Commit 888d83b9 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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selftests/bpf: Validate libbpf's auto-sizing of LD/ST/STX instructions 



Add selftests validating libbpf's auto-resizing of load/store instructions
when used with CO-RE relocations. An explicit and manual approach with using
bpf_core_read() is also demonstrated and tested. Separate BPF program is
supposed to fail due to using signed integers of sizes that differ from
kernel's sizes.

To reliably simulate 32-bit BTF (i.e., the one with sizeof(long) ==
sizeof(void *) == 4), selftest generates its own custom BTF and passes it as
a replacement for real kernel BTF. This allows to test 32/64-bitness mix on
all architectures.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201008001025.292064-5-andrii@kernel.org
parent 2b7d88c2

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

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2020 Facebook */



#include <test_progs.h>

#include <bpf/btf.h>



/* real layout and sizes according to test's (32-bit) BTF

 * needs to be defined before skeleton is included */

struct test_struct___real {

	unsigned int ptr; /* can't use `void *`, it is always 8 byte in BPF target */

	unsigned int val2;

	unsigned long long val1;

	unsigned short val3;

	unsigned char val4;

	unsigned char _pad;

};



#include "test_core_autosize.skel.h"



static int duration = 0;



static struct {

	unsigned long long ptr_samesized;

	unsigned long long val1_samesized;

	unsigned long long val2_samesized;

	unsigned long long val3_samesized;

	unsigned long long val4_samesized;

	struct test_struct___real output_samesized;



	unsigned long long ptr_downsized;

	unsigned long long val1_downsized;

	unsigned long long val2_downsized;

	unsigned long long val3_downsized;

	unsigned long long val4_downsized;

	struct test_struct___real output_downsized;



	unsigned long long ptr_probed;

	unsigned long long val1_probed;

	unsigned long long val2_probed;

	unsigned long long val3_probed;

	unsigned long long val4_probed;



	unsigned long long ptr_signed;

	unsigned long long val1_signed;

	unsigned long long val2_signed;

	unsigned long long val3_signed;

	unsigned long long val4_signed;

	struct test_struct___real output_signed;

} out;



void test_core_autosize(void)

{

	char btf_file[] = "/tmp/core_autosize.btf.XXXXXX";

	int err, fd = -1, zero = 0;

	int char_id, short_id, int_id, long_long_id, void_ptr_id, id;

	struct test_core_autosize* skel = NULL;

	struct bpf_object_load_attr load_attr = {};

	struct bpf_program *prog;

	struct bpf_map *bss_map;

	struct btf *btf = NULL;

	size_t written;

	const void *raw_data;

	__u32 raw_sz;

	FILE *f = NULL;



	btf = btf__new_empty();

	if (!ASSERT_OK_PTR(btf, "empty_btf"))

		return;

	/* Emit the following struct with 32-bit pointer size:

	 *

	 * struct test_struct {

	 *     void *ptr;

	 *     unsigned long val2;

	 *     unsigned long long val1;

	 *     unsigned short val3;

	 *     unsigned char val4;

	 *     char: 8;

	 * };

	 *

	 * This struct is going to be used as the "kernel BTF" for this test.

	 * It's equivalent memory-layout-wise to test_struct__real above.

	 */



	/* force 32-bit pointer size */

	btf__set_pointer_size(btf, 4);



	char_id = btf__add_int(btf, "unsigned char", 1, 0);

	ASSERT_EQ(char_id, 1, "char_id");

	short_id = btf__add_int(btf, "unsigned short", 2, 0);

	ASSERT_EQ(short_id, 2, "short_id");

	/* "long unsigned int" of 4 byte size tells BTF that sizeof(void *) == 4 */

	int_id = btf__add_int(btf, "long unsigned int", 4, 0);

	ASSERT_EQ(int_id, 3, "int_id");

	long_long_id = btf__add_int(btf, "unsigned long long", 8, 0);

