From: Eugeniy Meshcheryakov <eugeniy.meshcheryakov@googlemail.com>
To: "Stone, Joshua I" <joshua.i.stone@intel.com>
Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>,
Systemtap <systemtap@sources.redhat.com>
Subject: Re: Stap is translating to functions in __exit sections...and later module load fails
Date: Fri, 13 Oct 2006 23:07:00 -0000 [thread overview]
Message-ID: <20061013230704.GA3414@localhost.localdomain> (raw)
In-Reply-To: <C56DB814FAA30B418C75310AC4BB279DC4C843@scsmsx413.amr.corp.intel.com>
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13 жовтня 2006 о 15:28 -0700 Stone, Joshua I написав(-ла):
> This seems to support the notion that the linker elided that function.
>
> So, as Eugeniy wondered, why did the translator pick up that function at
> all? I'm also curious what IP it chose for the kprobe, if the function
> no longer exists... Please try this command:
>
> $ stap -p2 -vv -e 'probe kernel.function("exit_pfm_fs"){}' 2>&1 | grep
> 'pc='
>
> I suspect that either elfutils is giving 'stale' debug information, or
> the translator is misinterpreting its results.
It loks like a bug in some version of gcc. I tried to compile the
following program with version from Debian stable and unstable on ia64:
$ cat test.c
static void __attribute__((section(".exit.text"))) exit_pfm_fs(void)
{
return;
}
$
With gcc 3.3.5:
$ readelf -a test.o | grep exit_
9: 0000000000000000 16 FUNC LOCAL DEFAULT 9 exit_pfm_fs
$ objdump -W test.o
...
The section .debug_info contains:
Compilation Unit @ offset 0x0:
Length: 52
Version: 2
Abbrev Offset: 0
Pointer Size: 8
<0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
DW_AT_stmt_list : 0
DW_AT_name : (indirect string, offset: 0x38): test.c
DW_AT_comp_dir : (indirect string, offset: 0x0): /home/eugen
DW_AT_producer : (indirect string, offset: 0xc): GNU C 3.3.5
(Debian 1:3.3.5-13)
DW_AT_language : 1 (ANSI C)
<1><1d>: Abbrev Number: 2 (DW_TAG_subprogram)
DW_AT_name : (indirect string, offset: 0x2c): exit_pfm_fs
DW_AT_decl_file : 1
DW_AT_decl_line : 2
DW_AT_prototyped : 1
DW_AT_low_pc : 0
DW_AT_high_pc : 0x10
DW_AT_frame_base : 1 byte block: 5c (DW_OP_reg12)
...
$
With gcc 4.1.2:
$ readelf -a t.o | grep exit_
$ objdump -W t.o | grep exit_
objdump: Error: No comp units in .debug_info section ?objdump: Error: No
comp units in .debug_info section ?$
--
Eugeniy Meshcheryakov
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next prev parent reply other threads:[~2006-10-13 23:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-13 22:28 Stone, Joshua I
2006-10-13 22:37 ` Keshavamurthy Anil S
2006-10-13 23:07 ` Eugeniy Meshcheryakov [this message]
2006-10-16 11:27 ` bibo,mao
-- strict thread matches above, loose matches on Subject: below --
2006-10-18 1:06 Stone, Joshua I
2006-10-18 22:15 ` Keshavamurthy Anil S
2006-10-18 0:52 Keshavamurthy, Anil S
2006-10-13 21:26 Stone, Joshua I
2006-10-13 21:56 ` Keshavamurthy Anil S
2006-10-13 21:02 Stone, Joshua I
2006-10-13 21:10 ` Keshavamurthy Anil S
2006-10-13 21:29 ` Eugeniy Meshcheryakov
2006-10-13 20:26 Keshavamurthy, Anil S
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