selftests/bpf: Add field size relocation tests

Add test verifying correctness and logic of field size relocation support in
libbpf.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191101222810.1246166-6-andriin@fb.com

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

@@ -174,15 +174,11 @@
 	.fails = true,							\
 }
 
-#define EXISTENCE_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) {	\
-	.a = 42,							\
-}
-
 #define EXISTENCE_CASE_COMMON(name)					\
 	.case_name = #name,						\
 	.bpf_obj_file = "test_core_reloc_existence.o",			\
 	.btf_src_file = "btf__core_reloc_" #name ".o",			\
-	.relaxed_core_relocs = true					\
+	.relaxed_core_relocs = true
 
 #define EXISTENCE_ERR_CASE(name) {					\
 	EXISTENCE_CASE_COMMON(name),					\
@@ -225,6 +221,35 @@
 	.fails = true,							\
 }
 
+#define SIZE_CASE_COMMON(name)						\
+	.case_name = #name,						\
+	.bpf_obj_file = "test_core_reloc_size.o",			\
+	.btf_src_file = "btf__core_reloc_" #name ".o",			\
+	.relaxed_core_relocs = true
+
+#define SIZE_OUTPUT_DATA(type)						\
+	STRUCT_TO_CHAR_PTR(core_reloc_size_output) {			\
+		.int_sz = sizeof(((type *)0)->int_field),		\
+		.struct_sz = sizeof(((type *)0)->struct_field),		\
+		.union_sz = sizeof(((type *)0)->union_field),		\
+		.arr_sz = sizeof(((type *)0)->arr_field),		\
+		.arr_elem_sz = sizeof(((type *)0)->arr_field[0]),	\
+		.ptr_sz = sizeof(((type *)0)->ptr_field),		\
+		.enum_sz = sizeof(((type *)0)->enum_field),	\
+	}
+
+#define SIZE_CASE(name) {						\
+	SIZE_CASE_COMMON(name),						\
+	.input_len = 0,							\
+	.output = SIZE_OUTPUT_DATA(struct core_reloc_##name),		\
+	.output_len = sizeof(struct core_reloc_size_output),		\
+}
+
+#define SIZE_ERR_CASE(name) {						\
+	SIZE_CASE_COMMON(name),						\
+	.fails = true,							\
+}
+
 struct core_reloc_test_case {
 	const char *case_name;
 	const char *bpf_obj_file;
@@ -423,6 +448,10 @@ static struct core_reloc_test_case test_cases[] = {
 		.ub2 = 0x0812345678FEDCBA,
 	}),
 	BITFIELDS_ERR_CASE(bitfields___err_too_big_bitfield),
+
+	/* size relocation checks */
+	SIZE_CASE(size),
+	SIZE_CASE(size___diff_sz),
 };
 
 struct data {

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

+#include "core_reloc_types.h"
+
+void f(struct core_reloc_size x) {}

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

+#include "core_reloc_types.h"
+
+void f(struct core_reloc_size___diff_sz x) {}

tools/testing/selftests/bpf/progs/core_reloc_types.h

@@ -734,3 +734,34 @@ struct core_reloc_bitfields___err_too_big_bitfield {
 	uint32_t	u32;
 	uint32_t	s32;
 } __attribute__((packed)) ;
+
+/*
+ * SIZE
+ */
+struct core_reloc_size_output {
+	int int_sz;
+	int struct_sz;
+	int union_sz;
+	int arr_sz;
+	int arr_elem_sz;
+	int ptr_sz;
+	int enum_sz;
+};
+
+struct core_reloc_size {
+	int int_field;
+	struct { int x; } struct_field;
+	union { int x; } union_field;
+	int arr_field[4];
+	void *ptr_field;
+	enum { VALUE = 123 } enum_field;
+};
+
+struct core_reloc_size___diff_sz {
+	uint64_t int_field;
+	struct { int x; int y; int z; } struct_field;
+	union { int x; char bla[123]; } union_field;
+	char arr_field[10];
+	void *ptr_field;
+	enum { OTHER_VALUE = 0xFFFFFFFFFFFFFFFF } enum_field;
+};

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

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+#include "bpf_core_read.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+	char in[256];
+	char out[256];
+} data;
+
+struct core_reloc_size_output {
+	int int_sz;
+	int struct_sz;
+	int union_sz;
+	int arr_sz;
+	int arr_elem_sz;
+	int ptr_sz;
+	int enum_sz;
+};
+
+struct core_reloc_size {
+	int int_field;
+	struct { int x; } struct_field;
+	union { int x; } union_field;
+	int arr_field[4];
+	void *ptr_field;
+	enum { VALUE = 123 } enum_field;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_size(void *ctx)
+{
+	struct core_reloc_size *in = (void *)&data.in;
+	struct core_reloc_size_output *out = (void *)&data.out;
+
+	out->int_sz = bpf_core_field_size(in->int_field);
+	out->struct_sz = bpf_core_field_size(in->struct_field);
+	out->union_sz = bpf_core_field_size(in->union_field);
+	out->arr_sz = bpf_core_field_size(in->arr_field);
+	out->arr_elem_sz = bpf_core_field_size(in->arr_field[0]);
+	out->ptr_sz = bpf_core_field_size(in->ptr_field);
+	out->enum_sz = bpf_core_field_size(in->enum_field);
+
+	return 0;
+}
+