bpf: Allow BPF_PROG_TYPE_STRUCT_OPS programs to be sleepable

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>
Link: https://lore.kernel.org/r/20230125164735.785732-2-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index bb38b01..c8907df 100644 (file)
--- 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 bea0dae..1f0d2bd 100644 (file)
--- 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,
 },