Merge branch 'bpf-core changes for preparation of HID-bpf'

Benjamin Tissoires says:

====================

Hi,

well, given that the HID changes haven't moved a lot in the past
revisions and that I am cc-ing a bunch of people, I have dropped them
while we focus on the last 2 requirements in bpf-core changes.

I'll submit a HID targeted series when we get these in tree, which
would make things a lore more independent.

For reference, the whole reasons for these 2 main changes are at
https://lore.kernel.org/bpf/20220902132938.2409206-1-benjamin.tissoires@redhat.com/

Compared to v10 (in addition of dropping the HID changes), I have
changed the selftests so we can test both light skeletons and libbbpf
calls.

Cheers,
Benjamin
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -1944,13 +1944,22 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
 			   const char *func_name,
 			   struct btf_func_model *m);
 
+struct bpf_kfunc_arg_meta {
+	u64 r0_size;
+	bool r0_rdonly;
+	int ref_obj_id;
+	u32 flags;
+};
+
 struct bpf_reg_state;
 int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
 				struct bpf_reg_state *regs);
+int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
+			   struct bpf_reg_state *regs);
 int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
 			      const struct btf *btf, u32 func_id,
 			      struct bpf_reg_state *regs,
-			      u32 kfunc_flags);
+			      struct bpf_kfunc_arg_meta *meta);
 int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
 			  struct bpf_reg_state *reg);
 int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,

include/linux/bpf_verifier.h

@@ -598,6 +598,8 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 			    struct bpf_attach_target_info *tgt_info);
 void bpf_free_kfunc_btf_tab(struct bpf_kfunc_btf_tab *tab);
 
+int mark_chain_precision(struct bpf_verifier_env *env, int regno);
+
 #define BPF_BASE_TYPE_MASK	GENMASK(BPF_BASE_TYPE_BITS - 1, 0)
 
 /* extract base type from bpf_{arg, return, reg}_type. */

include/linux/btf.h

@@ -441,4 +441,14 @@ static inline int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dt
 }
 #endif
 
+static inline bool btf_type_is_struct_ptr(struct btf *btf, const struct btf_type *t)
+{
+	if (!btf_type_is_ptr(t))
+		return false;
+
+	t = btf_type_skip_modifiers(btf, t->type, NULL);
+
+	return btf_type_is_struct(t);
+}
+
 #endif

kernel/bpf/btf.c

@@ -208,7 +208,7 @@ enum btf_kfunc_hook {
 };
 
 enum {
-	BTF_KFUNC_SET_MAX_CNT = 32,
+	BTF_KFUNC_SET_MAX_CNT = 256,
 	BTF_DTOR_KFUNC_MAX_CNT = 256,
 };
 
@@ -6199,11 +6199,37 @@ static bool is_kfunc_arg_mem_size(const struct btf *btf,
 	return true;
 }
 
+static bool btf_is_kfunc_arg_mem_size(const struct btf *btf,
+				      const struct btf_param *arg,
+				      const struct bpf_reg_state *reg,
+				      const char *name)
+{
+	int len, target_len = strlen(name);
+	const struct btf_type *t;
+	const char *param_name;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
+		return false;
+
+	param_name = btf_name_by_offset(btf, arg->name_off);
+	if (str_is_empty(param_name))
+		return false;
+	len = strlen(param_name);
+	if (len != target_len)
+		return false;
+	if (strcmp(param_name, name))
+		return false;
+
+	return true;
+}
+
 static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				    const struct btf *btf, u32 func_id,
 				    struct bpf_reg_state *regs,
 				    bool ptr_to_mem_ok,
-				    u32 kfunc_flags)
+				    struct bpf_kfunc_arg_meta *kfunc_meta,
+				    bool processing_call)
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
 	bool rel = false, kptr_get = false, trusted_arg = false;
@@ -6240,12 +6266,12 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		return -EINVAL;
 	}
 
-	if (is_kfunc) {
+	if (is_kfunc && kfunc_meta) {
 		/* Only kfunc can be release func */
-		rel = kfunc_flags & KF_RELEASE;
-		kptr_get = kfunc_flags & KF_KPTR_GET;
-		trusted_arg = kfunc_flags & KF_TRUSTED_ARGS;
-		sleepable = kfunc_flags & KF_SLEEPABLE;
+		rel = kfunc_meta->flags & KF_RELEASE;
+		kptr_get = kfunc_meta->flags & KF_KPTR_GET;
+		trusted_arg = kfunc_meta->flags & KF_TRUSTED_ARGS;
+		sleepable = kfunc_meta->flags & KF_SLEEPABLE;
 	}
 
