Re: [PATCH 13/14] bpf: Add dispatchers to kallsyms
From: Andrii Nakryiko <hidden>
Date: 2020-02-11 19:03:35
Also in:
bpf
On Sat, Feb 8, 2020 at 7:43 AM Jiri Olsa [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Adding dispatchers to kallsyms. It's displayed as bpf_dispatcher_<NAME> where NAME is the name of dispatcher. Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- include/linux/bpf.h | 19 ++++++++++++------- kernel/bpf/dispatcher.c | 6 ++++++ 2 files changed, 18 insertions(+), 7 deletions(-)diff --git a/include/linux/bpf.h b/include/linux/bpf.h index b91bac10d3ea..837cdc093d2c 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h@@ -520,6 +520,7 @@ struct bpf_dispatcher { int num_progs; void *image; u32 image_off; + struct bpf_ksym ksym; }; static __always_inline unsigned int bpf_dispatcher_nop_func(@@ -535,13 +536,17 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key); int bpf_trampoline_link_prog(struct bpf_prog *prog); int bpf_trampoline_unlink_prog(struct bpf_prog *prog); void bpf_trampoline_put(struct bpf_trampoline *tr); -#define BPF_DISPATCHER_INIT(name) { \ - .mutex = __MUTEX_INITIALIZER(name.mutex), \ - .func = &name##_func, \ - .progs = {}, \ - .num_progs = 0, \ - .image = NULL, \ - .image_off = 0 \ +#define BPF_DISPATCHER_INIT(_name) { \ + .mutex = __MUTEX_INITIALIZER(_name.mutex), \ + .func = &_name##_func, \ + .progs = {}, \ + .num_progs = 0, \ + .image = NULL, \ + .image_off = 0, \ + .ksym = { \ + .name = #_name, \ + .lnode = LIST_HEAD_INIT(_name.ksym.lnode), \ + }, \ } #define DEFINE_BPF_DISPATCHER(name) \diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index b3e5b214fed8..8771d2cc5840 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c@@ -152,6 +152,12 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from, if (!changed) goto out; + if (!prev_num_progs) + bpf_image_ksym_add(d->image, &d->ksym); + + if (!d->num_progs) + bpf_ksym_del(&d->ksym); + bpf_dispatcher_update(d, prev_num_progs);
On slightly unrelated note: seems like bpf_dispatcher_update won't propagate any lower-level errors back, which seems pretty bad as a bunch of stuff can go wrong. Björn, was it a conscious decision or this just slipped through the cracks? Jiri, reason I started looking at this was twofold: 1. you add/remove symbol before dispatcher is updated, which is different order from BPF trampoline updates. I think updating symbols after successful update makes more sense, no? 2. I was wondering if bpf_dispatcher_update() could return 0/1 (and <0 on error, of course), depending on whether dispatcher is present or not. Though I'm not hard set on this.
out:
mutex_unlock(&d->mutex);
--
2.24.1