The match_count variable is a sum of the number of duplicates node sets
that have been encountered and discarded. Rename it to better reflect what
it is doing.
Signed-off-by: John Johansen <john.johansen@canonical.com>
Embedding the nodes are part of the state gives fast back reference from
the state to the nodes that created it. This is useful for the state to
nodes mapping dump as it lets us output the states in order. It will also
let us avoid certain nodemap lookup in the future.
Overlay the nodes field (used only in dfa construction) with the partition
field which is only used during dfa minimization to avoid making the state
any larger.
Signed-off-by: John Johansen <john.johansen@canonical.com>
commits were made (as well as a few other minor warnings elsewhere).
The Makefile change is to avoid passing -Wstrict-prototypes and
-Wnested-externs to the C++ compiler, which the compiler yells about and
then ignores.
Since we compile with -Wmissing-field-initializers I dropped the
unreferenced zero-width fields in the header structs, and then explicitly
initialized the remaining fields.
I tagged several unused function parameters to silence those warnings.
And finally, I dropped the unused filter_escapes() too.
Embedding the the partition mapping into the State structure significantly
speeds up dfa minimization, by converting rbtree finds to straight direct
references when checking for same mappings.
The overall time improvement is small but it can half the time spent in
minimization.
The nodemap.size() increases by one with each node added, every time we
add a state we label it so this provides the proper labeling without needing
a separate variable.
help reduce peak memory usage in some cases.
Also disbale remove_unreachable, as the current dfa code isn't generating
unreachable states, and minimization removes any states that are connected
but redundant.
hold permission information. We currently keep them in a table with a
refcount so that they don't go away, until we delete the table.
We can simulate this by getting rid of the refcount, and making dup and release
virtual, and overriding it for the special accept nodes.
improves minimization performance, it can slow down total creation time and
result in larger compressed dfas.
This is because it results in the dfa not being completely minimized which
with the current O(n2) dfa table compression algorithm can result in slower
compressed dfa generation.
first hash does hashing on state just state transitions, which always results
in a performance improvement.
The second does hashing based off of accept permissions, which can create
more initial states but can result in not being able to achieve a true
minimum dfa. This can also lead to slowing down total dfa creation because
while minimization, compression can take longer if the dfa isn't completely
minimized.
permission hashing is currently required, as minimization does not accumulate
redundant Node permissions.
memory than just using the NodeSet size to short circuit comparison but it
improves on the case where compared sets have the same size. It is possible
that this will slow down small dfa generation slightly but the trade off for
large dfa's (which are the slow ones to generate) is worth it.
This results in another performance bump over using the NodeSize is NodeSet
comparison, and the amount of improvement increases with larger dfas
of pointers when it isn't necessary. This results in a nice little
performance increase in dfa creation.
This is more of a proof of concept patch, and is replaced by the next
patch which does better short circuiting via hashing
the large side, and I experimented with different ways to split this up but in
the end, anything I could do would result in a series of dependent patches
that would require all of them to be applied to get meaningful functional
changes.
The patch structural reworks the dfa so that
- there is a new State class, it takes the place of sets of nodes in the
dfa, and allows storing state information within the state
- removes the dfa transition table, which mapped sets of nodes to a
transition table, by moving the transition into the new state class
- computes dfa state permissions once (stored in the state)
- expression tree nodes are independent from a created dfa. This allows
computed expression trees, and sets of Nodes (used as protostates when
computing the dfa). To be managed independent of the dfa life time.
This will allow reducing the amount of memory used, in the future,
and will also allow separating the expression tree logic out into
its own file.
The patch has some effect on reducing peak memory usage, and computation
time. The actual amount of reduction is dependent on the number of states
in the dfa with larger saving being achieved on larger dfas. Eg. for
the test evince profile I was using it makes the parser about 7% faster with a
peak memory usage about 12% less.
This patch changes the initial partition hashing of minimization resulting
in slightly smaller dfas.
tree. It is limited in that it doesn't currently handle the permissions of a rule.
conversion output presents an aare -> prce conversion followed by 1 or more expression
tree rules, governed by what the rule does.
eg.
aare: /** -> /[^/\x00][^\x00]*
rule: /[^/\x00][^\x00]* -> /[^\0000/]([^\0000])*
eg.
echo "/foo { /** rwlkmix, } " | ./apparmor_parser -QT -D rule-exprs -D expr-tree
aare: /foo -> /foo
aare: /** -> /[^/\x00][^\x00]*
rule: /[^/\x00][^\x00]* -> /[^\0000/]([^\0000])*
rule: /[^/\x00][^\x00]*\x00/[^/].* -> /[^\0000/]([^\0000])*\0000/[^/](.)*
DFA: Expression Tree
(/[^\0000/]([^\0000])*(((((((((((((<513>|<2>)|<4>)|<8>)|<16>)|<32>)|<64>)|<8404992>)|<32768>)|<65536>)|<131072>)|<262144>)|<524288>)|<1048576>)|/[^\0000/]([^\0000])*\0000/[^/](.)*((<16>|<32>)|<262144>))
This simple example shows many things
1. The profile name under goes pcre conversion. But since no regular expressions where found
it doesn't generate any expr rules
2. /** is converted into the pcre expression /[^\0000/]([^\0000])*
3. The pcre expression /[^\0000/]([^\0000])* is converted into two rules that are then
converted into expression trees.
The reason for this can not be seen by the output as this is actually triggered by
permissions separation for the rule. In this case the link permission is separated
into what is shown as the second rule: statement.
4. DFA: Expression Tree dump shows how these rules are combined together
You will notice that the rule conversion statement is fairly redundant currently as it just
show pcre to expression tree pcre. This will change when direct aare parsing occurs,
but currently serves to verify the pcre conversion step.
It is not the prettiest patch, as its touching some ugly code that is schedule to be cleaned
up/replaced. eg. convert_aaregex_to_pcre is going to replaced with native parse conversion
from an aare straight to the expression tree, and dfaflag passing will become part of the
rule set.
It changes the table resizing so that there is always sufficient
high entries in the table, preventing bounds violations from
occurring.
Previously the resize allocation was always based on the character
set range for a state, which could be more or less than actually
required, and packing would waste some space when over allocation
was done.
As a result this patch in general results in slightly smaller
transition tables even though it enforcing the minimum required
padding to avoid bounds violations.
are computed and stored in a map, that is not cleaned up. This means that the labeling
is retained across different dfas.
Move the labeling into expr node as this takes less memory than using a map and will
also separates node labeling so its per dfa instead of global. In addition this means
the labeling is cleanedup/freed when the expr tree is freed without any extra work.
each expression tree node and then used as input to create the dfa states.
Currently they are not being freed until the nodes are destroyed, but the information
is no longer needed once the dfa has been created. Cleaning them up early reduces
peak memory usage.
imediately after the current partition being considered, instead of
at the back of the parition list. This does two things, it makes it
more likely the data is in cache, and it also in general results in
more partitions being created in a single pass.
