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bpf: Support bpf tracing/iter programs for BPF_LINK_UPDATE 

Added BPF_LINK_UPDATE support for tracing/iter programs.
This way, a file based bpf iterator, which holds a reference
to the link, can have its bpf program updated without
creating new files.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175902.2475262-1-yhs@fb.com
This commit is contained in:
Yonghong Song 2020-05-09 10:59:02 -07:00 committed by Alexei Starovoitov
parent de4e05cac4
commit 2057c92bc9
1 changed files with 31 additions and 0 deletions
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31
kernel/bpf/bpf_iter.c
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@ -23,6 +23,9 @@ struct bpf_iter_link {
static struct list_head targets = LIST_HEAD_INIT(targets);
static DEFINE_MUTEX(targets_mutex);
/* protect bpf_iter_link changes */
static DEFINE_MUTEX(link_mutex);
int bpf_iter_reg_target(struct bpf_iter_reg *reg_info)
{
struct bpf_iter_target_info *tinfo;
@ -111,9 +114,37 @@ static void bpf_iter_link_dealloc(struct bpf_link *link)
kfree(iter_link);
}
static int bpf_iter_link_replace(struct bpf_link *link,
struct bpf_prog *new_prog,
struct bpf_prog *old_prog)
{
int ret = 0;
mutex_lock(&link_mutex);
if (old_prog && link->prog != old_prog) {
ret = -EPERM;
goto out_unlock;
}
if (link->prog->type != new_prog->type ||
link->prog->expected_attach_type != new_prog->expected_attach_type ||
link->prog->aux->attach_btf_id != new_prog->aux->attach_btf_id) {
ret = -EINVAL;
goto out_unlock;
}
old_prog = xchg(&link->prog, new_prog);
bpf_prog_put(old_prog);
out_unlock:
mutex_unlock(&link_mutex);
return ret;
}
static const struct bpf_link_ops bpf_iter_link_lops = {
.release = bpf_iter_link_release,
.dealloc = bpf_iter_link_dealloc,
.update_prog = bpf_iter_link_replace,
};
int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)