bpf-developer-tutorial/17-biopattern/trace_helpers.c

/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
// Copyright (c) 2020 Wenbo Zhang
//
// Based on ksyms improvements from Andrii Nakryiko, add more helpers.
// 28-Feb-2020   Wenbo Zhang   Created this.
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/resource.h>
#include <time.h>
#include <bpf/bpf.h>
#include <bpf/btf.h>
#include <bpf/libbpf.h>
#include <limits.h>
#include "trace_helpers.h"

#define min(x, y) ({				\
	typeof(x) _min1 = (x);			\
	typeof(y) _min2 = (y);			\
	(void) (&_min1 == &_min2);		\
	_min1 < _min2 ? _min1 : _min2; })

#define DISK_NAME_LEN	32

#define MINORBITS	20
#define MINORMASK	((1U << MINORBITS) - 1)

#define MKDEV(ma, mi)	(((ma) << MINORBITS) | (mi))

struct ksyms {
	struct ksym *syms;
	int syms_sz;
	int syms_cap;
	char *strs;
	int strs_sz;
	int strs_cap;
};

struct partitions {
	struct partition *items;
	int sz;
};

static int partitions__add_partition(struct partitions *partitions,
				     const char *name, unsigned int dev)
{
	struct partition *partition;
	void *tmp;

	tmp = realloc(partitions->items, (partitions->sz + 1) *
		sizeof(*partitions->items));
	if (!tmp)
		return -1;
	partitions->items = tmp;
	partition = &partitions->items[partitions->sz];
	partition->name = strdup(name);
	partition->dev = dev;
	partitions->sz++;

	return 0;
}

struct partitions *partitions__load(void)
{
	char part_name[DISK_NAME_LEN];
	unsigned int devmaj, devmin;
	unsigned long long nop;
	struct partitions *partitions;
	char buf[64];
	FILE *f;

	f = fopen("/proc/partitions", "r");
	if (!f)
		return NULL;

	partitions = calloc(1, sizeof(*partitions));
	if (!partitions)
		goto err_out;

	while (fgets(buf, sizeof(buf), f) != NULL) {
		/* skip heading */
		if (buf[0] != ' ' || buf[0] == '\n')
			continue;
		if (sscanf(buf, "%u %u %llu %s", &devmaj, &devmin, &nop,
				part_name) != 4)
			goto err_out;
		if (partitions__add_partition(partitions, part_name,
						MKDEV(devmaj, devmin)))
			goto err_out;
	}

	fclose(f);
	return partitions;

err_out:
	partitions__free(partitions);
	fclose(f);
	return NULL;
}

void partitions__free(struct partitions *partitions)
{
	int i;

	if (!partitions)
		return;

	for (i = 0; i < partitions->sz; i++)
		free(partitions->items[i].name);
	free(partitions->items);
	free(partitions);
}

const struct partition *
partitions__get_by_dev(const struct partitions *partitions, unsigned int dev)
{
	int i;

	for (i = 0; i < partitions->sz; i++) {
		if (partitions->items[i].dev == dev)
			return &partitions->items[i];
	}

	return NULL;
}

const struct partition *
partitions__get_by_name(const struct partitions *partitions, const char *name)
{
	int i;

	for (i = 0; i < partitions->sz; i++) {
		if (strcmp(partitions->items[i].name, name) == 0)
			return &partitions->items[i];
	}

	return NULL;
}

static void print_stars(unsigned int val, unsigned int val_max, int width)
{
	int num_stars, num_spaces, i;
	bool need_plus;

	num_stars = min(val, val_max) * width / val_max;
	num_spaces = width - num_stars;
	need_plus = val > val_max;

	for (i = 0; i < num_stars; i++)
		printf("*");
	for (i = 0; i < num_spaces; i++)
		printf(" ");
	if (need_plus)
		printf("+");
}