 	/* check that BTF function arguments match actual types that the
@@ -6258,6 +6284,38 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 
 		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
 		if (btf_type_is_scalar(t)) {
+			if (is_kfunc && kfunc_meta) {
+				bool is_buf_size = false;
+
+				/* check for any const scalar parameter of name "rdonly_buf_size"
+				 * or "rdwr_buf_size"
+				 */
+				if (btf_is_kfunc_arg_mem_size(btf, &args[i], reg,
+							      "rdonly_buf_size")) {
+					kfunc_meta->r0_rdonly = true;
+					is_buf_size = true;
+				} else if (btf_is_kfunc_arg_mem_size(btf, &args[i], reg,
+								     "rdwr_buf_size"))
+					is_buf_size = true;
+
+				if (is_buf_size) {
+					if (kfunc_meta->r0_size) {
+						bpf_log(log, "2 or more rdonly/rdwr_buf_size parameters for kfunc");
+						return -EINVAL;
+					}
+
+					if (!tnum_is_const(reg->var_off)) {
+						bpf_log(log, "R%d is not a const\n", regno);
+						return -EINVAL;
+					}
+
+					kfunc_meta->r0_size = reg->var_off.value;
+					ret = mark_chain_precision(env, regno);
+					if (ret)
+						return ret;
+				}
+			}
+
 			if (reg->type == SCALAR_VALUE)
 				continue;
 			bpf_log(log, "R%d is not a scalar\n", regno);
@@ -6288,6 +6346,17 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		if (ret < 0)
 			return ret;
 
+		if (is_kfunc && reg->ref_obj_id) {
+			/* Ensure only one argument is referenced PTR_TO_BTF_ID */
+			if (ref_obj_id) {
+				bpf_log(log, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
+					regno, reg->ref_obj_id, ref_obj_id);
+				return -EFAULT;
+			}
+			ref_regno = regno;
+			ref_obj_id = reg->ref_obj_id;
+		}
+
 		/* kptr_get is only true for kfunc */
 		if (i == 0 && kptr_get) {
 			struct bpf_map_value_off_desc *off_desc;
@@ -6360,16 +6429,6 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (reg->type == PTR_TO_BTF_ID) {
 				reg_btf = reg->btf;
 				reg_ref_id = reg->btf_id;
-				/* Ensure only one argument is referenced PTR_TO_BTF_ID */
-				if (reg->ref_obj_id) {
-					if (ref_obj_id) {
-						bpf_log(log, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
-							regno, reg->ref_obj_id, ref_obj_id);
-						return -EFAULT;
-					}
-					ref_regno = regno;
-					ref_obj_id = reg->ref_obj_id;
-				}
 			} else {
 				reg_btf = btf_vmlinux;
 				reg_ref_id = *reg2btf_ids[base_type(reg->type)];
@@ -6389,7 +6448,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					reg_ref_tname);
 				return -EINVAL;
 			}
-		} else if (ptr_to_mem_ok) {
+		} else if (ptr_to_mem_ok && processing_call) {
 			const struct btf_type *resolve_ret;
 			u32 type_size;
 
@@ -6460,11 +6519,14 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		return -EINVAL;
 	}
 
+	if (kfunc_meta && ref_obj_id)
+		kfunc_meta->ref_obj_id = ref_obj_id;
+
 	/* returns argument register number > 0 in case of reference release kfunc */
 	return rel ? ref_regno : 0;
 }
 
-/* Compare BTF of a function with given bpf_reg_state.
+/* Compare BTF of a function declaration with given bpf_reg_state.
  * Returns:
  * EFAULT - there is a verifier bug. Abort verification.
  * EINVAL - there is a type mismatch or BTF is not available.
@@ -6491,7 +6553,50 @@ int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
 		return -EINVAL;
 
 	is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
-	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, 0);
+	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, NULL, false);
+
+	/* Compiler optimizations can remove arguments from static functions
+	 * or mismatched type can be passed into a global function.
+	 * In such cases mark the function as unreliable from BTF point of view.
+	 */
+	if (err)
+		prog->aux->func_info_aux[subprog].unreliable = true;
+	return err;
+}
+
+/* Compare BTF of a function call with given bpf_reg_state.
+ * Returns:
+ * EFAULT - there is a verifier bug. Abort verification.
+ * EINVAL - there is a type mismatch or BTF is not available.
+ * 0 - BTF matches with what bpf_reg_state expects.
+ * Only PTR_TO_CTX and SCALAR_VALUE states are recognized.
+ *
+ * NOTE: the code is duplicated from btf_check_subprog_arg_match()
+ * because btf_check_func_arg_match() is still doing both. Once that
+ * function is split in 2, we can call from here btf_check_subprog_arg_match()
+ * first, and then treat the calling part in a new code path.
+ */
+int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
+			   struct bpf_reg_state *regs)
+{
+	struct bpf_prog *prog = env->prog;
+	struct btf *btf = prog->aux->btf;
+	bool is_global;
+	u32 btf_id;
+	int err;
+
+	if (!prog->aux->func_info)
+		return -EINVAL;
+
+	btf_id = prog->aux->func_info[subprog].type_id;
+	if (!btf_id)
+		return -EFAULT;
+
+	if (prog->aux->func_info_aux[subprog].unreliable)
+		return -EINVAL;
+
+	is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
+	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, NULL, true);
 
