* [Bug runtime/13546] New: improve map hashing
@ 2011-12-31 1:37 fche at redhat dot com
2012-01-05 16:46 ` [Bug runtime/13546] " cmeek at redhat dot com
0 siblings, 1 reply; 2+ messages in thread
From: fche at redhat dot com @ 2011-12-31 1:37 UTC (permalink / raw)
To: systemtap
http://sourceware.org/bugzilla/show_bug.cgi?id=13546
Bug #: 13546
Summary: improve map hashing
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: runtime
AssignedTo: systemtap@sourceware.org
ReportedBy: fche@redhat.com
Classification: Unclassified
The runtime/map* functions have several weaknesses w.r.t. hashing
that we should improve.
1) HASH_TABLE_BITS/SIZE should probably be a function of MAXMAPENTRIES.
2) str_hash() should be more hashy. It looks rather wimpy.
3) With deliberate hash-collision-inducing data conceivably fed to stap,
we should investigate salting the map FOO_hash functions with some
runtime-random value, such as a few bytes collected at startup time with
get_random_bytes(), as in
static unsigned long stap_hash_seed; /* init during module startup */
static unsigned int int64_hash (const int64_t v)
{
return (unsigned int)hash_long (((unsigned long)v) ^ stap_hash_seed,
HASH_TABLE_BITS);
}
/* and similarly for str_hash */
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* [Bug runtime/13546] improve map hashing
2011-12-31 1:37 [Bug runtime/13546] New: improve map hashing fche at redhat dot com
@ 2012-01-05 16:46 ` cmeek at redhat dot com
0 siblings, 0 replies; 2+ messages in thread
From: cmeek at redhat dot com @ 2012-01-05 16:46 UTC (permalink / raw)
To: systemtap
http://sourceware.org/bugzilla/show_bug.cgi?id=13546
Chris Meek <cmeek at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |cmeek at redhat dot com
AssignedTo|systemtap at sourceware dot |cmeek at redhat dot com
|org |
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