[PATCH v2] audit: unify audit_filter_{uring(), inode_name(), syscall()}

[Ankur Arora]

audit_filter_uring(), audit_filter_inode_name() are substantially
similar to audit_filter_syscall(). Move the core logic to
__audit_filter_op() which can be parametrized for all three.

On a Skylakex system, getpid() latency (all results aggregated
across 12 boot cycles):

         Min     Mean    Median   Max      pstdev
         (ns)    (ns)    (ns)     (ns)

 -    196.63   207.86  206.60  230.98      (+- 3.92%)
 +    183.73   196.95  192.31  232.49	   (+- 6.04%)

Performance counter stats for 'bin/getpid' (3 runs) go from:
    cycles               805.58  (  +-  4.11% )
    instructions        1654.11  (  +-   .05% )
    IPC                    2.06  (  +-  3.39% )
    branches             430.02  (  +-   .05% )
    branch-misses          1.55  (  +-  7.09% )
    L1-dcache-loads      440.01  (  +-   .09% )
    L1-dcache-load-misses  9.05  (  +- 74.03% )
to:
    cycles		 765.37  (  +-  6.66% )
    instructions        1677.07  (  +-  0.04% )
    IPC		           2.20  (  +-  5.90% )
    branches	         431.10  (  +-  0.04% )
    branch-misses	   1.60  (  +- 11.25% )
    L1-dcache-loads	 521.04  (  +-  0.05% )
    L1-dcache-load-misses  6.92  (  +- 77.60% )

(Both aggregated over 12 boot cycles.)

The increased L1-dcache-loads are due to some intermediate values now
coming from the stack.

The improvement in cycles is due to a slightly denser loop (the list
parameter in the list_for_each_entry_rcu() exit check now comes from
a register rather than a constant as before.)

Signed-off-by: Ankur Arora <ankur.a.arora at oracle.com>
---
 kernel/auditsc.c | 76 +++++++++++++++++++++++++-----------------------
 1 file changed, 39 insertions(+), 37 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 2206cdf1ba2c..4991348e300a 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -807,6 +807,40 @@ static int audit_in_mask(const struct audit_krule *rule, unsigned long val)
 	return rule->mask[word] & bit;
 }
 
+/**
+ * __audit_filter_op - common filter helper for operations (syscall/uring/etc)
+ * @tsk: associated task
+ * @ctx: audit context
+ * @list: audit filter list
+ * @name: audit_name (can be NULL)
+ * @op: current syscall/uring_op
+ *
+ * Run the udit filters specified in @list against @tsk using @ctx,
+ * @name, and @op, as necessary; the caller is responsible for ensuring
+ * that the call is made while the RCU read lock is held. The @name
+ * parameter can be NULL, but all others must be specified.
+ * Returns 1/true if the filter finds a match, 0/false if none are found.
+ */
+static int __audit_filter_op(struct task_struct *tsk,
+			   struct audit_context *ctx,
+			   struct list_head *list,
+			   struct audit_names *name,
+			   unsigned long op)
+{
+	struct audit_entry *e;
+	enum audit_state state;
+
+	list_for_each_entry_rcu(e, list, list) {
+		if (audit_in_mask(&e->rule, op) &&
+		    audit_filter_rules(tsk, &e->rule, ctx, name,
+				       &state, false)) {
+			ctx->current_state = state;
+			return 1;
+		}
+	}
+	return 0;
+}
+
 /**
  * audit_filter_uring - apply filters to an io_uring operation
  * @tsk: associated task
@@ -815,23 +849,12 @@ static int audit_in_mask(const struct audit_krule *rule, unsigned long val)
 static void audit_filter_uring(struct task_struct *tsk,
 			       struct audit_context *ctx)
 {
-	struct audit_entry *e;
-	enum audit_state state;
-
 	if (auditd_test_task(tsk))
 		return;
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_URING_EXIT],
-				list) {
-		if (audit_in_mask(&e->rule, ctx->uring_op) &&
-		    audit_filter_rules(tsk, &e->rule, ctx, NULL, &state,
-				       false)) {
-			rcu_read_unlock();
-			ctx->current_state = state;
-			return;
-		}
-	}
+	__audit_filter_op(tsk, ctx, &audit_filter_list[AUDIT_FILTER_URING_EXIT],
+			NULL, ctx->uring_op);
 	rcu_read_unlock();
 }
 
@@ -843,25 +866,13 @@ static void audit_filter_uring(struct task_struct *tsk,
 static void audit_filter_syscall(struct task_struct *tsk,
 				 struct audit_context *ctx)
 {
-	struct audit_entry *e;
-	enum audit_state state;
-	unsigned long major = ctx->major;
-
 	if (auditd_test_task(tsk))
 		return;
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_EXIT], list) {
-		if (audit_in_mask(&e->rule, major) &&
-		    audit_filter_rules(tsk, &e->rule, ctx, NULL,
-				       &state, false)) {
-			rcu_read_unlock();
-			ctx->current_state = state;
-			return;
-		}
-	}
+	__audit_filter_op(tsk, ctx, &audit_filter_list[AUDIT_FILTER_EXIT],
+			NULL, ctx->major);
 	rcu_read_unlock();
-	return;
 }
 
 /*
@@ -873,17 +884,8 @@ static int audit_filter_inode_name(struct task_struct *tsk,
 				   struct audit_context *ctx) {
 	int h = audit_hash_ino((u32)n->ino);
 	struct list_head *list = &audit_inode_hash[h];
-	struct audit_entry *e;
-	enum audit_state state;
 
-	list_for_each_entry_rcu(e, list, list) {
-		if (audit_in_mask(&e->rule, ctx->major) &&
-		    audit_filter_rules(tsk, &e->rule, ctx, n, &state, false)) {
-			ctx->current_state = state;
-			return 1;
-		}
-	}
-	return 0;
+	return __audit_filter_op(tsk, ctx, list, n, ctx->major);
 }
 
 /* At syscall exit time, this filter is called if any audit_names have been
-- 
2.31.1