 	/* Compiler optimizations can remove arguments from static functions
 	 * or mismatched type can be passed into a global function.
@@ -6505,9 +6610,9 @@ int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
 int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
 			      const struct btf *btf, u32 func_id,
 			      struct bpf_reg_state *regs,
-			      u32 kfunc_flags)
+			      struct bpf_kfunc_arg_meta *meta)
 {
-	return btf_check_func_arg_match(env, btf, func_id, regs, true, kfunc_flags);
+	return btf_check_func_arg_match(env, btf, func_id, regs, true, meta, true);
 }
 
 /* Convert BTF of a function into bpf_reg_state if possible

kernel/bpf/verifier.c

@@ -2908,7 +2908,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 	return 0;
 }
 
-static int mark_chain_precision(struct bpf_verifier_env *env, int regno)
+int mark_chain_precision(struct bpf_verifier_env *env, int regno)
 {
 	return __mark_chain_precision(env, regno, -1);
 }
@@ -5233,6 +5233,25 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
 				env,
 				regno, reg->off, access_size,
 				zero_size_allowed, ACCESS_HELPER, meta);
+	case PTR_TO_CTX:
+		/* in case the function doesn't know how to access the context,
+		 * (because we are in a program of type SYSCALL for example), we
+		 * can not statically check its size.
+		 * Dynamically check it now.
+		 */
+		if (!env->ops->convert_ctx_access) {
+			enum bpf_access_type atype = meta && meta->raw_mode ? BPF_WRITE : BPF_READ;
+			int offset = access_size - 1;
+
+			/* Allow zero-byte read from PTR_TO_CTX */
+			if (access_size == 0)
+				return zero_size_allowed ? 0 : -EACCES;
+
+			return check_mem_access(env, env->insn_idx, regno, offset, BPF_B,
+						atype, -1, false);
+		}
+
+		fallthrough;
 	default: /* scalar_value or invalid ptr */
 		/* Allow zero-byte read from NULL, regardless of pointer type */
 		if (zero_size_allowed && access_size == 0 &&
@@ -6629,7 +6648,7 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	func_info_aux = env->prog->aux->func_info_aux;
 	if (func_info_aux)
 		is_global = func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
-	err = btf_check_subprog_arg_match(env, subprog, caller->regs);
+	err = btf_check_subprog_call(env, subprog, caller->regs);
 	if (err == -EFAULT)
 		return err;
 	if (is_global) {
@@ -7576,6 +7595,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 {
 	const struct btf_type *t, *func, *func_proto, *ptr_type;
 	struct bpf_reg_state *regs = cur_regs(env);
+	struct bpf_kfunc_arg_meta meta = { 0 };
 	const char *func_name, *ptr_type_name;
 	u32 i, nargs, func_id, ptr_type_id;
 	int err, insn_idx = *insn_idx_p;
@@ -7610,8 +7630,10 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 
 	acq = *kfunc_flags & KF_ACQUIRE;
 
+	meta.flags = *kfunc_flags;
+
 	/* Check the arguments */
-	err = btf_check_kfunc_arg_match(env, desc_btf, func_id, regs, *kfunc_flags);
+	err = btf_check_kfunc_arg_match(env, desc_btf, func_id, regs, &meta);
 	if (err < 0)
 		return err;
 	/* In case of release function, we get register number of refcounted
@@ -7632,7 +7654,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	/* Check return type */
 	t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
 
