* [Bug runtime/2738] deref error on ppc64
2006-06-09 12:59 [Bug runtime/2738] New: deref error on ppc64 guanglei at cn dot ibm dot com
@ 2006-06-09 17:21 ` joshua dot i dot stone at intel dot com
2006-06-09 23:25 ` guanglei at cn dot ibm dot com
` (4 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: joshua dot i dot stone at intel dot com @ 2006-06-09 17:21 UTC (permalink / raw)
To: systemtap
------- Additional Comments From joshua dot i dot stone at intel dot com 2006-06-09 17:20 -------
FWIW, it's nice to see that the translator is safely catching this deref without
crashing the system.
Anyway, a recent change here was to use $return to get the task struct instead
of retval(), as per bug #1132. This works fine for me on i686 and x86_64.
Can you try changing it back to retval() and see if that works? If so, we can
reclassify this bug as a ppc64 problem with $return.
--
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^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug runtime/2738] deref error on ppc64
2006-06-09 12:59 [Bug runtime/2738] New: deref error on ppc64 guanglei at cn dot ibm dot com
2006-06-09 17:21 ` [Bug runtime/2738] " joshua dot i dot stone at intel dot com
@ 2006-06-09 23:25 ` guanglei at cn dot ibm dot com
2006-06-09 23:32 ` fche at redhat dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: guanglei at cn dot ibm dot com @ 2006-06-09 23:25 UTC (permalink / raw)
To: systemtap
------- Additional Comments From guanglei at cn dot ibm dot com 2006-06-09 23:25 -------
(In reply to comment #1)
> Can you try changing it back to retval() and see if that works? If so, we can
> reclassify this bug as a ppc64 problem with $return.
retval() works.
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^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug runtime/2738] deref error on ppc64
2006-06-09 12:59 [Bug runtime/2738] New: deref error on ppc64 guanglei at cn dot ibm dot com
2006-06-09 17:21 ` [Bug runtime/2738] " joshua dot i dot stone at intel dot com
2006-06-09 23:25 ` guanglei at cn dot ibm dot com
@ 2006-06-09 23:32 ` fche at redhat dot com
2006-06-12 8:39 ` guanglei at cn dot ibm dot com
` (2 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: fche at redhat dot com @ 2006-06-09 23:32 UTC (permalink / raw)
To: systemtap
------- Additional Comments From fche at redhat dot com 2006-06-09 23:32 -------
Please attach a disassembly of the relevant segment of the probed kernel function,
a relevant segment of the "stap -p3 -k" generated C code (the $return fetching
function). Unless something else is obviously amiss, please assign this probable
elfutils bug to roland. Bon appetit!
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^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug runtime/2738] deref error on ppc64
2006-06-09 12:59 [Bug runtime/2738] New: deref error on ppc64 guanglei at cn dot ibm dot com
` (2 preceding siblings ...)
2006-06-09 23:32 ` fche at redhat dot com
@ 2006-06-12 8:39 ` guanglei at cn dot ibm dot com
2006-06-12 17:24 ` fche at redhat dot com
2006-06-13 19:56 ` roland at gnu dot org
5 siblings, 0 replies; 8+ messages in thread
From: guanglei at cn dot ibm dot com @ 2006-06-12 8:39 UTC (permalink / raw)
To: systemtap
------- Additional Comments From guanglei at cn dot ibm dot com 2006-06-12 08:38 -------
Created an attachment (id=1080)
--> (http://sourceware.org/bugzilla/attachment.cgi?id=1080&action=view)
stap -p3 generated .c file
attached .c file is generated by stap -p3 a.stp
a.stp is:
probe kernel.function("sys_read").return
{
printf("%p\n", $return)
}
"stap a.stp" will give an error:
root:/home/root> stap a.stp
ERROR: pointer dereference fault near identifier '$return' at a.stp:3:17
WARNING: Number of errors: 1, skipped probes: 0
objdump of sys_read:
c0000000000b380c <.sys_read>:
c0000000000b380c: 7c 08 02 a6 mflr r0
c0000000000b3810: fb 81 ff e0 std r28,-32(r1)
c0000000000b3814: fb a1 ff e8 std r29,-24(r1)
c0000000000b3818: 7c 9c 23 78 mr r28,r4
c0000000000b381c: 7c bd 2b 78 mr r29,r5
c0000000000b3820: f8 01 00 10 std r0,16(r1)
c0000000000b3824: f8 21 ff 61 stdu r1,-160(r1)
c0000000000b3828: 38 81 00 70 addi r4,r1,112
c0000000000b382c: 48 00 11 e5 bl c0000000000b4a10 <.fget_light>
c0000000000b3830: 60 00 00 00 nop
c0000000000b3834: 7f a5 eb 78 mr r5,r29
c0000000000b3838: 7f 84 e3 78 mr r4,r28
c0000000000b383c: 38 c1 00 78 addi r6,r1,120
c0000000000b3840: 3b 80 ff f7 li r28,-9
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^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug runtime/2738] deref error on ppc64
2006-06-09 12:59 [Bug runtime/2738] New: deref error on ppc64 guanglei at cn dot ibm dot com
` (3 preceding siblings ...)
2006-06-12 8:39 ` guanglei at cn dot ibm dot com
@ 2006-06-12 17:24 ` fche at redhat dot com
2006-06-13 19:56 ` roland at gnu dot org
5 siblings, 0 replies; 8+ messages in thread
From: fche at redhat dot com @ 2006-06-12 17:24 UTC (permalink / raw)
To: systemtap
------- Additional Comments From fche at redhat dot com 2006-06-12 17:23 -------
Here is the $return tvar extractor function in the attached .c file.
intptr_t addr;
{ // DWARF expression: 0x73
{
intptr_t s0;
s0 = fetch_register (3) + 0L;
addr = s0;
}
}
THIS->__retvalue = deref (8, addr);
Compared to the ppc64 retval() function, this does one extra round of
dereference. According the ppc64 ABI [1], r3 should only be dereferenced
for aggregates/unions/longer character strings. Integers are returned simply
without indirection. So here we have an ABI misunderstanding. It may
be a bug in the new $return code handling (thus cc:ing dsmith), or
inadequacy of the elfutils api for this distinction (thus cc:ing roland).
[1] http://freestandards.org/spec/ELF/ppc64/spec/x280.html#RETURN-VAL
--
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CC| |dsmith at redhat dot com,
| |roland at redhat dot com
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^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug runtime/2738] deref error on ppc64
2006-06-09 12:59 [Bug runtime/2738] New: deref error on ppc64 guanglei at cn dot ibm dot com
` (4 preceding siblings ...)
2006-06-12 17:24 ` fche at redhat dot com
@ 2006-06-13 19:56 ` roland at gnu dot org
5 siblings, 0 replies; 8+ messages in thread
From: roland at gnu dot org @ 2006-06-13 19:56 UTC (permalink / raw)
To: systemtap
------- Additional Comments From roland at gnu dot org 2006-06-13 19:55 -------
There was a simple bug in the ppc64 return value support.
It should be fixed with the next elfutils release.
--
What |Removed |Added
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AssignedTo|systemtap at sources dot |roland at redhat dot com
|redhat dot com |
Status|NEW |ASSIGNED
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