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kernel.c
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kernel.c
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/*
* Linux kernel ftrace support code.
*
* Copyright (c) 2015-2018 LG Electronics, Namhyung Kim <namhyung@gmail.com>
*
* Released under the GPL v2.
*/
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <dirent.h>
#include <sys/stat.h>
#include <sys/mman.h>
/* This should be defined before #include "utils.h" */
#define PR_FMT "kernel"
#define PR_DOMAIN DBG_KERNEL
#include "uftrace.h"
#include "utils/utils.h"
#include "utils/fstack.h"
#include "utils/filter.h"
#include "utils/rbtree.h"
#include "utils/kernel.h"
#include "libtraceevent/kbuffer.h"
#include "libtraceevent/event-parse.h"
#define TRACING_DIR "/sys/kernel/debug/tracing"
static bool kernel_tracing_enabled;
/* tree of executed kernel functions */
static struct rb_root kfunc_tree = RB_ROOT;
static int prepare_kbuffer(struct uftrace_kernel_reader *kernel, int cpu);
static int
funcgraph_entry_handler(struct trace_seq *s, struct pevent_record *record,
struct event_format *event, void *context);
static int
funcgraph_exit_handler(struct trace_seq *s, struct pevent_record *record,
struct event_format *event, void *context);
static int
generic_event_handler(struct trace_seq *s, struct pevent_record *record,
struct event_format *event, void *context);
static int save_kernel_files(struct uftrace_kernel_writer *kernel);
static int load_kernel_files(struct uftrace_kernel_reader *kernel);
static char *get_tracing_file(const char *name)
{
char *file = NULL;
xasprintf(&file, "%s/%s", TRACING_DIR, name);
return file;
}
static void put_tracing_file(char *file)
{
free(file);
}
static int open_tracing_file(const char *name, bool append)
{
char *file;
int fd;
int flags = O_WRONLY;
file = get_tracing_file(name);
if (!file) {
pr_dbg("cannot get tracing file: %s: %m\n", name);
return -1;
}
if (append)
flags |= O_APPEND;
else
flags |= O_TRUNC;
fd = open(file, flags);
if (fd < 0)
pr_dbg("cannot open tracing file: %s: %m\n", name);
put_tracing_file(file);
return fd;
}
static int __write_tracing_file(int fd, const char *name, const char *val,
bool append, bool correct_sys_prefix)
{
int ret = -1;
ssize_t size = strlen(val);
if (correct_sys_prefix) {
char *newval = (char *)val;
if (!strncmp(val, "sys_", 4))
newval[0] = newval[2] = 'S';
else if (!strncmp(val, "compat_sys_", 11))
newval[7] = newval[9] = 'S';
else
correct_sys_prefix = false;
}
pr_dbg2("%s '%s' to tracing/%s\n", append ? "appending" : "writing",
val, name);
if (write(fd, val, size) == size)
ret = 0;
if (correct_sys_prefix) {
char *newval = (char *)val;
if (!strncmp(val, "SyS_", 4))
newval[0] = newval[2] = 's';
else if (!strncmp(val, "compat_SyS_", 11))
newval[7] = newval[9] = 's';
/* write a whitespace to distinguish the previous pattern */
if (write(fd, " ", 1) < 0)
ret = -1;
pr_dbg2("%s '%s' to tracing/%s\n", append ? "appending" : "writing",
val, name);
if (write(fd, val, size) == size)
ret = 0;
}
if (ret < 0)
pr_dbg("write '%s' to tracing/%s failed: %m\n", val, name);
return ret;
}
static int write_tracing_file(const char *name, const char *val)
{
int ret;
int fd = open_tracing_file(name, false);
if (fd < 0)
return -1;
ret = __write_tracing_file(fd, name, val, false, false);
close(fd);
return ret;
}
static int append_tracing_file(const char *name, const char *val)
{
int ret;
int fd = open_tracing_file(name, true);
if (fd < 0)
return -1;
ret = __write_tracing_file(fd, name, val, true, false);
close(fd);
return ret;
}
static int set_tracing_pid(int pid)
{
char buf[16];
snprintf(buf, sizeof(buf), "%d", pid);
if (append_tracing_file("set_ftrace_pid", buf) < 0)
return -1;
/* ignore error on old kernel */
append_tracing_file("set_event_pid", buf);
return 0;
}
static int set_tracing_clock(void)
{
return write_tracing_file("trace_clock", "mono");
}
struct kfilter {
struct list_head list;
char name[];
};
static int set_filter_file(const char *filter_file, struct list_head *filters)
{
struct kfilter *pos, *tmp;
int ret = -1;
int fd;
fd = open_tracing_file(filter_file, true);
if (fd < 0)
return -1;
list_for_each_entry_safe(pos, tmp, filters, list) {
/*
* it might fail with non-existing functions added by
* add_single_filter() or skip_kernel_functions().