void print_log2_hist(unsigned int *vals, int vals_size, const char *val_type)
{
	int stars_max = 40, idx_max = -1;
	unsigned int val, val_max = 0;
	unsigned long long low, high;
	int stars, width, i;

	for (i = 0; i < vals_size; i++) {
		val = vals[i];
		if (val > 0)
			idx_max = i;
		if (val > val_max)
			val_max = val;
	}

	if (idx_max < 0)
		return;

	printf("%*s%-*s : count    distribution\n", idx_max <= 32 ? 5 : 15, "",
		idx_max <= 32 ? 19 : 29, val_type);

	if (idx_max <= 32)
		stars = stars_max;
	else
		stars = stars_max / 2;

	for (i = 0; i <= idx_max; i++) {
		low = (1ULL << (i + 1)) >> 1;
		high = (1ULL << (i + 1)) - 1;
		if (low == high)
			low -= 1;
		val = vals[i];
		width = idx_max <= 32 ? 10 : 20;
		printf("%*lld -> %-*lld : %-8d |", width, low, width, high, val);
		print_stars(val, val_max, stars);
		printf("|\n");
	}
}

void print_linear_hist(unsigned int *vals, int vals_size, unsigned int base,
		       unsigned int step, const char *val_type)
{
	int i, stars_max = 40, idx_min = -1, idx_max = -1;
	unsigned int val, val_max = 0;

	for (i = 0; i < vals_size; i++) {
		val = vals[i];
		if (val > 0) {
			idx_max = i;
			if (idx_min < 0)
				idx_min = i;
		}
		if (val > val_max)
			val_max = val;
	}

	if (idx_max < 0)
		return;

	printf("     %-13s : count     distribution\n", val_type);
	for (i = idx_min; i <= idx_max; i++) {
		val = vals[i];
		if (!val)
			continue;
		printf("        %-10d : %-8d |", base + i * step, val);
		print_stars(val, val_max, stars_max);
		printf("|\n");
	}
}

unsigned long long get_ktime_ns(void)
{
	struct timespec ts;

	clock_gettime(CLOCK_MONOTONIC, &ts);
	return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
}

bool is_kernel_module(const char *name)
{
	bool found = false;
	char buf[64];
	FILE *f;

	f = fopen("/proc/modules", "r");
	if (!f)
		return false;

	while (fgets(buf, sizeof(buf), f) != NULL) {
		if (sscanf(buf, "%s %*s\n", buf) != 1)
			break;
		if (!strcmp(buf, name)) {
			found = true;
			break;
		}
	}

	fclose(f);
	return found;
}

static bool fentry_try_attach(int id)
{
	int prog_fd, attach_fd;
	char error[4096];
	struct bpf_insn insns[] = {
		{ .code = BPF_ALU64 | BPF_MOV | BPF_K, .dst_reg = BPF_REG_0, .imm = 0 },
		{ .code = BPF_JMP | BPF_EXIT },
	};
	LIBBPF_OPTS(bpf_prog_load_opts, opts,
			.expected_attach_type = BPF_TRACE_FENTRY,
			.attach_btf_id = id,
			.log_buf = error,
			.log_size = sizeof(error),
	);

	prog_fd = bpf_prog_load(BPF_PROG_TYPE_TRACING, "test", "GPL", insns,
			sizeof(insns) / sizeof(struct bpf_insn), &opts);
	if (prog_fd < 0)
		return false;

	attach_fd = bpf_raw_tracepoint_open(NULL, prog_fd);
	if (attach_fd >= 0)
		close(attach_fd);

	close(prog_fd);
	return attach_fd >= 0;
}

bool fentry_can_attach(const char *name, const char *mod)
{
	struct btf *btf, *vmlinux_btf, *module_btf = NULL;
	int err, id;

	vmlinux_btf = btf__load_vmlinux_btf();
	err = libbpf_get_error(vmlinux_btf);
	if (err)
		return false;

	btf = vmlinux_btf;

