samples, bpf: Refactor test_current_task_under_cgroup - separate out helpers (1a922fee) · Commits · e / devices / android_kernel_fairphone_FP5

samples/bpf/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -59,7 +59,7 @@ test_cgrp2_sock2-objs := bpf_load.o libbpf.o test_cgrp2_sock2.o
		xdp1-objs := bpf_load.o libbpf.o xdp1_user.o
		# reuse xdp1 source intentionally
		xdp2-objs := bpf_load.o libbpf.o xdp1_user.o
		test_current_task_under_cgroup-objs := bpf_load.o libbpf.o \
		test_current_task_under_cgroup-objs := bpf_load.o libbpf.o cgroup_helpers.o \
		test_current_task_under_cgroup_user.o
		trace_event-objs := bpf_load.o libbpf.o trace_event_user.o
		sampleip-objs := bpf_load.o libbpf.o sampleip_user.o

samples/bpf/cgroup_helpers.c

0 → 100644

+177 −0

Original line number	Diff line number	Diff line
		#define _GNU_SOURCE
		#include <sched.h>
		#include <sys/mount.h>
		#include <sys/stat.h>
		#include <sys/types.h>
		#include <linux/limits.h>
		#include <stdio.h>
		#include <linux/sched.h>
		#include <fcntl.h>
		#include <unistd.h>
		#include <ftw.h>


		#include "cgroup_helpers.h"

		/*
		* To avoid relying on the system setup, when setup_cgroup_env is called
		* we create a new mount namespace, and cgroup namespace. The cgroup2
		* root is mounted at CGROUP_MOUNT_PATH
		*
		* Unfortunately, most people don't have cgroupv2 enabled at this point in time.
		* It's easier to create our own mount namespace and manage it ourselves.
		*
		* We assume /mnt exists.
		*/

		#define WALK_FD_LIMIT 16
		#define CGROUP_MOUNT_PATH "/mnt"
		#define CGROUP_WORK_DIR "/cgroup-test-work-dir"
		#define format_cgroup_path(buf, path) \
		snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
		CGROUP_WORK_DIR, path)

		/**
		* setup_cgroup_environment() - Setup the cgroup environment
		*
		* After calling this function, cleanup_cgroup_environment should be called
		* once testing is complete.
		*
		* This function will print an error to stderr and return 1 if it is unable
		* to setup the cgroup environment. If setup is successful, 0 is returned.
		*/
		int setup_cgroup_environment(void)
		{
		char cgroup_workdir[PATH_MAX + 1];

		format_cgroup_path(cgroup_workdir, "");

		if (unshare(CLONE_NEWNS)) {
		log_err("unshare");
		return 1;
		}

		if (mount("none", "/", NULL, MS_REC \| MS_PRIVATE, NULL)) {
		log_err("mount fakeroot");
		return 1;
		}

		if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL)) {
		log_err("mount cgroup2");
		return 1;
		}

		/* Cleanup existing failed runs, now that the environment is setup */
		cleanup_cgroup_environment();

		if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
		log_err("mkdir cgroup work dir");
		return 1;
		}

		return 0;
		}

		static int nftwfunc(const char filename, const struct stat statptr,
		int fileflags, struct FTW *pfwt)
		{
		if ((fileflags & FTW_D) && rmdir(filename))
		log_err("Removing cgroup: %s", filename);
		return 0;
		}


		static int join_cgroup_from_top(char *cgroup_path)
		{
		char cgroup_procs_path[PATH_MAX + 1];
		pid_t pid = getpid();
		int fd, rc = 0;

		snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
		"%s/cgroup.procs", cgroup_path);

		fd = open(cgroup_procs_path, O_WRONLY);
		if (fd < 0) {
		log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
		return 1;
		}

		if (dprintf(fd, "%d\n", pid) < 0) {
		log_err("Joining Cgroup");
		rc = 1;
		}

		close(fd);
		return rc;
		}

		/**
		* join_cgroup() - Join a cgroup
		* @path: The cgroup path, relative to the workdir, to join
		*
		* This function expects a cgroup to already be created, relative to the cgroup
		* work dir, and it joins it. For example, passing "/my-cgroup" as the path
		* would actually put the calling process into the cgroup
		* "/cgroup-test-work-dir/my-cgroup"
		*
		* On success, it returns 0, otherwise on failure it returns 1.
		*/
		int join_cgroup(char *path)
		{
		char cgroup_path[PATH_MAX + 1];

		format_cgroup_path(cgroup_path, path);
		return join_cgroup_from_top(cgroup_path);
		}

		/**
		* cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
		*
		* This is an idempotent function to delete all temporary cgroups that
		* have been created during the test, including the cgroup testing work
		* directory.
		*
		* At call time, it moves the calling process to the root cgroup, and then
		* runs the deletion process. It is idempotent, and should not fail, unless
		* a process is lingering.
		*
		* On failure, it will print an error to stderr, and try to continue.
		*/
		void cleanup_cgroup_environment(void)
		{
		char cgroup_workdir[PATH_MAX + 1];

		format_cgroup_path(cgroup_workdir, "");
		join_cgroup_from_top(CGROUP_MOUNT_PATH);
		nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH \| FTW_MOUNT);
		}

