mconsole_kern.c

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/*
 * Copyright (C) 2001 Lennert Buytenhek ([email protected])
 * Copyright (C) 2001 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <linux/console.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/utsname.h>
#include <linux/socket.h>
#include <linux/un.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <asm/uaccess.h>
#include <asm/switch_to.h>

#include <init.h>
#include <irq_kern.h>
#include <irq_user.h>
#include <kern_util.h>
#include "mconsole.h"
#include "mconsole_kern.h"
#include <os.h>

static int do_unlink_socket(struct notifier_block *notifier,
                unsigned long what, void *data)
{
    return mconsole_unlink_socket();
}


static struct notifier_block reboot_notifier = {
    .notifier_call      = do_unlink_socket,
    .priority       = 0,
};

/* Safe without explicit locking for now.  Tasklets provide their own
 * locking, and the interrupt handler is safe because it can't interrupt
 * itself and it can only happen on CPU 0.
 */

static LIST_HEAD(mc_requests);

static void mc_work_proc(struct work_struct *unused)
{
    struct mconsole_entry *req;
    unsigned long flags;

    while (!list_empty(&mc_requests)) {
        local_irq_save(flags);
        req = list_entry(mc_requests.next, struct mconsole_entry, list);
        list_del(&req->list);
        local_irq_restore(flags);
        req->request.cmd->handler(&req->request);
        kfree(req);
    }
}

static DECLARE_WORK(mconsole_work, mc_work_proc);

static irqreturn_t mconsole_interrupt(int irq, void *dev_id)
{
    /* long to avoid size mismatch warnings from gcc */
    long fd;
    struct mconsole_entry *new;
    static struct mc_request req;   /* that's OK */

    fd = (long) dev_id;
    while (mconsole_get_request(fd, &req)) {
        if (req.cmd->context == MCONSOLE_INTR)
            (*req.cmd->handler)(&req);
        else {
            new = kmalloc(sizeof(*new), GFP_NOWAIT);
            if (new == NULL)
                mconsole_reply(&req, "Out of memory", 1, 0);
            else {
                new->request = req;
                new->request.regs = get_irq_regs()->regs;
                list_add(&new->list, &mc_requests);
            }
        }
    }
    if (!list_empty(&mc_requests))
        schedule_work(&mconsole_work);
    reactivate_fd(fd, MCONSOLE_IRQ);
    return IRQ_HANDLED;
}

void mconsole_version(struct mc_request *req)
{
    char version[256];

    sprintf(version, "%s %s %s %s %s", utsname()->sysname,
        utsname()->nodename, utsname()->release, utsname()->version,
        utsname()->machine);
    mconsole_reply(req, version, 0, 0);
}

void mconsole_log(struct mc_request *req)
{
    int len;
    char *ptr = req->request.data;

    ptr += strlen("log ");

    len = req->len - (ptr - req->request.data);
    printk(KERN_WARNING "%.*s", len, ptr);
    mconsole_reply(req, "", 0, 0);
}

void mconsole_proc(struct mc_request *req)
{
    struct vfsmount *mnt = current->nsproxy->pid_ns->proc_mnt;
    char *buf;
    int len;
    struct file *file;
    int first_chunk = 1;
    char *ptr = req->request.data;

    ptr += strlen("proc");
    ptr = skip_spaces(ptr);

    file = file_open_root(mnt->mnt_root, mnt, ptr, O_RDONLY);
    if (IS_ERR(file)) {
        mconsole_reply(req, "Failed to open file", 1, 0);
        printk(KERN_ERR "open /proc/%s: %ld\n", ptr, PTR_ERR(file));
        goto out;
    }

    buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
    if (buf == NULL) {
        mconsole_reply(req, "Failed to allocate buffer", 1, 0);
        goto out_fput;
    }

    do {
        loff_t pos;
        mm_segment_t old_fs = get_fs();
        set_fs(KERNEL_DS);
        len = vfs_read(file, buf, PAGE_SIZE - 1, &pos);
        set_fs(old_fs);
        file->f_pos = pos;
        if (len < 0) {
            mconsole_reply(req, "Read of file failed", 1, 0);
            goto out_free;
        }
        /* Begin the file content on his own line. */
        if (first_chunk) {
            mconsole_reply(req, "\n", 0, 1);
            first_chunk = 0;
        }
        buf[len] = '\0';
        mconsole_reply(req, buf, 0, (len > 0));
    } while (len > 0);
 out_free:
    kfree(buf);
 out_fput:
    fput(file);
 out: ;
}

