From c0da3908de47ffb1f9f4ec18f1ddf41d349da800 Mon Sep 17 00:00:00 2001 From: Joel Fernandes Date: Sat, 13 Jan 2018 20:09:19 -0800 Subject: [PATCH] bpf/stackmap: Implement bpf_get_next_key Currently stackmaps can't be iterated over. The keys are obtained through other maps and look ups have to be performed. In new usecases, its useful to be able to iterate over the stackmap independently. Implement bpf_get_next_key to make this possible. More details of use case: Currently iterating over stack maps is done like so, for example in BCC tools offcputime script: 1. Obtain keys from the 'counts' hash map. 2. Look up stackmap with each of the keys obtained from step 1. This makes the iteration of stackmap dependent on the counts map. In a new tool I'm working on called BPFd [1], it gives a huge speed up when I dump entire maps before transmitting them to BCC tools on a different machine [2]. This patch makes it possible to dump stackmaps independent of other maps. Tested on x86 and arm64 machines. [1] https://lkml.org/lkml/2017/12/29/137 [2] https://github.com/joelagnel/bpfd/issues/8 Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Brendan Gregg Cc: Brenden Blanco Signed-off-by: Joel Fernandes --- kernel/bpf/stackmap.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index a15bc636cc98..b0bf7d009f76 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -228,7 +228,23 @@ int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value) static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key) { - return -EINVAL; + struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); + u32 id = 0; + + if (key) { + id = *(u32 *)key; + if (unlikely(id >= smap->n_buckets)) + return -ENOENT; + id++; + } + + for ( ; id < smap->n_buckets; id++) { + if (READ_ONCE(smap->buckets[id])) { + *(u32 *)next_key = id; + return 0; + } + } + return -ENOENT; } static int stack_map_update_elem(struct bpf_map *map, void *key, void *value, -- 2.16.0.rc1.238.g530d649a79-goog