This splits out the cgroup helper code from
test_current_task_under_cgroup_user.c This code can be used to test any
program that needs to setup a cgroup v2 hierarchy temporarily, and put
itself into said hierarchy. It also includes some functions that make
moving around in the hierarchy a bit easier.
This patch is used in follow on samples.
Signed-off-by: Sargun Dhillon <sar...@sargun.me>
---
samples/bpf/Makefile | 2 +-
samples/bpf/cgroup_helpers.c | 103 ++++++++++++++++++++++
samples/bpf/cgroup_helpers.h | 15 ++++
samples/bpf/test_current_task_under_cgroup_user.c | 72 +++------------
4 files changed, 129 insertions(+), 63 deletions(-)
create mode 100644 samples/bpf/cgroup_helpers.c
create mode 100644 samples/bpf/cgroup_helpers.h
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index db3cb06..5d2c178 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -50,7 +50,7 @@ test_cgrp2_array_pin-objs := libbpf.o test_cgrp2_array_pin.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
# Tell kbuild to always build the programs
diff --git a/samples/bpf/cgroup_helpers.c b/samples/bpf/cgroup_helpers.c
new file mode 100644
index 0000000..e465497
--- /dev/null
+++ b/samples/bpf/cgroup_helpers.c
@@ -0,0 +1,103 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include "cgroup_helpers.h"
+
+#define CGROUP_MOUNT_PATH "/mnt"
+
+int add_controller(char *controller)
+{
+ int fd, rc = 0;
+
+ fd = open("cgroup.subtree_control", O_WRONLY);
+ if (fd < 0) {
+ log_err("Unable to open subtree_control");
+ return 1;
+ }
+ if (dprintf(fd, "+%s\n", controller) < 0) {
+ log_err("Adding Controller");
+ rc = 1;
+ }
+ close(fd);
+ return rc;
+}
+
+int mkdirp(char *path)
+{
+ int rc;
+
+ rc = mkdir(path, 0777);
+ if (rc && errno == EEXIST)
+ return 0;
+ return rc;
+}
+
+/*
+ * 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. This function drops you into the top of that cgroup2
+ * mount point, so make sure you call load_bpf before calling this.
+ */
+int setup_cgroups(void)
+{
+ 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 (chdir(CGROUP_MOUNT_PATH)) {
+ log_err("chdir");
+ return 1;
+ }
+
+ return 0;
+}
+
+int join_cgroup(char *path)
+{
+ char cgroup_path[1024];
+ pid_t pid = getpid();
+ int fd, rc = 0;
+
+ 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;
+}
+
+int reset_bpf_hook(int fd)
+{
+ if (dprintf(fd, "0\n") < 0) {
+ log_err("Unable to reset BPF hook");
+ return 1;
+ }
+ return 0;
+}
diff --git a/samples/bpf/cgroup_helpers.h b/samples/bpf/cgroup_helpers.h
new file mode 100644
index 0000000..f9f1bdf
--- /dev/null
+++ b/samples/bpf/cgroup_helpers.h
@@ -0,0 +1,15 @@
+#ifndef __CGROUP_HELPERS_H
+#define __CGROUP_HELPERS_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 mkdirp(char *path);
+int setup_cgroups(void);
+int join_cgroup(char *path);
+int reset_bpf_hook(int fd);
+int add_controller(char *controller);
+
+#endif
diff --git a/samples/bpf/test_current_task_under_cgroup_user.c
b/samples/bpf/test_current_task_under_cgroup_user.c
index 30b0bce..752a254 100644
--- a/samples/bpf/test_current_task_under_cgroup_user.c
+++ b/samples/bpf/test_current_task_under_cgroup_user.c
@@ -11,44 +11,12 @@
#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_NAME "test_current_task_under"
int main(int argc, char **argv)
{
@@ -62,33 +30,13 @@ 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");
+ if (setup_cgroups())
return 1;
- }
- if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL)) {
- log_err("mount cgroup2");
+ if (mkdirp(CGROUP_NAME))
return 1;
- }
-
- if (mkdir(CGROUP_PATH, 0777) && errno != EEXIST) {
- log_err("mkdir cgroup");
- return 1;
- }
- cg2 = open(CGROUP_PATH, O_RDONLY);
+ cg2 = open(CGROUP_NAME, O_RDONLY);
if (cg2 < 0) {
log_err("opening target cgroup");
goto cleanup_cgroup_err;
@@ -98,7 +46,7 @@ int main(int argc, char **argv)
log_err("Adding target cgroup to map");
goto cleanup_cgroup_err;
}
- if (join_cgroup("/mnt/my-cgroup")) {
+ if (join_cgroup(CGROUP_NAME)) {
log_err("Leaving target cgroup");
goto cleanup_cgroup_err;
}
@@ -119,7 +67,7 @@ int main(int argc, char **argv)
}
/* Verify the negative scenario; leave the cgroup */
- if (join_cgroup(CGROUP_MOUNT_PATH))
+ if (join_cgroup("."))
goto leave_cgroup_err;
remote_pid = 0;
@@ -133,13 +81,13 @@ int main(int argc, char **argv)
goto cleanup_cgroup_err;
}
- rmdir(CGROUP_PATH);
+ rmdir(CGROUP_NAME);
return 0;
/* Error condition, cleanup */
leave_cgroup_err:
- join_cgroup(CGROUP_MOUNT_PATH);
+ join_cgroup(".");
cleanup_cgroup_err:
- rmdir(CGROUP_PATH);
+ rmdir(CGROUP_NAME);
return 1;
}
--
2.7.4