	ASSERT_EQ(long_long_id, 4, "long_long_id");

	void_ptr_id = btf__add_ptr(btf, 0);

	ASSERT_EQ(void_ptr_id, 5, "void_ptr_id");



	id = btf__add_struct(btf, "test_struct", 20 /* bytes */);

	ASSERT_EQ(id, 6, "struct_id");

	err = btf__add_field(btf, "ptr", void_ptr_id, 0, 0);

	err = err ?: btf__add_field(btf, "val2", int_id, 32, 0);

	err = err ?: btf__add_field(btf, "val1", long_long_id, 64, 0);

	err = err ?: btf__add_field(btf, "val3", short_id, 128, 0);

	err = err ?: btf__add_field(btf, "val4", char_id, 144, 0);

	ASSERT_OK(err, "struct_fields");



	fd = mkstemp(btf_file);

	if (CHECK(fd < 0, "btf_tmp", "failed to create file: %d\n", fd))

		goto cleanup;

	f = fdopen(fd, "w");

	if (!ASSERT_OK_PTR(f, "btf_fdopen"))

		goto cleanup;



	raw_data = btf__get_raw_data(btf, &raw_sz);

	if (!ASSERT_OK_PTR(raw_data, "raw_data"))

		goto cleanup;

	written = fwrite(raw_data, 1, raw_sz, f);

	if (CHECK(written != raw_sz, "btf_write", "written: %zu, errno: %d\n", written, errno))

		goto cleanup;

	fflush(f);

	fclose(f);

	f = NULL;

	close(fd);

	fd = -1;



	/* open and load BPF program with custom BTF as the kernel BTF */

	skel = test_core_autosize__open();

	if (!ASSERT_OK_PTR(skel, "skel_open"))

		return;



	/* disable handle_signed() for now */

	prog = bpf_object__find_program_by_name(skel->obj, "handle_signed");

	if (!ASSERT_OK_PTR(prog, "prog_find"))

		goto cleanup;

	bpf_program__set_autoload(prog, false);



	load_attr.obj = skel->obj;

	load_attr.target_btf_path = btf_file;

	err = bpf_object__load_xattr(&load_attr);

	if (!ASSERT_OK(err, "prog_load"))

		goto cleanup;



	prog = bpf_object__find_program_by_name(skel->obj, "handle_samesize");

	if (!ASSERT_OK_PTR(prog, "prog_find"))

		goto cleanup;

	skel->links.handle_samesize = bpf_program__attach(prog);

	if (!ASSERT_OK_PTR(skel->links.handle_samesize, "prog_attach"))

		goto cleanup;



	prog = bpf_object__find_program_by_name(skel->obj, "handle_downsize");

	if (!ASSERT_OK_PTR(prog, "prog_find"))

		goto cleanup;

	skel->links.handle_downsize = bpf_program__attach(prog);

	if (!ASSERT_OK_PTR(skel->links.handle_downsize, "prog_attach"))

		goto cleanup;



	prog = bpf_object__find_program_by_name(skel->obj, "handle_probed");

	if (!ASSERT_OK_PTR(prog, "prog_find"))

		goto cleanup;

	skel->links.handle_probed = bpf_program__attach(prog);

	if (!ASSERT_OK_PTR(skel->links.handle_probed, "prog_attach"))

		goto cleanup;



	usleep(1);



	bss_map = bpf_object__find_map_by_name(skel->obj, "test_cor.bss");

	if (!ASSERT_OK_PTR(bss_map, "bss_map_find"))

		goto cleanup;



	err = bpf_map_lookup_elem(bpf_map__fd(bss_map), &zero, (void *)&out);

	if (!ASSERT_OK(err, "bss_lookup"))

		goto cleanup;



	ASSERT_EQ(out.ptr_samesized, 0x01020304, "ptr_samesized");

	ASSERT_EQ(out.val1_samesized, 0x1020304050607080, "val1_samesized");

