alistair23-linux/tools/testing/selftests/bpf/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 volatile 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 int perf_event_read(perf_event_print_fn fn)
{
	__u64 data_tail = header->data_tail;
	__u64 data_head = header->data_head;
	__u64 buffer_size = page_cnt * page_size;
	void *base, *begin, *end;
	char buf[256];
	int ret;

	asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */
	if (data_head == data_tail)
		return PERF_EVENT_CONT;

	base = ((char *)header) + page_size;

	begin = base + data_tail % buffer_size;
	end = base + data_head % buffer_size;

	while (begin != end) {
		struct perf_event_sample *e;

		e = begin;
		if (begin + e->header.size > base + buffer_size) {
			long len = base + buffer_size - begin;

			assert(len < e->header.size);
			memcpy(buf, begin, len);
			memcpy(buf + len, base, e->header.size - len);
			e = (void *) buf;
			begin = base + e->header.size - len;
		} else if (begin + e->header.size == base + buffer_size) {
			begin = base;
		} else {
			begin += e->header.size;
		}

		if (e->header.type == PERF_RECORD_SAMPLE) {
			ret = fn(e->data, e->size);
			if (ret != 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);
		}
	}

	__sync_synchronize(); /* smp_mb() */
	header->data_tail = data_head;
	return PERF_EVENT_CONT;
}

int perf_event_poller(int fd, perf_event_print_fn output_fn)
{
	int ret;

	for (;;) {
		perf_event_poll(fd);
		ret = perf_event_read(output_fn);
		if (ret != PERF_EVENT_CONT)
			return ret;
	}

	return PERF_EVENT_DONE;
}