selftests/bpf: Add selftests validating the user ringbuf

This change includes selftests that validate the expected behavior and
APIs of the new BPF_MAP_TYPE_USER_RINGBUF map type.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220920000100.477320-5-void@manifault.com

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

@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct sample {
+	int pid;
+	int seq;
+	long value;
+	char comm[16];
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_USER_RINGBUF);
+} user_ringbuf SEC(".maps");
+
+static long
+bad_access1(struct bpf_dynptr *dynptr, void *context)
+{
+	const struct sample *sample;
+
+	sample = bpf_dynptr_data(dynptr - 1, 0, sizeof(*sample));
+	bpf_printk("Was able to pass bad pointer %lx\n", (__u64)dynptr - 1);
+
+	return 0;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to read before the pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_bad_access1(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, bad_access1, NULL, 0);
+
+	return 0;
+}
+
+static long
+bad_access2(struct bpf_dynptr *dynptr, void *context)
+{
+	const struct sample *sample;
+
+	sample = bpf_dynptr_data(dynptr + 1, 0, sizeof(*sample));
+	bpf_printk("Was able to pass bad pointer %lx\n", (__u64)dynptr + 1);
+
+	return 0;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to read past the end of the pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_bad_access2(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, bad_access2, NULL, 0);
+
+	return 0;
+}
+
+static long
+write_forbidden(struct bpf_dynptr *dynptr, void *context)
+{
+	*((long *)dynptr) = 0;
+
+	return 0;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to write to that pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_write_forbidden(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, write_forbidden, NULL, 0);
+
+	return 0;
+}
+
+static long
+null_context_write(struct bpf_dynptr *dynptr, void *context)
+{
+	*((__u64 *)context) = 0;
+
+	return 0;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to write to that pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_null_context_write(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, null_context_write, NULL, 0);
+
+	return 0;
+}
+
+static long
+null_context_read(struct bpf_dynptr *dynptr, void *context)
+{
+	__u64 id = *((__u64 *)context);
+
+	bpf_printk("Read id %lu\n", id);
+
+	return 0;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to write to that pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_null_context_read(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, null_context_read, NULL, 0);
+
+	return 0;
+}
+
+static long
+try_discard_dynptr(struct bpf_dynptr *dynptr, void *context)
+{
+	bpf_ringbuf_discard_dynptr(dynptr, 0);
+
+	return 0;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to read past the end of the pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_discard_dynptr(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, try_discard_dynptr, NULL, 0);
+
+	return 0;
+}
+
+static long
+try_submit_dynptr(struct bpf_dynptr *dynptr, void *context)
+{
+	bpf_ringbuf_submit_dynptr(dynptr, 0);
+
+	return 0;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to read past the end of the pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_submit_dynptr(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, try_submit_dynptr, NULL, 0);
+
+	return 0;
+}
+
+static long
+invalid_drain_callback_return(struct bpf_dynptr *dynptr, void *context)
+{
+	return 2;
+}
+
+/* A callback that accesses a dynptr in a bpf_user_ringbuf_drain callback should
+ * not be able to write to that pointer.
+ */
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_invalid_return(void *ctx)
+{
+	bpf_user_ringbuf_drain(&user_ringbuf, invalid_drain_callback_return, NULL, 0);
+
+	return 0;
+}