[PATCH bpf-next v13 4/6] bpf: Verifier support for sleepable tracepoint programs

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

From: Mykyta Yatsenko <yatsenko@meta.com>

Allow BPF_PROG_TYPE_RAW_TRACEPOINT, BPF_PROG_TYPE_TRACEPOINT, and
BPF_TRACE_RAW_TP (tp_btf) programs to be sleepable by adding them
to can_be_sleepable().

For BTF-based raw tracepoints (tp_btf), add a load-time check in
bpf_check_attach_target() that rejects sleepable programs attaching
to non-faultable tracepoints with a descriptive error message.

For raw tracepoints (raw_tp), add an attach-time check in
bpf_raw_tp_link_attach() that rejects sleepable programs on
non-faultable tracepoints. The attach-time check is needed because
the tracepoint name is not known at load time for raw_tp.

The attach-time check for classic tracepoints (tp) in
__perf_event_set_bpf_prog() was added in the previous patch.

Replace the verbose error message that enumerates allowed program
types with a generic "Program of this type cannot be sleepable"
message, since the list of sleepable-capable types keeps growing.

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
 kernel/bpf/syscall.c  |  5 +++++
 kernel/bpf/verifier.c | 13 +++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a3c0214ca934..3b1f0ba02f61 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4281,6 +4281,11 @@ static int bpf_raw_tp_link_attach(struct bpf_prog *prog,
 	if (!btp)
 		return -ENOENT;
 
+	if (prog->sleepable && !tracepoint_is_faultable(btp->tp)) {
+		bpf_put_raw_tracepoint(btp);
+		return -EINVAL;
+	}
+
 	link = kzalloc_obj(*link, GFP_USER);
 	if (!link) {
 		err = -ENOMEM;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 185210b73385..5b4806fdb648 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19267,6 +19267,12 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 		btp = bpf_get_raw_tracepoint(tname);
 		if (!btp)
 			return -EINVAL;
+		if (prog->sleepable && !tracepoint_is_faultable(btp->tp)) {
+			bpf_log(log, "Sleepable program cannot attach to non-faultable tracepoint %s\n",
+				tname);
+			bpf_put_raw_tracepoint(btp);
+			return -EINVAL;
+		}
 		fname = kallsyms_lookup((unsigned long)btp->bpf_func, NULL, NULL, NULL,
 					trace_symbol);
 		bpf_put_raw_tracepoint(btp);
@@ -19483,6 +19489,7 @@ static bool can_be_sleepable(struct bpf_prog *prog)
 		case BPF_MODIFY_RETURN:
 		case BPF_TRACE_ITER:
 		case BPF_TRACE_FSESSION:
+		case BPF_TRACE_RAW_TP:
 			return true;
 		default:
 			return false;
@@ -19490,7 +19497,9 @@ 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_STRUCT_OPS;
+	       prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
+	       prog->type == BPF_PROG_TYPE_RAW_TRACEPOINT ||
+	       prog->type == BPF_PROG_TYPE_TRACEPOINT;
 }
 
 static int check_attach_btf_id(struct bpf_verifier_env *env)
@@ -19512,7 +19521,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 	}
 
 	if (prog->sleepable && !can_be_sleepable(prog)) {
-		verbose(env, "Only fentry/fexit/fsession/fmod_ret, lsm, iter, uprobe, and struct_ops programs can be sleepable\n");
+		verbose(env, "Program of this type cannot be sleepable\n");
 		return -EINVAL;
 	}
 

-- 
2.52.0