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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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