Since I'm asking Oren to send out cr patches I suppose I should
really be doing the same things with cr_tests patches that I intend
to apply to git://git.sr71.net/~hallyn/cr_tests.git.
This one lets ns_exec be used to emulate the way ns cgroup auto-creates
cgroups, without having ns_cgroup mounted. This will be used in
some of the tests, process-tree being first.
>From a03283de1ff71a9100db63883dde690350e0592a Mon Sep 17 00:00:00 2001
From: root <root@xxxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 1 Jul 2009 19:11:04 -0400
Subject: [PATCH 1/1] ns_exec: define -g option to emulate ns cgroup
Add a -g option to ns_exec. When given, ns_exec will start the
new task in a new cgroup, named for the pid (in the pidns of
ns_exec itself) of the new child.
Signed-off-by: Serge Hallyn <serue@xxxxxxxxxx>
---
ns_exec.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 108 insertions(+), 3 deletions(-)
diff --git a/ns_exec.c b/ns_exec.c
index 8adace9..3c3aa9e 100644
--- a/ns_exec.c
+++ b/ns_exec.c
@@ -30,6 +30,7 @@ static void usage(const char *name)
printf(" -h this message\n");
printf("\n");
printf(" -c use 'clone' rather than 'unshare' system call\n");
+ printf(" -g launch in new cgroup\n");
printf(" -m mount namespace\n");
printf(" -n network namespace\n");
printf(" -u utsname namespace\n");
@@ -104,9 +105,94 @@ opentty(const char * tty) {
}
// Code copy end
+int do_newcgrp = 0;
+
+int load_cgroup_dir(char *dest, int len)
+{
+ FILE *f = fopen("/proc/mounts", "r");
+ char buf[200];
+ char *name, *path, *fsname, *options, *p1, *p2, *s;
+ if (!f)
+ return 0;
+ while (fgets(buf, 200, f)) {
+ name = strtok_r(buf, " ", &p1);
+ path = strtok_r(NULL, " ", &p1);
+ fsname = strtok_r(NULL, " ", &p1);
+ options = strtok_r(NULL, " ", &p1);
+ if (strcmp(fsname, "cgroup") != 0)
+ continue;
+
+ /* make sure the freezer is composed */
+ s = strtok_r(options, ",", &p2);
+ while (s && strcmp(s, "freezer") != 0)
+ s = strtok_r(NULL, ",", &p2);
+ if (!s)
+ continue;
+ strncpy(dest, path, len);
+ fclose(f);
+ return 1;
+ }
+ fclose(f);
+ printf("Freezer not mounted\n");
+ return 0;
+}
+
+int move_to_new_cgroup(int newcgroup)
+{
+ char cgroupname[150], cgroupbase[100], tasksfname[200];
+ FILE *fout;
+ int ret;
+
+ if (!load_cgroup_dir(cgroupbase, 100))
+ return 0;
+
+ snprintf(cgroupname, 150, "%s/%d", cgroupbase, newcgroup);
+ ret = mkdir(cgroupname, 0755);
+ if (ret)
+ return 0;
+ snprintf(tasksfname, 200, "%s/tasks", cgroupname);
+ fout = fopen(tasksfname, "w");
+ if (!fout)
+ return 0;
+ fprintf(fout, "%d\n", getpid());
+ fclose(fout);
+ return 1;
+}
+
+int pipefd[2];
+
+/* gah. opentty will close the pipefd */
+int check_newcgrp(void)
+{
+ int ret, newgroup;
+ char buf[20];
+
+ if (!do_newcgrp)
+ return 0;
+
+ close(pipefd[1]);
+ ret = read(pipefd[0], buf, 20);
+ close(pipefd[0]);
+ if (ret == -1) {
+ perror("read");
+ return 1;
+ }
+ newgroup = atoi(buf);
+ if (!move_to_new_cgroup(newgroup))
+ return 1;
+ do_newcgrp = 0;
+ return 0;
+}
+
int do_child(void *vargv)
{
char **argv = (char **)vargv;
+ int ret, newgroup = 0;
+ char buf[20];
+
+ if (check_newcgrp())
+ return 1;
+
execve(argv[0], argv, __environ);
perror("execve");
return 1;
@@ -145,10 +231,11 @@ int main(int argc, char *argv[])
memset(ttyname, '\0', sizeof(ttyname));
readlink("/proc/self/fd/0", ttyname, sizeof(ttyname));
- while ((c = getopt(argc, argv, "+muUiphcnf:P:")) != EOF) {
+ while ((c = getopt(argc, argv, "+mguUiphcnf:P:")) != EOF) {
switch (c) {
- case 'm': flags |= CLONE_NEWNS; break;
- case 'c': use_clone = 1; break;
+ case 'g': do_newcgrp = getpid(); break;
+ case 'm': flags |= CLONE_NEWNS; break;
+ case 'c': use_clone = 1; break;
case 'P': pid_file = optarg; break;
case 'u': flags |= CLONE_NEWUTS; break;
case 'i': flags |= CLONE_NEWIPC; break;
@@ -168,6 +255,15 @@ int main(int argc, char *argv[])
argv = &argv[optind];
argc = argc - optind;
+ if (do_newcgrp) {
+ ret = pipe(pipefd);
+ if (ret) {
+ perror("pipe");
+ return -1;
+ }
+ do_newcgrp = pipefd[0];
+ }
+
if (use_clone) {
int stacksize = 4*getpagesize();
void *childstack, *stack = malloc(stacksize);
@@ -189,6 +285,8 @@ int main(int argc, char *argv[])
// Child.
//print_my_info(procname, ttyname);
+ if (check_newcgrp())
+ return 1;
opentty(ttyname);
printf("about to unshare with %lx\n", flags);
@@ -202,6 +300,13 @@ int main(int argc, char *argv[])
}
}
+ if (pid != -1 && do_newcgrp) {
+ char buf[20];
+ snprintf(buf, 20, "%d", pid);
+ close(pipefd[0]);
+ write(pipefd[1], buf, strlen(buf)+1);
+ close(pipefd[1]);
+ }
write_pid(pid_file, pid);
--
1.6.1.1
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