Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Alexei Starovoitov says:

====================
1) libbpf should not attempt to load unused subprogs, from Andrii.

2) Make strncpy_from_user() mask out bytes after NUL terminator, from Daniel.

3) Relax return code check for subprograms in the BPF verifier, from Dmitrii.

4) Fix several sockmap issues, from John.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
  fail_function: Remove a redundant mutex unlock
  selftest/bpf: Test bpf_probe_read_user_str() strips trailing bytes after NUL
  lib/strncpy_from_user.c: Mask out bytes after NUL terminator.
  libbpf: Fix VERSIONED_SYM_COUNT number parsing
  bpf, sockmap: Avoid failures from skb_to_sgvec when skb has frag_list
  bpf, sockmap: Handle memory acct if skb_verdict prog redirects to self
  bpf, sockmap: Avoid returning unneeded EAGAIN when redirecting to self
  bpf, sockmap: Use truesize with sk_rmem_schedule()
  bpf, sockmap: Ensure SO_RCVBUF memory is observed on ingress redirect
  bpf, sockmap: Fix partial copy_page_to_iter so progress can still be made
  selftests/bpf: Fix error return code in run_getsockopt_test()
  bpf: Relax return code check for subprograms
  tools, bpftool: Add missing close before bpftool net attach exit
  MAINTAINERS/bpf: Update Andrii's entry.
  selftests/bpf: Fix unused attribute usage in subprogs_unused test
  bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id
  bpf: Fix passing zero to PTR_ERR() in bpf_btf_printf_prepare
  libbpf: Don't attempt to load unused subprog as an entry-point BPF program
====================

Link: https://lore.kernel.org/r/20201119200721.288-1-alexei.starovoitov@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

MAINTAINERS

@@ -3243,10 +3243,10 @@ F:	drivers/iio/accel/bma400*
 BPF (Safe dynamic programs and tools)
 M:	Alexei Starovoitov <ast@kernel.org>
 M:	Daniel Borkmann <daniel@iogearbox.net>
+M:	Andrii Nakryiko <andrii@kernel.org>
 R:	Martin KaFai Lau <kafai@fb.com>
 R:	Song Liu <songliubraving@fb.com>
 R:	Yonghong Song <yhs@fb.com>
-R:	Andrii Nakryiko <andrii@kernel.org>
 R:	John Fastabend <john.fastabend@gmail.com>
 R:	KP Singh <kpsingh@chromium.org>
 L:	netdev@vger.kernel.org

kernel/bpf/verifier.c

@@ -7786,9 +7786,11 @@ static int check_return_code(struct bpf_verifier_env *env)
 	struct tnum range = tnum_range(0, 1);
 	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
 	int err;
+	const bool is_subprog = env->cur_state->frame[0]->subprogno;
 
 	/* LSM and struct_ops func-ptr's return type could be "void" */
-	if ((prog_type == BPF_PROG_TYPE_STRUCT_OPS ||
+	if (!is_subprog &&
+	    (prog_type == BPF_PROG_TYPE_STRUCT_OPS ||
 	     prog_type == BPF_PROG_TYPE_LSM) &&
 	    !prog->aux->attach_func_proto->type)
 		return 0;
@@ -7808,6 +7810,16 @@ static int check_return_code(struct bpf_verifier_env *env)
 		return -EACCES;
 	}
 
+	reg = cur_regs(env) + BPF_REG_0;
+	if (is_subprog) {
+		if (reg->type != SCALAR_VALUE) {
+			verbose(env, "At subprogram exit the register R0 is not a scalar value (%s)\n",
+				reg_type_str[reg->type]);
+			return -EINVAL;
+		}
+		return 0;
+	}
+
 	switch (prog_type) {
 	case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
 		if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
@@ -7861,7 +7873,6 @@ static int check_return_code(struct bpf_verifier_env *env)
 		return 0;
 	}
 
