On 4/28/20 5:54 PM, Martin KaFai Lau wrote:
On Mon, Apr 27, 2020 at 01:12:39PM -0700, Yonghong Song wrote:
A bpf_iter program is a tracing program with attach type
BPF_TRACE_ITER. The load attribute
attach_btf_id
is used by the verifier against a particular kernel function,
e.g., __bpf_iter__bpf_map in our previous bpf_map iterator.
The program return value must be 0 for now. In the
future, other return values may be used for filtering or
teminating the iterator.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
include/uapi/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 20 ++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 1 +
3 files changed, 22 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4a6c47f3febe..f39b9fec37ab 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -215,6 +215,7 @@ enum bpf_attach_type {
BPF_TRACE_FEXIT,
BPF_MODIFY_RETURN,
BPF_LSM_MAC,
+ BPF_TRACE_ITER,
__MAX_BPF_ATTACH_TYPE
};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 91728e0f27eb..fd36c22685d9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7074,6 +7074,11 @@ static int check_return_code(struct bpf_verifier_env *env)
return 0;
range = tnum_const(0);
break;
+ case BPF_PROG_TYPE_TRACING:
+ if (env->prog->expected_attach_type != BPF_TRACE_ITER)
+ return 0;
+ range = tnum_const(0);
+ break;
default:
return 0;
}
@@ -10454,6 +10459,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
struct bpf_prog *tgt_prog = prog->aux->linked_prog;
u32 btf_id = prog->aux->attach_btf_id;
const char prefix[] = "btf_trace_";
+ struct btf_func_model fmodel;
int ret = 0, subprog = -1, i;
struct bpf_trampoline *tr;
const struct btf_type *t;
@@ -10595,6 +10601,20 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
prog->aux->attach_func_proto = t;
prog->aux->attach_btf_trace = true;
return 0;
+ case BPF_TRACE_ITER:
+ if (!btf_type_is_func(t)) {
+ verbose(env, "attach_btf_id %u is not a function\n",
+ btf_id);
+ return -EINVAL;
+ }
+ t = btf_type_by_id(btf, t->type);
+ if (!btf_type_is_func_proto(t))
Other than the type tests,
to ensure the attach_btf_id is a supported bpf_iter target,
should the prog be checked against the target list
("struct list_head targets") here also during the prog load time?
This is a good question. In my RFC v2, I did this, checking against
registered targets (essentially, program loading + attaching to the target).
In this version, program loading and attaching are separated.
- program loading: against btf_id
- attaching: linking bpf program to target
current linking parameter only bpf_program, but later on
there may be additional parameters like map_id, pid, cgroup_id
etc. for tailoring the iterator behavior.
This seems having a better separation. Agreed that checking
at load time may return error earlier instead at link_create
time. Let me think about this.
+ return -EINVAL;
+ prog->aux->attach_func_name = tname;
+ prog->aux->attach_func_proto = t;
+ ret = btf_distill_func_proto(&env->log, btf, t,
+ tname, &fmodel);
+ return ret;
default:
if (!prog_extension)
return -EINVAL;
