Subject: [PATCH 06/18] bpf: Add bpf_ksym_tree tree

From: Jiri Olsa <[email-masked]>
Date: Sun, 16 Feb 2020 20:29:53 +0100

The bpf_tree is used both for kallsyms iterations and searching
for exception tables of bpf programs, which is needed only for
bpf programs.

Adding bpf_ksym_tree that will hold symbols for all bpf_prog
bpf_trampoline and bpf_dispatcher objects and keeping bpf_tree
only for bpf_prog objects to keep it fast.

Signed-off-by: Jiri Olsa <[email-masked]>
---
 include/linux/bpf.h |  1 +
 kernel/bpf/core.c   | 60 ++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f1174d24c185..5d6649cdc3df 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -468,6 +468,7 @@ struct bpf_ksym {
 	unsigned long		 end;
 	char			 name[KSYM_NAME_LEN];
 	struct list_head	 lnode;
+	struct latch_tree_node	 tnode;
 };
 
 enum bpf_tramp_prog_type {
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 604093d2153a..9fb08b4d01f7 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -606,8 +606,46 @@ static const struct latch_tree_ops bpf_tree_ops = {
 	.comp	= bpf_tree_comp,
 };
 
+static unsigned long
+bpf_get_ksym_start(struct latch_tree_node *n)
+{
+	const struct bpf_ksym *ksym;
+
+	ksym = container_of(n, struct bpf_ksym, tnode);
+	return ksym->start;
+}
+
+static bool
+bpf_ksym_tree_less(struct latch_tree_node *a,
+		   struct latch_tree_node *b)
+{
+	return bpf_get_ksym_start(a) < bpf_get_ksym_start(b);
+}
+
+static int
+bpf_ksym_tree_comp(void *key, struct latch_tree_node *n)
+{
+	unsigned long val = (unsigned long)key;
+	const struct bpf_ksym *ksym;
+
+	ksym = container_of(n, struct bpf_ksym, tnode);
+
+	if (val < ksym->start)
+		return -1;
+	if (val >= ksym->end)
+		return  1;
+
+	return 0;
+}
+
+static const struct latch_tree_ops bpf_ksym_tree_ops = {
+	.less	= bpf_ksym_tree_less,
+	.comp	= bpf_ksym_tree_comp,
+};
+
 static DEFINE_SPINLOCK(bpf_lock);
 static LIST_HEAD(bpf_kallsyms);
+static struct latch_tree_root bpf_ksym_tree __cacheline_aligned;
 static struct latch_tree_root bpf_tree __cacheline_aligned;
 
 static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux)
@@ -615,6 +653,7 @@ static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux)
 	WARN_ON_ONCE(!list_empty(&aux->ksym.lnode));
 	list_add_tail_rcu(&aux->ksym.lnode, &bpf_kallsyms);
 	latch_tree_insert(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops);
+	latch_tree_insert(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops);
 }
 
 static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux)
@@ -623,6 +662,7 @@ static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux)
 		return;
 
 	latch_tree_erase(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops);
+	latch_tree_erase(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops);
 	list_del_rcu(&aux->ksym.lnode);
 }
 
@@ -671,19 +711,27 @@ static struct bpf_prog *bpf_prog_kallsyms_find(unsigned long addr)
 	       NULL;
 }
 
+static struct bpf_ksym *bpf_ksym_find(unsigned long addr)
+{
+	struct latch_tree_node *n;
+
+	n = latch_tree_find((void *)addr, &bpf_ksym_tree, &bpf_ksym_tree_ops);
+	return n ? container_of(n, struct bpf_ksym, tnode) : NULL;
+}
+
 const char *__bpf_address_lookup(unsigned long addr, unsigned long *size,
 				 unsigned long *off, char *sym)
 {
-	struct bpf_prog *prog;
+	struct bpf_ksym *ksym;
 	char *ret = NULL;
 
 	rcu_read_lock();
-	prog = bpf_prog_kallsyms_find(addr);
-	if (prog) {
-		unsigned long symbol_start = prog->aux->ksym.start;
-		unsigned long symbol_end = prog->aux->ksym.end;
+	ksym = bpf_ksym_find(addr);
+	if (ksym) {
+		unsigned long symbol_start = ksym->start;
+		unsigned long symbol_end = ksym->end;
 
-		strncpy(sym, prog->aux->ksym.name, KSYM_NAME_LEN);
+		strncpy(sym, ksym->name, KSYM_NAME_LEN);
 
 		ret = sym;
 		if (size)
-- 
2.24.1