-	reg = cur_regs(env) + BPF_REG_0;
 	if (reg->type != SCALAR_VALUE) {
 		verbose(env, "At program exit the register R0 is not a known value (%s)\n",
 			reg_type_str[reg->type]);
@@ -9572,12 +9583,13 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
 			       struct bpf_insn *insn,
 			       struct bpf_insn_aux_data *aux)
 {
-	u32 datasec_id, type, id = insn->imm;
 	const struct btf_var_secinfo *vsi;
 	const struct btf_type *datasec;
 	const struct btf_type *t;
 	const char *sym_name;
 	bool percpu = false;
+	u32 type, id = insn->imm;
+	s32 datasec_id;
 	u64 addr;
 	int i;
 

kernel/fail_function.c

@@ -253,7 +253,7 @@ static ssize_t fei_write(struct file *file, const char __user *buffer,
 
 	if (copy_from_user(buf, buffer, count)) {
 		ret = -EFAULT;
-		goto out;
+		goto out_free;
 	}
 	buf[count] = '\0';
 	sym = strstrip(buf);
@@ -307,8 +307,9 @@ static ssize_t fei_write(struct file *file, const char __user *buffer,
 		ret = count;
 	}
 out:
-	kfree(buf);
 	mutex_unlock(&fei_lock);
+out_free:
+	kfree(buf);
 	return ret;
 }
 

kernel/trace/bpf_trace.c

@@ -181,6 +181,16 @@ bpf_probe_read_user_str_common(void *dst, u32 size,
 {
 	int ret;
 
+	/*
+	 * NB: We rely on strncpy_from_user() not copying junk past the NUL
+	 * terminator into `dst`.
+	 *
+	 * strncpy_from_user() does long-sized strides in the fast path. If the
+	 * strncpy does not mask out the bytes after the NUL in `unsafe_ptr`,
+	 * then there could be junk after the NUL in `dst`. If user takes `dst`
+	 * and keys a hash map with it, then semantically identical strings can
+	 * occupy multiple entries in the map.
+	 */
 	ret = strncpy_from_user_nofault(dst, unsafe_ptr, size);
 	if (unlikely(ret < 0))
 		memset(dst, 0, size);
@@ -1198,7 +1208,7 @@ static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
 	*btf = bpf_get_btf_vmlinux();
 
 	if (IS_ERR_OR_NULL(*btf))
-		return PTR_ERR(*btf);
+		return IS_ERR(*btf) ? PTR_ERR(*btf) : -EINVAL;
 
 	if (ptr->type_id > 0)
 		*btf_id = ptr->type_id;

lib/strncpy_from_user.c

@@ -35,17 +35,32 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src,
 		goto byte_at_a_time;
 
 	while (max >= sizeof(unsigned long)) {
-		unsigned long c, data;
+		unsigned long c, data, mask;
 
 		/* Fall back to byte-at-a-time if we get a page fault */
 		unsafe_get_user(c, (unsigned long __user *)(src+res), byte_at_a_time);
 
-		*(unsigned long *)(dst+res) = c;
+		/*
+		 * Note that we mask out the bytes following the NUL. This is
+		 * important to do because string oblivious code may read past
+		 * the NUL. For those routines, we don't want to give them
+		 * potentially random bytes after the NUL in `src`.
+		 *
+		 * One example of such code is BPF map keys. BPF treats map keys
+		 * as an opaque set of bytes. Without the post-NUL mask, any BPF
+		 * maps keyed by strings returned from strncpy_from_user() may
+		 * have multiple entries for semantically identical strings.
+		 */
 		if (has_zero(c, &data, &constants)) {
 			data = prep_zero_mask(c, data, &constants);
 			data = create_zero_mask(data);
+			mask = zero_bytemask(data);
+			*(unsigned long *)(dst+res) = c & mask;
 			return res + find_zero(data);
 		}
+
+		*(unsigned long *)(dst+res) = c;
+
 		res += sizeof(unsigned long);
 		max -= sizeof(unsigned long);
 	}

net/core/skmsg.c

@@ -170,10 +170,12 @@ static int sk_msg_free_elem(struct sock *sk, struct sk_msg *msg, u32 i,
 	struct scatterlist *sge = sk_msg_elem(msg, i);
 	u32 len = sge->length;
 
