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linux/tools/testing/selftests/bpf/prog_tests/usdt.c
Andrii Nakryiko 00a0fa2d7d selftests/bpf: Add urandom_read shared lib and USDTs 
Extend urandom_read helper binary to include USDTs of 4 combinations:
semaphore/semaphoreless (refcounted and non-refcounted) and based in
executable or shared library. We also extend urandom_read with ability
to report it's own PID to parent process and wait for parent process to
ready itself up for tracing urandom_read. We utilize popen() and
underlying pipe properties for proper signaling.

Once urandom_read is ready, we add few tests to validate that libbpf's
USDT attachment handles all the above combinations of semaphore (or lack
of it) and static or shared library USDTs. Also, we validate that libbpf
handles shared libraries both with PID filter and without one (i.e., -1
for PID argument).

Having the shared library case tested with and without PID is important
because internal logic differs on kernels that don't support BPF
cookies. On such older kernels, attaching to USDTs in shared libraries
without specifying concrete PID doesn't work in principle, because it's
impossible to determine shared library's load address to derive absolute
IPs for uprobe attachments. Without absolute IPs, it's impossible to
perform correct look up of USDT spec based on uprobe's absolute IP (the
only kind available from BPF at runtime). This is not the problem on
newer kernels with BPF cookie as we don't need IP-to-ID lookup because
BPF cookie value *is* spec ID.

So having those two situations as separate subtests is good because
libbpf CI is able to test latest selftests against old kernels (e.g.,
4.9 and 5.5), so we'll be able to disable PID-less shared lib attachment
for old kernels, but will still leave PID-specific one enabled to validate
this legacy logic is working correctly.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/bpf/20220404234202.331384-8-andrii@kernel.org
2022-04-05 13:16:08 -07:00

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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
#include <test_progs.h>
#define _SDT_HAS_SEMAPHORES 1
#include "../sdt.h"
#include "test_usdt.skel.h"
#include "test_urandom_usdt.skel.h"
int lets_test_this(int);
static volatile int idx = 2;
static volatile __u64 bla = 0xFEDCBA9876543210ULL;
static volatile short nums[] = {-1, -2, -3, };
static volatile struct {
int x;
signed char y;
} t1 = { 1, -127 };
#define SEC(name) __attribute__((section(name), used))
unsigned short test_usdt0_semaphore SEC(".probes");
unsigned short test_usdt3_semaphore SEC(".probes");
unsigned short test_usdt12_semaphore SEC(".probes");
static void __always_inline trigger_func(int x) {
long y = 42;
if (test_usdt0_semaphore)
STAP_PROBE(test, usdt0);
if (test_usdt3_semaphore)
STAP_PROBE3(test, usdt3, x, y, &bla);
if (test_usdt12_semaphore) {
STAP_PROBE12(test, usdt12,
x, x + 1, y, x + y, 5,
y / 7, bla, &bla, -9, nums[x],
nums[idx], t1.y);
}
}
static void subtest_basic_usdt(void)
{
LIBBPF_OPTS(bpf_usdt_opts, opts);
struct test_usdt *skel;
struct test_usdt__bss *bss;
int err;
skel = test_usdt__open_and_load();
if (!ASSERT_OK_PTR(skel, "skel_open"))
return;
bss = skel->bss;
bss->my_pid = getpid();
err = test_usdt__attach(skel);
if (!ASSERT_OK(err, "skel_attach"))
goto cleanup;
/* usdt0 won't be auto-attached */
opts.usdt_cookie = 0xcafedeadbeeffeed;
skel->links.usdt0 = bpf_program__attach_usdt(skel->progs.usdt0,
0 /*self*/, "/proc/self/exe",
"test", "usdt0", &opts);
if (!ASSERT_OK_PTR(skel->links.usdt0, "usdt0_link"))
goto cleanup;
trigger_func(1);
ASSERT_EQ(bss->usdt0_called, 1, "usdt0_called");