-	if (acq && !btf_type_is_ptr(t)) {
+	if (acq && !btf_type_is_struct_ptr(desc_btf, t)) {
 		verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
 		return -EINVAL;
 	}
@@ -7644,17 +7666,33 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		ptr_type = btf_type_skip_modifiers(desc_btf, t->type,
 						   &ptr_type_id);
 		if (!btf_type_is_struct(ptr_type)) {
-			ptr_type_name = btf_name_by_offset(desc_btf,
-							   ptr_type->name_off);
-			verbose(env, "kernel function %s returns pointer type %s %s is not supported\n",
-				func_name, btf_type_str(ptr_type),
-				ptr_type_name);
-			return -EINVAL;
+			if (!meta.r0_size) {
+				ptr_type_name = btf_name_by_offset(desc_btf,
+								   ptr_type->name_off);
+				verbose(env,
+					"kernel function %s returns pointer type %s %s is not supported\n",
+					func_name,
+					btf_type_str(ptr_type),
+					ptr_type_name);
+				return -EINVAL;
+			}
+
+			mark_reg_known_zero(env, regs, BPF_REG_0);
+			regs[BPF_REG_0].type = PTR_TO_MEM;
+			regs[BPF_REG_0].mem_size = meta.r0_size;
+
+			if (meta.r0_rdonly)
+				regs[BPF_REG_0].type |= MEM_RDONLY;
+
+			/* Ensures we don't access the memory after a release_reference() */
+			if (meta.ref_obj_id)
+				regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id;
+		} else {
+			mark_reg_known_zero(env, regs, BPF_REG_0);
+			regs[BPF_REG_0].btf = desc_btf;
+			regs[BPF_REG_0].type = PTR_TO_BTF_ID;
+			regs[BPF_REG_0].btf_id = ptr_type_id;
 		}
-		mark_reg_known_zero(env, regs, BPF_REG_0);
-		regs[BPF_REG_0].btf = desc_btf;
-		regs[BPF_REG_0].type = PTR_TO_BTF_ID;
-		regs[BPF_REG_0].btf_id = ptr_type_id;
 		if (*kfunc_flags & KF_RET_NULL) {
 			regs[BPF_REG_0].type |= PTR_MAYBE_NULL;
 			/* For mark_ptr_or_null_reg, see 93c230e3f5bd6 */

net/bpf/test_run.c

@@ -606,6 +606,38 @@ noinline void bpf_kfunc_call_memb1_release(struct prog_test_member1 *p)
 	WARN_ON_ONCE(1);
 }
 
+static int *__bpf_kfunc_call_test_get_mem(struct prog_test_ref_kfunc *p, const int size)
+{
+	if (size > 2 * sizeof(int))
+		return NULL;
+
+	return (int *)p;
+}
+
+noinline int *bpf_kfunc_call_test_get_rdwr_mem(struct prog_test_ref_kfunc *p, const int rdwr_buf_size)
+{
+	return __bpf_kfunc_call_test_get_mem(p, rdwr_buf_size);
+}
+
+noinline int *bpf_kfunc_call_test_get_rdonly_mem(struct prog_test_ref_kfunc *p, const int rdonly_buf_size)
+{
+	return __bpf_kfunc_call_test_get_mem(p, rdonly_buf_size);
+}
+
+/* the next 2 ones can't be really used for testing expect to ensure
+ * that the verifier rejects the call.
+ * Acquire functions must return struct pointers, so these ones are
+ * failing.
+ */
+noinline int *bpf_kfunc_call_test_acq_rdonly_mem(struct prog_test_ref_kfunc *p, const int rdonly_buf_size)
+{
+	return __bpf_kfunc_call_test_get_mem(p, rdonly_buf_size);
+}
+
+noinline void bpf_kfunc_call_int_mem_release(int *p)
+{
+}
+
 noinline struct prog_test_ref_kfunc *
 bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **pp, int a, int b)
 {
@@ -712,6 +744,10 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_memb_acquire, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_kfunc_call_memb_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_kfunc_call_memb1_release, KF_RELEASE)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test_get_rdwr_mem, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test_get_rdonly_mem, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test_acq_rdonly_mem, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_kfunc_call_int_mem_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_kptr_get, KF_ACQUIRE | KF_RET_NULL | KF_KPTR_GET)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_pass_ctx)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_pass1)
@@ -1634,6 +1670,7 @@ static int __init bpf_prog_test_run_init(void)
 
 	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_prog_test_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_prog_test_kfunc_set);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_prog_test_kfunc_set);
 	return ret ?: register_btf_id_dtor_kfuncs(bpf_prog_test_dtor_kfunc,
 						  ARRAY_SIZE(bpf_prog_test_dtor_kfunc),
 						  THIS_MODULE);

tools/testing/selftests/bpf/Makefile

@@ -351,11 +351,12 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h		\
 		test_subskeleton.skel.h test_subskeleton_lib.skel.h	\
 		test_usdt.skel.h
 