*/
__write_tracing_file(fd, filter_file, pos->name, true, true);
list_del(&pos->list);
free(pos);
/* separate filters by space */
if (write(fd, " ", 1) != 1)
pr_dbg2("writing filter file failed, but ignoring...\n");
}
ret = 0;
close(fd);
return ret;
}
static int set_tracing_filter(struct uftrace_kernel_writer *kernel)
{
if (set_filter_file("set_graph_function", &kernel->filters) < 0)
return -1;
/* ignore error on old kernel */
set_filter_file("set_graph_notrace", &kernel->notrace);
if (set_filter_file("set_ftrace_filter", &kernel->patches) < 0)
return -1;
if (set_filter_file("set_ftrace_notrace", &kernel->nopatch) < 0)
return -1;
return 0;
}
static int set_tracing_depth(struct uftrace_kernel_writer *kernel)
{
int ret = 0;
char buf[32];
snprintf(buf, sizeof(buf), "%d", kernel->depth);
ret = write_tracing_file("max_graph_depth", buf);
return ret;
}
static int set_tracing_bufsize(struct uftrace_kernel_writer *kernel)
{
int ret = 0;
char buf[32];
if (kernel->bufsize) {
snprintf(buf, sizeof(buf), "%lu", kernel->bufsize >> 10);
ret = write_tracing_file("buffer_size_kb", buf);
}
return ret;
}
/* check whether the kernel supports pid filter inheritance */
bool check_kernel_pid_filter(void)
{
bool ret = true;
char *filename = get_tracing_file("options/function-fork");
if (!access(filename, F_OK))
ret = false;
put_tracing_file(filename);
return ret;
}
static int set_tracing_options(struct uftrace_kernel_writer *kernel)
{
/* old kernels don't have the options, ignore errors */
if (!write_tracing_file("options/function-fork", "1"))
write_tracing_file("options/event-fork", "1");
return 0;
}
static void add_single_filter(struct list_head *head, char *name)
{
struct kfilter *kfilter;
kfilter = xmalloc(sizeof(*kfilter) + strlen(name) + 1);
strcpy(kfilter->name, name);
list_add(&kfilter->list, head);
}
static void add_pattern_filter(struct list_head *head,
struct uftrace_pattern *patt)
{
char *filename;
FILE *fp;
char buf[1024];
filename = get_tracing_file("available_filter_functions");
fp = fopen(filename, "r");
if (fp == NULL)
pr_err("failed to open 'tracing/available_filter_functions' file");
while (fgets(buf, sizeof(buf), fp) != NULL) {
/* remove module name part */
char *pos = strchr(buf, '[');
size_t len;
if (pos)
*pos = '\0';
/* remove trailing whitespace */
len = strlen(buf);
if (isspace(buf[len - 1]))
buf[len - 1] = '\0';
if (match_filter_pattern(patt, buf))
add_single_filter(head, buf);
}
fclose(fp);
put_tracing_file(filename);
}
static void build_kernel_filter(struct uftrace_kernel_writer *kernel,
char *filter_str,
enum uftrace_pattern_type ptype,
struct list_head *filters,
struct list_head *notrace)
{
struct list_head *head;
struct strv strv = STRV_INIT;
char *pos, *name;
int j;
if (filter_str == NULL)
return;
strv_split(&strv, filter_str, ";");
strv_for_each(&strv, name, j) {
struct uftrace_pattern patt;
pos = has_kernel_filter(name);
if (pos == NULL)
continue;
*pos = '\0';
if (name[0] == '!') {
head = notrace;
name++;
}
else
head = filters;
init_filter_pattern(ptype, &patt, name);
if (patt.type == PATT_SIMPLE)
add_single_filter(head, name);
else
add_pattern_filter(head, &patt);
free_filter_pattern(&patt);
}
strv_free(&strv);
}
struct kevent {
struct list_head list;
char name[];
};
static int set_tracing_event(struct uftrace_kernel_writer *kernel)
{
struct kevent *pos, *tmp;