#define UML_MCONSOLE_HELPTEXT \
"Commands: \n\
    version - Get kernel version \n\
    help - Print this message \n\
    halt - Halt UML \n\
    reboot - Reboot UML \n\
    config <dev>=<config> - Add a new device to UML;  \n\
    same syntax as command line \n\
    config <dev> - Query the configuration of a device \n\
    remove <dev> - Remove a device from UML \n\
    sysrq <letter> - Performs the SysRq action controlled by the letter \n\
    cad - invoke the Ctrl-Alt-Del handler \n\
    stop - pause the UML; it will do nothing until it receives a 'go' \n\
    go - continue the UML after a 'stop' \n\
    log <string> - make UML enter <string> into the kernel log\n\
    proc <file> - returns the contents of the UML's /proc/<file>\n\
    stack <pid> - returns the stack of the specified pid\n\
"

void mconsole_help(struct mc_request *req)
{
    mconsole_reply(req, UML_MCONSOLE_HELPTEXT, 0, 0);
}

void mconsole_halt(struct mc_request *req)
{
    mconsole_reply(req, "", 0, 0);
    machine_halt();
}

void mconsole_reboot(struct mc_request *req)
{
    mconsole_reply(req, "", 0, 0);
    machine_restart(NULL);
}

void mconsole_cad(struct mc_request *req)
{
    mconsole_reply(req, "", 0, 0);
    ctrl_alt_del();
}

void mconsole_go(struct mc_request *req)
{
    mconsole_reply(req, "Not stopped", 1, 0);
}

void mconsole_stop(struct mc_request *req)
{
    deactivate_fd(req->originating_fd, MCONSOLE_IRQ);
    os_set_fd_block(req->originating_fd, 1);
    mconsole_reply(req, "stopped", 0, 0);
    for (;;) {
        if (!mconsole_get_request(req->originating_fd, req))
            continue;
        if (req->cmd->handler == mconsole_go)
            break;
        if (req->cmd->handler == mconsole_stop) {
            mconsole_reply(req, "Already stopped", 1, 0);
            continue;
        }
        if (req->cmd->handler == mconsole_sysrq) {
            struct pt_regs *old_regs;
            old_regs = set_irq_regs((struct pt_regs *)&req->regs);
            mconsole_sysrq(req);
            set_irq_regs(old_regs);
            continue;
        }
        (*req->cmd->handler)(req);
    }
    os_set_fd_block(req->originating_fd, 0);
    reactivate_fd(req->originating_fd, MCONSOLE_IRQ);
    mconsole_reply(req, "", 0, 0);
}

static DEFINE_SPINLOCK(mc_devices_lock);
static LIST_HEAD(mconsole_devices);

void mconsole_register_dev(struct mc_device *new)
{
    spin_lock(&mc_devices_lock);
    BUG_ON(!list_empty(&new->list));
    list_add(&new->list, &mconsole_devices);
    spin_unlock(&mc_devices_lock);
}

static struct mc_device *mconsole_find_dev(char *name)
{
    struct list_head *ele;
    struct mc_device *dev;

    list_for_each(ele, &mconsole_devices) {
        dev = list_entry(ele, struct mc_device, list);
        if (!strncmp(name, dev->name, strlen(dev->name)))
            return dev;
    }
    return NULL;
}

#define UNPLUGGED_PER_PAGE \
    ((PAGE_SIZE - sizeof(struct list_head)) / sizeof(unsigned long))

struct unplugged_pages {
    struct list_head list;
    void *pages[UNPLUGGED_PER_PAGE];
};

static DEFINE_MUTEX(plug_mem_mutex);
static unsigned long long unplugged_pages_count = 0;
static LIST_HEAD(unplugged_pages);
static int unplug_index = UNPLUGGED_PER_PAGE;

static int mem_config(char *str, char **error_out)
{
    unsigned long long diff;
    int err = -EINVAL, i, add;
    char *ret;

    if (str[0] != '=') {
        *error_out = "Expected '=' after 'mem'";
        goto out;
    }

    str++;
    if (str[0] == '-')
        add = 0;
    else if (str[0] == '+') {
        add = 1;
    }
    else {
        *error_out = "Expected increment to start with '-' or '+'";
        goto out;
    }

    str++;
    diff = memparse(str, &ret);
    if (*ret != '\0') {
        *error_out = "Failed to parse memory increment";
        goto out;
    }

    diff /= PAGE_SIZE;

    mutex_lock(&plug_mem_mutex);
    for (i = 0; i < diff; i++) {
        struct unplugged_pages *unplugged;
        void *addr;

        if (add) {
            if (list_empty(&unplugged_pages))
                break;

