bpf: mini eBPF library, test stubs and verifier testsuite

1.
the library includes a trivial set of BPF syscall wrappers:
int bpf_create_map(int key_size, int value_size, int max_entries);
int bpf_update_elem(int fd, void *key, void *value);
int bpf_lookup_elem(int fd, void *key, void *value);
int bpf_delete_elem(int fd, void *key);
int bpf_get_next_key(int fd, void *key, void *next_key);
int bpf_prog_load(enum bpf_prog_type prog_type,
		  const struct sock_filter_int *insns, int insn_len,
		  const char *license);
bpf_prog_load() stores verifier log into global bpf_log_buf[] array

and BPF_*() macros to build instructions

2.
test stubs configure eBPF infra with 'unspec' map and program types.
These are fake types used by user space testsuite only.

3.
verifier tests valid and invalid programs and expects predefined
error log messages from kernel.
40 tests so far.

$ sudo ./test_verifier
 #0 add+sub+mul OK
 #1 unreachable OK
 #2 unreachable2 OK
 #3 out of range jump OK
 #4 out of range jump2 OK
 #5 test1 ld_imm64 OK
 ...

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 120 insertions, 0 deletions

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 3c726b0..4542723 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -1 +1,5 @@
 obj-y := core.o syscall.o verifier.o
+
+ifdef CONFIG_TEST_BPF
+obj-y += test_stub.o
+endif
diff --git a/kernel/bpf/test_stub.c b/kernel/bpf/test_stub.c
new file mode 100644
index 0000000..fcaddff
--- /dev/null
+++ b/kernel/bpf/test_stub.c
@@ -0,0 +1,116 @@
+/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/bpf.h>
+
+/* test stubs for BPF_MAP_TYPE_UNSPEC and for BPF_PROG_TYPE_UNSPEC
+ * to be used by user space verifier testsuite
+ */
+struct bpf_context {
+	u64 arg1;
+	u64 arg2;
+};
+
+static u64 test_func(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	return 0;
+}
+
+static struct bpf_func_proto test_funcs[] = {
+	[BPF_FUNC_unspec] = {
+		.func = test_func,
+		.gpl_only = true,
+		.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
+		.arg1_type = ARG_CONST_MAP_PTR,
+		.arg2_type = ARG_PTR_TO_MAP_KEY,
+	},
+};
+
+static const struct bpf_func_proto *test_func_proto(enum bpf_func_id func_id)
+{
+	if (func_id < 0 || func_id >= ARRAY_SIZE(test_funcs))
+		return NULL;
+	return &test_funcs[func_id];
+}
+
+static const struct bpf_context_access {
+	int size;
+	enum bpf_access_type type;
+} test_ctx_access[] = {
+	[offsetof(struct bpf_context, arg1)] = {
+		FIELD_SIZEOF(struct bpf_context, arg1),
+		BPF_READ
+	},
+	[offsetof(struct bpf_context, arg2)] = {
+		FIELD_SIZEOF(struct bpf_context, arg2),
+		BPF_READ
+	},
+};
+
+static bool test_is_valid_access(int off, int size, enum bpf_access_type type)
+{
+	const struct bpf_context_access *access;
+
+	if (off < 0 || off >= ARRAY_SIZE(test_ctx_access))
+		return false;
+
+	access = &test_ctx_access[off];
+	if (access->size == size && (access->type & type))
+		return true;
+
+	return false;
+}
+
+static struct bpf_verifier_ops test_ops = {
+	.get_func_proto = test_func_proto,
+	.is_valid_access = test_is_valid_access,
+};
+
+static struct bpf_prog_type_list tl_prog = {
+	.ops = &test_ops,
+	.type = BPF_PROG_TYPE_UNSPEC,
+};
+
+static struct bpf_map *test_map_alloc(union bpf_attr *attr)
+{
+	struct bpf_map *map;
+
+	map = kzalloc(sizeof(*map), GFP_USER);
+	if (!map)
+		return ERR_PTR(-ENOMEM);
+
+	map->key_size = attr->key_size;
+	map->value_size = attr->value_size;
+	map->max_entries = attr->max_entries;
+	return map;
+}
+
+static void test_map_free(struct bpf_map *map)
+{
+	kfree(map);
+}
+
+static struct bpf_map_ops test_map_ops = {
+	.map_alloc = test_map_alloc,
+	.map_free = test_map_free,
+};
+
+static struct bpf_map_type_list tl_map = {
+	.ops = &test_map_ops,
+	.type = BPF_MAP_TYPE_UNSPEC,
+};
+
+static int __init register_test_ops(void)
+{
+	bpf_register_map_type(&tl_map);
+	bpf_register_prog_type(&tl_prog);
+	return 0;
+}
+late_initcall(register_test_ops);