ASSERT_EQ(bss->usdt3_called, 1, "usdt3_called");
ASSERT_EQ(bss->usdt12_called, 1, "usdt12_called");
ASSERT_EQ(bss->usdt0_cookie, 0xcafedeadbeeffeed, "usdt0_cookie");
ASSERT_EQ(bss->usdt0_arg_cnt, 0, "usdt0_arg_cnt");
ASSERT_EQ(bss->usdt0_arg_ret, -ENOENT, "usdt0_arg_ret");
/* auto-attached usdt3 gets default zero cookie value */
ASSERT_EQ(bss->usdt3_cookie, 0, "usdt3_cookie");
ASSERT_EQ(bss->usdt3_arg_cnt, 3, "usdt3_arg_cnt");
ASSERT_EQ(bss->usdt3_arg_rets[0], 0, "usdt3_arg1_ret");
ASSERT_EQ(bss->usdt3_arg_rets[1], 0, "usdt3_arg2_ret");
ASSERT_EQ(bss->usdt3_arg_rets[2], 0, "usdt3_arg3_ret");
ASSERT_EQ(bss->usdt3_args[0], 1, "usdt3_arg1");
ASSERT_EQ(bss->usdt3_args[1], 42, "usdt3_arg2");
ASSERT_EQ(bss->usdt3_args[2], (uintptr_t)&bla, "usdt3_arg3");
/* auto-attached usdt12 gets default zero cookie value */
ASSERT_EQ(bss->usdt12_cookie, 0, "usdt12_cookie");
ASSERT_EQ(bss->usdt12_arg_cnt, 12, "usdt12_arg_cnt");
ASSERT_EQ(bss->usdt12_args[0], 1, "usdt12_arg1");
ASSERT_EQ(bss->usdt12_args[1], 1 + 1, "usdt12_arg2");
ASSERT_EQ(bss->usdt12_args[2], 42, "usdt12_arg3");
ASSERT_EQ(bss->usdt12_args[3], 42 + 1, "usdt12_arg4");
ASSERT_EQ(bss->usdt12_args[4], 5, "usdt12_arg5");
ASSERT_EQ(bss->usdt12_args[5], 42 / 7, "usdt12_arg6");
ASSERT_EQ(bss->usdt12_args[6], bla, "usdt12_arg7");
ASSERT_EQ(bss->usdt12_args[7], (uintptr_t)&bla, "usdt12_arg8");
ASSERT_EQ(bss->usdt12_args[8], -9, "usdt12_arg9");
ASSERT_EQ(bss->usdt12_args[9], nums[1], "usdt12_arg10");
ASSERT_EQ(bss->usdt12_args[10], nums[idx], "usdt12_arg11");
ASSERT_EQ(bss->usdt12_args[11], t1.y, "usdt12_arg12");
/* trigger_func() is marked __always_inline, so USDT invocations will be
* inlined in two different places, meaning that each USDT will have
* at least 2 different places to be attached to. This verifies that
* bpf_program__attach_usdt() handles this properly and attaches to
* all possible places of USDT invocation.
*/
trigger_func(2);
ASSERT_EQ(bss->usdt0_called, 2, "usdt0_called");
ASSERT_EQ(bss->usdt3_called, 2, "usdt3_called");
ASSERT_EQ(bss->usdt12_called, 2, "usdt12_called");
/* only check values that depend on trigger_func()'s input value */
ASSERT_EQ(bss->usdt3_args[0], 2, "usdt3_arg1");
ASSERT_EQ(bss->usdt12_args[0], 2, "usdt12_arg1");
ASSERT_EQ(bss->usdt12_args[1], 2 + 1, "usdt12_arg2");
ASSERT_EQ(bss->usdt12_args[3], 42 + 2, "usdt12_arg4");
ASSERT_EQ(bss->usdt12_args[9], nums[2], "usdt12_arg10");
/* detach and re-attach usdt3 */
bpf_link__destroy(skel->links.usdt3);
opts.usdt_cookie = 0xBADC00C51E;
skel->links.usdt3 = bpf_program__attach_usdt(skel->progs.usdt3, -1 /* any pid */,
"/proc/self/exe", "test", "usdt3", &opts);
if (!ASSERT_OK_PTR(skel->links.usdt3, "usdt3_reattach"))
goto cleanup;
trigger_func(3);
ASSERT_EQ(bss->usdt3_called, 3, "usdt3_called");
/* this time usdt3 has custom cookie */
ASSERT_EQ(bss->usdt3_cookie, 0xBADC00C51E, "usdt3_cookie");
ASSERT_EQ(bss->usdt3_arg_cnt, 3, "usdt3_arg_cnt");
ASSERT_EQ(bss->usdt3_arg_rets[0], 0, "usdt3_arg1_ret");
ASSERT_EQ(bss->usdt3_arg_rets[1], 0, "usdt3_arg2_ret");
ASSERT_EQ(bss->usdt3_arg_rets[2], 0, "usdt3_arg3_ret");
ASSERT_EQ(bss->usdt3_args[0], 3, "usdt3_arg1");
ASSERT_EQ(bss->usdt3_args[1], 42, "usdt3_arg2");
ASSERT_EQ(bss->usdt3_args[2], (uintptr_t)&bla, "usdt3_arg3");
cleanup:
test_usdt__destroy(skel);
}
unsigned short test_usdt_100_semaphore SEC(".probes");
unsigned short test_usdt_300_semaphore SEC(".probes");
unsigned short test_usdt_400_semaphore SEC(".probes");
#define R10(F, X) F(X+0); F(X+1);F(X+2); F(X+3); F(X+4); \
F(X+5); F(X+6); F(X+7); F(X+8); F(X+9);
#define R100(F, X) R10(F,X+ 0);R10(F,X+10);R10(F,X+20);R10(F,X+30);R10(F,X+40); \