            unplugged = list_entry(unplugged_pages.next,
                           struct unplugged_pages, list);
            if (unplug_index > 0)
                addr = unplugged->pages[--unplug_index];
            else {
                list_del(&unplugged->list);
                addr = unplugged;
                unplug_index = UNPLUGGED_PER_PAGE;
            }

            free_page((unsigned long) addr);
            unplugged_pages_count--;
        }
        else {
            struct page *page;

            page = alloc_page(GFP_ATOMIC);
            if (page == NULL)
                break;

            unplugged = page_address(page);
            if (unplug_index == UNPLUGGED_PER_PAGE) {
                list_add(&unplugged->list, &unplugged_pages);
                unplug_index = 0;
            }
            else {
                struct list_head *entry = unplugged_pages.next;
                addr = unplugged;

                unplugged = list_entry(entry,
                               struct unplugged_pages,
                               list);
                err = os_drop_memory(addr, PAGE_SIZE);
                if (err) {
                    printk(KERN_ERR "Failed to release "
                           "memory - errno = %d\n", err);
                    *error_out = "Failed to release memory";
                    goto out_unlock;
                }
                unplugged->pages[unplug_index++] = addr;
            }

            unplugged_pages_count++;
        }
    }

    err = 0;
out_unlock:
    mutex_unlock(&plug_mem_mutex);
out:
    return err;
}

static int mem_get_config(char *name, char *str, int size, char **error_out)
{
    char buf[sizeof("18446744073709551615")];
    int len = 0;

    sprintf(buf, "%ld", uml_physmem);
    CONFIG_CHUNK(str, size, len, buf, 1);

    return len;
}

static int mem_id(char **str, int *start_out, int *end_out)
{
    *start_out = 0;
    *end_out = 0;

    return 0;
}

static int mem_remove(int n, char **error_out)
{
    *error_out = "Memory doesn't support the remove operation";
    return -EBUSY;
}

static struct mc_device mem_mc = {
    .list       = LIST_HEAD_INIT(mem_mc.list),
    .name       = "mem",
    .config     = mem_config,
    .get_config = mem_get_config,
    .id     = mem_id,
    .remove     = mem_remove,
};

static int __init mem_mc_init(void)
{
    if (can_drop_memory())
        mconsole_register_dev(&mem_mc);
    else printk(KERN_ERR "Can't release memory to the host - memory "
            "hotplug won't be supported\n");
    return 0;
}

__initcall(mem_mc_init);

#define CONFIG_BUF_SIZE 64

static void mconsole_get_config(int (*get_config)(char *, char *, int,
                          char **),
                struct mc_request *req, char *name)
{
    char default_buf[CONFIG_BUF_SIZE], *error, *buf;
    int n, size;

    if (get_config == NULL) {
        mconsole_reply(req, "No get_config routine defined", 1, 0);
        return;
    }

    error = NULL;
    size = ARRAY_SIZE(default_buf);
    buf = default_buf;

    while (1) {
        n = (*get_config)(name, buf, size, &error);
        if (error != NULL) {
            mconsole_reply(req, error, 1, 0);
            goto out;
        }

        if (n <= size) {
            mconsole_reply(req, buf, 0, 0);
            goto out;
        }

        if (buf != default_buf)
            kfree(buf);

        size = n;
        buf = kmalloc(size, GFP_KERNEL);
        if (buf == NULL) {
            mconsole_reply(req, "Failed to allocate buffer", 1, 0);
            return;
        }
    }
 out:
    if (buf != default_buf)
        kfree(buf);
}

void mconsole_config(struct mc_request *req)
{
    struct mc_device *dev;
    char *ptr = req->request.data, *name, *error_string = "";
    int err;

    ptr += strlen("config");
    ptr = skip_spaces(ptr);
    dev = mconsole_find_dev(ptr);
    if (dev == NULL) {
        mconsole_reply(req, "Bad configuration option", 1, 0);
        return;
    }

    name = &ptr[strlen(dev->name)];
    ptr = name;
    while ((*ptr != '=') && (*ptr != '\0'))
        ptr++;

    if (*ptr == '=') {
        err = (*dev->config)(name, &error_string);
        mconsole_reply(req, error_string, err, 0);
    }
    else mconsole_get_config(dev->get_config, req, name);
}

void mconsole_remove(struct mc_request *req)
{
    struct mc_device *dev;
    char *ptr = req->request.data, *err_msg = "";
    char error[256];
    int err, start, end, n;

    ptr += strlen("remove");
    ptr = skip_spaces(ptr);
    dev = mconsole_find_dev(ptr);
    if (dev == NULL) {
        mconsole_reply(req, "Bad remove option", 1, 0);
        return;
    }

