[PATCH bpf-next v4 1/4] bpf: Allow BPF_PROG_TYPE_STRUCT_OPS programs to be sleepable

David Vernet
2023-01-25T16:47:49Z

BPF struct_ops programs currently cannot be marked as sleepable. This
need not be the case -- struct_ops programs can be sleepable, and e.g.
invoke kfuncs that export the KF_SLEEPABLE flag. So as to allow future
struct_ops programs to invoke such kfuncs, this patch updates the
verifier to allow struct_ops programs to be sleepable. A follow-on patch
will add support to libbpf for specifying struct_ops.s as a sleepable
struct_ops program, and then another patch will add testcases to the
dummy_st_ops selftest suite which test sleepable struct_ops behavior.

Signed-off-by: David Vernet <void@manifault.com>
---
kernel/bpf/verifier.c | 5 +++--
tools/testing/selftests/bpf/verifier/sleepable.c | 2 +-
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index bb38b01b738f..c8907df49f81 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -17114,7 +17114,8 @@ static bool can_be_sleepable(struct bpf_prog *prog)
}
}
return prog->type == BPF_PROG_TYPE_LSM ||
- prog->type == BPF_PROG_TYPE_KPROBE; /* only for uprobes */
+ prog->type == BPF_PROG_TYPE_KPROBE /* only for uprobes */ ||
+ prog->type == BPF_PROG_TYPE_STRUCT_OPS;
}

static int check_attach_btf_id(struct bpf_verifier_env *env)
@@ -17136,7 +17137,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
}

if (prog->aux->sleepable && !can_be_sleepable(prog)) {
- verbose(env, "Only fentry/fexit/fmod_ret, lsm, iter and uprobe programs can be sleepable\n");
+ verbose(env, "Only fentry/fexit/fmod_ret, lsm, iter, uprobe, and struct_ops programs can be sleepable\n");
return -EINVAL;
}

diff --git a/tools/testing/selftests/bpf/verifier/sleepable.c b/tools/testing/selftests/bpf/verifier/sleepable.c
index bea0daef908a..1f0d2bdc673f 100644
--- a/tools/testing/selftests/bpf/verifier/sleepable.c
+++ b/tools/testing/selftests/bpf/verifier/sleepable.c
@@ -85,7 +85,7 @@
.expected_attach_type = BPF_TRACE_RAW_TP,
.kfunc = "sched_switch",
.result = REJECT,
- .errstr = "Only fentry/fexit/fmod_ret, lsm, iter and uprobe programs can be sleepable",
+ .errstr = "Only fentry/fexit/fmod_ret, lsm, iter, uprobe, and struct_ops programs can be sleepable",
.flags = BPF_F_SLEEPABLE,
.runs = -1,
},
--
2.39.0