  DW_CFA_def_cfa: r14 ofs 0

00000010 00000014 00000000 FDE cie=00000000 pc=00080074..00080080
  DW_CFA_advance_loc: 0 to 00080074
  DW_CFA_def_cfa: r8 ofs 4
  DW_CFA_offset: r8 at cfa-4
  DW_CFA_nop
  DW_CFA_nop

00000028 00000014 00000000 FDE cie=00000000 pc=00080080..00080096
  DW_CFA_advance_loc: 0 to 00080080
  DW_CFA_def_cfa: r8 ofs 8
  DW_CFA_offset: r16 at cfa-4
  DW_CFA_offset: r8 at cfa-8

00000040 00000014 00000000 FDE cie=00000000 pc=00080096..000800b0
  DW_CFA_advance_loc: 0 to 00080096
  DW_CFA_def_cfa: r8 ofs 8
  DW_CFA_offset: r16 at cfa-4
  DW_CFA_offset: r8 at cfa-8

Contents of the .debug_str section:

  0x00000000 2f686f6d 652f6f72 6a616e66 00474e55 /home/orjanf.GNU
  0x00000010 20432033 2e322e31 20417869 73207265  C 3.2.1 Axis re
  0x00000020 6c656173 65205235 352f312e 3535006d lease R55/1.55.m
  0x00000030 61696e00 74657374 2e6300            ain.test.c.