list_for_each_entry_safe(pos, tmp, &kernel->events, list) {
if (append_tracing_file("set_event", pos->name) < 0)
return -1;
list_del(&pos->list);
free(pos);
}
return 0;
}
static void add_single_event(struct list_head *events, char *name)
{
struct kevent *kevent;
kevent = xmalloc(sizeof(*kevent) + strlen(name) + 1);
strcpy(kevent->name, name);
list_add_tail(&kevent->list, events);
}
static void add_pattern_event(struct list_head *events,
struct uftrace_pattern *patt)
{
char *filename;
FILE *fp;
char buf[1024];
filename = get_tracing_file("available_events");
fp = fopen(filename, "r");
if (fp == NULL)
pr_err("failed to open 'tracing/available_event' file");
while (fgets(buf, sizeof(buf), fp) != NULL) {
/* it's ok to have a trailing '\n' */
if (match_filter_pattern(patt, buf))
add_single_event(events, buf);
}
fclose(fp);
put_tracing_file(filename);
}
static void build_kernel_event(struct uftrace_kernel_writer *kernel,
char *event_str, enum uftrace_pattern_type ptype,
struct list_head *events)
{
struct strv strv = STRV_INIT;
char *pos, *name;
int j;
if (event_str == NULL)
return;
strv_split(&strv, event_str, ";");
strv_for_each(&strv, name, j) {
struct uftrace_pattern patt;
pos = has_kernel_filter(name);
if (pos == NULL)
continue;
*pos = '\0';
init_filter_pattern(ptype, &patt, name);
if (patt.type == PATT_SIMPLE)
add_single_event(events, name);
else
add_pattern_event(events, &patt);
free_filter_pattern(&patt);
}
strv_free(&strv);
}
static int reset_tracing_files(void)
{
if (write_tracing_file("tracing_on", "1") < 0)
return -1;
if (write_tracing_file("current_tracer", "nop") < 0)
return -1;
if (write_tracing_file("trace_clock", "local") < 0)
return -1;
if (write_tracing_file("set_ftrace_pid", " ") < 0)
return -1;
if (write_tracing_file("set_graph_function", " ") < 0)
return -1;
/* ignore error on old kernel */
write_tracing_file("set_event_pid", " ");
write_tracing_file("set_graph_notrace", " ");
write_tracing_file("options/event-fork", "0");
write_tracing_file("options/function-fork", "0");
if (write_tracing_file("set_ftrace_filter", " ") < 0)
return -1;
if (write_tracing_file("set_ftrace_notrace", " ") < 0)
return -1;
if (write_tracing_file("max_graph_depth", "0") < 0)
return -1;
if (write_tracing_file("set_event", " ") < 0)
return -1;
/* default kernel buffer size: 16384 * 88 / 1024 = 1408 */
if (write_tracing_file("buffer_size_kb", "1408") < 0)
return -1;
kernel_tracing_enabled = false;
return 0;
}
static int __setup_kernel_tracing(struct uftrace_kernel_writer *kernel)
{
if (geteuid() != 0)
return -EPERM;
if (reset_tracing_files() < 0) {
pr_dbg("failed to reset tracing files\n");
return -ENOSYS;
}
pr_dbg("setting up kernel tracing\n");
/* disable tracing */
if (write_tracing_file("tracing_on", "0") < 0)
return -ENOSYS;
/* reset ftrace buffer */
if (write_tracing_file("trace", "0") < 0)
goto out;
if (set_tracing_clock() < 0)
goto out;
if (set_tracing_pid(kernel->pid) < 0)
goto out;
if (set_tracing_filter(kernel) < 0)
goto out;
if (set_tracing_depth(kernel) < 0)
goto out;
if (set_tracing_event(kernel) < 0)
goto out;
if (set_tracing_options(kernel) < 0)
goto out;
if (set_tracing_bufsize(kernel) < 0)
goto out;
if (write_tracing_file("current_tracer", kernel->tracer) < 0)
goto out;
kernel_tracing_enabled = true;
return 0;
out:
reset_tracing_files();
return -EINVAL;
}
