selftests/bpf: Add few corner cases to test padding handling of btf_dump

Add few hand-crafted cases and few randomized cases found using script
from [0] that tests btf_dump's padding logic.

[0] https://lore.kernel.org/bpf/[e-mail]/

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

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

···
 	} __attribute__((packed));
 };
 
-/*------ END-EXPECTED-OUTPUT ------ */
+/* ----- START-EXPECTED-OUTPUT ----- */
+/*
+ *struct nested_packed_but_aligned_struct {
+ *	int x1;
+ *	int x2;
+ *};
+ *
+ *struct outer_implicitly_packed_struct {
+ *	char y1;
+ *	struct nested_packed_but_aligned_struct y2;
+ *} __attribute__((packed));
+ *
+ */
+/* ------ END-EXPECTED-OUTPUT ------ */
+
+struct nested_packed_but_aligned_struct {
+	int x1;
+	int x2;
+} __attribute__((packed));
+
+struct outer_implicitly_packed_struct {
+	char y1;
+	struct nested_packed_but_aligned_struct y2;
+};
+/* ----- START-EXPECTED-OUTPUT ----- */
+/*
+ *struct usb_ss_ep_comp_descriptor {
+ *	char: 8;
+ *	char bDescriptorType;
+ *	char bMaxBurst;
+ *	short wBytesPerInterval;
+ *};
+ *
+ *struct usb_host_endpoint {
+ *	long: 64;
+ *	char: 8;
+ *	struct usb_ss_ep_comp_descriptor ss_ep_comp;
+ *	long: 0;
+ *} __attribute__((packed));
+ *
+ */
+/* ------ END-EXPECTED-OUTPUT ------ */
+
+struct usb_ss_ep_comp_descriptor {
+	char: 8;
+	char bDescriptorType;
+	char bMaxBurst;
+	int: 0;
+	short wBytesPerInterval;
+} __attribute__((packed));
+
+struct usb_host_endpoint {
+	long: 64;
+	char: 8;
+	struct usb_ss_ep_comp_descriptor ss_ep_comp;
+	long: 0;
+};
+
 
 int f(struct {
 	struct packed_trailing_space _1;
···
 	union union_is_never_packed _6;
 	union union_does_not_need_packing _7;
 	union jump_code_union _8;
+	struct outer_implicitly_packed_struct _9;
+	struct usb_host_endpoint _10;
 } *_)
 {
 	return 0;

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

···
 	char: 8;
 };
 
+/* ----- START-EXPECTED-OUTPUT ----- */
+struct exact_1byte {
+	char x;
+};
+
+struct padded_1byte {
+	char: 8;
+};
+
+struct exact_2bytes {
+	short x;
+};
+
+struct padded_2bytes {
+	short: 16;
+};
+
+struct exact_4bytes {
+	int x;
+};
+
+struct padded_4bytes {
+	int: 32;
+};
+
+struct exact_8bytes {
+	long x;
+};
+
+struct padded_8bytes {
+	long: 64;
+};
+
+struct ff_periodic_effect {
+	int: 32;
+	short magnitude;
+	long: 0;
+	short phase;
+	long: 0;
+	int: 32;
+	int custom_len;
+	short *custom_data;
+};
+
+struct ib_wc {
+	long: 64;
+	long: 64;
+	int: 32;
+	int byte_len;
+	void *qp;
+	union {} ex;
+	long: 64;
+	int slid;
+	int wc_flags;
+	long: 64;
+	char smac[6];
+	long: 0;
+	char network_hdr_type;
+};
+
+struct acpi_object_method {
+	long: 64;
+	char: 8;
+	char type;
+	short reference_count;
+	char flags;
+	short: 0;
+	char: 8;
+	char sync_level;
+	long: 64;
+	void *node;
+	void *aml_start;
+	union {} dispatch;
+	long: 64;
+	int aml_length;
+};
+
+struct nested_unpacked {
+	int x;
+};
+
+struct nested_packed {
+	struct nested_unpacked a;
+	char c;
+} __attribute__((packed));
+
+struct outer_mixed_but_unpacked {
+	struct nested_packed b1;
+	short a1;
+	struct nested_packed b2;
+};
+
 /* ------ END-EXPECTED-OUTPUT ------ */
 
 int f(struct {
···
 	struct padding_wo_named_members _6;
 	struct padding_weird_1 _7;
 	struct padding_weird_2 _8;
+	struct exact_1byte _100;
+	struct padded_1byte _101;
+	struct exact_2bytes _102;
+	struct padded_2bytes _103;
+	struct exact_4bytes _104;
+	struct padded_4bytes _105;
+	struct exact_8bytes _106;
+	struct padded_8bytes _107;
+	struct ff_periodic_effect _200;
+	struct ib_wc _201;
+	struct acpi_object_method _202;
+	struct outer_mixed_but_unpacked _203;
 } *_)
 {
 	return 0;