-LSKELS := kfunc_call_test.c fentry_test.c fexit_test.c fexit_sleep.c \
+LSKELS := fentry_test.c fexit_test.c fexit_sleep.c \
 	test_ringbuf.c atomics.c trace_printk.c trace_vprintk.c \
 	map_ptr_kern.c core_kern.c core_kern_overflow.c
 # Generate both light skeleton and libbpf skeleton for these
-LSKELS_EXTRA := test_ksyms_module.c test_ksyms_weak.c kfunc_call_test_subprog.c
+LSKELS_EXTRA := test_ksyms_module.c test_ksyms_weak.c kfunc_call_test.c \
+	kfunc_call_test_subprog.c
 SKEL_BLACKLIST += $$(LSKELS)
 
 test_static_linked.skel.h-deps := test_static_linked1.bpf.o test_static_linked2.bpf.o

tools/testing/selftests/bpf/prog_tests/kfunc_call.c

@@ -2,6 +2,8 @@
 /* Copyright (c) 2021 Facebook */
 #include <test_progs.h>
 #include <network_helpers.h>
+#include "kfunc_call_fail.skel.h"
+#include "kfunc_call_test.skel.h"
 #include "kfunc_call_test.lskel.h"
 #include "kfunc_call_test_subprog.skel.h"
 #include "kfunc_call_test_subprog.lskel.h"
@@ -9,36 +11,220 @@
 
 #include "cap_helpers.h"
 
-static void test_main(void)
-{
-	struct kfunc_call_test_lskel *skel;
-	int prog_fd, err;
-	LIBBPF_OPTS(bpf_test_run_opts, topts,
-		.data_in = &pkt_v4,
-		.data_size_in = sizeof(pkt_v4),
-		.repeat = 1,
-	);
+static size_t log_buf_sz = 1048576; /* 1 MB */
+static char obj_log_buf[1048576];
 
-	skel = kfunc_call_test_lskel__open_and_load();
+enum kfunc_test_type {
+	tc_test = 0,
+	syscall_test,
+	syscall_null_ctx_test,
+};
+
+struct kfunc_test_params {
+	const char *prog_name;
+	unsigned long lskel_prog_desc_offset;
+	int retval;
+	enum kfunc_test_type test_type;
+	const char *expected_err_msg;
+};
+
+#define __BPF_TEST_SUCCESS(name, __retval, type) \
+	{ \
+	  .prog_name = #name, \
+	  .lskel_prog_desc_offset = offsetof(struct kfunc_call_test_lskel, progs.name), \
+	  .retval = __retval, \
+	  .test_type = type, \
+	  .expected_err_msg = NULL, \
+	}
+
+#define __BPF_TEST_FAIL(name, __retval, type, error_msg) \
+	{ \
+	  .prog_name = #name, \
+	  .lskel_prog_desc_offset = 0 /* unused when test is failing */, \
+	  .retval = __retval, \
+	  .test_type = type, \
+	  .expected_err_msg = error_msg, \
+	}
+
+#define TC_TEST(name, retval) __BPF_TEST_SUCCESS(name, retval, tc_test)
+#define SYSCALL_TEST(name, retval) __BPF_TEST_SUCCESS(name, retval, syscall_test)
+#define SYSCALL_NULL_CTX_TEST(name, retval) __BPF_TEST_SUCCESS(name, retval, syscall_null_ctx_test)
+
+#define TC_FAIL(name, retval, error_msg) __BPF_TEST_FAIL(name, retval, tc_test, error_msg)
+#define SYSCALL_NULL_CTX_FAIL(name, retval, error_msg) \
+	__BPF_TEST_FAIL(name, retval, syscall_null_ctx_test, error_msg)
+
+static struct kfunc_test_params kfunc_tests[] = {
+	/* failure cases:
+	 * if retval is 0 -> the program will fail to load and the error message is an error
+	 * if retval is not 0 -> the program can be loaded but running it will gives the
+	 *                       provided return value. The error message is thus the one
+	 *                       from a successful load
+	 */
+	SYSCALL_NULL_CTX_FAIL(kfunc_syscall_test_fail, -EINVAL, "processed 4 insns"),
+	SYSCALL_NULL_CTX_FAIL(kfunc_syscall_test_null_fail, -EINVAL, "processed 4 insns"),
+	TC_FAIL(kfunc_call_test_get_mem_fail_rdonly, 0, "R0 cannot write into rdonly_mem"),
+	TC_FAIL(kfunc_call_test_get_mem_fail_use_after_free, 0, "invalid mem access 'scalar'"),
+	TC_FAIL(kfunc_call_test_get_mem_fail_oob, 0, "min value is outside of the allowed memory range"),
+	TC_FAIL(kfunc_call_test_get_mem_fail_not_const, 0, "is not a const"),
+	TC_FAIL(kfunc_call_test_mem_acquire_fail, 0, "acquire kernel function does not return PTR_TO_BTF_ID"),
+
+	/* success cases */
+	TC_TEST(kfunc_call_test1, 12),
+	TC_TEST(kfunc_call_test2, 3),
+	TC_TEST(kfunc_call_test_ref_btf_id, 0),
+	TC_TEST(kfunc_call_test_get_mem, 42),
+	SYSCALL_TEST(kfunc_syscall_test, 0),
+	SYSCALL_NULL_CTX_TEST(kfunc_syscall_test_null, 0),
+};
+
+struct syscall_test_args {
+	__u8 data[16];
+	size_t size;
+};
+
+static void verify_success(struct kfunc_test_params *param)
+{
+	struct kfunc_call_test_lskel *lskel = NULL;
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct bpf_prog_desc *lskel_prog;
+	struct kfunc_call_test *skel;
+	struct bpf_program *prog;
+	int prog_fd, err;
+	struct syscall_test_args args = {
+		.size = 10,
+	};
+
+	switch (param->test_type) {
+	case syscall_test:
+		topts.ctx_in = &args;
+		topts.ctx_size_in = sizeof(args);
+		/* fallthrough */
+	case syscall_null_ctx_test:
+		break;
+	case tc_test:
+		topts.data_in = &pkt_v4;
+		topts.data_size_in = sizeof(pkt_v4);
+		topts.repeat = 1;
+		break;
+	}
+
+	/* first test with normal libbpf */
+	skel = kfunc_call_test__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "skel"))
 		return;
 