	if (mod) {
		module_btf = btf__load_module_btf(mod, vmlinux_btf);
		err = libbpf_get_error(module_btf);
		if (!err)
			btf = module_btf;
	}

	id = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);

	btf__free(module_btf);
	btf__free(vmlinux_btf);
	return id > 0 && fentry_try_attach(id);
}

bool kprobe_exists(const char *name)
{
	char addr_range[256];
	char sym_name[256];
	FILE *f;
	int ret;

	f = fopen("/sys/kernel/debug/kprobes/blacklist", "r");
	if (!f)
		goto avail_filter;

	while (true) {
		ret = fscanf(f, "%s %s%*[^\n]\n", addr_range, sym_name);
		if (ret == EOF && feof(f))
			break;
		if (ret != 2) {
			fprintf(stderr, "failed to read symbol from kprobe blacklist\n");
			break;
		}
		if (!strcmp(name, sym_name)) {
			fclose(f);
			return false;
		}
	}
	fclose(f);

avail_filter:
	f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
	if (!f)
		goto slow_path;

	while (true) {
		ret = fscanf(f, "%s%*[^\n]\n", sym_name);
		if (ret == EOF && feof(f))
			break;
		if (ret != 1) {
			fprintf(stderr, "failed to read symbol from available_filter_functions\n");
			break;
		}
		if (!strcmp(name, sym_name)) {
			fclose(f);
			return true;
		}
	}

	fclose(f);
	return false;

slow_path:
	f = fopen("/proc/kallsyms", "r");
	if (!f)
		return false;

	while (true) {
		ret = fscanf(f, "%*x %*c %s%*[^\n]\n", sym_name);
		if (ret == EOF && feof(f))
			break;
		if (ret != 1) {
			fprintf(stderr, "failed to read symbol from kallsyms\n");
			break;
		}
		if (!strcmp(name, sym_name)) {
			fclose(f);
			return true;
		}
	}

	fclose(f);
	return false;
}

bool tracepoint_exists(const char *category, const char *event)
{
	char path[PATH_MAX];

	snprintf(path, sizeof(path), "/sys/kernel/debug/tracing/events/%s/%s/format", category, event);
	if (!access(path, F_OK))
		return true;
	return false;
}

bool vmlinux_btf_exists(void)
{
	struct btf *btf;
	int err;

	btf = btf__load_vmlinux_btf();
	err = libbpf_get_error(btf);
	if (err)
		return false;

	btf__free(btf);
	return true;
}

bool module_btf_exists(const char *mod)
{
	char sysfs_mod[80];

	if (mod) {
		snprintf(sysfs_mod, sizeof(sysfs_mod), "/sys/kernel/btf/%s", mod);
		if (!access(sysfs_mod, R_OK))
			return true;
	}
	return false;
}

bool probe_tp_btf(const char *name)
{
	LIBBPF_OPTS(bpf_prog_load_opts, opts, .expected_attach_type = BPF_TRACE_RAW_TP);
	struct bpf_insn insns[] = {
		{ .code = BPF_ALU64 | BPF_MOV | BPF_K, .dst_reg = BPF_REG_0, .imm = 0 },
		{ .code = BPF_JMP | BPF_EXIT },
	};
	int fd, insn_cnt = sizeof(insns) / sizeof(struct bpf_insn);

	opts.attach_btf_id = libbpf_find_vmlinux_btf_id(name, BPF_TRACE_RAW_TP);
	fd = bpf_prog_load(BPF_PROG_TYPE_TRACING, NULL, "GPL", insns, insn_cnt, &opts);
	if (fd >= 0)
		close(fd);
	return fd >= 0;
}

bool probe_ringbuf()
{
	int map_fd;

	map_fd = bpf_map_create(BPF_MAP_TYPE_RINGBUF, NULL, 0, 0, getpagesize(), NULL);
	if (map_fd < 0)
		return false;

	close(map_fd);
	return true;
}