/* SPDX-License-Identifier: GPL-2.0 */
/**
* Generic event filter for sampling events in BPF.
*
* The BPF program is fixed and just to read filter expressions in the 'filters'
* map and compare the sample data in order to reject samples that don't match.
* Each filter expression contains a sample flag (term) to compare, an operation
* (==, >=, and so on) and a value.
*
* Note that each entry has an array of filter expressions and it only succeeds
* when all of the expressions are satisfied. But it supports the logical OR
* using a GROUP operation which is satisfied when any of its member expression
* is evaluated to true. But it doesn't allow nested GROUP operations for now.
*
* To support non-root users, the filters map can be loaded and pinned in the BPF
* filesystem by root (perf record --setup-filter pin). Then each user will get
* a new entry in the shared filters map to fill the filter expressions. And the
* BPF program will find the filter using (task-id, event-id) as a key.
*
* The pinned BPF object (shared for regular users) has:
*
* event_hash |
* | | |
* event->id ---> | id | ---+ idx_hash | filters
* | | | | | | | |
* | .... | +-> | idx | --+--> | exprs | ---> perf_bpf_filter_entry[]
* | | | | | | .op
* task id (tgid) --------------+ | .... | | | ... | .term (+ part)
* | .value
* |
* ======= (root would skip this part) ======== (compares it in a loop)
*
* This is used for per-task use cases while system-wide profiling (normally from
* root user) uses a separate copy of the program and the maps for its own so that
* it can proceed even if a lot of non-root users are using the filters at the
* same time. In this case the filters map has a single entry and no need to use
* the hash maps to get the index (key) of the filters map (IOW it's always 0).
*
* The BPF program returns 1 to accept the sample or 0 to drop it.
* The 'dropped' map is to keep how many samples it dropped by the filter and
* it will be reported as lost samples.
*/
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <bpf/bpf.h>
#include <linux/err.h>
#include <linux/list.h>
#include <api/fs/fs.h>
#include <internal/xyarray.h>
#include <perf/threadmap.h>
#include "util/debug.h"
#include "util/evsel.h"
#include "util/target.h"
#include "util/bpf-filter.h"
#include <util/bpf-filter-flex.h>
#include <util/bpf-filter-bison.h>
#include "bpf_skel/sample-filter.h"
#include "bpf_skel/sample_filter.skel.h"
#define FD(e, x, y) (*(int *)xyarray__entry(e->core.fd, x, y))
#define __PERF_SAMPLE_TYPE(tt, st, opt) { tt, #st, opt }
#define PERF_SAMPLE_TYPE(_st, opt) __PERF_SAMPLE_TYPE(PBF_TERM_##_st, PERF_SAMPLE_##_st, opt)
/* Index in the pinned 'filters' map. Should be released after use. */
struct pinned_filter_idx {
struct list_head list;
struct evsel *evsel;
u64 event_id;
int hash_idx;
};
static LIST_HEAD(pinned_filters);
static const struct perf_sample_info {
enum perf_bpf_filter_term type;
const char *name;
const char *option;
} sample_table[] = {
/* default sample flags */
PERF_SAMPLE_TYPE(IP, NULL),
PERF_SAMPLE_TYPE(TID, NULL),
PERF_SAMPLE_TYPE(PERIOD, NULL),
/* flags mostly set by default, but still have options */
PERF_SAMPLE_TYPE(ID, "--sample-identifier"),
PERF_SAMPLE_TYPE(CPU, "--sample-cpu"),
PERF_SAMPLE_TYPE(TIME, "-T"),
/* optional sample flags */
PERF_SAMPLE_TYPE(ADDR, "-d"),
PERF_SAMPLE_TYPE(DATA_SRC, "-d"),
PERF_SAMPLE_TYPE(PHYS_ADDR, "--phys-data"),
PERF_SAMPLE_TYPE(WEIGHT, "-W"),
PERF_SAMPLE_TYPE(WEIGHT_STRUCT, "-W"),
PERF_SAMPLE_TYPE(TRANSACTION, "--transaction"),
PERF_SAMPLE_TYPE(CODE_PAGE_SIZE, "--code-page-size"),
PERF_SAMPLE_TYPE(DATA_PAGE_SIZE, "--data-page-size"),
PERF_SAMPLE_TYPE(CGROUP, "--all-cgroups"),
};