R10(F,X+50);R10(F,X+60);R10(F,X+70);R10(F,X+80);R10(F,X+90);
/* carefully control that we get exactly 100 inlines by preventing inlining */
static void __always_inline f100(int x)
{
STAP_PROBE1(test, usdt_100, x);
}
__weak void trigger_100_usdts(void)
{
R100(f100, 0);
}
/* we shouldn't be able to attach to test:usdt2_300 USDT as we don't have as
* many slots for specs. It's important that each STAP_PROBE2() invocation
* (after untolling) gets different arg spec due to compiler inlining i as
* a constant
*/
static void __always_inline f300(int x)
{
STAP_PROBE1(test, usdt_300, x);
}
__weak void trigger_300_usdts(void)
{
R100(f300, 0);
R100(f300, 100);
R100(f300, 200);
}
static void __always_inline f400(int x __attribute__((unused)))
{
static int y;
STAP_PROBE1(test, usdt_400, y++);
}
/* this time we have 400 different USDT call sites, but they have uniform
* argument location, so libbpf's spec string deduplication logic should keep
* spec count use very small and so we should be able to attach to all 400
* call sites
*/
__weak void trigger_400_usdts(void)
{
R100(f400, 0);
R100(f400, 100);
R100(f400, 200);
R100(f400, 300);
}
static void subtest_multispec_usdt(void)
{
LIBBPF_OPTS(bpf_usdt_opts, opts);
struct test_usdt *skel;
struct test_usdt__bss *bss;
int err, i;
skel = test_usdt__open_and_load();
if (!ASSERT_OK_PTR(skel, "skel_open"))
return;
bss = skel->bss;
bss->my_pid = getpid();
err = test_usdt__attach(skel);
if (!ASSERT_OK(err, "skel_attach"))
goto cleanup;
/* usdt_100 is auto-attached and there are 100 inlined call sites,
* let's validate that all of them are properly attached to and
* handled from BPF side
*/
trigger_100_usdts();
ASSERT_EQ(bss->usdt_100_called, 100, "usdt_100_called");
ASSERT_EQ(bss->usdt_100_sum, 99 * 100 / 2, "usdt_100_sum");
/* Stress test free spec ID tracking. By default libbpf allows up to
* 256 specs to be used, so if we don't return free spec IDs back
* after few detachments and re-attachments we should run out of
* available spec IDs.
*/
for (i = 0; i < 2; i++) {
bpf_link__destroy(skel->links.usdt_100);
skel->links.usdt_100 = bpf_program__attach_usdt(skel->progs.usdt_100, -1,
"/proc/self/exe",
"test", "usdt_100", NULL);
if (!ASSERT_OK_PTR(skel->links.usdt_100, "usdt_100_reattach"))
goto cleanup;
bss->usdt_100_sum = 0;
trigger_100_usdts();
ASSERT_EQ(bss->usdt_100_called, (i + 1) * 100 + 100, "usdt_100_called");
ASSERT_EQ(bss->usdt_100_sum, 99 * 100 / 2, "usdt_100_sum");
}
/* Now let's step it up and try to attach USDT that requires more than
* 256 attach points with different specs for each.
* Note that we need trigger_300_usdts() only to actually have 300
* USDT call sites, we are not going to actually trace them.
*/
trigger_300_usdts();
/* we'll reuse usdt_100 BPF program for usdt_300 test */
bpf_link__destroy(skel->links.usdt_100);
skel->links.usdt_100 = bpf_program__attach_usdt(skel->progs.usdt_100, -1, "/proc/self/exe",
"test", "usdt_300", NULL);
err = -errno;
if (!ASSERT_ERR_PTR(skel->links.usdt_100, "usdt_300_bad_attach"))
goto cleanup;
ASSERT_EQ(err, -E2BIG, "usdt_300_attach_err");
/* let's check that there are no "dangling" BPF programs attached due
* to partial success of the above test:usdt_300 attachment
*/
bss->usdt_100_called = 0;
bss->usdt_100_sum = 0;
f300(777); /* this is 301st instance of usdt_300 */
ASSERT_EQ(bss->usdt_100_called, 0, "usdt_301_called");
ASSERT_EQ(bss->usdt_100_sum, 0, "usdt_301_sum");
/* This time we have USDT with 400 inlined invocations, but arg specs
* should be the same across all sites, so libbpf will only need to
* use one spec and thus we'll be able to attach 400 uprobes
* successfully.
*
* Again, we are reusing usdt_100 BPF program.