		/**
		* create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
		* @path: The cgroup path, relative to the workdir, to join
		*
		* This function creates a cgroup under the top level workdir and returns the
		* file descriptor. It is idempotent.
		*
		* On success, it returns the file descriptor. On failure it returns 0.
		* If there is a failure, it prints the error to stderr.
		*/
		int create_and_get_cgroup(char *path)
		{
		char cgroup_path[PATH_MAX + 1];
		int fd;

		format_cgroup_path(cgroup_path, path);
		if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
		log_err("mkdiring cgroup");
		return 0;
		}

		fd = open(cgroup_path, O_RDONLY);
		if (fd < 0) {
		log_err("Opening Cgroup");
		return 0;
		}

		return fd;
		}

samples/bpf/cgroup_helpers.h

0 → 100644

+16 −0

Original line number	Diff line number	Diff line
		#ifndef __CGROUP_HELPERS_H
		#define __CGROUP_HELPERS_H
		#include <errno.h>
		#include <string.h>

		#define clean_errno() (errno == 0 ? "None" : strerror(errno))
		#define log_err(MSG, ...) fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", \
		__FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)


		int create_and_get_cgroup(char *path);
		int join_cgroup(char *path);
		int setup_cgroup_environment(void);
		void cleanup_cgroup_environment(void);

		#endif

samples/bpf/test_current_task_under_cgroup_user.c

+24 −84

Original line number	Diff line number	Diff line
		@@ -11,50 +11,16 @@
		#include <unistd.h>
		#include "libbpf.h"
		#include "bpf_load.h"
		#include <string.h>
		#include <fcntl.h>
		#include <errno.h>
		#include <linux/bpf.h>
		#include <sched.h>
		#include <sys/mount.h>
		#include <sys/stat.h>
		#include <sys/types.h>
		#include <linux/limits.h>
		#include "cgroup_helpers.h"

		#define CGROUP_MOUNT_PATH "/mnt"
		#define CGROUP_PATH "/mnt/my-cgroup"

		#define clean_errno() (errno == 0 ? "None" : strerror(errno))
		#define log_err(MSG, ...) fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", \
		__FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)

		static int join_cgroup(char *path)
		{
		int fd, rc = 0;
		pid_t pid = getpid();
		char cgroup_path[PATH_MAX + 1];

		snprintf(cgroup_path, sizeof(cgroup_path), "%s/cgroup.procs", path);

		fd = open(cgroup_path, O_WRONLY);
		if (fd < 0) {
		log_err("Opening Cgroup");
		return 1;
		}

		if (dprintf(fd, "%d\n", pid) < 0) {
		log_err("Joining Cgroup");
		rc = 1;
		}
		close(fd);
		return rc;
		}
		#define CGROUP_PATH "/my-cgroup"

		int main(int argc, char **argv)
		{
		char filename[256];
		int cg2, idx = 0;
		pid_t remote_pid, local_pid = getpid();
		int cg2, idx = 0, rc = 0;
		char filename[256];

		snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
		if (load_bpf_file(filename)) {
		@@ -62,47 +28,22 @@ int main(int argc, char **argv)
		return 1;
		}

		/*
		* This is to avoid interfering with existing cgroups. Unfortunately,
		* most people don't have cgroupv2 enabled at this point in time.
		* It's easier to create our own mount namespace and manage it
		* ourselves.
		*/
		if (unshare(CLONE_NEWNS)) {
		log_err("unshare");
		return 1;
		}

		if (mount("none", "/", NULL, MS_REC \| MS_PRIVATE, NULL)) {
		log_err("mount fakeroot");
		return 1;
		}

		if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL)) {
		log_err("mount cgroup2");
		return 1;
		}
		if (setup_cgroup_environment())
		goto err;

		if (mkdir(CGROUP_PATH, 0777) && errno != EEXIST) {
		log_err("mkdir cgroup");
		return 1;
		}
		cg2 = create_and_get_cgroup(CGROUP_PATH);

		cg2 = open(CGROUP_PATH, O_RDONLY);
		if (cg2 < 0) {
		log_err("opening target cgroup");
		goto cleanup_cgroup_err;
		}
		if (!cg2)
		goto err;

		if (bpf_update_elem(map_fd[0], &idx, &cg2, BPF_ANY)) {
		log_err("Adding target cgroup to map");
		goto cleanup_cgroup_err;
		}
		if (join_cgroup("/mnt/my-cgroup")) {
		log_err("Leaving target cgroup");
		goto cleanup_cgroup_err;
		goto err;
		}

		if (join_cgroup(CGROUP_PATH))
		goto err;

		/*
		* The installed helper program catched the sync call, and should
		* write it to the map.
		@@ -115,12 +56,12 @@ int main(int argc, char **argv)
		fprintf(stderr,
		"BPF Helper didn't write correct PID to map, but: %d\n",
		remote_pid);
		goto leave_cgroup_err;
		goto err;
		}

		/* Verify the negative scenario; leave the cgroup */
		if (join_cgroup(CGROUP_MOUNT_PATH))
		goto leave_cgroup_err;
		if (join_cgroup("/"))
		goto err;

		remote_pid = 0;
		bpf_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
		@@ -130,16 +71,15 @@ int main(int argc, char **argv)

		if (local_pid == remote_pid) {
		fprintf(stderr, "BPF cgroup negative test did not work\n");
		goto cleanup_cgroup_err;
		goto err;
		}

		rmdir(CGROUP_PATH);
		return 0;
		goto out;
		err:
		rc = 1;

		/* Error condition, cleanup */
		leave_cgroup_err:
		join_cgroup(CGROUP_MOUNT_PATH);
		cleanup_cgroup_err:
		rmdir(CGROUP_PATH);
		return 1;
		out:
		close(cg2);
		cleanup_cgroup_environment();
		return rc;
		}