trace_helpers.c

// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <poll.h>
#include <unistd.h>
#include <linux/perf_event.h>
#include <sys/mman.h>
#include "trace_helpers.h"

#define MAX_SYMS 300000
static struct ksym syms[MAX_SYMS];
static int sym_cnt;

static int ksym_cmp(const void *p1, const void *p2)
{
	return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
}

int load_kallsyms(void)
{
	FILE *f = fopen("/proc/kallsyms", "r");
	char func[256], buf[256];
	char symbol;
	void *addr;
	int i = 0;

	if (!f)
		return -ENOENT;

	while (!feof(f)) {
		if (!fgets(buf, sizeof(buf), f))
			break;
		if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
			break;
		if (!addr)
			continue;
		syms[i].addr = (long) addr;
		syms[i].name = strdup(func);
		i++;
	}
	sym_cnt = i;
	qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
	return 0;
}

struct ksym *ksym_search(long key)
{
	int start = 0, end = sym_cnt;
	int result;

	while (start < end) {
		size_t mid = start + (end - start) / 2;

		result = key - syms[mid].addr;
		if (result < 0)
			end = mid;
		else if (result > 0)
			start = mid + 1;
		else
			return &syms[mid];
	}

	if (start >= 1 && syms[start - 1].addr < key &&
	    key < syms[start].addr)
		/* valid ksym */
		return &syms[start - 1];

	/* out of range. return _stext */
	return &syms[0];
}

static int page_size;
static int page_cnt = 8;
static struct perf_event_mmap_page *header;

int perf_event_mmap(int fd)
{
	void *base;
	int mmap_size;

	page_size = getpagesize();
	mmap_size = page_size * (page_cnt + 1);

	base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	if (base == MAP_FAILED) {
		printf("mmap err\n");
		return -1;
	}

	header = base;
	return 0;
}

static int perf_event_poll(int fd)
{
	struct pollfd pfd = { .fd = fd, .events = POLLIN };

	return poll(&pfd, 1, 1000);
}

struct perf_event_sample {
	struct perf_event_header header;
	__u32 size;
	char data[];
};

static enum bpf_perf_event_ret bpf_perf_event_print(void *event, void *priv)
{
	struct perf_event_sample *e = event;
	perf_event_print_fn fn = priv;
	int ret;

	if (e->header.type == PERF_RECORD_SAMPLE) {
		ret = fn(e->data, e->size);
		if (ret != LIBBPF_PERF_EVENT_CONT)
			return ret;
	} else if (e->header.type == PERF_RECORD_LOST) {
		struct {
			struct perf_event_header header;
			__u64 id;
			__u64 lost;
		} *lost = (void *) e;
		printf("lost %lld events\n", lost->lost);
	} else {
		printf("unknown event type=%d size=%d\n",
		       e->header.type, e->header.size);
	}

	return LIBBPF_PERF_EVENT_CONT;
}

int perf_event_poller(int fd, perf_event_print_fn output_fn)
{
	enum bpf_perf_event_ret ret;
	void *buf = NULL;
	size_t len = 0;

	for (;;) {
		perf_event_poll(fd);
		ret = bpf_perf_event_read_simple(header, page_cnt * page_size,
						 page_size, &buf, &len,
						 bpf_perf_event_print,
						 output_fn);
		if (ret != LIBBPF_PERF_EVENT_CONT)
			break;
	}
	free(buf);

	return ret;
}