*/
skel->links.usdt_100 = bpf_program__attach_usdt(skel->progs.usdt_100, -1,
"/proc/self/exe",
"test", "usdt_400", NULL);
if (!ASSERT_OK_PTR(skel->links.usdt_100, "usdt_400_attach"))
goto cleanup;
trigger_400_usdts();
ASSERT_EQ(bss->usdt_100_called, 400, "usdt_400_called");
ASSERT_EQ(bss->usdt_100_sum, 399 * 400 / 2, "usdt_400_sum");
cleanup:
test_usdt__destroy(skel);
}
static FILE *urand_spawn(int *pid)
{
FILE *f;
/* urandom_read's stdout is wired into f */
f = popen("./urandom_read 1 report-pid", "r");
if (!f)
return NULL;
if (fscanf(f, "%d", pid) != 1) {
pclose(f);
return NULL;
}
return f;
}
static int urand_trigger(FILE **urand_pipe)
{
int exit_code;
/* pclose() waits for child process to exit and returns their exit code */
exit_code = pclose(*urand_pipe);
*urand_pipe = NULL;
return exit_code;
}
static void subtest_urandom_usdt(bool auto_attach)
{
struct test_urandom_usdt *skel;
struct test_urandom_usdt__bss *bss;
struct bpf_link *l;
FILE *urand_pipe = NULL;
int err, urand_pid = 0;
skel = test_urandom_usdt__open_and_load();
if (!ASSERT_OK_PTR(skel, "skel_open"))
return;
urand_pipe = urand_spawn(&urand_pid);
if (!ASSERT_OK_PTR(urand_pipe, "urand_spawn"))
goto cleanup;
bss = skel->bss;
bss->urand_pid = urand_pid;
if (auto_attach) {
err = test_urandom_usdt__attach(skel);
if (!ASSERT_OK(err, "skel_auto_attach"))
goto cleanup;
} else {
l = bpf_program__attach_usdt(skel->progs.urand_read_without_sema,
urand_pid, "./urandom_read",
"urand", "read_without_sema", NULL);
if (!ASSERT_OK_PTR(l, "urand_without_sema_attach"))
goto cleanup;
skel->links.urand_read_without_sema = l;
l = bpf_program__attach_usdt(skel->progs.urand_read_with_sema,
urand_pid, "./urandom_read",
"urand", "read_with_sema", NULL);
if (!ASSERT_OK_PTR(l, "urand_with_sema_attach"))
goto cleanup;
skel->links.urand_read_with_sema = l;
l = bpf_program__attach_usdt(skel->progs.urandlib_read_without_sema,
urand_pid, "./liburandom_read.so",
"urandlib", "read_without_sema", NULL);
if (!ASSERT_OK_PTR(l, "urandlib_without_sema_attach"))
goto cleanup;
skel->links.urandlib_read_without_sema = l;
l = bpf_program__attach_usdt(skel->progs.urandlib_read_with_sema,
urand_pid, "./liburandom_read.so",
"urandlib", "read_with_sema", NULL);
if (!ASSERT_OK_PTR(l, "urandlib_with_sema_attach"))
goto cleanup;
skel->links.urandlib_read_with_sema = l;
}
/* trigger urandom_read USDTs */
ASSERT_OK(urand_trigger(&urand_pipe), "urand_exit_code");
ASSERT_EQ(bss->urand_read_without_sema_call_cnt, 1, "urand_wo_sema_cnt");
ASSERT_EQ(bss->urand_read_without_sema_buf_sz_sum, 256, "urand_wo_sema_sum");
ASSERT_EQ(bss->urand_read_with_sema_call_cnt, 1, "urand_w_sema_cnt");
ASSERT_EQ(bss->urand_read_with_sema_buf_sz_sum, 256, "urand_w_sema_sum");
ASSERT_EQ(bss->urandlib_read_without_sema_call_cnt, 1, "urandlib_wo_sema_cnt");
ASSERT_EQ(bss->urandlib_read_without_sema_buf_sz_sum, 256, "urandlib_wo_sema_sum");
ASSERT_EQ(bss->urandlib_read_with_sema_call_cnt, 1, "urandlib_w_sema_cnt");
ASSERT_EQ(bss->urandlib_read_with_sema_buf_sz_sum, 256, "urandlib_w_sema_sum");
cleanup:
if (urand_pipe)
pclose(urand_pipe);
test_urandom_usdt__destroy(skel);
}
void test_usdt(void)
{
if (test__start_subtest("basic"))
subtest_basic_usdt();
if (test__start_subtest("multispec"))
subtest_multispec_usdt();
if (test__start_subtest("urand_auto_attach"))
subtest_urandom_usdt(true /* auto_attach */);
if (test__start_subtest("urand_pid_attach"))
subtest_urandom_usdt(false /* auto_attach */);
}
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