    ptr = &ptr[strlen(dev->name)];

    err = 1;
    n = (*dev->id)(&ptr, &start, &end);
    if (n < 0) {
        err_msg = "Couldn't parse device number";
        goto out;
    }
    else if ((n < start) || (n > end)) {
        sprintf(error, "Invalid device number - must be between "
            "%d and %d", start, end);
        err_msg = error;
        goto out;
    }

    err_msg = NULL;
    err = (*dev->remove)(n, &err_msg);
    switch(err) {
    case 0:
        err_msg = "";
        break;
    case -ENODEV:
        if (err_msg == NULL)
            err_msg = "Device doesn't exist";
        break;
    case -EBUSY:
        if (err_msg == NULL)
            err_msg = "Device is currently open";
        break;
    default:
        break;
    }
out:
    mconsole_reply(req, err_msg, err, 0);
}

struct mconsole_output {
    struct list_head list;
    struct mc_request *req;
};

static DEFINE_SPINLOCK(client_lock);
static LIST_HEAD(clients);
static char console_buf[MCONSOLE_MAX_DATA];

static void console_write(struct console *console, const char *string,
              unsigned int len)
{
    struct list_head *ele;
    int n;

    if (list_empty(&clients))
        return;

    while (len > 0) {
        n = min((size_t) len, ARRAY_SIZE(console_buf));
        strncpy(console_buf, string, n);
        string += n;
        len -= n;

        list_for_each(ele, &clients) {
            struct mconsole_output *entry;

            entry = list_entry(ele, struct mconsole_output, list);
            mconsole_reply_len(entry->req, console_buf, n, 0, 1);
        }
    }
}

static struct console mc_console = { .name  = "mc",
                     .write = console_write,
                     .flags = CON_ENABLED,
                     .index = -1 };

static int mc_add_console(void)
{
    register_console(&mc_console);
    return 0;
}

late_initcall(mc_add_console);

static void with_console(struct mc_request *req, void (*proc)(void *),
             void *arg)
{
    struct mconsole_output entry;
    unsigned long flags;

    entry.req = req;
    spin_lock_irqsave(&client_lock, flags);
    list_add(&entry.list, &clients);
    spin_unlock_irqrestore(&client_lock, flags);

    (*proc)(arg);

    mconsole_reply_len(req, "", 0, 0, 0);

    spin_lock_irqsave(&client_lock, flags);
    list_del(&entry.list);
    spin_unlock_irqrestore(&client_lock, flags);
}

#ifdef CONFIG_MAGIC_SYSRQ

#include <linux/sysrq.h>

static void sysrq_proc(void *arg)
{
    char *op = arg;
    handle_sysrq(*op);
}

void mconsole_sysrq(struct mc_request *req)
{
    char *ptr = req->request.data;

    ptr += strlen("sysrq");
    ptr = skip_spaces(ptr);

    /*
     * With 'b', the system will shut down without a chance to reply,
     * so in this case, we reply first.
     */
    if (*ptr == 'b')
        mconsole_reply(req, "", 0, 0);

    with_console(req, sysrq_proc, ptr);
}
#else
void mconsole_sysrq(struct mc_request *req)
{
    mconsole_reply(req, "Sysrq not compiled in", 1, 0);
}
#endif

static void stack_proc(void *arg)
{
    struct task_struct *from = current, *to = arg;

    to->thread.saved_task = from;
    rcu_switch(from, to);
    switch_to(from, to, from);
}

/*
 * Mconsole stack trace
 *  Added by Allan Graves, Jeff Dike
 *  Dumps a stacks registers to the linux console.
 *  Usage stack <pid>.
 */
void mconsole_stack(struct mc_request *req)
{
    char *ptr = req->request.data;
    int pid_requested= -1;
    struct task_struct *to = NULL;

    /*
     * Would be nice:
     * 1) Send showregs output to mconsole.
     * 2) Add a way to stack dump all pids.
     */

    ptr += strlen("stack");
    ptr = skip_spaces(ptr);

    /*
     * Should really check for multiple pids or reject bad args here
     */
    /* What do the arguments in mconsole_reply mean? */
    if (sscanf(ptr, "%d", &pid_requested) == 0) {
        mconsole_reply(req, "Please specify a pid", 1, 0);
        return;
    }

    to = find_task_by_pid_ns(pid_requested, &init_pid_ns);
    if ((to == NULL) || (pid_requested == 0)) {
        mconsole_reply(req, "Couldn't find that pid", 1, 0);
        return;
    }
    with_console(req, stack_proc, to);
}

