kernel/exec_domain.c

   1 /*
   2  * Handling of different ABIs (personalities).
   3  *
   4  * We group personalities into execution domains which have their
   5  * own handlers for kernel entry points, signal mapping, etc...
   6  *
   7  * 2001-05-06   Complete rewrite,  Christoph Hellwig (hch@infradead.org)
   8  */
   9
  10 #include <linux/init.h>
  11 #include <linux/kernel.h>
  12 #include <linux/kmod.h>
  13 #include <linux/module.h>
  14 #include <linux/personality.h>
  15 #include <linux/proc_fs.h>
  16 #include <linux/sched.h>
  17 #include <linux/seq_file.h>
  18 #include <linux/syscalls.h>
  19 #include <linux/sysctl.h>
  20 #include <linux/types.h>
  21 #include <linux/fs_struct.h>
  22
  23
  24 static void default_handler(int, struct pt_regs *);
  25
  26 static struct exec_domain *exec_domains = &default_exec_domain;
  27 static DEFINE_RWLOCK(exec_domains_lock);
  28
  29
  30 static unsigned long ident_map[32] = {
  31         0,      1,      2,      3,      4,      5,      6,      7,
  32         8,      9,      10,     11,     12,     13,     14,     15,
  33         16,     17,     18,     19,     20,     21,     22,     23,
  34         24,     25,     26,     27,     28,     29,     30,     31
  35 };
  36
  37 struct exec_domain default_exec_domain = {
  38         .name           = "Linux",              /* name */
  39         .handler        = default_handler,      /* lcall7 causes a seg fault. */
  40         .pers_low       = 0,                    /* PER_LINUX personality. */
  41         .pers_high      = 0,                    /* PER_LINUX personality. */
  42         .signal_map     = ident_map,            /* Identity map signals. */
  43         .signal_invmap  = ident_map,            /*  - both ways. */
  44 };
  45
  46
  47 static void
  48 default_handler(int segment, struct pt_regs *regp)
  49 {
  50         set_personality(0);
  51
  52         if (current_thread_info()->exec_domain->handler != default_handler)
  53                 current_thread_info()->exec_domain->handler(segment, regp);
  54         else
  55                 send_sig(SIGSEGV, current, 1);
  56 }
  57
  58 static struct exec_domain *
  59 lookup_exec_domain(unsigned int personality)
  60 {
  61         unsigned int pers = personality(personality);
  62         struct exec_domain *ep;
  63
  64         read_lock(&exec_domains_lock);
  65         for (ep = exec_domains; ep; ep = ep->next) {
  66                 if (pers >= ep->pers_low && pers <= ep->pers_high)
  67                         if (try_module_get(ep->module))
  68                                 goto out;
  69         }
  70
  71 #ifdef CONFIG_MODULES
  72         read_unlock(&exec_domains_lock);
  73         request_module("personality-%d", pers);
  74         read_lock(&exec_domains_lock);
  75
  76         for (ep = exec_domains; ep; ep = ep->next) {
  77                 if (pers >= ep->pers_low && pers <= ep->pers_high)
  78                         if (try_module_get(ep->module))
  79                                 goto out;
  80         }
  81 #endif
  82
  83         ep = &default_exec_domain;
  84 out:
  85         read_unlock(&exec_domains_lock);
  86         return (ep);
  87 }
  88
  89 int
  90 register_exec_domain(struct exec_domain *ep)
  91 {
  92         struct exec_domain      *tmp;
  93         int                     err = -EBUSY;
  94
  95         if (ep == NULL)
  96                 return -EINVAL;
  97
  98         if (ep->next != NULL)
  99                 return -EBUSY;
 100
 101         write_lock(&exec_domains_lock);
 102         for (tmp = exec_domains; tmp; tmp = tmp->next) {
 103                 if (tmp == ep)
 104                         goto out;
 105         }
 106
 107         ep->next = exec_domains;
 108         exec_domains = ep;
 109         err = 0;
 110
 111 out:
 112         write_unlock(&exec_domains_lock);
 113         return (err);
 114 }
 115
 116 int
 117 unregister_exec_domain(struct exec_domain *ep)
 118 {
 119         struct exec_domain      **epp;
 120
 121         epp = &exec_domains;
 122         write_lock(&exec_domains_lock);
 123         for (epp = &exec_domains; *epp; epp = &(*epp)->next) {
 124                 if (ep == *epp)
 125                         goto unregister;
 126         }
 127         write_unlock(&exec_domains_lock);
 128         return -EINVAL;
 129
 130 unregister:
 131         *epp = ep->next;
 132         ep->next = NULL;
 133         write_unlock(&exec_domains_lock);
 134         return 0;
 135 }
 136
 137 int
 138 __set_personality(unsigned int personality)
 139 {
 140         struct exec_domain      *ep, *oep;
 141
 142         ep = lookup_exec_domain(personality);
 143         if (ep == current_thread_info()->exec_domain) {
 144                 current->personality = personality;
 145                 module_put(ep->module);
 146                 return 0;
 147         }
 148
 149         current->personality = personality;
 150         oep = current_thread_info()->exec_domain;
 151         current_thread_info()->exec_domain = ep;
 152
 153         module_put(oep->module);
 154         return 0;
 155 }
 156
 157 #ifdef CONFIG_PROC_FS
 158 static int execdomains_proc_show(struct seq_file *m, void *v)
 159 {
 160         struct exec_domain      *ep;
 161
 162         read_lock(&exec_domains_lock);
 163         for (ep = exec_domains; ep; ep = ep->next)
 164                 seq_printf(m, "%d-%d\t%-16s\t[%s]\n",
 165                                ep->pers_low, ep->pers_high, ep->name,
 166                                module_name(ep->module));
 167         read_unlock(&exec_domains_lock);
 168         return 0;
 169 }
 170
 171 static int execdomains_proc_open(struct inode *inode, struct file *file)
 172 {
 173         return single_open(file, execdomains_proc_show, NULL);
 174 }
 175
 176 static const struct file_operations execdomains_proc_fops = {
 177         .open           = execdomains_proc_open,
 178         .read           = seq_read,
 179         .llseek         = seq_lseek,
 180         .release        = single_release,
 181 };
 182
 183 static int __init proc_execdomains_init(void)
 184 {
 185         proc_create("execdomains", 0, NULL, &execdomains_proc_fops);
 186         return 0;
 187 }
 188 module_init(proc_execdomains_init);
 189 #endif
 190
 191 SYSCALL_DEFINE1(personality, unsigned int, personality)
 192 {
 193         unsigned int old = current->personality;
 194
 195         if (personality != 0xffffffff) {
 196                 set_personality(personality);
 197                 if (current->personality != personality)
 198                         return -EINVAL;
 199         }
 200
 201         return old;
 202 }
 203
 204
 205 EXPORT_SYMBOL(register_exec_domain);
 206 EXPORT_SYMBOL(unregister_exec_domain);
 207 EXPORT_SYMBOL(__set_personality);