[PATCH bpf-next 2/2] bpf: Show total linked progs cnt instead of selector in trampoline ksym

[Yafang Shao <laoar.shao@gmail.com>]

After commit e21aa341785c ("bpf: Fix fexit trampoline."), the selector
is only used to indicate how many times the bpf trampoline image are
updated and been displayed in the trampoline ksym name. After the
trampoline is freed, the count will start from 0 again.
So the count is a useless value to the user, we'd better
show a more meaningful value like how many progs are linked to this
trampoline. After that change, the selector can be removed eventally.
If the user want to check whether the bpf trampoline image has been updated
or not, the user can also compare the address. Each time the trampoline
image is updated, the address will change consequently.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/bpf.h     | 1 -
 kernel/bpf/trampoline.c | 7 ++-----
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 456f33b..36e4b2d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1125,7 +1125,6 @@ struct bpf_trampoline {
 	int progs_cnt[BPF_TRAMP_MAX];
 	/* Executable image of trampoline */
 	struct bpf_tramp_image *cur_image;
-	u64 selector;
 	struct module *mod;
 };
 
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 7067cdf..be37d87 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -410,11 +410,10 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
 		err = unregister_fentry(tr, tr->cur_image->image);
 		bpf_tramp_image_put(tr->cur_image);
 		tr->cur_image = NULL;
-		tr->selector = 0;
 		goto out;
 	}
 
-	im = bpf_tramp_image_alloc(tr->key, tr->selector);
+	im = bpf_tramp_image_alloc(tr->key, total);
 	if (IS_ERR(im)) {
 		err = PTR_ERR(im);
 		goto out;
@@ -451,8 +450,7 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
 
 	set_memory_rox((long)im->image, 1);
 
-	WARN_ON(tr->cur_image && tr->selector == 0);
-	WARN_ON(!tr->cur_image && tr->selector);
+	WARN_ON(tr->cur_image && total == 0);
 	if (tr->cur_image)
 		/* progs already running at this address */
 		err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
@@ -482,7 +480,6 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
 	if (tr->cur_image)
 		bpf_tramp_image_put(tr->cur_image);
 	tr->cur_image = im;
-	tr->selector++;
 out:
 	/* If any error happens, restore previous flags */
 	if (err)
-- 
1.8.3.1