src/perf.c

// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
// Copyright (C) 2018 Facebook
// Author: Yonghong Song <yhs@fb.com>

#define _GNU_SOURCE
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <ftw.h>

#include <bpf/bpf.h>

#include "main.h"

/* musl libc doesn't implement these GNU extensions.  They are used below
 * to optimize out walking unnecessary subtrees of /proc, #defining them
 * to 0 here disables the optimization but leaves the functionality otherwise
 * unchanged.
 */
#ifndef FTW_SKIP_SUBTREE
#define FTW_SKIP_SUBTREE 0
#endif

#ifndef FTW_ACTIONRETVAL
#define FTW_ACTIONRETVAL 0
#endif

/* 0: undecided, 1: supported, 2: not supported */
static int perf_query_supported;
static bool has_perf_query_support(void)
{
	__u64 probe_offset, probe_addr;
	__u32 len, prog_id, fd_type;
	char buf[256];
	int fd;

	if (perf_query_supported)
		goto out;

	fd = open("/", O_RDONLY);
	if (fd < 0) {
		p_err("perf_query_support: cannot open directory \"/\" (%s)",
		      strerror(errno));
		goto out;
	}

	/* the following query will fail as no bpf attachment,
	 * the expected errno is ENOTSUPP
	 */
	errno = 0;
	len = sizeof(buf);
	bpf_task_fd_query(getpid(), fd, 0, buf, &len, &prog_id,
			  &fd_type, &probe_offset, &probe_addr);

	if (errno == 524 /* ENOTSUPP */) {
		perf_query_supported = 1;
		goto close_fd;
	}

	perf_query_supported = 2;
	p_err("perf_query_support: %s", strerror(errno));
	fprintf(stderr,
		"HINT: non root or kernel doesn't support TASK_FD_QUERY\n");

close_fd:
	close(fd);
out:
	return perf_query_supported == 1;
}

static void print_perf_json(int pid, int fd, __u32 prog_id, __u32 fd_type,
			    char *buf, __u64 probe_offset, __u64 probe_addr)
{
	jsonw_start_object(json_wtr);
	jsonw_int_field(json_wtr, "pid", pid);
	jsonw_int_field(json_wtr, "fd", fd);
	jsonw_uint_field(json_wtr, "prog_id", prog_id);
	switch (fd_type) {
	case BPF_FD_TYPE_RAW_TRACEPOINT:
		jsonw_string_field(json_wtr, "fd_type", "raw_tracepoint");
		jsonw_string_field(json_wtr, "tracepoint", buf);
		break;
	case BPF_FD_TYPE_TRACEPOINT:
		jsonw_string_field(json_wtr, "fd_type", "tracepoint");
		jsonw_string_field(json_wtr, "tracepoint", buf);
		break;
	case BPF_FD_TYPE_KPROBE:
		jsonw_string_field(json_wtr, "fd_type", "kprobe");
		if (buf[0] != '\0') {
			jsonw_string_field(json_wtr, "func", buf);
			jsonw_lluint_field(json_wtr, "offset", probe_offset);
		} else {
			jsonw_lluint_field(json_wtr, "addr", probe_addr);
		}
		break;
	case BPF_FD_TYPE_KRETPROBE:
		jsonw_string_field(json_wtr, "fd_type", "kretprobe");
		if (buf[0] != '\0') {
			jsonw_string_field(json_wtr, "func", buf);
			jsonw_lluint_field(json_wtr, "offset", probe_offset);
		} else {
			jsonw_lluint_field(json_wtr, "addr", probe_addr);
		}
		break;
	case BPF_FD_TYPE_UPROBE:
		jsonw_string_field(json_wtr, "fd_type", "uprobe");
		jsonw_string_field(json_wtr, "filename", buf);
		jsonw_lluint_field(json_wtr, "offset", probe_offset);
		break;
	case BPF_FD_TYPE_URETPROBE:
		jsonw_string_field(json_wtr, "fd_type", "uretprobe");
		jsonw_string_field(json_wtr, "filename", buf);
		jsonw_lluint_field(json_wtr, "offset", probe_offset);
		break;
	default:
		break;
	}
	jsonw_end_object(json_wtr);
}

