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/config.h>
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/kmod.h>
  14 #include <linux/module.h>
  15 #include <linux/personality.h>
  16 #include <linux/sched.h>
  17 #include <linux/syscalls.h>
  18 #include <linux/sysctl.h>
  19 #include <linux/types.h>
  20
  21
  22 static void default_handler(int, struct pt_regs *);
  23
  24 static struct exec_domain *exec_domains = &default_exec_domain;
  25 static DEFINE_RWLOCK(exec_domains_lock);
  26
  27
  28 static u_long ident_map[32] = {
  29         0,      1,      2,      3,      4,      5,      6,      7,
  30         8,      9,      10,     11,     12,     13,     14,     15,
  31         16,     17,     18,     19,     20,     21,     22,     23,
  32         24,     25,     26,     27,     28,     29,     30,     31
  33 };
  34
  35 struct exec_domain default_exec_domain = {
  36         .name           = "Linux",              /* name */
  37         .handler        = default_handler,      /* lcall7 causes a seg fault. */
  38         .pers_low       = 0,                    /* PER_LINUX personality. */
  39         .pers_high      = 0,                    /* PER_LINUX personality. */
  40         .signal_map     = ident_map,            /* Identity map signals. */
  41         .signal_invmap  = ident_map,            /*  - both ways. */
  42 };
  43
  44
  45 static void
  46 default_handler(int segment, struct pt_regs *regp)
  47 {
  48         set_personality(0);
  49
  50         if (current_thread_info()->exec_domain->handler != default_handler)
  51                 current_thread_info()->exec_domain->handler(segment, regp);
  52         else
  53                 send_sig(SIGSEGV, current, 1);
  54 }
  55
  56 static struct exec_domain *
  57 lookup_exec_domain(u_long personality)
  58 {
  59         struct exec_domain *    ep;
  60         u_long                  pers = personality(personality);
  61
  62         read_lock(&exec_domains_lock);
  63         for (ep = exec_domains; ep; ep = ep->next) {
  64                 if (pers >= ep->pers_low && pers <= ep->pers_high)
  65                         if (try_module_get(ep->module))
  66                                 goto out;
  67         }
  68
  69 #ifdef CONFIG_KMOD
  70         read_unlock(&exec_domains_lock);
  71         request_module("personality-%ld", pers);
  72         read_lock(&exec_domains_lock);
  73
  74         for (ep = exec_domains; ep; ep = ep->next) {
  75                 if (pers >= ep->pers_low && pers <= ep->pers_high)
  76                         if (try_module_get(ep->module))
  77                                 goto out;
  78         }
  79 #endif
  80
  81         ep = &default_exec_domain;
  82 out:
  83         read_unlock(&exec_domains_lock);
  84         return (ep);
  85 }
  86
  87 int
  88 register_exec_domain(struct exec_domain *ep)
  89 {
  90         struct exec_domain      *tmp;
  91         int                     err = -EBUSY;
  92
  93         if (ep == NULL)
  94                 return -EINVAL;
  95
  96         if (ep->next != NULL)
  97                 return -EBUSY;
  98
  99         write_lock(&exec_domains_lock);
 100         for (tmp = exec_domains; tmp; tmp = tmp->next) {
 101                 if (tmp == ep)
 102                         goto out;
 103         }
 104
 105         ep->next = exec_domains;
 106         exec_domains = ep;
 107         err = 0;
 108
 109 out:
 110         write_unlock(&exec_domains_lock);
 111         return (err);
 112 }
 113
 114 int
 115 unregister_exec_domain(struct exec_domain *ep)
 116 {
 117         struct exec_domain      **epp;
 118
 119         epp = &exec_domains;
 120         write_lock(&exec_domains_lock);
 121         for (epp = &exec_domains; *epp; epp = &(*epp)->next) {
 122                 if (ep == *epp)
 123                         goto unregister;
 124         }
 125         write_unlock(&exec_domains_lock);
 126         return -EINVAL;
 127
 128 unregister:
 129         *epp = ep->next;
 130         ep->next = NULL;
 131         write_unlock(&exec_domains_lock);
 132         return 0;
 133 }
 134
 135 int
 136 __set_personality(u_long personality)
 137 {
 138         struct exec_domain      *ep, *oep;
 139
 140         ep = lookup_exec_domain(personality);
 141         if (ep == current_thread_info()->exec_domain) {
 142                 current->personality = personality;
 143                 module_put(ep->module);
 144                 return 0;
 145         }
 146
 147         if (atomic_read(&current->fs->count) != 1) {
 148                 struct fs_struct *fsp, *ofsp;
 149
 150                 fsp = copy_fs_struct(current->fs);
 151                 if (fsp == NULL) {
 152                         module_put(ep->module);
 153                         return -ENOMEM;
 154                 }
 155
 156                 task_lock(current);
 157                 ofsp = current->fs;
 158                 current->fs = fsp;
 159                 task_unlock(current);
 160
 161                 put_fs_struct(ofsp);
 162         }
 163
 164         /*
 165          * At that point we are guaranteed to be the sole owner of
 166          * current->fs.
 167          */
 168
 169         current->personality = personality;
 170         oep = current_thread_info()->exec_domain;
 171         current_thread_info()->exec_domain = ep;
 172         set_fs_altroot();
 173
 174         module_put(oep->module);
 175         return 0;
 176 }
 177
 178 int
 179 get_exec_domain_list(char *page)
 180 {
 181         struct exec_domain      *ep;
 182         int                     len = 0;
 183
 184         read_lock(&exec_domains_lock);
 185         for (ep = exec_domains; ep && len < PAGE_SIZE - 80; ep = ep->next)
 186                 len += sprintf(page + len, "%d-%d\t%-16s\t[%s]\n",
 187                                ep->pers_low, ep->pers_high, ep->name,
 188                                module_name(ep->module));
 189         read_unlock(&exec_domains_lock);
 190         return (len);
 191 }
 192
 193 asmlinkage long
 194 sys_personality(u_long personality)
 195 {
 196         u_long old = current->personality;
 197
 198         if (personality != 0xffffffff) {
 199                 set_personality(personality);
 200                 if (current->personality != personality)
 201                         return -EINVAL;
 202         }
 203
 204         return (long)old;
 205 }
 206
 207
 208 EXPORT_SYMBOL(register_exec_domain);
 209 EXPORT_SYMBOL(unregister_exec_domain);
 210 EXPORT_SYMBOL(__set_personality);