+	/* When the skb owns the memory we free it from consume_skb path. */
+	if (!msg->skb) {
 		if (charge)
 			sk_mem_uncharge(sk, len);
-	if (!msg->skb)
 		put_page(sg_page(sge));
+	}
 	memset(sge, 0, sizeof(*sge));
 	return len;
 }
@@ -397,28 +399,45 @@ out:
 }
 EXPORT_SYMBOL_GPL(sk_msg_memcopy_from_iter);
 
-static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
+static struct sk_msg *sk_psock_create_ingress_msg(struct sock *sk,
+						  struct sk_buff *skb)
 {
-	struct sock *sk = psock->sk;
-	int copied = 0, num_sge;
 	struct sk_msg *msg;
 
+	if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
+		return NULL;
+
+	if (!sk_rmem_schedule(sk, skb, skb->truesize))
+		return NULL;
+
 	msg = kzalloc(sizeof(*msg), __GFP_NOWARN | GFP_ATOMIC);
 	if (unlikely(!msg))
-		return -EAGAIN;
-	if (!sk_rmem_schedule(sk, skb, skb->len)) {
-		kfree(msg);
-		return -EAGAIN;
-	}
+		return NULL;
 
 	sk_msg_init(msg);
+	return msg;
+}
+
+static int sk_psock_skb_ingress_enqueue(struct sk_buff *skb,
+					struct sk_psock *psock,
+					struct sock *sk,
+					struct sk_msg *msg)
+{
+	int num_sge, copied;
+
+	/* skb linearize may fail with ENOMEM, but lets simply try again
+	 * later if this happens. Under memory pressure we don't want to
+	 * drop the skb. We need to linearize the skb so that the mapping
+	 * in skb_to_sgvec can not error.
+	 */
+	if (skb_linearize(skb))
+		return -EAGAIN;
 	num_sge = skb_to_sgvec(skb, msg->sg.data, 0, skb->len);
 	if (unlikely(num_sge < 0)) {
 		kfree(msg);
 		return num_sge;
 	}
 
-	sk_mem_charge(sk, skb->len);
 	copied = skb->len;
 	msg->sg.start = 0;
 	msg->sg.size = copied;
@@ -430,6 +449,48 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
 	return copied;
 }
 
+static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buff *skb);
+
+static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
+{
+	struct sock *sk = psock->sk;
+	struct sk_msg *msg;
+
+	/* If we are receiving on the same sock skb->sk is already assigned,
+	 * skip memory accounting and owner transition seeing it already set
+	 * correctly.
+	 */
+	if (unlikely(skb->sk == sk))
+		return sk_psock_skb_ingress_self(psock, skb);
+	msg = sk_psock_create_ingress_msg(sk, skb);
+	if (!msg)
+		return -EAGAIN;
+
+	/* This will transition ownership of the data from the socket where
+	 * the BPF program was run initiating the redirect to the socket
+	 * we will eventually receive this data on. The data will be released
+	 * from skb_consume found in __tcp_bpf_recvmsg() after its been copied
+	 * into user buffers.
+	 */
+	skb_set_owner_r(skb, sk);
+	return sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+}
+
+/* Puts an skb on the ingress queue of the socket already assigned to the
+ * skb. In this case we do not need to check memory limits or skb_set_owner_r
+ * because the skb is already accounted for here.
+ */
+static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buff *skb)
+{
+	struct sk_msg *msg = kzalloc(sizeof(*msg), __GFP_NOWARN | GFP_ATOMIC);
+	struct sock *sk = psock->sk;
+
+	if (unlikely(!msg))
+		return -EAGAIN;
+	sk_msg_init(msg);
+	return sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+}
+
 static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
 			       u32 off, u32 len, bool ingress)
 {
@@ -789,7 +850,7 @@ static void sk_psock_verdict_apply(struct sk_psock *psock,
 		 * retrying later from workqueue.
 		 */
 		if (skb_queue_empty(&psock->ingress_skb)) {
-			err = sk_psock_skb_ingress(psock, skb);
+			err = sk_psock_skb_ingress_self(psock, skb);
 		}
 		if (err < 0) {
 			skb_queue_tail(&psock->ingress_skb, skb);