static void print_perf_plain(int pid, int fd, __u32 prog_id, __u32 fd_type,
			     char *buf, __u64 probe_offset, __u64 probe_addr)
{
	printf("pid %d  fd %d: prog_id %u  ", pid, fd, prog_id);
	switch (fd_type) {
	case BPF_FD_TYPE_RAW_TRACEPOINT:
		printf("raw_tracepoint  %s\n", buf);
		break;
	case BPF_FD_TYPE_TRACEPOINT:
		printf("tracepoint  %s\n", buf);
		break;
	case BPF_FD_TYPE_KPROBE:
		if (buf[0] != '\0')
			printf("kprobe  func %s  offset %llu\n", buf,
			       probe_offset);
		else
			printf("kprobe  addr %llu\n", probe_addr);
		break;
	case BPF_FD_TYPE_KRETPROBE:
		if (buf[0] != '\0')
			printf("kretprobe  func %s  offset %llu\n", buf,
			       probe_offset);
		else
			printf("kretprobe  addr %llu\n", probe_addr);
		break;
	case BPF_FD_TYPE_UPROBE:
		printf("uprobe  filename %s  offset %llu\n", buf, probe_offset);
		break;
	case BPF_FD_TYPE_URETPROBE:
		printf("uretprobe  filename %s  offset %llu\n", buf,
		       probe_offset);
		break;
	default:
		break;
	}
}

static int show_proc(const char *fpath, const struct stat *sb,
		     int tflag, struct FTW *ftwbuf)
{
	__u64 probe_offset, probe_addr;
	__u32 len, prog_id, fd_type;
	int err, pid = 0, fd = 0;
	const char *pch;
	char buf[4096];

	/* prefix always /proc */
	pch = fpath + 5;
	if (*pch == '\0')
		return 0;

	/* pid should be all numbers */
	pch++;
	while (isdigit(*pch)) {
		pid = pid * 10 + *pch - '0';
		pch++;
	}
	if (*pch == '\0')
		return 0;
	if (*pch != '/')
		return FTW_SKIP_SUBTREE;

	/* check /proc/<pid>/fd directory */
	pch++;
	if (strncmp(pch, "fd", 2))
		return FTW_SKIP_SUBTREE;
	pch += 2;
	if (*pch == '\0')
		return 0;
	if (*pch != '/')
		return FTW_SKIP_SUBTREE;

	/* check /proc/<pid>/fd/<fd_num> */
	pch++;
	while (isdigit(*pch)) {
		fd = fd * 10 + *pch - '0';
		pch++;
	}
	if (*pch != '\0')
		return FTW_SKIP_SUBTREE;

	/* query (pid, fd) for potential perf events */
	len = sizeof(buf);
	err = bpf_task_fd_query(pid, fd, 0, buf, &len, &prog_id, &fd_type,
				&probe_offset, &probe_addr);
	if (err < 0)
		return 0;

	if (json_output)
		print_perf_json(pid, fd, prog_id, fd_type, buf, probe_offset,
				probe_addr);
	else
		print_perf_plain(pid, fd, prog_id, fd_type, buf, probe_offset,
				 probe_addr);

	return 0;
}

static int do_show(int argc, char **argv)
{
	int flags = FTW_ACTIONRETVAL | FTW_PHYS;
	int err = 0, nopenfd = 16;

	if (!has_perf_query_support())
		return -1;

	if (json_output)
		jsonw_start_array(json_wtr);
	if (nftw("/proc", show_proc, nopenfd, flags) == -1) {
		p_err("%s", strerror(errno));
		err = -1;
	}
	if (json_output)
		jsonw_end_array(json_wtr);

	return err;
}

static int do_help(int argc, char **argv)
{
	fprintf(stderr,
		"Usage: %1$s %2$s { show | list }\n"
		"       %1$s %2$s help }\n"
		"\n"
		"       " HELP_SPEC_OPTIONS " }\n"
		"",
		bin_name, argv[-2]);

	return 0;
}

static const struct cmd cmds[] = {
	{ "show",	do_show },
	{ "list",	do_show },
	{ "help",	do_help },
	{ 0 }
};

int do_perf(int argc, char **argv)
{
	return cmd_select(cmds, argc, argv, do_help);
}