-	prog_fd = skel->progs.kfunc_call_test1.prog_fd;
-	err = bpf_prog_test_run_opts(prog_fd, &topts);
-	ASSERT_OK(err, "bpf_prog_test_run(test1)");
-	ASSERT_EQ(topts.retval, 12, "test1-retval");
+	prog = bpf_object__find_program_by_name(skel->obj, param->prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto cleanup;
 
-	prog_fd = skel->progs.kfunc_call_test2.prog_fd;
+	prog_fd = bpf_program__fd(prog);
 	err = bpf_prog_test_run_opts(prog_fd, &topts);
-	ASSERT_OK(err, "bpf_prog_test_run(test2)");
-	ASSERT_EQ(topts.retval, 3, "test2-retval");
+	if (!ASSERT_OK(err, param->prog_name))
+		goto cleanup;
 
-	prog_fd = skel->progs.kfunc_call_test_ref_btf_id.prog_fd;
+	if (!ASSERT_EQ(topts.retval, param->retval, "retval"))
+		goto cleanup;
+
+	/* second test with light skeletons */
+	lskel = kfunc_call_test_lskel__open_and_load();
+	if (!ASSERT_OK_PTR(lskel, "lskel"))
+		goto cleanup;
+
+	lskel_prog = (struct bpf_prog_desc *)((char *)lskel + param->lskel_prog_desc_offset);
+
+	prog_fd = lskel_prog->prog_fd;
 	err = bpf_prog_test_run_opts(prog_fd, &topts);
-	ASSERT_OK(err, "bpf_prog_test_run(test_ref_btf_id)");
-	ASSERT_EQ(topts.retval, 0, "test_ref_btf_id-retval");
+	if (!ASSERT_OK(err, param->prog_name))
+		goto cleanup;
 
-	kfunc_call_test_lskel__destroy(skel);
+	ASSERT_EQ(topts.retval, param->retval, "retval");
+
+cleanup:
+	kfunc_call_test__destroy(skel);
+	if (lskel)
+		kfunc_call_test_lskel__destroy(lskel);
+}
+
+static void verify_fail(struct kfunc_test_params *param)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct bpf_program *prog;
+	struct kfunc_call_fail *skel;
+	int prog_fd, err;
+	struct syscall_test_args args = {
+		.size = 10,
+	};
+
+	opts.kernel_log_buf = obj_log_buf;
+	opts.kernel_log_size = log_buf_sz;
+	opts.kernel_log_level = 1;
+
+	switch (param->test_type) {
+	case syscall_test:
+		topts.ctx_in = &args;
+		topts.ctx_size_in = sizeof(args);
+		/* fallthrough */
+	case syscall_null_ctx_test:
+		break;
+	case tc_test:
+		topts.data_in = &pkt_v4;
+		topts.data_size_in = sizeof(pkt_v4);
+		break;
+		topts.repeat = 1;
+	}
+
+	skel = kfunc_call_fail__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "kfunc_call_fail__open_opts"))
+		goto cleanup;
+
+	prog = bpf_object__find_program_by_name(skel->obj, param->prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto cleanup;
+
+	bpf_program__set_autoload(prog, true);
+
+	err = kfunc_call_fail__load(skel);
+	if (!param->retval) {
+		/* the verifier is supposed to complain and refuses to load */
+		if (!ASSERT_ERR(err, "unexpected load success"))
+			goto out_err;
+
+	} else {
+		/* the program is loaded but must dynamically fail */
+		if (!ASSERT_OK(err, "unexpected load error"))
+			goto out_err;
+
+		prog_fd = bpf_program__fd(prog);
+		err = bpf_prog_test_run_opts(prog_fd, &topts);
+		if (!ASSERT_EQ(err, param->retval, param->prog_name))
+			goto out_err;
+	}
+
+out_err:
+	if (!ASSERT_OK_PTR(strstr(obj_log_buf, param->expected_err_msg), "expected_err_msg")) {
+		fprintf(stderr, "Expected err_msg: %s\n", param->expected_err_msg);
+		fprintf(stderr, "Verifier output: %s\n", obj_log_buf);
+	}
+
+cleanup:
+	kfunc_call_fail__destroy(skel);
+}
+
+static void test_main(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(kfunc_tests); i++) {
+		if (!test__start_subtest(kfunc_tests[i].prog_name))
+			continue;
+
+		if (!kfunc_tests[i].expected_err_msg)
+			verify_success(&kfunc_tests[i]);
+		else
+			verify_fail(&kfunc_tests[i]);
+	}
 }
 
