Commit 025bd7c7 authored by Song Liu's avatar Song Liu Committed by Alexei Starovoitov

selftests/bpf: Add test for bpf_get_branch_snapshot

This test uses bpf_get_branch_snapshot from a fexit program. The test uses
a target function (bpf_testmod_loop_test) and compares the record against
kallsyms. If there isn't enough record matching kallsyms, the test fails.
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210910183352.3151445-4-songliubraving@fb.com
parent 856c02db
......@@ -13,6 +13,18 @@
DEFINE_PER_CPU(int, bpf_testmod_ksym_percpu) = 123;
noinline int bpf_testmod_loop_test(int n)
{
int i, sum = 0;
/* the primary goal of this test is to test LBR. Create a lot of
* branches in the function, so we can catch it easily.
*/
for (i = 0; i < n; i++)
sum += i;
return sum;
}
noinline ssize_t
bpf_testmod_test_read(struct file *file, struct kobject *kobj,
struct bin_attribute *bin_attr,
......@@ -24,7 +36,11 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj,
.len = len,
};
trace_bpf_testmod_test_read(current, &ctx);
/* This is always true. Use the check to make sure the compiler
* doesn't remove bpf_testmod_loop_test.
*/
if (bpf_testmod_loop_test(101) > 100)
trace_bpf_testmod_test_read(current, &ctx);
return -EIO; /* always fail */
}
......@@ -71,4 +87,3 @@ module_exit(bpf_testmod_exit);
MODULE_AUTHOR("Andrii Nakryiko");
MODULE_DESCRIPTION("BPF selftests module");
MODULE_LICENSE("Dual BSD/GPL");
......@@ -30,7 +30,7 @@ static int duration = 0;
.output_len = sizeof(struct core_reloc_module_output), \
.prog_sec_name = sec_name, \
.raw_tp_name = tp_name, \
.trigger = trigger_module_test_read, \
.trigger = __trigger_module_test_read, \
.needs_testmod = true, \
}
......@@ -475,19 +475,11 @@ static int setup_type_id_case_failure(struct core_reloc_test_case *test)
return 0;
}
static int trigger_module_test_read(const struct core_reloc_test_case *test)
static int __trigger_module_test_read(const struct core_reloc_test_case *test)
{
struct core_reloc_module_output *exp = (void *)test->output;
int fd, err;
fd = open("/sys/kernel/bpf_testmod", O_RDONLY);
err = -errno;
if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err))
return err;
read(fd, NULL, exp->len); /* request expected number of bytes */
close(fd);
trigger_module_test_read(exp->len);
return 0;
}
......
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include <test_progs.h>
#include "get_branch_snapshot.skel.h"
static int *pfd_array;
static int cpu_cnt;
static int create_perf_events(void)
{
struct perf_event_attr attr = {0};
int cpu;
/* create perf event */
attr.size = sizeof(attr);
attr.type = PERF_TYPE_RAW;
attr.config = 0x1b00;
attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
attr.branch_sample_type = PERF_SAMPLE_BRANCH_KERNEL |
PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY;
cpu_cnt = libbpf_num_possible_cpus();
pfd_array = malloc(sizeof(int) * cpu_cnt);
if (!pfd_array) {
cpu_cnt = 0;
return 1;
}
for (cpu = 0; cpu < cpu_cnt; cpu++) {
pfd_array[cpu] = syscall(__NR_perf_event_open, &attr,
-1, cpu, -1, PERF_FLAG_FD_CLOEXEC);
if (pfd_array[cpu] < 0)
break;
}
return cpu == 0;
}
static void close_perf_events(void)
{
int cpu = 0;
int fd;
while (cpu++ < cpu_cnt) {
fd = pfd_array[cpu];
if (fd < 0)
break;
close(fd);
}
free(pfd_array);
}
void test_get_branch_snapshot(void)
{
struct get_branch_snapshot *skel = NULL;
int err;
if (create_perf_events()) {
test__skip(); /* system doesn't support LBR */
goto cleanup;
}
skel = get_branch_snapshot__open_and_load();
if (!ASSERT_OK_PTR(skel, "get_branch_snapshot__open_and_load"))
goto cleanup;
err = kallsyms_find("bpf_testmod_loop_test", &skel->bss->address_low);
if (!ASSERT_OK(err, "kallsyms_find"))
goto cleanup;
err = kallsyms_find_next("bpf_testmod_loop_test", &skel->bss->address_high);
if (!ASSERT_OK(err, "kallsyms_find_next"))
goto cleanup;
err = get_branch_snapshot__attach(skel);
if (!ASSERT_OK(err, "get_branch_snapshot__attach"))
goto cleanup;
trigger_module_test_read(100);
if (skel->bss->total_entries < 16) {
/* too few entries for the hit/waste test */
test__skip();
goto cleanup;
}
ASSERT_GT(skel->bss->test1_hits, 6, "find_looptest_in_lbr");
/* Given we stop LBR in software, we will waste a few entries.
* But we should try to waste as few as possible entries. We are at
* about 7 on x86_64 systems.