static int get_pinned_fd(const char *name);
static const struct perf_sample_info *get_sample_info(enum perf_bpf_filter_term type)
{
size_t i;
for (i = 0; i < ARRAY_SIZE(sample_table); i++) {
if (sample_table[i].type == type)
return &sample_table[i];
}
return NULL;
}
static int check_sample_flags(struct evsel *evsel, struct perf_bpf_filter_expr *expr)
{
const struct perf_sample_info *info;
if (expr->term >= PBF_TERM_SAMPLE_START && expr->term <= PBF_TERM_SAMPLE_END &&
(evsel->core.attr.sample_type & (1 << (expr->term - PBF_TERM_SAMPLE_START))))
return 0;
if (expr->term == PBF_TERM_UID || expr->term == PBF_TERM_GID) {
/* Not dependent on the sample_type as computed from a BPF helper. */
return 0;
}
if (expr->op == PBF_OP_GROUP_BEGIN) {
struct perf_bpf_filter_expr *group;
list_for_each_entry(group, &expr->groups, list) {
if (check_sample_flags(evsel, group) < 0)
return -1;
}
return 0;
}
info = get_sample_info(expr->term);
if (info == NULL) {
pr_err("Error: %s event does not have sample flags %d\n",
evsel__name(evsel), expr->term);
return -1;
}
pr_err("Error: %s event does not have %s\n", evsel__name(evsel), info->name);
if (info->option)
pr_err(" Hint: please add %s option to perf record\n", info->option);
return -1;
}
static int get_filter_entries(struct evsel *evsel, struct perf_bpf_filter_entry *entry)
{
int i = 0;
struct perf_bpf_filter_expr *expr;
list_for_each_entry(expr, &evsel->bpf_filters, list) {
if (check_sample_flags(evsel, expr) < 0)
return -EINVAL;
if (i == MAX_FILTERS)
return -E2BIG;
entry[i].op = expr->op;
entry[i].part = expr->part;
entry[i].term = expr->term;
entry[i].value = expr->val;
i++;
if (expr->op == PBF_OP_GROUP_BEGIN) {
struct perf_bpf_filter_expr *group;
list_for_each_entry(group, &expr->groups, list) {
if (i == MAX_FILTERS)
return -E2BIG;
entry[i].op = group->op;
entry[i].part = group->part;
entry[i].term = group->term;
entry[i].value = group->val;
i++;
}
if (i == MAX_FILTERS)
return -E2BIG;
entry[i].op = PBF_OP_GROUP_END;
i++;
}
}
if (i < MAX_FILTERS) {
/* to terminate the loop early */
entry[i].op = PBF_OP_DONE;
i++;
}
return 0;
}
static int convert_to_tgid(int tid)
{
char path[128];
char *buf, *p, *q;
int tgid;
size_t len;
scnprintf(path, sizeof(path), "%d/status", tid);
if (procfs__read_str(path, &buf, &len) < 0)
return -1;
p = strstr(buf, "Tgid:");
if (p == NULL) {
free(buf);
return -1;
}
tgid = strtol(p + 6, &q, 0);
free(buf);
if (*q != '\n')
return -1;
return tgid;
}
/*
* The event might be closed already so we cannot get the list of ids using FD
* like in create_event_hash() below, let's iterate the event_hash map and
* delete all entries that have the event id as a key.
*/
static void destroy_event_hash(u64 event_id)
{
int fd;
u64 key, *prev_key = NULL;
int num = 0, alloced = 32;
u64 *ids = calloc(alloced, sizeof(*ids));
if (ids == NULL)
return;
fd = get_pinned_fd("event_hash");
if (fd < 0) {
pr_debug("cannot get fd for 'event_hash' map\n");
free(ids);
return;
}
/* Iterate the whole map to collect keys for the event id. */
while (!bpf_map_get_next_key(fd, prev_key, &key)) {
u64 id;
if (bpf_map_lookup_elem(fd, &key, &id) == 0 && id == event_id) {
if (num == alloced) {
void *tmp;
alloced *= 2;
tmp = realloc(ids, alloced * sizeof(*ids));
if (tmp == NULL)
break;
ids = tmp;
}
ids[num++] = key;
}
prev_key = &key;
}
for (int i = 0; i < num; i++)
bpf_map_delete_elem(fd, &ids[i]);
free(ids);
close(fd);
}
/*
* Return a representative id if ok, or 0 for failures.
*
* The perf_event->id is good for this, but an evsel would have multiple
* instances for CPUs and tasks. So pick up the first id and setup a hash
* from id of each instance to the representative id (the first one).