 static void test_subprog(void)
@@ -121,8 +307,7 @@ static void test_destructive(void)
 
 void test_kfunc_call(void)
 {
-	if (test__start_subtest("main"))
-		test_main();
+	test_main();
 
 	if (test__start_subtest("subprog"))
 		test_subprog();

tools/testing/selftests/bpf/progs/kfunc_call_fail.c

@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+
+extern struct prog_test_ref_kfunc *bpf_kfunc_call_test_acquire(unsigned long *sp) __ksym;
+extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
+extern void bpf_kfunc_call_test_mem_len_pass1(void *mem, int len) __ksym;
+extern int *bpf_kfunc_call_test_get_rdwr_mem(struct prog_test_ref_kfunc *p, const int rdwr_buf_size) __ksym;
+extern int *bpf_kfunc_call_test_get_rdonly_mem(struct prog_test_ref_kfunc *p, const int rdonly_buf_size) __ksym;
+extern int *bpf_kfunc_call_test_acq_rdonly_mem(struct prog_test_ref_kfunc *p, const int rdonly_buf_size) __ksym;
+extern void bpf_kfunc_call_int_mem_release(int *p) __ksym;
+
+struct syscall_test_args {
+	__u8 data[16];
+	size_t size;
+};
+
+SEC("?syscall")
+int kfunc_syscall_test_fail(struct syscall_test_args *args)
+{
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args) + 1);
+
+	return 0;
+}
+
+SEC("?syscall")
+int kfunc_syscall_test_null_fail(struct syscall_test_args *args)
+{
+	/* Must be called with args as a NULL pointer
+	 * we do not check for it to have the verifier consider that
+	 * the pointer might not be null, and so we can load it.
+	 *
+	 * So the following can not be added:
+	 *
+	 * if (args)
+	 *      return -22;
+	 */
+
+	bpf_kfunc_call_test_mem_len_pass1(args, sizeof(*args));
+
+	return 0;
+}
+
+SEC("?tc")
+int kfunc_call_test_get_mem_fail_rdonly(struct __sk_buff *skb)
+{
+	struct prog_test_ref_kfunc *pt;
+	unsigned long s = 0;
+	int *p = NULL;
+	int ret = 0;
+
+	pt = bpf_kfunc_call_test_acquire(&s);
+	if (pt) {
+		p = bpf_kfunc_call_test_get_rdonly_mem(pt, 2 * sizeof(int));
+		if (p)
+			p[0] = 42; /* this is a read-only buffer, so -EACCES */
+		else
+			ret = -1;
+
+		bpf_kfunc_call_test_release(pt);
+	}
+	return ret;
+}
+
+SEC("?tc")
+int kfunc_call_test_get_mem_fail_use_after_free(struct __sk_buff *skb)
+{
+	struct prog_test_ref_kfunc *pt;
+	unsigned long s = 0;
+	int *p = NULL;
+	int ret = 0;
+
+	pt = bpf_kfunc_call_test_acquire(&s);
+	if (pt) {
+		p = bpf_kfunc_call_test_get_rdwr_mem(pt, 2 * sizeof(int));
+		if (p) {
+			p[0] = 42;
+			ret = p[1]; /* 108 */
+		} else {
+			ret = -1;
+		}
+
+		bpf_kfunc_call_test_release(pt);
+	}
+	if (p)
+		ret = p[0]; /* p is not valid anymore */
+
+	return ret;
+}
+
+SEC("?tc")
+int kfunc_call_test_get_mem_fail_oob(struct __sk_buff *skb)
+{
+	struct prog_test_ref_kfunc *pt;
+	unsigned long s = 0;
+	int *p = NULL;
+	int ret = 0;
+
+	pt = bpf_kfunc_call_test_acquire(&s);
+	if (pt) {
+		p = bpf_kfunc_call_test_get_rdonly_mem(pt, 2 * sizeof(int));
+		if (p)
+			ret = p[2 * sizeof(int)]; /* oob access, so -EACCES */
+		else
+			ret = -1;
+
+		bpf_kfunc_call_test_release(pt);
+	}
+	return ret;
+}
+
+int not_const_size = 2 * sizeof(int);
+
+SEC("?tc")
+int kfunc_call_test_get_mem_fail_not_const(struct __sk_buff *skb)
+{
+	struct prog_test_ref_kfunc *pt;
+	unsigned long s = 0;
+	int *p = NULL;
+	int ret = 0;
+
+	pt = bpf_kfunc_call_test_acquire(&s);
+	if (pt) {
+		p = bpf_kfunc_call_test_get_rdonly_mem(pt, not_const_size); /* non const size, -EINVAL */
+		if (p)
+			ret = p[0];
+		else
+			ret = -1;
+
+		bpf_kfunc_call_test_release(pt);
+	}
+	return ret;
+}
+
+SEC("?tc")
+int kfunc_call_test_mem_acquire_fail(struct __sk_buff *skb)
+{
+	struct prog_test_ref_kfunc *pt;
+	unsigned long s = 0;
+	int *p = NULL;
+	int ret = 0;
+
+	pt = bpf_kfunc_call_test_acquire(&s);
+	if (pt) {
+		/* we are failing on this one, because we are not acquiring a PTR_TO_BTF_ID (a struct ptr) */
+		p = bpf_kfunc_call_test_acq_rdonly_mem(pt, 2 * sizeof(int));
+		if (p)
+			ret = p[0];
+		else
+			ret = -1;
+
+		bpf_kfunc_call_int_mem_release(p);
+
+		bpf_kfunc_call_test_release(pt);
+	}
+	return ret;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/kfunc_call_test.c