net/ipv4/tcp_bpf.c

@@ -15,8 +15,8 @@ int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
 {
 	struct iov_iter *iter = &msg->msg_iter;
 	int peek = flags & MSG_PEEK;
-	int i, ret, copied = 0;
 	struct sk_msg *msg_rx;
+	int i, copied = 0;
 
 	msg_rx = list_first_entry_or_null(&psock->ingress_msg,
 					  struct sk_msg, list);
@@ -37,16 +37,15 @@ int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
 			page = sg_page(sge);
 			if (copied + copy > len)
 				copy = len - copied;
-			ret = copy_page_to_iter(page, sge->offset, copy, iter);
-			if (ret != copy) {
-				msg_rx->sg.start = i;
-				return -EFAULT;
-			}
+			copy = copy_page_to_iter(page, sge->offset, copy, iter);
+			if (!copy)
+				return copied ? copied : -EFAULT;
 
 			copied += copy;
 			if (likely(!peek)) {
 				sge->offset += copy;
 				sge->length -= copy;
+				if (!msg_rx->skb)
 					sk_mem_uncharge(sk, copy);
 				msg_rx->sg.size -= copy;
 
@@ -56,6 +55,11 @@ int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
 						put_page(page);
 				}
 			} else {
+				/* Lets not optimize peek case if copy_page_to_iter
+				 * didn't copy the entire length lets just break.
+				 */
+				if (copy != sge->length)
+					return copied;
 				sk_msg_iter_var_next(i);
 			}
 

tools/bpf/bpftool/net.c

@@ -578,8 +578,8 @@ static int do_attach(int argc, char **argv)
 
 	ifindex = net_parse_dev(&argc, &argv);
 	if (ifindex < 1) {
-		close(progfd);
-		return -EINVAL;
+		err = -EINVAL;
+		goto cleanup;
 	}
 
 	if (argc) {
@@ -587,8 +587,8 @@ static int do_attach(int argc, char **argv)
 			overwrite = true;
 		} else {
 			p_err("expected 'overwrite', got: '%s'?", *argv);
-			close(progfd);
-			return -EINVAL;
+			err = -EINVAL;
+			goto cleanup;
 		}
 	}
 
@@ -596,17 +596,17 @@ static int do_attach(int argc, char **argv)
 	if (is_prefix("xdp", attach_type_strings[attach_type]))
 		err = do_attach_detach_xdp(progfd, attach_type, ifindex,
 					   overwrite);
-
-	if (err < 0) {
+	if (err) {
 		p_err("interface %s attach failed: %s",
 		      attach_type_strings[attach_type], strerror(-err));
-		return err;
+		goto cleanup;
 	}
 
 	if (json_output)
 		jsonw_null(json_wtr);
-
-	return 0;
+cleanup:
+	close(progfd);
+	return err;
 }
 
 static int do_detach(int argc, char **argv)

tools/lib/bpf/Makefile

@@ -146,6 +146,7 @@ GLOBAL_SYM_COUNT = $(shell readelf -s --wide $(BPF_IN_SHARED) | \
 			   awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
 			   sort -u | wc -l)
 VERSIONED_SYM_COUNT = $(shell readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
+			      sed 's/\[.*\]//' | \
 			      awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
 			      grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | sort -u | wc -l)
 
