Re: [PATCH 06/14] bpf: Add bpf_kallsyms_tree tree

On Tue, Feb 11, 2020 at 10:21:10AM -0800, Andrii Nakryiko wrote:

On Sat, Feb 8, 2020 at 7:43 AM Jiri Olsa [off-list ref] wrote:

quoted

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_kallsyms_tree that will hold symbols for all bpf_prog,
bpf_trampoline and bpf_dispatcher objects and keeping bpf_tree
only for bpf_prog objects exception tables search to keep it fast.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 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 da67ca3afa2f..151d7b1c8435 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 b9b7077e60f3..1daa72341450 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 __always_inline unsigned long
+bpf_get_ksym_start(struct latch_tree_node *n)

I thought static functions are never marked as inline in kernel
sources. Are there some special cases when its ok/necessary?

I followed the other latch tree ops functions and did not think
much about that.. will check

quoted

+{
+       const struct bpf_ksym *ksym;
+
+       ksym = container_of(n, struct bpf_ksym, tnode);
+       return ksym->start;
+}
+
+static __always_inline 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 __always_inline 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_kallsyms_tree_ops = {

Given all the helper functions use bpf_ksym_tree and bpf_ksym
(bpf_ksym_find) prefixes, call this bpf_ksym_tree_ops?

right, should be bpf_ksym_tree_ops as you said

quoted

+       .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_kallsyms_tree __cacheline_aligned;

same as above, bpf_ksym_tree for consistency?

right, thanks

jirka