SELinux: improve performance when AVC misses.
* We add ebitmap_for_each_positive_bit() which enables to walk on
any positive bit on the given ebitmap, to improve its performance
using common bit-operations defined in linux/bitops.h.
In the previous version, this logic was implemented using a combination
of ebitmap_for_each_bit() and ebitmap_node_get_bit(), but is was worse
in performance aspect.
This logic is most frequestly used to compute a new AVC entry,
so this patch can improve SELinux performance when AVC misses are happen.
* struct ebitmap_node is redefined as an array of "unsigned long", to get
suitable for using find_next_bit() which is fasted than iteration of
shift and logical operation, and to maximize memory usage allocated
from general purpose slab.
* Any ebitmap_for_each_bit() are repleced by the new implementation
in ss/service.c and ss/mls.c. Some of related implementation are
changed, however, there is no incompatibility with the previous
version.
* The width of any new line are less or equal than 80-chars.
The following benchmark shows the effect of this patch, when we
access many files which have different security context one after
another. The number is more than /selinux/avc/cache_threshold, so
any access always causes AVC misses.
selinux-2.6 selinux-2.6-ebitmap
AVG: 22.763 [s] 8.750 [s]
STD: 0.265 0.019
------------------------------------------
1st: 22.558 [s] 8.786 [s]
2nd: 22.458 [s] 8.750 [s]
3rd: 22.478 [s] 8.754 [s]
4th: 22.724 [s] 8.745 [s]
5th: 22.918 [s] 8.748 [s]
6th: 22.905 [s] 8.764 [s]
7th: 23.238 [s] 8.726 [s]
8th: 22.822 [s] 8.729 [s]
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
index 4a8bab2..9a11dea 100644
--- a/security/selinux/ss/mls.c
+++ b/security/selinux/ss/mls.c
@@ -34,7 +34,9 @@
*/
int mls_compute_context_len(struct context * context)
{
- int i, l, len, range;
+ int i, l, len, head, prev;
+ char *nm;
+ struct ebitmap *e;
struct ebitmap_node *node;
if (!selinux_mls_enabled)
@@ -42,31 +44,33 @@
len = 1; /* for the beginning ":" */
for (l = 0; l < 2; l++) {
- range = 0;
- len += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
+ int index_sens = context->range.level[l].sens;
+ len += strlen(policydb.p_sens_val_to_name[index_sens - 1]);
- ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
- if (ebitmap_node_get_bit(node, i)) {
- if (range) {
- range++;
- continue;
+ /* categories */
+ head = -2;
+ prev = -2;
+ e = &context->range.level[l].cat;
+ ebitmap_for_each_positive_bit(e, node, i) {
+ if (i - prev > 1) {
+ /* one or more negative bits are skipped */
+ if (head != prev) {
+ nm = policydb.p_cat_val_to_name[prev];
+ len += strlen(nm) + 1;
}
-
- len += strlen(policydb.p_cat_val_to_name[i]) + 1;
- range++;
- } else {
- if (range > 1)
- len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
- range = 0;
+ nm = policydb.p_cat_val_to_name[i];
+ len += strlen(nm) + 1;
+ head = i;
}
+ prev = i;
}
- /* Handle case where last category is the end of range */
- if (range > 1)
- len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
-
+ if (prev != head) {
+ nm = policydb.p_cat_val_to_name[prev];
+ len += strlen(nm) + 1;
+ }
if (l == 0) {
if (mls_level_eq(&context->range.level[0],
- &context->range.level[1]))
+ &context->range.level[1]))
break;
else
len++;
@@ -84,8 +88,9 @@
void mls_sid_to_context(struct context *context,
char **scontext)
{
- char *scontextp;
- int i, l, range, wrote_sep;
+ char *scontextp, *nm;
+ int i, l, head, prev;
+ struct ebitmap *e;
struct ebitmap_node *node;
if (!selinux_mls_enabled)
@@ -97,61 +102,54 @@
scontextp++;
for (l = 0; l < 2; l++) {
- range = 0;
- wrote_sep = 0;
strcpy(scontextp,
policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
- scontextp += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
+ scontextp += strlen(scontextp);
/* categories */
- ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
- if (ebitmap_node_get_bit(node, i)) {
- if (range) {
- range++;
- continue;
- }
-
- if (!wrote_sep) {
- *scontextp++ = ':';
- wrote_sep = 1;
- } else
- *scontextp++ = ',';
- strcpy(scontextp, policydb.p_cat_val_to_name[i]);
- scontextp += strlen(policydb.p_cat_val_to_name[i]);
- range++;
- } else {
- if (range > 1) {
- if (range > 2)
+ head = -2;
+ prev = -2;
+ e = &context->range.level[l].cat;
+ ebitmap_for_each_positive_bit(e, node, i) {
+ if (i - prev > 1) {
+ /* one or more negative bits are skipped */
+ if (prev != head) {
+ if (prev - head > 1)
*scontextp++ = '.';
else
*scontextp++ = ',';
-
- strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
- scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
+ nm = policydb.p_cat_val_to_name[prev];
+ strcpy(scontextp, nm);
+ scontextp += strlen(nm);
}
- range = 0;
+ if (prev < 0)
+ *scontextp++ = ':';
+ else
+ *scontextp++ = ',';
+ nm = policydb.p_cat_val_to_name[i];
+ strcpy(scontextp, nm);
+ scontextp += strlen(nm);
+ head = i;
}
+ prev = i;
}
- /* Handle case where last category is the end of range */
- if (range > 1) {
- if (range > 2)
+ if (prev != head) {
+ if (prev - head > 1)
*scontextp++ = '.';
else
*scontextp++ = ',';
-
- strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
- scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
+ nm = policydb.p_cat_val_to_name[prev];
+ strcpy(scontextp, nm);
+ scontextp += strlen(nm);
}
if (l == 0) {
if (mls_level_eq(&context->range.level[0],
&context->range.level[1]))
break;
- else {
- *scontextp = '-';
- scontextp++;
- }
+ else
+ *scontextp++ = '-';
}
}
@@ -190,17 +188,15 @@
if (!levdatum)
return 0;
- ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
- if (ebitmap_node_get_bit(node, i)) {
- if (i > p->p_cats.nprim)
- return 0;
- if (!ebitmap_get_bit(&levdatum->level->cat, i))
- /*
- * Category may not be associated with
- * sensitivity in low level.
- */
- return 0;
- }
+ ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
+ if (i > p->p_cats.nprim)
+ return 0;
+ if (!ebitmap_get_bit(&levdatum->level->cat, i))
+ /*
+ * Category may not be associated with
+ * sensitivity in low level.
+ */
+ return 0;
}
}
@@ -485,18 +481,16 @@
c->range.level[l].sens = levdatum->level->sens;
ebitmap_init(&bitmap);
- ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
- if (ebitmap_node_get_bit(node, i)) {
- int rc;
+ ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
+ int rc;
- catdatum = hashtab_search(newp->p_cats.table,
- oldp->p_cat_val_to_name[i]);
- if (!catdatum)
- return -EINVAL;
- rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
- if (rc)
- return rc;
- }
+ catdatum = hashtab_search(newp->p_cats.table,
+ oldp->p_cat_val_to_name[i]);
+ if (!catdatum)
+ return -EINVAL;
+ rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
+ if (rc)
+ return rc;
}
ebitmap_destroy(&c->range.level[l].cat);
c->range.level[l].cat = bitmap;