Commit 1a922fee authored by Sargun Dhillon's avatar Sargun Dhillon Committed by David S. Miller

samples, bpf: Refactor test_current_task_under_cgroup - separate out helpers

This patch modifies test_current_task_under_cgroup_user. The test has
several helpers around creating a temporary environment for cgroup
testing, and moving the current task around cgroups. This set of
helpers can then be used in other tests.
Signed-off-by: default avatarSargun Dhillon <sargun@sargun.me>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 69a9d09b
......@@ -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
......
#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;
}
#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
......@@ -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;
}
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