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bpf: add bpf_func_t and trampoline helpers

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I'll be adding lsm cgroup specific helpers that grab
trampoline mutex.

No functional changes.

Reviewed-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-2-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Stanislav Fomichev 2022-06-28 10:43:04 -07:00 • committed by Alexei Starovoitov
parent c5c7358e4c
commit af3f413400
2 changed files with 38 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

63
kernel/bpf/trampoline.c
View file

@ -410,7 +410,7 @@ static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
}
}
int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
enum bpf_tramp_prog_type kind;
struct bpf_tramp_link *link_exiting;
@ -418,44 +418,33 @@ int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline
int cnt = 0, i;
kind = bpf_attach_type_to_tramp(link->link.prog);
mutex_lock(&tr->mutex);
if (tr->extension_prog) {
if (tr->extension_prog)
/* cannot attach fentry/fexit if extension prog is attached.
* cannot overwrite extension prog either.
*/
err = -EBUSY;
goto out;
}
return -EBUSY;
for (i = 0; i < BPF_TRAMP_MAX; i++)
cnt += tr->progs_cnt[i];
if (kind == BPF_TRAMP_REPLACE) {
/* Cannot attach extension if fentry/fexit are in use. */
if (cnt) {
err = -EBUSY;
goto out;
}
if (cnt)
return -EBUSY;
tr->extension_prog = link->link.prog;
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
link->link.prog->bpf_func);
goto out;
return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
link->link.prog->bpf_func);
}
if (cnt >= BPF_MAX_TRAMP_LINKS) {
err = -E2BIG;
goto out;
}
if (!hlist_unhashed(&link->tramp_hlist)) {
if (cnt >= BPF_MAX_TRAMP_LINKS)
return -E2BIG;
if (!hlist_unhashed(&link->tramp_hlist))
/* prog already linked */
err = -EBUSY;
goto out;
}
return -EBUSY;
hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
if (link_exiting->link.prog != link->link.prog)
continue;
/* prog already linked */
err = -EBUSY;
goto out;
return -EBUSY;
}
hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
@ -465,30 +454,44 @@ int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline
hlist_del_init(&link->tramp_hlist);
tr->progs_cnt[kind]--;
}
out:
return err;
}
int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
int err;
mutex_lock(&tr->mutex);
err = __bpf_trampoline_link_prog(link, tr);
mutex_unlock(&tr->mutex);
return err;
}
/* bpf_trampoline_unlink_prog() should never fail. */
int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
enum bpf_tramp_prog_type kind;
int err;
kind = bpf_attach_type_to_tramp(link->link.prog);
mutex_lock(&tr->mutex);
if (kind == BPF_TRAMP_REPLACE) {
WARN_ON_ONCE(!tr->extension_prog);
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
tr->extension_prog->bpf_func, NULL);
tr->extension_prog = NULL;
goto out;
return err;
}
hlist_del_init(&link->tramp_hlist);
tr->progs_cnt[kind]--;
err = bpf_trampoline_update(tr);
out:
return bpf_trampoline_update(tr);
}
/* bpf_trampoline_unlink_prog() should never fail. */
int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
int err;
mutex_lock(&tr->mutex);
err = __bpf_trampoline_unlink_prog(link, tr);
mutex_unlock(&tr->mutex);
return err;
}