kperf_backtracing.c [plain text]
#include <CoreSymbolication/CoreSymbolication.h>
#include <darwintest.h>
#include <dispatch/dispatch.h>
#include <kperf/kperf.h>
#include <ktrace.h>
#include <pthread.h>
#include "kperf_helpers.h"
#define PERF_STK_KHDR UINT32_C(0x25020014)
#define PERF_STK_UHDR UINT32_C(0x25020018)
#define PERF_STK_KDATA UINT32_C(0x2502000c)
#define PERF_STK_UDATA UINT32_C(0x25020010)
static void
expect_frame(const char **bt, unsigned int bt_len, CSSymbolRef symbol,
unsigned long addr, unsigned int bt_idx, unsigned int max_frames)
{
const char *name;
unsigned int frame_idx = max_frames - bt_idx - 1;
if (!bt[frame_idx]) {
T_LOG("frame %2u: skipping system frame", frame_idx);
return;
}
if (CSIsNull(symbol)) {
T_FAIL("invalid symbol for address %#lx at frame %d", addr, frame_idx);
return;
}
if (frame_idx >= bt_len) {
T_FAIL("unexpected frame '%s' (%#lx) at index %u",
CSSymbolGetName(symbol), addr, frame_idx);
return;
}
name = CSSymbolGetName(symbol);
T_QUIET; T_ASSERT_NOTNULL(name, NULL);
T_EXPECT_EQ_STR(name, bt[frame_idx],
"frame %2u: saw '%s', expected '%s'",
frame_idx, name, bt[frame_idx]);
}
static void
expect_backtrace(ktrace_session_t s, uint64_t tid, unsigned int *stacks_seen,
bool kern, const char **bt, unsigned int bt_len)
{
CSSymbolicatorRef symb;
uint32_t hdr_debugid;
uint32_t data_debugid;
__block unsigned int stacks = 0;
__block unsigned int frames = 0;
__block unsigned int hdr_frames = 0;
if (kern) {
static CSSymbolicatorRef kern_symb;
static dispatch_once_t kern_symb_once;
hdr_debugid = PERF_STK_KHDR;
data_debugid = PERF_STK_KDATA;
dispatch_once(&kern_symb_once, ^(void) {
kern_symb = CSSymbolicatorCreateWithMachKernel();
T_QUIET; T_ASSERT_FALSE(CSIsNull(kern_symb), NULL);
});
symb = kern_symb;
} else {
static CSSymbolicatorRef user_symb;
static dispatch_once_t user_symb_once;
hdr_debugid = PERF_STK_UHDR;
data_debugid = PERF_STK_UDATA;
dispatch_once(&user_symb_once, ^(void) {
user_symb = CSSymbolicatorCreateWithTask(mach_task_self());
T_QUIET; T_ASSERT_FALSE(CSIsNull(user_symb), NULL);
T_QUIET; T_ASSERT_TRUE(CSSymbolicatorIsTaskValid(user_symb), NULL);
});
symb = user_symb;
}
ktrace_events_single(s, hdr_debugid, ^(struct trace_point *tp) {
if (tid != 0 && tid != tp->threadid) {
return;
}
stacks++;
if (!(tp->arg1 & 1)) {
T_FAIL("invalid %s stack on thread %#lx", kern ? "kernel" : "user",
tp->threadid);
return;
}
hdr_frames = (unsigned int)tp->arg2;
hdr_frames -= 1;
T_QUIET; T_EXPECT_EQ(hdr_frames, bt_len,
"number of frames in header");
T_LOG("%s stack seen", kern ? "kernel" : "user");
frames = 0;
});
ktrace_events_single(s, data_debugid, ^(struct trace_point *tp) {
if (tid != 0 && tid != tp->threadid) {
return;
}
for (int i = 0; i < 4 && frames < hdr_frames; i++, frames++) {
unsigned long addr = (&tp->arg1)[i];
CSSymbolRef symbol = CSSymbolicatorGetSymbolWithAddressAtTime(
symb, addr, kCSNow);
expect_frame(bt, bt_len, symbol, addr, frames, hdr_frames);
}
if (hdr_frames == frames) {
*stacks_seen += 1;
if (!kern) {
ktrace_end(s, 1);
}
}
});
}
#define TRIGGERING_DEBUGID (0xfeff0f00)
static int __attribute__((noinline,not_tail_called))
recurse_a(bool spin, unsigned int frames);
static int __attribute__((noinline,not_tail_called))
recurse_b(bool spin, unsigned int frames);
static int __attribute__((noinline,not_tail_called))
recurse_a(bool spin, unsigned int frames)
{
if (frames == 0) {
if (spin) {
for (;;);
} else {
kdebug_trace(TRIGGERING_DEBUGID, 0, 0, 0, 0);
return 0;
}
}
return recurse_b(spin, frames - 1) + 1;
}
static int __attribute__((noinline,not_tail_called))
recurse_b(bool spin, unsigned int frames)
{
if (frames == 0) {
if (spin) {
for (;;);
} else {
kdebug_trace(TRIGGERING_DEBUGID, 0, 0, 0, 0);
return 0;
}
}
return recurse_a(spin, frames - 1) + 1;
}
#define USER_FRAMES (12)
#if defined(__x86_64__)
#define RECURSE_START_OFFSET (4)
#else
#define RECURSE_START_OFFSET (3)
#endif
static const char *user_bt[USER_FRAMES] = {
#if defined(__x86_64__)