@@ -214,6 +215,7 @@ check_abi: $(OUTPUT)libbpf.so
 		    awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'|  \
 		    sort -u > $(OUTPUT)libbpf_global_syms.tmp;		 \
 		readelf --dyn-syms --wide $(OUTPUT)libbpf.so |		 \
+		    sed 's/\[.*\]//' |					 \
 		    awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'|  \
 		    grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 |		 \
 		    sort -u > $(OUTPUT)libbpf_versioned_syms.tmp; 	 \

tools/lib/bpf/libbpf.c

@@ -560,8 +560,6 @@ bpf_object__init_prog(struct bpf_object *obj, struct bpf_program *prog,
 		      const char *name, size_t sec_idx, const char *sec_name,
 		      size_t sec_off, void *insn_data, size_t insn_data_sz)
 {
-	int i;
-
 	if (insn_data_sz == 0 || insn_data_sz % BPF_INSN_SZ || sec_off % BPF_INSN_SZ) {
 		pr_warn("sec '%s': corrupted program '%s', offset %zu, size %zu\n",
 			sec_name, name, sec_off, insn_data_sz);
@@ -600,13 +598,6 @@ bpf_object__init_prog(struct bpf_object *obj, struct bpf_program *prog,
 		goto errout;
 	memcpy(prog->insns, insn_data, insn_data_sz);
 
-	for (i = 0; i < prog->insns_cnt; i++) {
-		if (insn_is_subprog_call(&prog->insns[i])) {
-			obj->has_subcalls = true;
-			break;
-		}
-	}
-
 	return 0;
 errout:
 	pr_warn("sec '%s': failed to allocate memory for prog '%s'\n", sec_name, name);
@@ -3280,7 +3271,19 @@ bpf_object__find_program_by_title(const struct bpf_object *obj,
 static bool prog_is_subprog(const struct bpf_object *obj,
 			    const struct bpf_program *prog)
 {
-	return prog->sec_idx == obj->efile.text_shndx && obj->has_subcalls;
+	/* For legacy reasons, libbpf supports an entry-point BPF programs
+	 * without SEC() attribute, i.e., those in the .text section. But if
+	 * there are 2 or more such programs in the .text section, they all
+	 * must be subprograms called from entry-point BPF programs in
+	 * designated SEC()'tions, otherwise there is no way to distinguish
+	 * which of those programs should be loaded vs which are a subprogram.
+	 * Similarly, if there is a function/program in .text and at least one
+	 * other BPF program with custom SEC() attribute, then we just assume
+	 * .text programs are subprograms (even if they are not called from
+	 * other programs), because libbpf never explicitly supported mixing
+	 * SEC()-designated BPF programs and .text entry-point BPF programs.
+	 */
+	return prog->sec_idx == obj->efile.text_shndx && obj->nr_programs > 1;
 }
 
 struct bpf_program *

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

@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "test_probe_read_user_str.skel.h"
+
+static const char str1[] = "mestring";
+static const char str2[] = "mestringalittlebigger";
+static const char str3[] = "mestringblubblubblubblubblub";
+
+static int test_one_str(struct test_probe_read_user_str *skel, const char *str,
+			size_t len)
+{
+	int err, duration = 0;
+	char buf[256];
+
+	/* Ensure bytes after string are ones */
+	memset(buf, 1, sizeof(buf));
+	memcpy(buf, str, len);
+
+	/* Give prog our userspace pointer */
+	skel->bss->user_ptr = buf;
+
+	/* Trigger tracepoint */
+	usleep(1);
+
+	/* Did helper fail? */
+	if (CHECK(skel->bss->ret < 0, "prog_ret", "prog returned: %ld\n",
+		  skel->bss->ret))
+		return 1;
+
+	/* Check that string was copied correctly */
+	err = memcmp(skel->bss->buf, str, len);
+	if (CHECK(err, "memcmp", "prog copied wrong string"))
+		return 1;
+
+	/* Now check that no extra trailing bytes were copied */
+	memset(buf, 0, sizeof(buf));
+	err = memcmp(skel->bss->buf + len, buf, sizeof(buf) - len);
+	if (CHECK(err, "memcmp", "trailing bytes were not stripped"))
+		return 1;
+
+	return 0;
+}
+
+void test_probe_read_user_str(void)
+{
+	struct test_probe_read_user_str *skel;
+	int err, duration = 0;
+
+	skel = test_probe_read_user_str__open_and_load();
+	if (CHECK(!skel, "test_probe_read_user_str__open_and_load",
+		  "skeleton open and load failed\n"))
+		return;
+
+	/* Give pid to bpf prog so it doesn't read from anyone else */
+	skel->bss->pid = getpid();
+
+	err = test_probe_read_user_str__attach(skel);
+	if (CHECK(err, "test_probe_read_user_str__attach",
+		  "skeleton attach failed: %d\n", err))
+		goto out;
+
+	if (test_one_str(skel, str1, sizeof(str1)))
+		goto out;
+	if (test_one_str(skel, str2, sizeof(str2)))
+		goto out;
+	if (test_one_str(skel, str3, sizeof(str3)))
+		goto out;
+
+out:
+	test_probe_read_user_str__destroy(skel);
+}