	ASSERT_EQ(out.val2_samesized, 0x0a0b0c0d, "val2_samesized");

	ASSERT_EQ(out.val3_samesized, 0xfeed, "val3_samesized");

	ASSERT_EQ(out.val4_samesized, 0xb9, "val4_samesized");

	ASSERT_EQ(out.output_samesized.ptr, 0x01020304, "ptr_samesized");

	ASSERT_EQ(out.output_samesized.val1, 0x1020304050607080, "val1_samesized");

	ASSERT_EQ(out.output_samesized.val2, 0x0a0b0c0d, "val2_samesized");

	ASSERT_EQ(out.output_samesized.val3, 0xfeed, "val3_samesized");

	ASSERT_EQ(out.output_samesized.val4, 0xb9, "val4_samesized");



	ASSERT_EQ(out.ptr_downsized, 0x01020304, "ptr_downsized");

	ASSERT_EQ(out.val1_downsized, 0x1020304050607080, "val1_downsized");

	ASSERT_EQ(out.val2_downsized, 0x0a0b0c0d, "val2_downsized");

	ASSERT_EQ(out.val3_downsized, 0xfeed, "val3_downsized");

	ASSERT_EQ(out.val4_downsized, 0xb9, "val4_downsized");

	ASSERT_EQ(out.output_downsized.ptr, 0x01020304, "ptr_downsized");

	ASSERT_EQ(out.output_downsized.val1, 0x1020304050607080, "val1_downsized");

	ASSERT_EQ(out.output_downsized.val2, 0x0a0b0c0d, "val2_downsized");

	ASSERT_EQ(out.output_downsized.val3, 0xfeed, "val3_downsized");

	ASSERT_EQ(out.output_downsized.val4, 0xb9, "val4_downsized");



	ASSERT_EQ(out.ptr_probed, 0x01020304, "ptr_probed");

	ASSERT_EQ(out.val1_probed, 0x1020304050607080, "val1_probed");

	ASSERT_EQ(out.val2_probed, 0x0a0b0c0d, "val2_probed");

	ASSERT_EQ(out.val3_probed, 0xfeed, "val3_probed");

	ASSERT_EQ(out.val4_probed, 0xb9, "val4_probed");



	test_core_autosize__destroy(skel);

	skel = NULL;



	/* now re-load with handle_signed() enabled, it should fail loading */

	skel = test_core_autosize__open();

	if (!ASSERT_OK_PTR(skel, "skel_open"))

		return;



	load_attr.obj = skel->obj;

	load_attr.target_btf_path = btf_file;

	err = bpf_object__load_xattr(&load_attr);

	if (!ASSERT_ERR(err, "bad_prog_load"))

		goto cleanup;



cleanup:

	if (f)

		fclose(f);

	if (fd >= 0)

		close(fd);

	remove(btf_file);

	btf__free(btf);

	test_core_autosize__destroy(skel);

}

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

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2020 Facebook */



#include <linux/bpf.h>

#include <stdint.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_core_read.h>



char _license[] SEC("license") = "GPL";



/* fields of exactly the same size */

struct test_struct___samesize {

	void *ptr;

	unsigned long long val1;

	unsigned int val2;

	unsigned short val3;

	unsigned char val4;

} __attribute((preserve_access_index));



/* unsigned fields that have to be downsized by libbpf */

struct test_struct___downsize {

	void *ptr;

	unsigned long val1;

	unsigned long val2;

	unsigned long val3;

	unsigned long val4;

	/* total sz: 40 */

} __attribute__((preserve_access_index));



/* fields with signed integers of wrong size, should be rejected */

struct test_struct___signed {

	void *ptr;

	long val1;

	long val2;

	long val3;

	long val4;

} __attribute((preserve_access_index));



/* real layout and sizes according to test's (32-bit) BTF */

struct test_struct___real {

	unsigned int ptr; /* can't use `void *`, it is always 8 byte in BPF target */

	unsigned int val2;

	unsigned long long val1;

	unsigned short val3;

	unsigned char val4;

	unsigned char _pad;