*/
static u64 create_event_hash(struct evsel *evsel)
{
int x, y, fd;
u64 the_id = 0, id;
fd = get_pinned_fd("event_hash");
if (fd < 0) {
pr_err("cannot get fd for 'event_hash' map\n");
return 0;
}
for (x = 0; x < xyarray__max_x(evsel->core.fd); x++) {
for (y = 0; y < xyarray__max_y(evsel->core.fd); y++) {
int ret = ioctl(FD(evsel, x, y), PERF_EVENT_IOC_ID, &id);
if (ret < 0) {
pr_err("Failed to get the event id\n");
if (the_id)
destroy_event_hash(the_id);
return 0;
}
if (the_id == 0)
the_id = id;
bpf_map_update_elem(fd, &id, &the_id, BPF_ANY);
}
}
close(fd);
return the_id;
}
static void destroy_idx_hash(struct pinned_filter_idx *pfi)
{
int fd, nr;
struct perf_thread_map *threads;
fd = get_pinned_fd("filters");
bpf_map_delete_elem(fd, &pfi->hash_idx);
close(fd);
if (pfi->event_id)
destroy_event_hash(pfi->event_id);
threads = perf_evsel__threads(&pfi->evsel->core);
if (threads == NULL)
return;
fd = get_pinned_fd("idx_hash");
nr = perf_thread_map__nr(threads);
for (int i = 0; i < nr; i++) {
/* The target task might be dead already, just try the pid */
struct idx_hash_key key = {
.evt_id = pfi->event_id,
.tgid = perf_thread_map__pid(threads, i),
};
bpf_map_delete_elem(fd, &key);
}
close(fd);
}
/* Maintain a hashmap from (tgid, event-id) to filter index */
static int create_idx_hash(struct evsel *evsel, struct perf_bpf_filter_entry *entry)
{
int filter_idx;
int fd, nr, last;
u64 event_id = 0;
struct pinned_filter_idx *pfi = NULL;
struct perf_thread_map *threads;
fd = get_pinned_fd("filters");
if (fd < 0) {
pr_err("cannot get fd for 'filters' map\n");
return fd;
}
/* Find the first available entry in the filters map */
for (filter_idx = 0; filter_idx < MAX_FILTERS; filter_idx++) {
if (bpf_map_update_elem(fd, &filter_idx, entry, BPF_NOEXIST) == 0)
break;
}
close(fd);
if (filter_idx == MAX_FILTERS) {
pr_err("Too many users for the filter map\n");
return -EBUSY;
}
pfi = zalloc(sizeof(*pfi));
if (pfi == NULL) {
pr_err("Cannot save pinned filter index\n");
goto err;
}
pfi->evsel = evsel;
pfi->hash_idx = filter_idx;
event_id = create_event_hash(evsel);
if (event_id == 0) {
pr_err("Cannot update the event hash\n");
goto err;
}
pfi->event_id = event_id;
threads = perf_evsel__threads(&evsel->core);
if (threads == NULL) {
pr_err("Cannot get the thread list of the event\n");
goto err;
}
/* save the index to a hash map */
fd = get_pinned_fd("idx_hash");
if (fd < 0) {
pr_err("cannot get fd for 'idx_hash' map\n");
goto err;
}
last = -1;
nr = perf_thread_map__nr(threads);
for (int i = 0; i < nr; i++) {
int pid = perf_thread_map__pid(threads, i);
int tgid;
struct idx_hash_key key = {
.evt_id = event_id,
};
/* it actually needs tgid, let's get tgid from /proc. */
tgid = convert_to_tgid(pid);
if (tgid < 0) {
/* the thread may be dead, ignore. */
continue;
}
if (tgid == last)
continue;
last = tgid;
key.tgid = tgid;
if (bpf_map_update_elem(fd, &key, &filter_idx, BPF_ANY) < 0) {
pr_err("Failed to update the idx_hash\n");
close(fd);
goto err;
}
pr_debug("bpf-filter: idx_hash (task=%d,%s) -> %d\n",
tgid, evsel__name(evsel), filter_idx);
}
list_add(&pfi->list, &pinned_filters);
close(fd);
return filter_idx;
err:
destroy_idx_hash(pfi);
free(pfi);
return -1;
}
int perf_bpf_filter__prepare(struct evsel *evsel, struct target *target)
{
int i, x, y, fd, ret;
struct sample_filter_bpf *skel = NULL;