* Add a check for < 10 so that we get heads-up when something
* changes and wastes too many entries.
*/
ASSERT_LT(skel->bss->wasted_entries, 10, "check_wasted_entries");
cleanup:
get_branch_snapshot__destroy(skel);
close_perf_events();
}
......@@ -6,45 +6,6 @@
static int duration;
static int trigger_module_test_read(int read_sz)
{
int fd, err;
fd = open("/sys/kernel/bpf_testmod", O_RDONLY);
err = -errno;
if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err))
return err;
read(fd, NULL, read_sz);
close(fd);
return 0;
}
static int trigger_module_test_write(int write_sz)
{
int fd, err;
char *buf = malloc(write_sz);
if (!buf)
return -ENOMEM;
memset(buf, 'a', write_sz);
buf[write_sz-1] = '\0';
fd = open("/sys/kernel/bpf_testmod", O_WRONLY);
err = -errno;
if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) {
free(buf);
return err;
}
write(fd, buf, write_sz);
close(fd);
free(buf);
return 0;
}
static int delete_module(const char *name, int flags)
{
return syscall(__NR_delete_module, name, flags);
......
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
char _license[] SEC("license") = "GPL";
__u64 test1_hits = 0;
__u64 address_low = 0;
__u64 address_high = 0;
int wasted_entries = 0;
long total_entries = 0;
#define ENTRY_CNT 32
struct perf_branch_entry entries[ENTRY_CNT] = {};
static inline bool in_range(__u64 val)
{
return (val >= address_low) && (val < address_high);
}
SEC("fexit/bpf_testmod_loop_test")
int BPF_PROG(test1, int n, int ret)
{
long i;
total_entries = bpf_get_branch_snapshot(entries, sizeof(entries), 0);
total_entries /= sizeof(struct perf_branch_entry);
for (i = 0; i < ENTRY_CNT; i++) {
if (i >= total_entries)
break;
if (in_range(entries[i].from) && in_range(entries[i].to))
test1_hits++;
else if (!test1_hits)
wasted_entries++;
}
return 0;
}
......@@ -743,6 +743,45 @@ int cd_flavor_subdir(const char *exec_name)
return chdir(flavor);
}
int trigger_module_test_read(int read_sz)
{
int fd, err;
fd = open("/sys/kernel/bpf_testmod", O_RDONLY);
err = -errno;
if (!ASSERT_GE(fd, 0, "testmod_file_open"))
return err;
read(fd, NULL, read_sz);
close(fd);
return 0;
}
int trigger_module_test_write(int write_sz)
{
int fd, err;
char *buf = malloc(write_sz);
if (!buf)
return -ENOMEM;
memset(buf, 'a', write_sz);
buf[write_sz-1] = '\0';
fd = open("/sys/kernel/bpf_testmod", O_WRONLY);
err = -errno;
if (!ASSERT_GE(fd, 0, "testmod_file_open")) {
free(buf);
return err;
}
write(fd, buf, write_sz);
close(fd);
free(buf);
return 0;
}
#define MAX_BACKTRACE_SZ 128
void crash_handler(int signum)
{
......
......@@ -291,6 +291,8 @@ int compare_map_keys(int map1_fd, int map2_fd);
int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len);
int extract_build_id(char *build_id, size_t size);
int kern_sync_rcu(void);
int trigger_module_test_read(int read_sz);
int trigger_module_test_write(int write_sz);
#ifdef __x86_64__
#define SYS_NANOSLEEP_KPROBE_NAME "__x64_sys_nanosleep"
......
// SPDX-License-Identifier: GPL-2.0
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
......@@ -117,6 +118,42 @@ int kallsyms_find(const char *sym, unsigned long long *addr)
return err;
}
/* find the address of the next symbol of the same type, this can be used
* to determine the end of a function.
*/
int kallsyms_find_next(const char *sym, unsigned long long *addr)
{
char type, found_type, name[500];
unsigned long long value;
bool found = false;
int err = 0;
FILE *f;
f = fopen("/proc/kallsyms", "r");
if (!f)
return -EINVAL;
while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) {
/* Different types of symbols in kernel modules are mixed
* in /proc/kallsyms. Only return the next matching type.
* Use tolower() for type so that 'T' matches 't'.
*/
if (found && found_type == tolower(type)) {
*addr = value;
goto out;
}
if (strcmp(name, sym) == 0) {
found = true;
found_type = tolower(type);
}
}
err = -ENOENT;
out:
fclose(f);
return err;
}
void read_trace_pipe(void)
{
int trace_fd;
......
......@@ -16,6 +16,11 @@ long ksym_get_addr(const char *name);
/* open kallsyms and find addresses on the fly, faster than load + search. */
int kallsyms_find(const char *sym, unsigned long long *addr);
/* find the address of the next symbol, this can be used to determine the
* end of a function
*/
int kallsyms_find_next(const char *sym, unsigned long long *addr);
void read_trace_pipe(void);
ssize_t get_uprobe_offset(const void *addr, ssize_t base);
......
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