* [Bug tapsets/16057] New: task_dentry_path fails to cross mount points
@ 2013-10-17 0:14 jistone at redhat dot com
2013-10-17 0:24 ` [Bug tapsets/16057] " jistone at redhat dot com
0 siblings, 1 reply; 2+ messages in thread
From: jistone at redhat dot com @ 2013-10-17 0:14 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=16057
Bug ID: 16057
Summary: task_dentry_path fails to cross mount points
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: tapsets
Assignee: systemtap at sourceware dot org
Reporter: jistone at redhat dot com
On kernel-3.11.4-201.fc19.x86_64, task_dentry_path always returns "<unknown>"
for paths which cross mount points. This can only occur when real_mount
returns 0. I found that it's failing the (vfsmnt > offset) test, because
vfsmnt as a signed quantity looks negative. (AFAIK all kernel pointers will
have the MSB set.)
After fixing that test to allow "negative" pointers, the iteration hits bogus
pointer values for dentry and vfsmnt. I got NULL, but on IRC ciupicri reported
values that look like random garbage. I tracked this to the assignment:
vfsmnt = @cast(mnt, "mount")->mnt_parent
... which is a problem because ->mnt_parent is another struct mount, not a
struct vfsmount as we are interpreting it from there. This works for me:
vfsmnt = &@cast(mnt, "mount")->mnt_parent->mnt
These bugs won't apply to kernels before the struct mount refactoring in 3.3.
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* [Bug tapsets/16057] task_dentry_path fails to cross mount points
2013-10-17 0:14 [Bug tapsets/16057] New: task_dentry_path fails to cross mount points jistone at redhat dot com
@ 2013-10-17 0:24 ` jistone at redhat dot com
0 siblings, 0 replies; 2+ messages in thread
From: jistone at redhat dot com @ 2013-10-17 0:24 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=16057
Josh Stone <jistone at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #1 from Josh Stone <jistone at redhat dot com> ---
Fixed in commit 45ad77bd0d1697f202209da7fc25499c488cc51f.
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2013-10-17 0:14 [Bug tapsets/16057] New: task_dentry_path fails to cross mount points jistone at redhat dot com
2013-10-17 0:24 ` [Bug tapsets/16057] " jistone at redhat dot com
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