* [Bug tapsets/15961] New: nd_syscall.exp failure on i686
@ 2013-09-16 21:30 dsmith at redhat dot com
2013-10-17 14:27 ` [Bug tapsets/15961] " dsmith at redhat dot com
2013-10-17 21:25 ` dsmith at redhat dot com
0 siblings, 2 replies; 3+ messages in thread
From: dsmith at redhat dot com @ 2013-09-16 21:30 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=15961
Bug ID: 15961
Summary: nd_syscall.exp failure on i686
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: tapsets
Assignee: systemtap at sourceware dot org
Reporter: dsmith at redhat dot com
The nd_syscall.exp testcase gets a failure on i686 RHEL6
(2.6.32-358.18.1.el6.i686) in the 'trunc' test:
FAIL: 32-bit trunc nd_syscall
This failure is because systemtap is getting the wrong value for the 'length'
convenience variable from the nd_syscall.truncate probe. Here's the source for
nd_syscall.truncate:
====
probe nd_syscall.truncate = kprobe.function("sys_truncate") ?,
kprobe.function("sys_truncate64") ?
{
name = "truncate"
// path_uaddr = $path
// path = user_string($path)
// length = $length
// argstr = sprintf("%s, %d", user_string_quoted($path), $length)
asmlinkage()
path_uaddr = pointer_arg(1)
path = user_string_quoted(path_uaddr)
if (symname(addr()) == "sys_truncate")
length = ulong_arg(2)
else
length = longlong_arg(2)
argstr = sprintf("%s, %d", user_string_quoted(path_uaddr), length)
}
====
The problem here was that a probe on "sys_truncate" was installed, but
'symname(addr())' failed, so that the wrong value was grabbed for 'length'.
'symname(addr())' shouldn't have failed, but that's a lot of work to do just to
figure out which function is being called. A call to 'ppfunc()' might be better
or breaking down the probe a bit more like the following (untested):
====
probe nd_syscall.truncate = __nd_syscall.truncate ?, __nd_syscall.truncate64 ?
{
name = "truncate"
// path_uaddr = $path
// path = user_string($path)
// length = $length
// argstr = sprintf("%s, %d", user_string_quoted($path), $length)
asmlinkage()
path_uaddr = pointer_arg(1)
path = user_string_quoted(path_uaddr)
argstr = sprintf("%s, %d", user_string_quoted(path_uaddr), length)
}
probe __nd_syscall.truncate = kprobe.function("sys_truncate")
{
asmlinkage()
length = ulong_arg(2)
}
probe __nd_syscall.truncate64 = kprobe.function("sys_truncate64")
{
asmlinkage()
length = longlong_arg(2)
}
====
Note that there are 3 other similar uses of 'symname(addr())' in the nd_syscall
tapset files.
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* [Bug tapsets/15961] nd_syscall.exp failure on i686
2013-09-16 21:30 [Bug tapsets/15961] New: nd_syscall.exp failure on i686 dsmith at redhat dot com
@ 2013-10-17 14:27 ` dsmith at redhat dot com
2013-10-17 21:25 ` dsmith at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: dsmith at redhat dot com @ 2013-10-17 14:27 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=15961
--- Comment #1 from David Smith <dsmith at redhat dot com> ---
I'm seeing a similar failure elsewhere (RHEL5 on s390x), that is a bit more
intermittent. The failure is in the 64-bit mmap nd_syscall test.
A mmap call that was supposed to match the following regexp:
===
mmap: mmap[2]* \([x0-9a-fA-F]+, 1030, PROT_READ, MAP_SHARED, [\-0-9]+,
[x0-9a-fA-F]+\) = [x0-9a-fA-F]+
====
came out like this:
====
mmap: mmap (0x0, 0, PROT_NON, MAP_PRIVATE, 0, 1) = 0x20000004000
====
I couldn't figure out how it was so wrong until I looked at the nd_syscall.mmap
probe alias source:
====
probe nd_syscall.mmap = kprobe.function("old_mmap") ?,
kprobe.function("old32_mmap") ?,
kprobe.function("SyS_s390_old_mmap") ?
{
asmlinkage()
if ((symname(addr()) == "old_mmap") || (symname(addr()) ==
"SyS_s390_old_mmap"))
argstr = get_mmap_args(pointer_arg(1))
else
argstr = get_32mmap_args(pointer_arg(1))
}
====
If 'symname(addr())' fails, the probe defaults to using the 32-bit function,
which interpreted the 64-bit data as 32-bit data.
The following seems to fix the problem:
====
probe nd_syscall.mmap = __nd_syscall.mmap, __nd_syscall.mmap32
{
name = "mmap"
}
probe __nd_syscall.mmap = kprobe.function("old_mmap") ?,
kprobe.function("SyS_s390_old_mmap") ?
{
asmlinkage()
argstr = get_mmap_args(pointer_arg(1))
}
probe __nd_syscall.mmap32 = kprobe.function("old32_mmap") ?
{
asmlinkage()
argstr = get_32mmap_args(pointer_arg(1))
}
====
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* [Bug tapsets/15961] nd_syscall.exp failure on i686
2013-09-16 21:30 [Bug tapsets/15961] New: nd_syscall.exp failure on i686 dsmith at redhat dot com
2013-10-17 14:27 ` [Bug tapsets/15961] " dsmith at redhat dot com
@ 2013-10-17 21:25 ` dsmith at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: dsmith at redhat dot com @ 2013-10-17 21:25 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=15961
David Smith <dsmith at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #2 from David Smith <dsmith at redhat dot com> ---
Fixed in commit 93fb14d. All 'symname(addr())' references in the
syscall/nd_syscall tapsets were either converted to use ppfunc() or broken down
into sub-probes.
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2013-10-17 21:25 ` dsmith at redhat dot com
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