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SubjectRFC [patch 30/34] PID Virtualization /proc/container filesystem
Provide the /proc/container directory to
containerize a process or retrieve an associated container.
We need a reasonable quick mechanism to trigger container creation.

A process becomes the root of a container if it writes
a unique name to the /proc/container file. If the process does
not already belong to a container and the name is unique,
a container is created and the calling process becomes the root.
Reading from the file returns the name of the container.

Signed-off-by: Hubertus Franke <frankeh@watson.ibm.com>
---
Makefile | 2
container_api.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 117 insertions(+), 1 deletion(-)
Index: linux-2.6.15/kernel/Makefile
===================================================================
--- linux-2.6.15.orig/kernel/Makefile 2006-01-17 08:37:08.000000000 -0500
+++ linux-2.6.15/kernel/Makefile 2006-01-17 08:37:09.000000000 -0500
@@ -8,7 +8,7 @@
signal.o sys.o kmod.o workqueue.o pid.o \
rcupdate.o intermodule.o extable.o params.o posix-timers.o \
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o \
- container.o
+ container.o container_api.o

obj-$(CONFIG_FUTEX) += futex.o
obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
Index: linux-2.6.15/kernel/container_api.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15/kernel/container_api.c 2006-01-17 08:37:09.000000000 -0500
@@ -0,0 +1,116 @@
+/*
+ * External Interface to containers
+ *
+ * This is only for quick bootstrapping the container support
+ * A proper external API needs to be found
+ *
+ * Copyright (C) Hubertus Franke, IBM Corp. 2005 <frankeh@watson.ibm.com>
+ *
+ */
+
+/* Changes
+ *
+ * 11/22/2005: Created
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+#include <linux/proc_fs.h>
+#include <linux/timer.h>
+#include <linux/mm.h>
+#include <linux/container.h>
+
+MODULE_LICENSE("GPL");
+
+#define DPRINTK( fmt, args...) // printk( "%s: " fmt, __FUNCTION__, ##args)
+
+/****************************************************************
+ * P R O C F S S T U F F
+ ****************************************************************/
+
+static ssize_t container_write(struct file *file, const char __user *ubuf,
+ size_t count, loff_t *p)
+{
+ const char *delims = " \t\n";
+ char kbuf[MAX_CONTAINER_NAME_LEN];
+ char *cptr;
+ char *cname;
+ int rc;
+
+ if (current->container)
+ return -EPERM;
+ if (count >= MAX_CONTAINER_NAME_LEN)
+ return -EINVAL;
+ if (copy_from_user(kbuf, ubuf, count))
+ return -EFAULT;
+ kbuf[MAX_CONTAINER_NAME_LEN-1] = '\0';
+
+ cptr = kbuf;
+ cname = strsep(&cptr,delims);
+ DPRINTK("<%s:%d>: <%s>\n", current->comm, task_pid(current), cname);
+ rc = container_new(cname);
+ if (rc < 0)
+ return rc;
+ return count;
+}
+
+static ssize_t container_read(struct file *file, char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ char kbuf[MAX_CONTAINER_NAME_LEN];
+ int len;
+ char *cname;
+ loff_t __ppos = *ppos;
+
+ cname = current->container ? current->container->name : "";
+ len = sprintf(kbuf,"%s\n",cname);
+ if (__ppos >= len)
+ return 0;
+ if (count > len-__ppos)
+ count = len-__ppos;
+ if (copy_to_user(ubuf, kbuf+__ppos, count))
+ return -EFAULT;
+ *ppos += __ppos + count;
+ DPRINTK("%s: caller <%s:%d>: <%s>\n",
+ current->comm, task_pid(current), cname);
+ return count;
+}
+
+static struct file_operations container_proc_operations = {
+ .read = container_read,
+ .write = container_write,
+};
+
+/****************************************************************
+ *
+ ****************************************************************/
+
+static int __init container_init(void)
+{
+ int rc = 0;
+ struct proc_dir_entry *entry;
+
+ entry = create_proc_entry("container", S_IWUGO|S_IRUGO, NULL);
+ if (entry)
+ entry->proc_fops = &container_proc_operations;
+ else
+ rc = -EINVAL;
+
+ /* Other initialization */
+
+ if (rc)
+ remove_proc_entry("container", NULL);
+ return rc;
+}
+
+static void __exit container_exit(void)
+{
+}
+
+module_init(container_init);
+module_exit(container_exit);
+
--

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