Bug 847510

After the GCC bug is resolved we should support DW_OP_GNU_parameter_ref in elfutils and systemtap. DW_OP_GNU_parameter_ref was only added recently to
elfutils (after 0.154 the latest release) as part of the DwarfExtensions overview: https://fedorahosted.org/elfutils/wiki/DwarfExtensions

+++ This bug was initially created as a clone of Bug #847497 +++

Description of problem:
Systemtap poorly parses dwarf and says "$SUMMARY".

Version-Release number of selected component (if applicable):
$ rpm -q bash bash-debuginfo systemtap
bash-4.2.37-2.fc17.x86_64
bash-debuginfo-4.2.37-2.fc17.x86_64
systemtap-1.8-4.fc17.x86_64


How reproducible:
100%

Steps to Reproduce:
1. stap -e 'probe process("bash").function("execute_builtin"){print("%p\n", $words)}'
2.
3.
  
Actual results:
$ stap -e 'probe process("bash").function("execute_builtin"){print("%p\n", $words)}'
semantic error: dwarf_getlocation_addr failed, invalid DWARF: identifier '$words' at <input>:1:65
        source: probe process("bash").function("execute_builtin"){print("%p\n", $words)}
                                                                                ^


Expected results:
semantic error: not accessible at this address (?)
The best would be if systemtap says the variable is optimized out, like GDB.

Additional info:

--- Additional comment from jan.kratochvil on 2012-08-12 06:50:50 EDT ---

GNU C 4.7.0 20120507 (Red Hat 4.7.0-5) -m64 -mtune=generic -march=x86-64 -g -O2 -fexceptions -fstack-protector --param ssp-buffer-size=4

GCC used DW_OP_GNU_parameter_ref at the callee but DW_OP_reg4 (rsi) at the caller.  Caller is inlined function.

(gdb) bt
#0  execute_builtin (..., words=<optimized out>) at execute_cmd.c:4047
#1  0x0000000000431873 in execute_builtin_or_function (words=0x6fb260)
                       at execute_cmd.c:4546
#2  execute_simple_command (...) at execute_cmd.c:3956
(gdb) set debug entry-values 1
(gdb) p words
Cannot find matching parameter at DW_TAG_GNU_call_site 0x431873 at execute_simple_command
$2 = <optimized out>

 <1><1c2c4>: Abbrev Number: 68 (DW_TAG_subprogram)
    <1c2c5>   DW_AT_abstract_origin: <0x1b17a>
         <1><1b17a>: Abbrev Number: 38 (DW_TAG_subprogram)
            <1b17b>   DW_AT_name        : execute_builtin
 <2><1c2fa>: Abbrev Number: 73 (DW_TAG_formal_parameter)
    <1c2fb>   DW_AT_abstract_origin: <0x1b197>
         <2><1b197>: Abbrev Number: 36 (DW_TAG_formal_parameter)
            <1b198>   DW_AT_name        : words
    <1c2ff>   DW_AT_location    : 6 byte block: fa d 18 0 0 9f
                         (DW_OP_GNU_parameter_ref: <0x1b197>; DW_OP_stack_value)
 <4><1eb7f>: Abbrev Number: 55 (DW_TAG_GNU_call_site)
    <1eb80>   DW_AT_low_pc      : 0x431873
 <5><1eb96>: Abbrev Number: 56 (DW_TAG_GNU_call_site_parameter)
    <1eb97>   DW_AT_location    : 1 byte block: 54      (DW_OP_reg4 (rsi))
    <1eb99>   DW_AT_GNU_call_site_value: 2 byte block: 73 0
                                                       (DW_OP_breg3 (rbx): 0)
        = it is really 'words'