selftests/bpf: Add bpf_core_field_offset() tests

Add test cases for bpf_core_field_offset() helper.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220509004148.1801791-7-andrii@kernel.org

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

@@ -277,13 +277,21 @@ static int duration = 0;
 #define SIZE_OUTPUT_DATA(type)						\
 	STRUCT_TO_CHAR_PTR(core_reloc_size_output) {			\
 		.int_sz = sizeof(((type *)0)->int_field),		\
+		.int_off = offsetof(type, int_field),			\
 		.struct_sz = sizeof(((type *)0)->struct_field),		\
+		.struct_off = offsetof(type, struct_field),		\
 		.union_sz = sizeof(((type *)0)->union_field),		\
+		.union_off = offsetof(type, union_field),		\
 		.arr_sz = sizeof(((type *)0)->arr_field),		\
-		.arr_elem_sz = sizeof(((type *)0)->arr_field[0]),	\
+		.arr_off = offsetof(type, arr_field),			\
+		.arr_elem_sz = sizeof(((type *)0)->arr_field[1]),	\
+		.arr_elem_off = offsetof(type, arr_field[1]),		\
 		.ptr_sz = 8, /* always 8-byte pointer for BPF */	\
+		.ptr_off = offsetof(type, ptr_field),			\
 		.enum_sz = sizeof(((type *)0)->enum_field),		\
+		.enum_off = offsetof(type, enum_field),			\
 		.float_sz = sizeof(((type *)0)->float_field),		\
+		.float_off = offsetof(type, float_field),		\
 	}
 
 #define SIZE_CASE(name) {						\
@@ -714,9 +722,10 @@ static const struct core_reloc_test_case test_cases[] = {
 	}),
 	BITFIELDS_ERR_CASE(bitfields___err_too_big_bitfield),
 
-	/* size relocation checks */
+	/* field size and offset relocation checks */
 	SIZE_CASE(size),
 	SIZE_CASE(size___diff_sz),
+	SIZE_CASE(size___diff_offs),
 	SIZE_ERR_CASE(size___err_ambiguous),
 
 	/* validate type existence and size relocations */

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

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

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

@@ -785,13 +785,21 @@ struct core_reloc_bitfields___err_too_big_bitfield {
  */
 struct core_reloc_size_output {
 	int int_sz;
+	int int_off;
 	int struct_sz;
+	int struct_off;
 	int union_sz;
+	int union_off;
 	int arr_sz;
+	int arr_off;
 	int arr_elem_sz;
+	int arr_elem_off;
 	int ptr_sz;
+	int ptr_off;
 	int enum_sz;
+	int enum_off;
 	int float_sz;
+	int float_off;
 };
 
 struct core_reloc_size {
@@ -814,6 +822,16 @@ struct core_reloc_size___diff_sz {
 	double float_field;
 };
 
+struct core_reloc_size___diff_offs {
+	float float_field;
+	enum { YET_OTHER_VALUE = 123 } enum_field;
+	void *ptr_field;
+	int arr_field[4];
+	union { int x; } union_field;
+	struct { int x; } struct_field;
+	int int_field;
+};
+
 /* Error case of two candidates with the fields (int_field) at the same
  * offset, but with differing final relocation values: size 4 vs size 1
  */

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

@@ -15,13 +15,21 @@ struct {
 
 struct core_reloc_size_output {
 	int int_sz;
+	int int_off;
 	int struct_sz;
+	int struct_off;
 	int union_sz;
+	int union_off;
 	int arr_sz;
+	int arr_off;
 	int arr_elem_sz;
+	int arr_elem_off;
 	int ptr_sz;
+	int ptr_off;
 	int enum_sz;
+	int enum_off;
 	int float_sz;
+	int float_off;
 };
 
 struct core_reloc_size {
@@ -41,13 +49,28 @@ int test_core_size(void *ctx)
 	struct core_reloc_size_output *out = (void *)&data.out;
 
 	out->int_sz = bpf_core_field_size(in->int_field);
+	out->int_off = bpf_core_field_offset(in->int_field);
+
 	out->struct_sz = bpf_core_field_size(in->struct_field);
+	out->struct_off = bpf_core_field_offset(in->struct_field);
+
 	out->union_sz = bpf_core_field_size(in->union_field);
+	out->union_off = bpf_core_field_offset(in->union_field);
+
 	out->arr_sz = bpf_core_field_size(in->arr_field);
-	out->arr_elem_sz = bpf_core_field_size(struct core_reloc_size, arr_field[0]);
+	out->arr_off = bpf_core_field_offset(in->arr_field);
+
+	out->arr_elem_sz = bpf_core_field_size(struct core_reloc_size, arr_field[1]);
+	out->arr_elem_off = bpf_core_field_offset(struct core_reloc_size, arr_field[1]);
+
 	out->ptr_sz = bpf_core_field_size(struct core_reloc_size, ptr_field);
+	out->ptr_off = bpf_core_field_offset(struct core_reloc_size, ptr_field);
+
 	out->enum_sz = bpf_core_field_size(struct core_reloc_size, enum_field);
+	out->enum_off = bpf_core_field_offset(struct core_reloc_size, enum_field);
+
 	out->float_sz = bpf_core_field_size(struct core_reloc_size, float_field);
+	out->float_off = bpf_core_field_offset(struct core_reloc_size, float_field);
 
 	return 0;
 }