From: Jarkko Sakkinen [mailto:jarkko@kernel.org] Sent: Tuesday, August 9, 2022 6:55 PM On Tue, Aug 09, 2022 at 03:45:54PM +0200, Roberto Sassu wrote:
From: Benjamin Tissoires benjamin.tissoires@redhat.com
From: Benjamin Tissoires benjamin.tissoires@redhat.com
This allows to declare a kfunc as sleepable and prevents its use in a non sleepable program.
Nit: "Declare a kfunc as sleepable and prevent its use in a non-sleepable program."
It's missing the part *how* the patch accomplishes its goals.
I will add:
If an eBPF program is going to call a kfunc declared as sleepable, eBPF will look at the eBPF program flags. If BPF_F_SLEEPABLE is not set, execution of that program is denied.
Roberto
Signed-off-by: Benjamin Tissoires benjamin.tissoires@redhat.com Co-developed-by: Yosry Ahmed yosryahmed@google.com Signed-off-by: Yosry Ahmed yosryahmed@google.com Signed-off-by: Hao Luo haoluo@google.com
Documentation/bpf/kfuncs.rst | 6 ++++++ include/linux/btf.h | 1 + kernel/bpf/btf.c | 9 +++++++++ 3 files changed, 16 insertions(+)
diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index c0b7dae6dbf5..c8b21de1c772 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -146,6 +146,12 @@ that operate (change some property, perform some
operation) on an object that
was obtained using an acquire kfunc. Such kfuncs need an unchanged pointer
to
ensure the integrity of the operation being performed on the expected object.
+2.4.6 KF_SLEEPABLE flag +-----------------------
+The KF_SLEEPABLE flag is used for kfuncs that may sleep. Such kfuncs can
only
+be called by sleepable BPF programs (BPF_F_SLEEPABLE).
2.5 Registering the kfuncs
diff --git a/include/linux/btf.h b/include/linux/btf.h index cdb376d53238..976cbdd2981f 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -49,6 +49,7 @@
- for this case.
*/ #define KF_TRUSTED_ARGS (1 << 4) /* kfunc only takes trusted pointer
arguments */
+#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
struct btf; struct btf_member; diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 7e64447659f3..d3e4c86b8fcd 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6175,6 +6175,7 @@ static int btf_check_func_arg_match(struct
bpf_verifier_env *env,
{ enum bpf_prog_type prog_type = resolve_prog_type(env->prog); bool rel = false, kptr_get = false, trusted_arg = false;
- bool sleepable = false; struct bpf_verifier_log *log = &env->log; u32 i, nargs, ref_id, ref_obj_id = 0; bool is_kfunc = btf_is_kernel(btf);
@@ -6212,6 +6213,7 @@ static int btf_check_func_arg_match(struct
bpf_verifier_env *env,
rel = kfunc_flags & KF_RELEASE; kptr_get = kfunc_flags & KF_KPTR_GET; trusted_arg = kfunc_flags & KF_TRUSTED_ARGS;
sleepable = kfunc_flags & KF_SLEEPABLE;}
/* check that BTF function arguments match actual types that the
@@ -6419,6 +6421,13 @@ static int btf_check_func_arg_match(struct
bpf_verifier_env *env,
func_name); return -EINVAL;}
- if (sleepable && !env->prog->aux->sleepable) {
bpf_log(log, "kernel function %s is sleepable but the program isnot\n",
func_name);return -EINVAL;- }
- /* returns argument register number > 0 in case of reference release
kfunc */
return rel ? ref_regno : 0; } -- 2.25.1
BR, Jarkko