struct bpf_program *prog;
struct bpf_link *link;
struct perf_bpf_filter_entry *entry;
bool needs_idx_hash = !target__has_cpu(target) && !target->uid_str;
entry = calloc(MAX_FILTERS, sizeof(*entry));
if (entry == NULL)
return -1;
ret = get_filter_entries(evsel, entry);
if (ret < 0) {
pr_err("Failed to process filter entries\n");
goto err;
}
if (needs_idx_hash && geteuid() != 0) {
int zero = 0;
/* The filters map is shared among other processes */
ret = create_idx_hash(evsel, entry);
if (ret < 0)
goto err;
fd = get_pinned_fd("dropped");
if (fd < 0) {
ret = fd;
goto err;
}
/* Reset the lost count */
bpf_map_update_elem(fd, &ret, &zero, BPF_ANY);
close(fd);
fd = get_pinned_fd("perf_sample_filter");
if (fd < 0) {
ret = fd;
goto err;
}
for (x = 0; x < xyarray__max_x(evsel->core.fd); x++) {
for (y = 0; y < xyarray__max_y(evsel->core.fd); y++) {
ret = ioctl(FD(evsel, x, y), PERF_EVENT_IOC_SET_BPF, fd);
if (ret < 0) {
pr_err("Failed to attach perf sample-filter\n");
close(fd);
goto err;
}
}
}
close(fd);
free(entry);
return 0;
}
skel = sample_filter_bpf__open_and_load();
if (!skel) {
ret = -errno;
pr_err("Failed to load perf sample-filter BPF skeleton\n");
goto err;
}
i = 0;
fd = bpf_map__fd(skel->maps.filters);
/* The filters map has only one entry in this case */
if (bpf_map_update_elem(fd, &i, entry, BPF_ANY) < 0) {
ret = -errno;
pr_err("Failed to update the filter map\n");
goto err;
}
prog = skel->progs.perf_sample_filter;
for (x = 0; x < xyarray__max_x(evsel->core.fd); x++) {
for (y = 0; y < xyarray__max_y(evsel->core.fd); y++) {
link = bpf_program__attach_perf_event(prog, FD(evsel, x, y));
if (IS_ERR(link)) {
pr_err("Failed to attach perf sample-filter program\n");
ret = PTR_ERR(link);
goto err;
}
}
}
free(entry);
evsel->bpf_skel = skel;
return 0;
err:
free(entry);
if (!list_empty(&pinned_filters)) {
struct pinned_filter_idx *pfi, *tmp;
list_for_each_entry_safe(pfi, tmp, &pinned_filters, list) {
destroy_idx_hash(pfi);
list_del(&pfi->list);
free(pfi);
}
}
sample_filter_bpf__destroy(skel);
return ret;
}
int perf_bpf_filter__destroy(struct evsel *evsel)
{
struct perf_bpf_filter_expr *expr, *tmp;
struct pinned_filter_idx *pfi, *pos;
list_for_each_entry_safe(expr, tmp, &evsel->bpf_filters, list) {
list_del(&expr->list);
free(expr);
}
sample_filter_bpf__destroy(evsel->bpf_skel);
list_for_each_entry_safe(pfi, pos, &pinned_filters, list) {
destroy_idx_hash(pfi);
list_del(&pfi->list);
free(pfi);
}
return 0;
}
u64 perf_bpf_filter__lost_count(struct evsel *evsel)
{
int count = 0;
if (list_empty(&evsel->bpf_filters))
return 0;
if (!list_empty(&pinned_filters)) {
int fd = get_pinned_fd("dropped");
struct pinned_filter_idx *pfi;
if (fd < 0)
return 0;
list_for_each_entry(pfi, &pinned_filters, list) {
if (pfi->evsel != evsel)
continue;
bpf_map_lookup_elem(fd, &pfi->hash_idx, &count);
break;
}
close(fd);
} else if (evsel->bpf_skel) {
struct sample_filter_bpf *skel = evsel->bpf_skel;
int fd = bpf_map__fd(skel->maps.dropped);
int idx = 0;
bpf_map_lookup_elem(fd, &idx, &count);
}
return count;
}
struct perf_bpf_filter_expr *perf_bpf_filter_expr__new(enum perf_bpf_filter_term term,
int part,
enum perf_bpf_filter_op op,
unsigned long val)
{
struct perf_bpf_filter_expr *expr;
expr = malloc(sizeof(*expr));
if (expr != NULL) {
expr->term = term;
expr->part = part;
expr->op = op;