NULL,
#endif
NULL, NULL,
"backtrace_thread",
"recurse_a", "recurse_b", "recurse_a", "recurse_b",
"recurse_a", "recurse_b", "recurse_a",
#if !defined(__x86_64__)
"recurse_b",
#endif
NULL
};
#if defined(__x86_64__)
#define KERNEL_FRAMES (2)
static const char *kernel_bt[KERNEL_FRAMES] = {
"unix_syscall64", "kdebug_trace64"
};
#else
#error "architecture unsupported"
#endif
static dispatch_once_t backtrace_start_once;
static dispatch_semaphore_t backtrace_start;
static void *
backtrace_thread(void *arg)
{
bool spin;
unsigned int calls;
spin = (bool)arg;
dispatch_semaphore_wait(backtrace_start, DISPATCH_TIME_FOREVER);
calls = USER_FRAMES - RECURSE_START_OFFSET - 1 ;
if (spin) {
calls -= 1;
}
T_LOG("backtrace thread calling into %d frames (already at %d frames)",
calls, RECURSE_START_OFFSET);
(void)recurse_a(spin, calls);
return NULL;
}
static uint64_t
create_backtrace_thread(bool spin)
{
pthread_t thread;
uint64_t tid;
dispatch_once(&backtrace_start_once, ^(void) {
backtrace_start = dispatch_semaphore_create(0);
});
T_QUIET; T_ASSERT_POSIX_ZERO(pthread_create(&thread, NULL, backtrace_thread,
(void *)spin), NULL);
T_QUIET; T_ASSERT_POSIX_ZERO(pthread_threadid_np(thread, &tid), NULL);
return tid;
}
static void
start_backtrace_thread(void)
{
T_QUIET; T_ASSERT_NOTNULL(backtrace_start,
"thread to backtrace created before starting it");
dispatch_semaphore_signal(backtrace_start);
}
#define TEST_TIMEOUT_NS (5 * NSEC_PER_SEC)
T_DECL(kdebug_trigger_backtraces,
"test that backtraces from kdebug trigger are correct",
T_META_ASROOT(YES))
{
static unsigned int stacks_seen = 0;
ktrace_session_t s;
kperf_kdebug_filter_t filter;
uint64_t tid;
s = ktrace_session_create();
T_ASSERT_NOTNULL(s, "ktrace session was created");
T_ASSERT_POSIX_ZERO(ktrace_filter_pid(s, getpid()), NULL);
tid = create_backtrace_thread(false);
expect_backtrace(s, tid, &stacks_seen, false, user_bt, USER_FRAMES);
expect_backtrace(s, tid, &stacks_seen, true, kernel_bt, KERNEL_FRAMES);
ktrace_events_single(s, TRIGGERING_DEBUGID,
^(__unused struct trace_point *tp){ });
ktrace_set_completion_handler(s, ^(void) {
T_EXPECT_GE(stacks_seen, 2U, "saw both kernel and user stacks");
ktrace_session_destroy(s);
kperf_reset();
T_END;
});
filter = kperf_kdebug_filter_create();
T_ASSERT_NOTNULL(filter, "kperf kdebug filter was created");
T_QUIET; T_ASSERT_POSIX_SUCCESS(kperf_kdebug_filter_add_debugid(filter,
TRIGGERING_DEBUGID), NULL);
T_QUIET; T_ASSERT_POSIX_SUCCESS(kperf_kdebug_filter_set(filter), NULL);
(void)kperf_action_count_set(1);
T_QUIET; T_ASSERT_POSIX_SUCCESS(kperf_action_samplers_set(1,
KPERF_SAMPLER_USTACK | KPERF_SAMPLER_KSTACK), NULL);
T_QUIET; T_ASSERT_POSIX_SUCCESS(kperf_kdebug_action_set(1), NULL);
kperf_kdebug_filter_destroy(filter);
T_ASSERT_POSIX_SUCCESS(kperf_sample_set(1), NULL);
T_ASSERT_POSIX_ZERO(ktrace_start(s, dispatch_get_main_queue()), NULL);
start_backtrace_thread();
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, TEST_TIMEOUT_NS),
dispatch_get_main_queue(), ^(void)
{
ktrace_end(s, 0);
});
dispatch_main();
}
T_DECL(user_backtraces_timer,
"test that user backtraces on a timer are correct",
T_META_ASROOT(YES))
{
static unsigned int stacks_seen = 0;
ktrace_session_t s;
uint64_t tid;
s = ktrace_session_create();
T_QUIET; T_ASSERT_NOTNULL(s, "ktrace_session_create");
ktrace_filter_pid(s, getpid());
configure_kperf_stacks_timer(getpid(), 10);
tid = create_backtrace_thread(true);
expect_backtrace(s, tid, &stacks_seen, false, user_bt, USER_FRAMES - 1);
ktrace_set_completion_handler(s, ^(void) {
T_EXPECT_GE(stacks_seen, 1U, "saw at least one stack");
ktrace_session_destroy(s);
kperf_reset();
T_END;
});
T_QUIET; T_ASSERT_POSIX_SUCCESS(kperf_sample_set(1), NULL);
T_ASSERT_POSIX_ZERO(ktrace_start(s, dispatch_get_main_queue()), NULL);
start_backtrace_thread();
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, TEST_TIMEOUT_NS),
dispatch_get_main_queue(), ^(void)
{
ktrace_end(s, 0);
});
dispatch_main();
}