selftests/bpf: Add flexible array relocation tests

Add few tests validation CO-RE relocation handling of flexible array accesses.

Signed-off-by: Andrii Nakryiko <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
 		.b123 = 2,						\
 		.c1c  = 3,						\
 		.d00d = 4,						\
+		.f10c = 0,						\
 	},								\
 	.output_len = sizeof(struct core_reloc_arrays_output)		\
 }
···
 	ARRAYS_CASE(arrays),
 	ARRAYS_CASE(arrays___diff_arr_dim),
 	ARRAYS_CASE(arrays___diff_arr_val_sz),
+	ARRAYS_CASE(arrays___equiv_zero_sz_arr),
+	ARRAYS_CASE(arrays___fixed_arr),
 
 	ARRAYS_ERR_CASE(arrays___err_too_small),
 	ARRAYS_ERR_CASE(arrays___err_too_shallow),
 	ARRAYS_ERR_CASE(arrays___err_non_array),
 	ARRAYS_ERR_CASE(arrays___err_wrong_val_type1),
 	ARRAYS_ERR_CASE(arrays___err_wrong_val_type2),
+	ARRAYS_ERR_CASE(arrays___err_bad_zero_sz_arr),
 
 	/* enum/ptr/int handling scenarios */
 	PRIMITIVES_CASE(primitives),

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

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

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

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

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

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

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

···
 	char b123;
 	int c1c;
 	int d00d;
+	int f10c;
 };
 
 struct core_reloc_arrays_substruct {
···
 	char b[2][3][4];
 	struct core_reloc_arrays_substruct c[3];
 	struct core_reloc_arrays_substruct d[1][2];
+	struct core_reloc_arrays_substruct f[][2];
 };
 
 /* bigger array dimensions */
···
 	char b[3][4][5];
 	struct core_reloc_arrays_substruct c[4];
 	struct core_reloc_arrays_substruct d[2][3];
+	struct core_reloc_arrays_substruct f[1][3];
 };
 
 /* different size of array's value (struct) */
···
 		int d;
 		int __padding2;
 	} d[1][2];
+	struct {
+		int __padding1;
+		int c;
+		int __padding2;
+	} f[][2];
+};
+
+struct core_reloc_arrays___equiv_zero_sz_arr {
+	int a[5];
+	char b[2][3][4];
+	struct core_reloc_arrays_substruct c[3];
+	struct core_reloc_arrays_substruct d[1][2];
+	/* equivalent to flexible array */
+	struct core_reloc_arrays_substruct f[0][2];
+};
+
+struct core_reloc_arrays___fixed_arr {
+	int a[5];
+	char b[2][3][4];
+	struct core_reloc_arrays_substruct c[3];
+	struct core_reloc_arrays_substruct d[1][2];
+	/* not a flexible array anymore, but within access bounds */
+	struct core_reloc_arrays_substruct f[1][2];
 };
 
 struct core_reloc_arrays___err_too_small {
···
 	char b[2][3][4];
 	struct core_reloc_arrays_substruct c[3];
 	struct core_reloc_arrays_substruct d[1][2];
+	struct core_reloc_arrays_substruct f[][2];
 };
 
 struct core_reloc_arrays___err_too_shallow {
···
 	char b[2][3]; /* this one lacks one dimension */
 	struct core_reloc_arrays_substruct c[3];
 	struct core_reloc_arrays_substruct d[1][2];
+	struct core_reloc_arrays_substruct f[][2];
 };
 
 struct core_reloc_arrays___err_non_array {
···
 	char b[2][3][4];
 	struct core_reloc_arrays_substruct c[3];
 	struct core_reloc_arrays_substruct d[1][2];
+	struct core_reloc_arrays_substruct f[][2];
 };
 
 struct core_reloc_arrays___err_wrong_val_type {
 	int a[5];
 	char b[2][3][4];
 	int c[3]; /* value is not a struct */
+	struct core_reloc_arrays_substruct d[1][2];
+	struct core_reloc_arrays_substruct f[][2];
+};
+
+struct core_reloc_arrays___err_bad_zero_sz_arr {
+	/* zero-sized array, but not at the end */
+	struct core_reloc_arrays_substruct f[0][2];
+	int a[5];
+	char b[2][3][4];
+	struct core_reloc_arrays_substruct c[3];
 	struct core_reloc_arrays_substruct d[1][2];
 };
 

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

···
 	char b123;
 	int c1c;
 	int d00d;
+	int f01c;
 };
 
 struct core_reloc_arrays_substruct {
···
 	char b[2][3][4];
 	struct core_reloc_arrays_substruct c[3];
 	struct core_reloc_arrays_substruct d[1][2];
+	struct core_reloc_arrays_substruct f[][2];
 };
 
 #define CORE_READ(dst, src) bpf_core_read(dst, sizeof(*(dst)), src)
···
 	struct core_reloc_arrays *in = (void *)&data.in;
 	struct core_reloc_arrays_output *out = (void *)&data.out;
 
-	/* in->a[2] */
 	if (CORE_READ(&out->a2, &in->a[2]))
 		return 1;
-	/* in->b[1][2][3] */
 	if (CORE_READ(&out->b123, &in->b[1][2][3]))
 		return 1;
-	/* in->c[1].c */
 	if (CORE_READ(&out->c1c, &in->c[1].c))
 		return 1;
-	/* in->d[0][0].d */
 	if (CORE_READ(&out->d00d, &in->d[0][0].d))
+		return 1;
+	if (CORE_READ(&out->f01c, &in->f[0][1].c))
 		return 1;
 
 	return 0;