[PATCH 06/15] bpf: Add bpf_ksym_tree tree

Jiri Olsa
2020-03-02T14:32:35Z

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.

Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/linux/bpf.h | 1 +
kernel/bpf/core.c | 56 ++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 51 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 084abfbc3362..c36558c44637 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -607,8 +607,42 @@ 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)
+{
+ return container_of(n, struct bpf_ksym, tnode)->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)
@@ -616,6 +650,7 @@ 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)
@@ -624,6 +659,7 @@ 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);
}

@@ -672,19 +708,27 @@ 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