/*
 * Changed by mconsole_setup, which is __setup, and called before SMP is
 * active.
 */
static char *notify_socket = NULL;

static int __init mconsole_init(void)
{
    /* long to avoid size mismatch warnings from gcc */
    long sock;
    int err;
    char file[UNIX_PATH_MAX];

    if (umid_file_name("mconsole", file, sizeof(file)))
        return -1;
    snprintf(mconsole_socket_name, sizeof(file), "%s", file);

    sock = os_create_unix_socket(file, sizeof(file), 1);
    if (sock < 0) {
        printk(KERN_ERR "Failed to initialize management console\n");
        return 1;
    }
    if (os_set_fd_block(sock, 0))
        goto out;

    register_reboot_notifier(&reboot_notifier);

    err = um_request_irq(MCONSOLE_IRQ, sock, IRQ_READ, mconsole_interrupt,
                 IRQF_SHARED, "mconsole", (void *)sock);
    if (err) {
        printk(KERN_ERR "Failed to get IRQ for management console\n");
        goto out;
    }

    if (notify_socket != NULL) {
        notify_socket = kstrdup(notify_socket, GFP_KERNEL);
        if (notify_socket != NULL)
            mconsole_notify(notify_socket, MCONSOLE_SOCKET,
                    mconsole_socket_name,
                    strlen(mconsole_socket_name) + 1);
        else printk(KERN_ERR "mconsole_setup failed to strdup "
                "string\n");
    }

    printk(KERN_INFO "mconsole (version %d) initialized on %s\n",
           MCONSOLE_VERSION, mconsole_socket_name);
    return 0;

 out:
    os_close_file(sock);
    return 1;
}

__initcall(mconsole_init);

static ssize_t mconsole_proc_write(struct file *file,
        const char __user *buffer, size_t count, loff_t *pos)
{
    char *buf;

    buf = kmalloc(count + 1, GFP_KERNEL);
    if (buf == NULL)
        return -ENOMEM;

    if (copy_from_user(buf, buffer, count)) {
        count = -EFAULT;
        goto out;
    }

    buf[count] = '\0';

    mconsole_notify(notify_socket, MCONSOLE_USER_NOTIFY, buf, count);
 out:
    kfree(buf);
    return count;
}

static const struct file_operations mconsole_proc_fops = {
    .owner      = THIS_MODULE,
    .write      = mconsole_proc_write,
    .llseek     = noop_llseek,
};

static int create_proc_mconsole(void)
{
    struct proc_dir_entry *ent;

    if (notify_socket == NULL)
        return 0;

    ent = proc_create("mconsole", 0200, NULL, &mconsole_proc_fops);
    if (ent == NULL) {
        printk(KERN_INFO "create_proc_mconsole : create_proc_entry "
               "failed\n");
        return 0;
    }
    return 0;
}

static DEFINE_SPINLOCK(notify_spinlock);

void lock_notify(void)
{
    spin_lock(&notify_spinlock);
}

void unlock_notify(void)
{
    spin_unlock(&notify_spinlock);
}

__initcall(create_proc_mconsole);

#define NOTIFY "notify:"

static int mconsole_setup(char *str)
{
    if (!strncmp(str, NOTIFY, strlen(NOTIFY))) {
        str += strlen(NOTIFY);
        notify_socket = str;
    }
    else printk(KERN_ERR "mconsole_setup : Unknown option - '%s'\n", str);
    return 1;
}

__setup("mconsole=", mconsole_setup);

__uml_help(mconsole_setup,
"mconsole=notify:<socket>\n"
"    Requests that the mconsole driver send a message to the named Unix\n"
"    socket containing the name of the mconsole socket.  This also serves\n"
"    to notify outside processes when UML has booted far enough to respond\n"
"    to mconsole requests.\n\n"
);

static int notify_panic(struct notifier_block *self, unsigned long unused1,
            void *ptr)
{
    char *message = ptr;

    if (notify_socket == NULL)
        return 0;

    mconsole_notify(notify_socket, MCONSOLE_PANIC, message,
            strlen(message) + 1);
    return 0;
}

static struct notifier_block panic_exit_notifier = {
    .notifier_call      = notify_panic,
    .next           = NULL,
    .priority       = 1
};

static int add_notifier(void)
{
    atomic_notifier_chain_register(&panic_notifier_list,
            &panic_exit_notifier);
    return 0;
}

__initcall(add_notifier);

char *mconsole_notify_socket(void)
{
    return notify_socket;
}

EXPORT_SYMBOL(mconsole_notify_socket);