/*
 * Handling of different ABIs (personalities).
 *
 * We group personalities into execution domains which have their
 * own handlers for kernel entry points, signal mapping, etc...
 *
 * 2001-05-06   Complete rewrite,  Christoph Hellwig (hch@infradead.org)
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/module.h>
#include <linux/personality.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/syscalls.h>
#include <linux/sysctl.h>
#include <linux/types.h>


static void default_handler(int, struct pt_regs *);

static struct exec_domain *exec_domains = &default_exec_domain;
static DEFINE_RWLOCK(exec_domains_lock);


static u_long ident_map[32] = {
        0,      1,      2,      3,      4,      5,      6,      7,
        8,      9,      10,     11,     12,     13,     14,     15,
        16,     17,     18,     19,     20,     21,     22,     23,
        24,     25,     26,     27,     28,     29,     30,     31
};

struct exec_domain default_exec_domain = {
        .name           = "Linux",              /* name */
        .handler        = default_handler,      /* lcall7 causes a seg fault. */
        .pers_low       = 0,                    /* PER_LINUX personality. */
        .pers_high      = 0,                    /* PER_LINUX personality. */
        .signal_map     = ident_map,            /* Identity map signals. */
        .signal_invmap  = ident_map,            /*  - both ways. */
};


static void
default_handler(int segment, struct pt_regs *regp)
{
        set_personality(0);

        if (current_thread_info()->exec_domain->handler != default_handler)
                current_thread_info()->exec_domain->handler(segment, regp);
        else
                send_sig(SIGSEGV, current, 1);
}

static struct exec_domain *
lookup_exec_domain(u_long personality)
{
        struct exec_domain *    ep;
        u_long                  pers = personality(personality);

        read_lock(&exec_domains_lock);
        for (ep = exec_domains; ep; ep = ep->next) {
                if (pers >= ep->pers_low && pers <= ep->pers_high)
                        if (try_module_get(ep->module))
                                goto out;
        }

#ifdef CONFIG_MODULES
        read_unlock(&exec_domains_lock);
        request_module("personality-%ld", pers);
        read_lock(&exec_domains_lock);

        for (ep = exec_domains; ep; ep = ep->next) {
                if (pers >= ep->pers_low && pers <= ep->pers_high)
                        if (try_module_get(ep->module))
                                goto out;
        }
#endif

        ep = &default_exec_domain;
out:
        read_unlock(&exec_domains_lock);
        return (ep);
}

int
register_exec_domain(struct exec_domain *ep)
{
        struct exec_domain      *tmp;
        int                     err = -EBUSY;

        if (ep == NULL)
                return -EINVAL;

        if (ep->next != NULL)
                return -EBUSY;

        write_lock(&exec_domains_lock);
        for (tmp = exec_domains; tmp; tmp = tmp->next) {
                if (tmp == ep)
                        goto out;
        }

        ep->next = exec_domains;
        exec_domains = ep;
        err = 0;

out:
        write_unlock(&exec_domains_lock);
        return (err);
}

int
unregister_exec_domain(struct exec_domain *ep)
{
        struct exec_domain      **epp;

        epp = &exec_domains;
        write_lock(&exec_domains_lock);
        for (epp = &exec_domains; *epp; epp = &(*epp)->next) {
                if (ep == *epp)
                        goto unregister;
        }
        write_unlock(&exec_domains_lock);
        return -EINVAL;

unregister:
        *epp = ep->next;
        ep->next = NULL;
        write_unlock(&exec_domains_lock);
        return 0;
}

int
__set_personality(u_long personality)
{
        struct exec_domain      *ep, *oep;

        ep = lookup_exec_domain(personality);
        if (ep == current_thread_info()->exec_domain) {
                current->personality = personality;
                module_put(ep->module);
                return 0;
        }

        if (atomic_read(&current->fs->count) != 1) {
                struct fs_struct *fsp, *ofsp;

                fsp = copy_fs_struct(current->fs);
                if (fsp == NULL) {
                        module_put(ep->module);
                        return -ENOMEM;
                }

                task_lock(current);
                ofsp = current->fs;
                current->fs = fsp;
                task_unlock(current);

                put_fs_struct(ofsp);
        }

        /*
         * At that point we are guaranteed to be the sole owner of
         * current->fs.
         */

        current->personality = personality;
        oep = current_thread_info()->exec_domain;
        current_thread_info()->exec_domain = ep;

        module_put(oep->module);
        return 0;
}

#ifdef CONFIG_PROC_FS
static int execdomains_proc_show(struct seq_file *m, void *v)
{
        struct exec_domain      *ep;

        read_lock(&exec_domains_lock);
        for (ep = exec_domains; ep; ep = ep->next)
                seq_printf(m, "%d-%d\t%-16s\t[%s]\n",
                               ep->pers_low, ep->pers_high, ep->name,
                               module_name(ep->module));
        read_unlock(&exec_domains_lock);
        return 0;
}

static int execdomains_proc_open(struct inode *inode, struct file *file)
{
        return single_open(file, execdomains_proc_show, NULL);
}

static const struct file_operations execdomains_proc_fops = {
        .open           = execdomains_proc_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};

static int __init proc_execdomains_init(void)
{
        proc_create("execdomains", 0, NULL, &execdomains_proc_fops);
        return 0;
}
module_init(proc_execdomains_init);
#endif

SYSCALL_DEFINE1(personality, u_long, personality)
{
        u_long old = current->personality;

        if (personality != 0xffffffff) {
                set_personality(personality);
                if (current->personality != personality)
                        return -EINVAL;
        }

        return (long)old;
}


EXPORT_SYMBOL(register_exec_domain);
EXPORT_SYMBOL(unregister_exec_domain);
EXPORT_SYMBOL(__set_personality);