[PATCH 6.4 126/800] bpf: Remove bpf trampoline selector

Greg Kroah-Hartman
2023-07-16T19:58:41Z

From: Yafang Shao <laoar.shao@gmail.com>

[ Upstream commit 47e79cbeea4b3891ad476047f4c68543eb51c8e0 ]

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
selector will start from 0 again. So the selector is a useless value to the
user. We can remove it.

If the user want to check whether the bpf trampoline image has been updated
or not, the user can compare the address. Each time the trampoline image is
updated, the address will change consequently. Jiri also pointed out another
issue that perf is still using the old name "bpf_trampoline_%lu", so this
change can fix the issue in perf.

Fixes: e21aa341785c ("bpf: Fix fexit trampoline.")
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <song@kernel.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Link: https://lore.kernel.org/bpf/ZFvOOlrmHiY9AgXE@krava
Link: https://lore.kernel.org/bpf/20230515130849.57502-3-laoar.shao@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/bpf.h | 1 -
kernel/bpf/trampoline.c | 11 ++++-------
2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e53ceee1df370..1ad211acf1d25 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 ac021bc43a66b..84850e66ce3d6 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -344,7 +344,7 @@ static void bpf_tramp_image_put(struct bpf_tramp_image *im)
call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
}

-static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
+static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key)
{
struct bpf_tramp_image *im;
struct bpf_ksym *ksym;
@@ -371,7 +371,7 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)

ksym = &im->ksym;
INIT_LIST_HEAD_RCU(&ksym->lnode);
- snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx);
+ snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", key);
bpf_image_ksym_add(image, ksym);
return im;

@@ -401,11 +401,10 @@ 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);
if (IS_ERR(im)) {
err = PTR_ERR(im);
goto out;
@@ -442,8 +441,7 @@ 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);
@@ -473,7 +471,6 @@ 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)
--
2.39.2