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

@@ -138,7 +138,8 @@ static int run_getsockopt_test(struct bpf_object *obj, int cg_parent,
 	 */
 
 	buf = 0x40;
-	if (setsockopt(sock_fd, SOL_IP, IP_TOS, &buf, 1) < 0) {
+	err = setsockopt(sock_fd, SOL_IP, IP_TOS, &buf, 1);
+	if (err < 0) {
 		log_err("Failed to call setsockopt(IP_TOS)");
 		goto detach;
 	}

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

@@ -3,12 +3,14 @@
 #include <test_progs.h>
 #include <time.h>
 #include "test_subprogs.skel.h"
+#include "test_subprogs_unused.skel.h"
 
 static int duration;
 
 void test_subprogs(void)
 {
 	struct test_subprogs *skel;
+	struct test_subprogs_unused *skel2;
 	int err;
 
 	skel = test_subprogs__open_and_load();
@@ -26,6 +28,10 @@ void test_subprogs(void)
 	CHECK(skel->bss->res3 != 19, "res3", "got %d, exp %d\n", skel->bss->res3, 19);
 	CHECK(skel->bss->res4 != 36, "res4", "got %d, exp %d\n", skel->bss->res4, 36);
 
+	skel2 = test_subprogs_unused__open_and_load();
+	ASSERT_OK_PTR(skel2, "unused_progs_skel");
+	test_subprogs_unused__destroy(skel2);
+
 cleanup:
 	test_subprogs__destroy(skel);
 }

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

@@ -60,6 +60,7 @@ void test_test_global_funcs(void)
 		{ "test_global_func5.o" , "expected pointer to ctx, but got PTR" },
 		{ "test_global_func6.o" , "modified ctx ptr R2" },
 		{ "test_global_func7.o" , "foo() doesn't return scalar" },
+		{ "test_global_func8.o" },
 	};
 	libbpf_print_fn_t old_print_fn = NULL;
 	int err, i, duration = 0;

tools/testing/selftests/bpf/progs/test_global_func8.c

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2020 Facebook */
+#include <stddef.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+__noinline int foo(struct __sk_buff *skb)
+{
+	return bpf_get_prandom_u32();
+}
+
+SEC("cgroup_skb/ingress")
+int test_cls(struct __sk_buff *skb)
+{
+	if (!foo(skb))
+		return 0;
+
+	return 1;
+}

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

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#include <sys/types.h>
+
+pid_t pid = 0;
+long ret = 0;
+void *user_ptr = 0;
+char buf[256] = {};
+
+SEC("tracepoint/syscalls/sys_enter_nanosleep")
+int on_write(void *ctx)
+{
+	if (pid != (bpf_get_current_pid_tgid() >> 32))
+		return 0;
+
+	ret = bpf_probe_read_user_str(buf, sizeof(buf), user_ptr);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

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

@@ -0,0 +1,21 @@
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+
+const char LICENSE[] SEC("license") = "GPL";
+
+__attribute__((unused)) __noinline int unused1(int x)
+{
+	return x + 1;
+}
+
+static __attribute__((unused)) __noinline int unused2(int x)
+{
+	return x + 2;
+}
+
+SEC("raw_tp/sys_enter")
+int main_prog(void *ctx)
+{
+	return 0;
+}