selftests/bpf: add btf_dump BTF-to-C conversion tests

Add new test_btf_dump set of tests, validating BTF-to-C conversion
correctness. Tests rely on clang to generate BTF from provided C test
cases.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 229 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c b/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c
new file mode 100644
index 000000000000..d4a02fe44a12
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+/*
+ * BTF-to-C dumper test for majority of C syntax quirks.
+ *
+ * Copyright (c) 2019 Facebook
+ */
+/* ----- START-EXPECTED-OUTPUT ----- */
+enum e1 {
+	A = 0,
+	B = 1,
+};
+
+enum e2 {
+	C = 100,
+	D = -100,
+	E = 0,
+};
+
+typedef enum e2 e2_t;
+
+typedef enum {
+	F = 0,
+	G = 1,
+	H = 2,
+} e3_t;
+
+typedef int int_t;
+
+typedef volatile const int * volatile const crazy_ptr_t;
+
+typedef int *****we_need_to_go_deeper_ptr_t;
+
+typedef volatile const we_need_to_go_deeper_ptr_t * restrict * volatile * const * restrict volatile * restrict const * volatile const * restrict volatile const how_about_this_ptr_t;
+
+typedef int *ptr_arr_t[10];
+
+typedef void (*fn_ptr1_t)(int);
+
+typedef void (*printf_fn_t)(const char *, ...);
+
+/* ------ END-EXPECTED-OUTPUT ------ */
+/*
+ * While previous function pointers are pretty trivial (C-syntax-level
+ * trivial), the following are deciphered here for future generations:
+ *
+ * - `fn_ptr2_t`: function, taking anonymous struct as a first arg and pointer
+ *   to a function, that takes int and returns int, as a second arg; returning
+ *   a pointer to a const pointer to a char. Equivalent to:
+ *	typedef struct { int a; } s_t;
+ *	typedef int (*fn_t)(int);
+ *	typedef char * const * (*fn_ptr2_t)(s_t, fn_t);
+ *
+ * - `fn_complext_t`: pointer to a function returning struct and accepting
+ *   union and struct. All structs and enum are anonymous and defined inline.
+ *
+ * - `signal_t: pointer to a function accepting a pointer to a function as an
+ *   argument and returning pointer to a function as a result. Sane equivalent:
+ *	typedef void (*signal_handler_t)(int);
+ *	typedef signal_handler_t (*signal_ptr_t)(int, signal_handler_t);
+ *
+ * - fn_ptr_arr1_t: array of pointers to a function accepting pointer to
+ *   a pointer to an int and returning pointer to a char. Easy.
+ *
+ * - fn_ptr_arr2_t: array of const pointers to a function taking no arguments
+ *   and returning a const pointer to a function, that takes pointer to a
+ *   `int -> char *` function and returns pointer to a char. Equivalent:
+ *   typedef char * (*fn_input_t)(int);
+ *   typedef char * (*fn_output_outer_t)(fn_input_t);
+ *   typedef const fn_output_outer_t (* fn_output_inner_t)();
+ *   typedef const fn_output_inner_t fn_ptr_arr2_t[5];
+ */
+/* ----- START-EXPECTED-OUTPUT ----- */
+typedef char * const * (*fn_ptr2_t)(struct {
+	int a;
+}, int (*)(int));
+
+typedef struct {
+	int a;
+	void (*b)(int, struct {
+		int c;
+	}, union {
+		char d;
+		int e[5];
+	});
+} (*fn_complex_t)(union {
+	void *f;
+	char g[16];
+}, struct {
+	int h;
+});
+
+typedef void (* (*signal_t)(int, void (*)(int)))(int);
+
+typedef char * (*fn_ptr_arr1_t[10])(int **);
+
+typedef char * (* const (* const fn_ptr_arr2_t[5])())(char * (*)(int));
+
+struct struct_w_typedefs {
+	int_t a;
+	crazy_ptr_t b;
+	we_need_to_go_deeper_ptr_t c;
+	how_about_this_ptr_t d;
+	ptr_arr_t e;
+	fn_ptr1_t f;
+	printf_fn_t g;
+	fn_ptr2_t h;
+	fn_complex_t i;
+	signal_t j;
+	fn_ptr_arr1_t k;
+	fn_ptr_arr2_t l;
+};
+
+typedef struct {
+	int x;
+	int y;
+	int z;
+} anon_struct_t;
+
+struct struct_fwd;
+
+typedef struct struct_fwd struct_fwd_t;
+
+typedef struct struct_fwd *struct_fwd_ptr_t;
+
+union union_fwd;
+
+typedef union union_fwd union_fwd_t;
+
+typedef union union_fwd *union_fwd_ptr_t;
+
+struct struct_empty {};
+
+struct struct_simple {
+	int a;
+	char b;
+	const int_t *p;
+	struct struct_empty s;
+	enum e2 e;
+	enum {
+		ANON_VAL1 = 1,
+		ANON_VAL2 = 2,
+	} f;
+	int arr1[13];
+	enum e2 arr2[5];
+};
+
+union union_empty {};
+
+union union_simple {
+	void *ptr;
+	int num;
+	int_t num2;
+	union union_empty u;
+};
+
+struct struct_in_struct {
+	struct struct_simple simple;
+	union union_simple also_simple;
+	struct {
+		int a;
+	} not_so_hard_as_well;
+	union {
+		int b;
+		int c;
+	} anon_union_is_good;
+	struct {
+		int d;
+		int e;
+	};
+	union {
+		int f;
+		int g;
+	};
+};
+
+struct struct_with_embedded_stuff {
+	int a;
+	struct {
+		int b;
+		struct {
+			struct struct_with_embedded_stuff *c;
+			const char *d;
+		} e;
+		union {
+			volatile long int f;
+			void * restrict g;
+		};
+	};
+	union {
+		const int_t *h;
+		void (*i)(char, int, void *);
+	} j;
+	enum {
+		K = 100,
+		L = 200,
+	} m;
+	char n[16];
+	struct {
+		char o;
+		int p;
+		void (*q)(int);
+	} r[5];
+	struct struct_in_struct s[10];
+	int t[11];
+};
+
+struct root_struct {
+	enum e1 _1;
+	enum e2 _2;
+	e2_t _2_1;
+	e3_t _2_2;
+	struct struct_w_typedefs _3;
+	anon_struct_t _7;
+	struct struct_fwd *_8;
+	struct_fwd_t *_9;
+	struct_fwd_ptr_t _10;
+	union union_fwd *_11;
+	union_fwd_t *_12;
+	union_fwd_ptr_t _13;
+	struct struct_with_embedded_stuff _14;
+};
+
+/* ------ END-EXPECTED-OUTPUT ------ */
+
+int f(struct root_struct *s)
+{
+	return 0;
+}