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selftests/bpf: add CO-RE relocs testing setup
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Add CO-RE relocation test runner. Add one simple test validating that
libbpf's logic for searching for kernel image and loading BTF out of it
works.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored and Alexei Starovoitov committed Aug 7, 2019
1 parent 2dc26d5 commit df36e62
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129 changes: 129 additions & 0 deletions tools/testing/selftests/bpf/prog_tests/core_reloc.c
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// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>

struct core_reloc_test_case {
const char *case_name;
const char *bpf_obj_file;
const char *btf_src_file;
const char *input;
int input_len;
const char *output;
int output_len;
bool fails;
};

static struct core_reloc_test_case test_cases[] = {
/* validate we can find kernel image and use its BTF for relocs */
{
.case_name = "kernel",
.bpf_obj_file = "test_core_reloc_kernel.o",
.btf_src_file = NULL, /* load from /lib/modules/$(uname -r) */
.input = "",
.input_len = 0,
.output = "\1", /* true */
.output_len = 1,
},
};

struct data {
char in[256];
char out[256];
};

void test_core_reloc(void)
{
const char *probe_name = "raw_tracepoint/sys_enter";
struct bpf_object_load_attr load_attr = {};
struct core_reloc_test_case *test_case;
int err, duration = 0, i, equal;
struct bpf_link *link = NULL;
struct bpf_map *data_map;
struct bpf_program *prog;
struct bpf_object *obj;
const int zero = 0;
struct data data;

for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
test_case = &test_cases[i];

if (!test__start_subtest(test_case->case_name))
continue;

obj = bpf_object__open(test_case->bpf_obj_file);
if (CHECK(IS_ERR_OR_NULL(obj), "obj_open",
"failed to open '%s': %ld\n",
test_case->bpf_obj_file, PTR_ERR(obj)))
continue;

prog = bpf_object__find_program_by_title(obj, probe_name);
if (CHECK(!prog, "find_probe",
"prog '%s' not found\n", probe_name))
goto cleanup;
bpf_program__set_type(prog, BPF_PROG_TYPE_RAW_TRACEPOINT);

load_attr.obj = obj;
load_attr.log_level = 0;
load_attr.target_btf_path = test_case->btf_src_file;
err = bpf_object__load_xattr(&load_attr);
if (test_case->fails) {
CHECK(!err, "obj_load_fail",
"should fail to load prog '%s'\n", probe_name);
goto cleanup;
} else {
if (CHECK(err, "obj_load",
"failed to load prog '%s': %d\n",
probe_name, err))
goto cleanup;
}

link = bpf_program__attach_raw_tracepoint(prog, "sys_enter");
if (CHECK(IS_ERR(link), "attach_raw_tp", "err %ld\n",
PTR_ERR(link)))
goto cleanup;

data_map = bpf_object__find_map_by_name(obj, "test_cor.bss");
if (CHECK(!data_map, "find_data_map", "data map not found\n"))
goto cleanup;

memset(&data, 0, sizeof(data));
memcpy(data.in, test_case->input, test_case->input_len);

err = bpf_map_update_elem(bpf_map__fd(data_map),
&zero, &data, 0);
if (CHECK(err, "update_data_map",
"failed to update .data map: %d\n", err))
goto cleanup;

/* trigger test run */
usleep(1);

err = bpf_map_lookup_elem(bpf_map__fd(data_map), &zero, &data);
if (CHECK(err, "get_result",
"failed to get output data: %d\n", err))
goto cleanup;

equal = memcmp(data.out, test_case->output,
test_case->output_len) == 0;
if (CHECK(!equal, "check_result",
"input/output data don't match\n")) {
int j;

for (j = 0; j < test_case->input_len; j++) {
printf("input byte #%d: 0x%02hhx\n",
j, test_case->input[j]);
}
for (j = 0; j < test_case->output_len; j++) {
printf("output byte #%d: EXP 0x%02hhx GOT 0x%02hhx\n",
j, test_case->output[j], data.out[j]);
}
goto cleanup;
}

cleanup:
if (!IS_ERR_OR_NULL(link)) {
bpf_link__destroy(link);
link = NULL;
}
bpf_object__close(obj);
}
}
36 changes: 36 additions & 0 deletions tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Facebook

#include <linux/bpf.h>
#include <stdint.h>
#include "bpf_helpers.h"

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

static volatile struct data {
char in[256];
char out[256];
} data;

struct task_struct {
int pid;
int tgid;
};

SEC("raw_tracepoint/sys_enter")
int test_core_kernel(void *ctx)
{
struct task_struct *task = (void *)bpf_get_current_task();
uint64_t pid_tgid = bpf_get_current_pid_tgid();
int pid, tgid;

if (BPF_CORE_READ(&pid, &task->pid) ||
BPF_CORE_READ(&tgid, &task->tgid))
return 1;

/* validate pid + tgid matches */
data.out[0] = (((uint64_t)pid << 32) | tgid) == pid_tgid;

return 0;
}

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