Commit 93bc2e9e authored by Dominique Martinet's avatar Dominique Martinet Committed by Daniel Borkmann
Browse files

bpftool, musl compat: Replace nftw with FTW_ACTIONRETVAL 

musl nftw implementation does not support FTW_ACTIONRETVAL. There have been
multiple attempts at pushing the feature in musl upstream, but it has been
refused or ignored all the times:

  https://www.openwall.com/lists/musl/2021/03/26/1
  https://www.openwall.com/lists/musl/2022/01/22/1



In this case we only care about /proc/<pid>/fd/<fd>, so it's not too difficult
to reimplement directly instead, and the new implementation makes 'bpftool perf'
slightly faster because it doesn't needlessly stat/readdir unneeded directories
(54ms -> 13ms on my machine).

Signed-off-by: default avatarDominique Martinet <asmadeus@codewreck.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarQuentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220424051022.2619648-4-asmadeus@codewreck.org
parent 003fed59

tools/bpf/bpftool/perf.c

+57 −55
Original line number Diff line number Diff line
@@ -11,7 +11,7 @@ 
#include <sys/stat.h>

#include <sys/types.h>

#include <unistd.h>

#include <ftw.h>

#include <dirent.h>



#include <bpf/bpf.h>
@@ -147,81 +147,83 @@ static void print_perf_plain(int pid, int fd, __u32 prog_id, __u32 fd_type, 
	}

}



static int show_proc(const char *fpath, const struct stat *sb,

		     int tflag, struct FTW *ftwbuf)

static int show_proc(void)

{

	struct dirent *proc_de, *pid_fd_de;

	__u64 probe_offset, probe_addr;

	__u32 len, prog_id, fd_type;

	int err, pid = 0, fd = 0;

	DIR *proc, *pid_fd;

	int err, pid, fd;

	const char *pch;

	char buf[4096];



	/* prefix always /proc */

	pch = fpath + 5;

	if (*pch == '\0')

		return 0;

	proc = opendir("/proc");

	if (!proc)

		return -1;



	while ((proc_de = readdir(proc))) {

		pid = 0;

		pch = proc_de->d_name;



		/* 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;

		if (*pch != '\0')

			continue;



	/* 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;

		err = snprintf(buf, sizeof(buf), "/proc/%s/fd", proc_de->d_name);

		if (err < 0 || err >= (int)sizeof(buf))

			continue;



	/* check /proc/<pid>/fd/<fd_num> */

	pch++;

		pid_fd = opendir(buf);

		if (!pid_fd)

			continue;



		while ((pid_fd_de = readdir(pid_fd))) {

			fd = 0;

			pch = pid_fd_de->d_name;



			/* fd should be all numbers */

			while (isdigit(*pch)) {

				fd = fd * 10 + *pch - '0';

				pch++;

			}

			if (*pch != '\0')

		return FTW_SKIP_SUBTREE;

				continue;



			/* query (pid, fd) for potential perf events */

			len = sizeof(buf);

	err = bpf_task_fd_query(pid, fd, 0, buf, &len, &prog_id, &fd_type,

			err = bpf_task_fd_query(pid, fd, 0, buf, &len,

						&prog_id, &fd_type,

						&probe_offset, &probe_addr);

			if (err < 0)

		return 0;

				continue;



			if (json_output)

		print_perf_json(pid, fd, prog_id, fd_type, buf, probe_offset,

				probe_addr);

				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);



				print_perf_plain(pid, fd, prog_id, fd_type, buf,

						 probe_offset, probe_addr);

		}

		closedir(pid_fd);

	}

	closedir(proc);

	return 0;

}



static int do_show(int argc, char **argv)

{

	int flags = FTW_ACTIONRETVAL | FTW_PHYS;

	int err = 0, nopenfd = 16;

	int err;



	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;

	}

	err = show_proc();

	if (json_output)

		jsonw_end_array(json_wtr);