expr->val = val;
INIT_LIST_HEAD(&expr->groups);
}
return expr;
}
int perf_bpf_filter__parse(struct list_head *expr_head, const char *str)
{
YY_BUFFER_STATE buffer;
int ret;
buffer = perf_bpf_filter__scan_string(str);
ret = perf_bpf_filter_parse(expr_head);
perf_bpf_filter__flush_buffer(buffer);
perf_bpf_filter__delete_buffer(buffer);
perf_bpf_filter_lex_destroy();
return ret;
}
int perf_bpf_filter__pin(void)
{
struct sample_filter_bpf *skel;
char *path = NULL;
int dir_fd, ret = -1;
skel = sample_filter_bpf__open();
if (!skel) {
ret = -errno;
pr_err("Failed to open perf sample-filter BPF skeleton\n");
goto err;
}
/* pinned program will use pid-hash */
bpf_map__set_max_entries(skel->maps.filters, MAX_FILTERS);
bpf_map__set_max_entries(skel->maps.event_hash, MAX_EVT_HASH);
bpf_map__set_max_entries(skel->maps.idx_hash, MAX_IDX_HASH);
bpf_map__set_max_entries(skel->maps.dropped, MAX_FILTERS);
skel->rodata->use_idx_hash = 1;
if (sample_filter_bpf__load(skel) < 0) {
ret = -errno;
pr_err("Failed to load perf sample-filter BPF skeleton\n");
goto err;
}
if (asprintf(&path, "%s/fs/bpf/%s", sysfs__mountpoint(),
PERF_BPF_FILTER_PIN_PATH) < 0) {
ret = -errno;
pr_err("Failed to allocate pathname in the BPF-fs\n");
goto err;
}
ret = bpf_object__pin(skel->obj, path);
if (ret < 0) {
pr_err("Failed to pin BPF filter objects\n");
goto err;
}
/* setup access permissions for the pinned objects */
dir_fd = open(path, O_PATH);
if (dir_fd < 0) {
bpf_object__unpin(skel->obj, path);
ret = dir_fd;
goto err;
}
/* BPF-fs root has the sticky bit */
if (fchmodat(dir_fd, "..", 01755, 0) < 0) {
pr_debug("chmod for BPF-fs failed\n");
ret = -errno;
goto err_close;
}
/* perf_filter directory */
if (fchmodat(dir_fd, ".", 0755, 0) < 0) {
pr_debug("chmod for perf_filter directory failed?\n");
ret = -errno;
goto err_close;
}
/* programs need write permission for some reason */
if (fchmodat(dir_fd, "perf_sample_filter", 0777, 0) < 0) {
pr_debug("chmod for perf_sample_filter failed\n");
ret = -errno;
}
/* maps */
if (fchmodat(dir_fd, "filters", 0666, 0) < 0) {
pr_debug("chmod for filters failed\n");
ret = -errno;
}
if (fchmodat(dir_fd, "event_hash", 0666, 0) < 0) {
pr_debug("chmod for event_hash failed\n");
ret = -errno;
}
if (fchmodat(dir_fd, "idx_hash", 0666, 0) < 0) {
pr_debug("chmod for idx_hash failed\n");
ret = -errno;
}
if (fchmodat(dir_fd, "dropped", 0666, 0) < 0) {
pr_debug("chmod for dropped failed\n");
ret = -errno;
}
err_close:
close(dir_fd);
err:
free(path);
sample_filter_bpf__destroy(skel);
return ret;
}
int perf_bpf_filter__unpin(void)
{
struct sample_filter_bpf *skel;
char *path = NULL;
int ret = -1;
skel = sample_filter_bpf__open_and_load();
if (!skel) {
ret = -errno;
pr_err("Failed to open perf sample-filter BPF skeleton\n");
goto err;
}
if (asprintf(&path, "%s/fs/bpf/%s", sysfs__mountpoint(),
PERF_BPF_FILTER_PIN_PATH) < 0) {
ret = -errno;
pr_err("Failed to allocate pathname in the BPF-fs\n");
goto err;
}
ret = bpf_object__unpin(skel->obj, path);
err:
free(path);
sample_filter_bpf__destroy(skel);
return ret;
}
static int get_pinned_fd(const char *name)
{
char *path = NULL;
int fd;
if (asprintf(&path, "%s/fs/bpf/%s/%s", sysfs__mountpoint(),
PERF_BPF_FILTER_PIN_PATH, name) < 0)
return -1;
fd = bpf_obj_get(path);
free(path);
return fd;
}
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