static void check_and_add_list(struct uftrace_kernel_writer *kernel,
const char *funcs[], size_t funcs_len,
struct list_head *list)
{
unsigned int i;
struct kfilter *kfilter;
for (i = 0; i < funcs_len; i++) {
bool add = true;
const char *name = funcs[i];
struct kfilter *pos;
/* Don't skip it if user particularly want to see them*/
list_for_each_entry(pos, &kernel->filters, list) {
if (!strcmp(pos->name, name)) {
add = false;
break;
}
}
list_for_each_entry(pos, &kernel->patches, list) {
if (!strcmp(pos->name, name)) {
add = false;
break;
}
}
if (add) {
kfilter = xmalloc(sizeof(*kfilter) + strlen(name) + 1);
strcpy(kfilter->name, name);
list_add_tail(&kfilter->list, list);
}
}
}
static void skip_kernel_functions(struct uftrace_kernel_writer *kernel)
{
const char *skip_funcs[] = {
/*
* Some (old) kernel and architecture doesn't support VDSO
* so there will be many sys_clock_gettime() in the output
* due to internal call in libmcount. It'd be better
* ignoring them not to confuse users. I think it does NOT
* affect to the output when VDSO is enabled.
*/
"sys_clock_gettime",
/*
* Currently kernel tracing seems to wake up uftrace writer
* threads too often using the irq_work interrupt. This
* messes up the trace output so it'd be better hiding them.
*/
"smp_irq_work_interrupt",
/* Disable syscall tracing in the kernel */
"syscall_trace_enter_phase1",
"syscall_slow_exit_work",
};
const char *skip_patches[] = {
/* kernel 4.17 changed syscall entry on x86_64 */
"do_syscall_64",
};
check_and_add_list(kernel, skip_funcs, ARRAY_SIZE(skip_funcs),
&kernel->notrace);
check_and_add_list(kernel, skip_patches, ARRAY_SIZE(skip_patches),
&kernel->nopatch);
}
/**
* setup_kernel_tracing - prepare to record kernel ftrace data (binary)
* @kernel : kernel ftrace handle
* @opts: option related to kernel tracing
*
* This function sets up all necessary data structures and configure
* kernel ftrace subsystem.
*/
int setup_kernel_tracing(struct uftrace_kernel_writer *kernel, struct opts *opts)
{
int i, n;
int ret;
INIT_LIST_HEAD(&kernel->filters);
INIT_LIST_HEAD(&kernel->notrace);
INIT_LIST_HEAD(&kernel->patches);
INIT_LIST_HEAD(&kernel->nopatch);
INIT_LIST_HEAD(&kernel->events);
build_kernel_filter(kernel, opts->filter, opts->patt_type,
&kernel->filters, &kernel->notrace);
build_kernel_filter(kernel, opts->patch, opts->patt_type,
&kernel->patches, &kernel->nopatch);
build_kernel_event(kernel, opts->event, opts->patt_type,
&kernel->events);
if (opts->kernel)
kernel->tracer = KERNEL_GRAPH_TRACER;
else
kernel->tracer = KERNEL_NOP_TRACER;
/* mark kernel tracing is enabled (for event tracing) */
opts->kernel = true;
if (opts->kernel_skip_out)
skip_kernel_functions(kernel);
ret = __setup_kernel_tracing(kernel);
if (ret < 0)
return ret;
kernel->nr_cpus = n = sysconf(_SC_NPROCESSORS_ONLN);
kernel->traces = xcalloc(n, sizeof(*kernel->traces));
kernel->fds = xcalloc(n, sizeof(*kernel->fds));
for (i = 0; i < kernel->nr_cpus; i++) {
kernel->traces[i] = -1;
kernel->fds[i] = -1;
}
return 0;
}
/**
* start_kernel_tracing - prepare to record kernel ftrace data (binary)
* @kernel : kernel ftrace handle
*
* This function sets up all necessary data structures and configure
* kernel ftrace subsystem. As this function modifies system ftrace
* configuration it should be used in pair with stop_kernel_tracing()
* function.
