- In ifc_name2unit(), disallow leading zeroes in a unit.
Exploit: ifconfig lo01 create
- In ifc_name2unit(), properly handle overflows. Otherwise,
either of two local panic()'s can occur, either because
no interface with such a name could be found after it was
successfully created, or because the code will bogusly
assume that it's a wildcard (unit < 0 due to overflow).
Exploit: ifconfig lo<overflowed_integer> create
- Previous revision made the following sequence trigger
a KASSERT() failure in queue(3):
Exploit: ifconfig lo0 destroy; ifconfig lo0 destroy
This is because IFC_IFLIST_REMOVE() is always called
before ifc->ifc_destroy() has been run, not accounting
for the fact that the latter can fail and leave the
interface operating (like is the case for "lo0").
So we ended up calling LIST_REMOVE() twice. We cannot
defer IFC_IFLIST_REMOVE() until after a call to
ifc->ifc_destroy() because the ifnet may have been
removed and its memory has been freed, so recover from
this by re-inserting the ifnet in the cloned interfaces
list if ifc->ifc_destroy() indicates a failure.
external mounting program list as well; otherwise, entry like the following
in /etc/fstab wouldn't work:
/dev/acd0 /mnt/cdrom cd9660 ro,-C=big5 0 0
Reviewed by: rodrigc
the geom creation to a seperate init function and ignore the tasting.
The config is now parsed only in the vinumdrive geom, which hopefully
fixes the problem, that the drive class tasted before the vinum class
had a chance, for good.
Also restore the behaviour that the module can be loaded at boot time
and on a running system.
- Remove dead code that I forgot to remove in the previous commit.
- Calculate the sum of the lower terms of the polynomial (divided by
x**5) in a single expression (sum of odd terms) + (sum of even terms)
with parentheses to control grouping. This is clearer and happens to
give better instruction scheduling for a tiny optimization (an
average of about ~0.5 cycles/call on Athlons).
- Calculate the final sum in a single expression with parentheses to
control grouping too. Change the grouping from
first_term + (second_term + sum_of_lower_terms) to
(first_term + second_term) + sum_of_lower_terms. Normally the first
grouping must be used for accuracy, but extra precision makes any
grouping give a correct result so we can group for efficiency. This
is a larger optimization (average 3-4 cycles/call or 5%).
- Use parentheses to indicate that the C order of left to right evaluation
is what is wanted (for efficiency) in a multiplication too.
The old fdlibm code has several optimizations related to these. 2
involve doing an extra operation that can be done almost in parallel
on some superscalar machines but are pessimizations on sequential
machines. Others involve statement ordering or expression grouping.
All of these except the ordering for the combining the sums of the odd
and even terms seem to be ideal for Athlons, but parallelism is still
limited so all of these optimizations combined together with the ones
in this commit save only ~6-8 cycles (~10%).
On an AXP, tanf() on uniformly distributed args in [-2pi, 2pi] now
takes 39-59 cycles. I don't know of any more optimizations for tanf()
short of writing it all in asm with very MD instruction scheduling.
Hardware fsin takes 122-138 cycles. Most of the optimizations for
tanf() don't work very well for tan[l](). fdlibm tan() now takes
145-365 cycles.
proxy for hosts that are reachable through the same interface the
request came in from. This feature is mainly for hosts reachable
through some P2P link, e.g. the gif(4) tunnel.
A single polynomial approximation for tan(x) works in infinite precision
up to |x| < pi/2, but in finite precision, to restrict the accumulated
roundoff error to < 1 ulp, |x| must be restricted to less than about
sqrt(0.5/((1.5+1.5)/3)) ~= 0.707. We restricted it a bit more to
give a safety margin including some slop for optimizations. Now that
we use double precision for the calculations, the accumulated roundoff
error is in double-precision ulps so it can easily be made almost 2**29
times smaller than a single-precision ulp. Near x = pi/4 its maximum
is about 0.5+(1.5+1.5)*x**2/3 ~= 1.117 double-precision ulps.
The minimax polynomial needs to be different to work for the larger
interval. I didn't increase its degree the old degree is just large
enough to keep the final error less than 1 ulp and increasing the
degree would be a pessimization. The maximum error is now ~0.80
ulps instead of ~0.53 ulps.
The speedup from this optimization for uniformly distributed args in
[-2pi, 2pi] is 28-43% on athlons, depending on how badly gcc selected
and scheduled the instructions in the old version. The old version
has some int-to-float conversions that are apparently difficult to schedule
well, but gcc-3.3 somehow did everything ~10 cycles or ~10% faster than
gcc-3.4, with the difference especially large on AXPs. On A64s, the
problem seems to be related to documented penalties for moving single
precision data to undead xmm registers. With this version, the speed
is cycles is almost independent of the athlon and gcc version despite
the large differences in instruction selection to use the FPU on AXPs
and SSE on A64s.
directly. We need to copyin() the strings in the iovec before
we can strcmp() them. Also, when we want to send the errmsg back
to userspace, we need to copyout()/copystr() the string.
Add a small helper function vfs_getopt_pos() which takes in the
name of an option, and returns the array index of the name in the iovec,
or -1 if not found. This allows us to locate an option in
the iovec without actually manipulating the iovec members. directly via
strcmp().
Noticed by: kris on sparc64
