Skip to content

Commit

Permalink
selftests/bpf: Validate libbpf's auto-sizing of LD/ST/STX instructions
Browse files Browse the repository at this point in the history 
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: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201008001025.292064-5-andrii@kernel.org
  • Loading branch information
Andrii Nakryiko authored and Alexei Starovoitov committed Oct 8, 2020
1 parent 2b7d88c commit 888d83b
Show file tree
Hide file tree
Showing 2 changed files with 397 additions and 0 deletions.
225 changes: 225 additions & 0 deletions tools/testing/selftests/bpf/prog_tests/core_autosize.c
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,225 @@
// 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);
}
172 changes: 172 additions & 0 deletions tools/testing/selftests/bpf/progs/test_core_autosize.c
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,172 @@
// 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;
}

0 comments on commit 888d83b

Please sign in to comment.