*
* The kernel ftrace data is captured from per-cpu trace_pipe_raw file
* as binary form and saved to kernel-cpuXX.dat file in the ftrace
* data directory.
*/
int start_kernel_tracing(struct uftrace_kernel_writer *kernel)
{
char *trace_file;
char buf[PATH_MAX];
int i;
int saved_errno;
for (i = 0; i < kernel->nr_cpus; i++) {
/* TODO: take an account of (currently) offline cpus */
snprintf(buf, sizeof(buf), "per_cpu/cpu%d/trace_pipe_raw", i);
trace_file = get_tracing_file(buf);
if (!trace_file) {
pr_dbg("failed to open %s: %m\n", buf);
goto out;
}
kernel->traces[i] = open(trace_file, O_RDONLY);
saved_errno = errno;
put_tracing_file(trace_file);
if (kernel->traces[i] < 0) {
errno = saved_errno;
pr_dbg("failed to open %s: %m\n", buf);
goto out;
}
fcntl(kernel->traces[i], F_SETFL, O_NONBLOCK);
snprintf(buf, sizeof(buf), "%s/kernel-cpu%d.dat",
kernel->output_dir, i);
kernel->fds[i] = open(buf, O_WRONLY | O_TRUNC | O_CREAT, 0600);
if (kernel->fds[i] < 0) {
pr_dbg("failed to open output file: %s: %m\n", buf);
goto out;
}
}
if (write_tracing_file("tracing_on", "1") < 0) {
pr_dbg("can't enable tracing\n");
goto out;
}
pr_dbg("kernel tracing started..\n");
return 0;
out:
for (i = 0; kernel->nr_cpus; i++) {
close(kernel->traces[i]);
close(kernel->fds[i]);
}
free(kernel->traces);
free(kernel->fds);
reset_tracing_files();
return -1;
}
/**
* record_kernel_trace_pipe - read and save kernel ftrace data for specific cpu
* @kernel - kernel ftrace handle
* @cpu - cpu to read
* @sock - socket descriptor (for network transfer)
*
* This function read trace data for @cpu and save it to file.
*/
int record_kernel_trace_pipe(struct uftrace_kernel_writer *kernel,
int cpu, int sock)
{
char buf[PATH_MAX];
ssize_t n;
if (cpu < 0 || cpu >= kernel->nr_cpus)
return 0;
retry:
n = read(kernel->traces[cpu], buf, sizeof(buf));
if (n < 0) {
if (errno == EINTR)
goto retry;
if (errno == EAGAIN)
return 0;
else
return -errno;
}
if (n == 0)
return 0;
if (sock > 0)
send_trace_kernel_data(sock, cpu, buf, n);
else
write_all(kernel->fds[cpu], buf, n);
return n;
}
/**
* record_kernel_tracing - read and save kernel ftrace data (binary)
* @kernel - kernel ftrace handle
*
* This function read every (online) per-cpu trace data in a
* round-robin fashion and save them to files.
*/
int record_kernel_tracing(struct uftrace_kernel_writer *kernel)
{
ssize_t bytes = 0;
ssize_t n;
int i;
if (!kernel_tracing_enabled)
return -1;
for (i = 0; i < kernel->nr_cpus; i++) {
n = record_kernel_trace_pipe(kernel, i, -1);
if (n < 0) {
pr_warn("record kernel data (cpu %d) failed: %m\n", i);
return n;
}
bytes += n;
}
pr_dbg2("kernel ftrace record wrote %zd bytes\n", bytes);
return bytes;
}
/**
* stop_kernel_tracing - stop recording kernel ftrace data
* @kernel - kernel ftrace handle
*
* This function signals kernel to stop generating trace data.
*/
int stop_kernel_tracing(struct uftrace_kernel_writer *kernel)
{
if (!kernel_tracing_enabled)
return 0;
return write_tracing_file("tracing_on", "0");
}
/**
* finish_kernel_tracing - finish kernel ftrace data
* @kernel - kernel ftrace handle
*
* This function reads out remaining ftrace data and restores kernel
* ftrace configuration.