@@ -14,6 +14,8 @@ extern void bpf_kfunc_call_test_pass1(struct prog_test_pass1 *p) __ksym;
 extern void bpf_kfunc_call_test_pass2(struct prog_test_pass2 *p) __ksym;
 extern void bpf_kfunc_call_test_mem_len_pass1(void *mem, int len) __ksym;
 extern void bpf_kfunc_call_test_mem_len_fail2(__u64 *mem, int len) __ksym;
+extern int *bpf_kfunc_call_test_get_rdwr_mem(struct prog_test_ref_kfunc *p, const int rdwr_buf_size) __ksym;
+extern int *bpf_kfunc_call_test_get_rdonly_mem(struct prog_test_ref_kfunc *p, const int rdonly_buf_size) __ksym;
 
 SEC("tc")
 int kfunc_call_test2(struct __sk_buff *skb)
@@ -92,4 +94,73 @@ int kfunc_call_test_pass(struct __sk_buff *skb)
 	return 0;
 }
 
+struct syscall_test_args {
+	__u8 data[16];
+	size_t size;
+};
+
+SEC("syscall")
+int kfunc_syscall_test(struct syscall_test_args *args)
+{
+	const long size = args->size;
+
+	if (size > sizeof(args->data))
+		return -7; /* -E2BIG */
+
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(args->data));
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args));
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, size);
+
+	return 0;
+}
+
+SEC("syscall")
+int kfunc_syscall_test_null(struct syscall_test_args *args)
+{
+	/* Must be called with args as a NULL pointer
+	 * we do not check for it to have the verifier consider that
+	 * the pointer might not be null, and so we can load it.
+	 *
+	 * So the following can not be added:
+	 *
+	 * if (args)
+	 *      return -22;
+	 */
+
+	bpf_kfunc_call_test_mem_len_pass1(args, 0);
+
+	return 0;
+}
+
+SEC("tc")
+int kfunc_call_test_get_mem(struct __sk_buff *skb)
+{
+	struct prog_test_ref_kfunc *pt;
+	unsigned long s = 0;
+	int *p = NULL;
+	int ret = 0;
+
+	pt = bpf_kfunc_call_test_acquire(&s);
+	if (pt) {
+		p = bpf_kfunc_call_test_get_rdwr_mem(pt, 2 * sizeof(int));
+		if (p) {
+			p[0] = 42;
+			ret = p[1]; /* 108 */
+		} else {
+			ret = -1;
+		}
+
+		if (ret >= 0) {
+			p = bpf_kfunc_call_test_get_rdonly_mem(pt, 2 * sizeof(int));
+			if (p)
+				ret = p[0]; /* 42 */
+			else
+				ret = -1;
+		}
+
+		bpf_kfunc_call_test_release(pt);
+	}
+	return ret;
+}
+
 char _license[] SEC("license") = "GPL";