	/* total sz: 20 */

};



struct test_struct___real input = {

	.ptr = 0x01020304,

	.val1 = 0x1020304050607080,

	.val2 = 0x0a0b0c0d,

	.val3 = 0xfeed,

	.val4 = 0xb9,

	._pad = 0xff, /* make sure no accidental zeros are present */

};



unsigned long long ptr_samesized = 0;

unsigned long long val1_samesized = 0;

unsigned long long val2_samesized = 0;

unsigned long long val3_samesized = 0;

unsigned long long val4_samesized = 0;

struct test_struct___real output_samesized = {};



unsigned long long ptr_downsized = 0;

unsigned long long val1_downsized = 0;

unsigned long long val2_downsized = 0;

unsigned long long val3_downsized = 0;

unsigned long long val4_downsized = 0;

struct test_struct___real output_downsized = {};



unsigned long long ptr_probed = 0;

unsigned long long val1_probed = 0;

unsigned long long val2_probed = 0;

unsigned long long val3_probed = 0;

unsigned long long val4_probed = 0;



unsigned long long ptr_signed = 0;

unsigned long long val1_signed = 0;

unsigned long long val2_signed = 0;

unsigned long long val3_signed = 0;

unsigned long long val4_signed = 0;

struct test_struct___real output_signed = {};



SEC("raw_tp/sys_exit")

int handle_samesize(void *ctx)

{

	struct test_struct___samesize *in = (void *)&input;

	struct test_struct___samesize *out = (void *)&output_samesized;



	ptr_samesized = (unsigned long long)in->ptr;

	val1_samesized = in->val1;

	val2_samesized = in->val2;

	val3_samesized = in->val3;

	val4_samesized = in->val4;



	out->ptr = in->ptr;

	out->val1 = in->val1;

	out->val2 = in->val2;

	out->val3 = in->val3;

	out->val4 = in->val4;



	return 0;

}



SEC("raw_tp/sys_exit")

int handle_downsize(void *ctx)

{

	struct test_struct___downsize *in = (void *)&input;

	struct test_struct___downsize *out = (void *)&output_downsized;



	ptr_downsized = (unsigned long long)in->ptr;

	val1_downsized = in->val1;

	val2_downsized = in->val2;

	val3_downsized = in->val3;

	val4_downsized = in->val4;



	out->ptr = in->ptr;

	out->val1 = in->val1;

	out->val2 = in->val2;

	out->val3 = in->val3;

	out->val4 = in->val4;



	return 0;

}



SEC("raw_tp/sys_enter")

int handle_probed(void *ctx)

{

	struct test_struct___downsize *in = (void *)&input;

	__u64 tmp;



	tmp = 0;

	bpf_core_read(&tmp, bpf_core_field_size(in->ptr), &in->ptr);

	ptr_probed = tmp;



	tmp = 0;

	bpf_core_read(&tmp, bpf_core_field_size(in->val1), &in->val1);

	val1_probed = tmp;



	tmp = 0;

	bpf_core_read(&tmp, bpf_core_field_size(in->val2), &in->val2);

	val2_probed = tmp;



	tmp = 0;

	bpf_core_read(&tmp, bpf_core_field_size(in->val3), &in->val3);

	val3_probed = tmp;



	tmp = 0;

	bpf_core_read(&tmp, bpf_core_field_size(in->val4), &in->val4);

	val4_probed = tmp;



	return 0;

}



SEC("raw_tp/sys_enter")

int handle_signed(void *ctx)

{

	struct test_struct___signed *in = (void *)&input;

	struct test_struct___signed *out = (void *)&output_signed;



	val2_signed = in->val2;

	val3_signed = in->val3;

	val4_signed = in->val4;



	out->val2= in->val2;

	out->val3= in->val3;

	out->val4= in->val4;



	return 0;

}

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