*/
int finish_kernel_tracing(struct uftrace_kernel_writer *kernel)
{
int i;
pr_dbg("kernel tracing stopped.\n");
while (record_kernel_tracing(kernel) > 0)
continue;
for (i = 0; i < kernel->nr_cpus; i++) {
close(kernel->traces[i]);
close(kernel->fds[i]);
}
free(kernel->traces);
free(kernel->fds);
if (kernel_tracing_enabled) {
save_kernel_files(kernel);
save_kernel_symbol(kernel->output_dir);
}
reset_tracing_files();
return 0;
}
void list_kernel_events(void)
{
char *filename;
FILE *fp;
char buf[BUFSIZ];
filename = get_tracing_file("available_events");
fp = fopen(filename, "r");
if (fp == NULL) {
pr_dbg("failed to open 'tracing/avaiable_events");
return;
}
while (fgets(buf, sizeof(buf), fp) != NULL)
pr_out("[kernel event] %s", buf);
fclose(fp);
put_tracing_file(filename);
}
static const char *get_endian_str(void)
{
if (get_elf_endian() == ELFDATA2LSB)
return "LE";
else
return "BE";
}
static int read_file(char *filename, char *buf, size_t len)
{
int fd, ret;
fd = open(filename, O_RDONLY);
if (fd < 0)
return -errno;
ret = read(fd, buf, len);
close(fd);
return ret;
}
static int save_kernel_file(FILE *fp, const char *name)
{
ssize_t len;
char buf[PATH_MAX];
snprintf(buf, sizeof(buf), "%s/%s", TRACING_DIR, name);
len = read_file(buf, buf, sizeof(buf));
if (len < 0)
return -1;
fprintf(fp, "TRACEFS: %s: %zd\n", name, len);
fwrite(buf, len, 1, fp);
return 0;
}
static int save_event_files(struct uftrace_kernel_writer *kernel, FILE *fp)
{
int ret = -1;
char buf[PATH_MAX];
DIR *subsys = NULL;
DIR *event = NULL;
struct dirent *sys, *name;
snprintf(buf, sizeof(buf), "%s/events/enable", TRACING_DIR);
if (read_file(buf, buf, sizeof(buf)) < 0)
goto out;
/* no events enabled: exit */
if (buf[0] == '0') {
ret = 0;
goto out;
}
snprintf(buf, sizeof(buf), "%s/events", TRACING_DIR);
subsys = opendir(buf);
if (subsys == NULL)
goto out;
while ((sys = readdir(subsys)) != NULL) {
if (sys->d_name[0] == '.' || sys->d_type != DT_DIR)
continue;
/* ftrace events are special - skip it */
if (!strcmp(sys->d_name, "ftrace"))
continue;
snprintf(buf, sizeof(buf), "%s/events/%s/enable",
TRACING_DIR, sys->d_name);
if (read_file(buf, buf, sizeof(buf)) < 0)
goto out;
/* this subsystem has no events enabled */
if (buf[0] == '0')
continue;
snprintf(buf, sizeof(buf), "%s/events/%s",
TRACING_DIR, sys->d_name);
event = opendir(buf);
if (event == NULL)
goto out;
while ((name = readdir(event)) != NULL) {
if (name->d_name[0] == '.' || name->d_type != DT_DIR)
continue;
snprintf(buf, sizeof(buf), "%s/events/%s/%s/enable",
TRACING_DIR, sys->d_name, name->d_name);
if (read_file(buf, buf, sizeof(buf)) < 0)
goto out;
/* this event is not enabled */
if (buf[0] == '0')
continue;
snprintf(buf, sizeof(buf), "events/%s/%s/format",
sys->d_name, name->d_name);
if (save_kernel_file(fp, buf) < 0)
goto out;
}
closedir(event);
event = NULL;
}
ret = 0;
out:
if (event)
closedir(event);
if (subsys)
closedir(subsys);
return ret;
}
static int save_kernel_files(struct uftrace_kernel_writer *kernel)
{