root/arch/i386/kernel/vm86.c

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DEFINITIONS

This source file includes following definitions.
  1. save_v86_state
  2. mark_screen_rdonly
  3. sys_vm86
  4. return_to_32bit
  5. set_IF
  6. clear_IF
  7. clear_TF
  8. set_vflags_long
  9. set_vflags_short
  10. get_vflags
  11. is_revectored
  12. do_int
  13. handle_vm86_debug
  14. handle_vm86_fault

   1 /*
   2  *  linux/kernel/vm86.c
   3  *
   4  *  Copyright (C) 1994  Linus Torvalds
   5  */
   6 #include <linux/errno.h>
   7 #include <linux/sched.h>
   8 #include <linux/kernel.h>
   9 #include <linux/signal.h>
  10 #include <linux/string.h>
  11 #include <linux/ptrace.h>
  12 #include <linux/mm.h>
  13 
  14 #include <asm/segment.h>
  15 #include <asm/pgtable.h>
  16 #include <asm/io.h>
  17 
  18 /*
  19  * Known problems:
  20  *
  21  * Interrupt handling is not guaranteed:
  22  * - a real x86 will disable all interrupts for one instruction
  23  *   after a "mov ss,xx" to make stack handling atomic even without
  24  *   the 'lss' instruction. We can't guarantee this in v86 mode,
  25  *   as the next instruction might result in a page fault or similar.
  26  * - a real x86 will have interrupts disabled for one instruction
  27  *   past the 'sti' that enables them. We don't bother with all the
  28  *   details yet..
  29  *
  30  * Hopefully these problems do not actually matter for anything.
  31  */
  32 
  33 /*
  34  * 8- and 16-bit register defines..
  35  */
  36 #define AL(regs)        (((unsigned char *)&((regs)->eax))[0])
  37 #define AH(regs)        (((unsigned char *)&((regs)->eax))[1])
  38 #define IP(regs)        (*(unsigned short *)&((regs)->eip))
  39 #define SP(regs)        (*(unsigned short *)&((regs)->esp))
  40 
  41 /*
  42  * virtual flags (16 and 32-bit versions)
  43  */
  44 #define VFLAGS  (*(unsigned short *)&(current->tss.v86flags))
  45 #define VEFLAGS (current->tss.v86flags)
  46 
  47 #define set_flags(X,new,mask) \
  48 ((X) = ((X) & ~(mask)) | ((new) & (mask)))
  49 
  50 #define SAFE_MASK       (0xDD5)
  51 #define RETURN_MASK     (0xDFF)
  52 
  53 asmlinkage struct pt_regs * save_v86_state(struct vm86_regs * regs)
     /* [previous][next][first][last][top][bottom][index][help] */
  54 {
  55         unsigned long tmp;
  56 
  57         if (!current->tss.vm86_info) {
  58                 printk("no vm86_info: BAD\n");
  59                 do_exit(SIGSEGV);
  60         }
  61         set_flags(regs->eflags, VEFLAGS, VIF_MASK | current->tss.v86mask);
  62         memcpy_tofs(&current->tss.vm86_info->regs,regs,sizeof(*regs));
  63         put_fs_long(current->tss.screen_bitmap,&current->tss.vm86_info->screen_bitmap);
  64         tmp = current->tss.esp0;
  65         current->tss.esp0 = current->saved_kernel_stack;
  66         current->saved_kernel_stack = 0;
  67         return (struct pt_regs *) tmp;
  68 }
  69 
  70 static void mark_screen_rdonly(struct task_struct * tsk)
     /* [previous][next][first][last][top][bottom][index][help] */
  71 {
  72         pgd_t *pg_dir;
  73 
  74         pg_dir = PAGE_DIR_OFFSET(tsk, 0);
  75         if (!pgd_none(*pg_dir)) {
  76                 pte_t *pg_table;
  77                 int i;
  78 
  79                 if (pgd_bad(*pg_dir)) {
  80                         printk("vm86: bad page table directory entry %08lx\n", pgd_val(*pg_dir));
  81                         pgd_clear(pg_dir);
  82                         return;
  83                 }
  84                 pg_table = (pte_t *) pgd_page(*pg_dir);
  85                 pg_table += 0xA0000 >> PAGE_SHIFT;
  86                 for (i = 0 ; i < 32 ; i++) {
  87                         if (pte_present(*pg_table))
  88                                 *pg_table = pte_wrprotect(*pg_table);
  89                         pg_table++;
  90                 }
  91         }
  92 }
  93 
  94 asmlinkage int sys_vm86(struct vm86_struct * v86)
     /* [previous][next][first][last][top][bottom][index][help] */
  95 {
  96         struct vm86_struct info;
  97         struct pt_regs * pt_regs = (struct pt_regs *) &v86;
  98         int error;
  99 
 100         if (current->saved_kernel_stack)
 101                 return -EPERM;
 102         /* v86 must be readable (now) and writable (for save_v86_state) */
 103         error = verify_area(VERIFY_WRITE,v86,sizeof(*v86));
 104         if (error)
 105                 return error;
 106         memcpy_fromfs(&info,v86,sizeof(info));
 107 /*
 108  * make sure the vm86() system call doesn't try to do anything silly
 109  */
 110         info.regs.__null_ds = 0;
 111         info.regs.__null_es = 0;
 112         info.regs.__null_fs = 0;
 113         info.regs.__null_gs = 0;
 114 /*
 115  * The eflags register is also special: we cannot trust that the user
 116  * has set it up safely, so this makes sure interrupt etc flags are
 117  * inherited from protected mode.
 118  */
 119         VEFLAGS = info.regs.eflags;
 120         info.regs.eflags &= SAFE_MASK;
 121         info.regs.eflags |= pt_regs->eflags & ~SAFE_MASK;
 122         info.regs.eflags |= VM_MASK;
 123 
 124         switch (info.cpu_type) {
 125                 case CPU_286:
 126                         current->tss.v86mask = 0;
 127                         break;
 128                 case CPU_386:
 129                         current->tss.v86mask = NT_MASK | IOPL_MASK;
 130                         break;
 131                 case CPU_486:
 132                         current->tss.v86mask = AC_MASK | NT_MASK | IOPL_MASK;
 133                         break;
 134                 default:
 135                         current->tss.v86mask = ID_MASK | AC_MASK | NT_MASK | IOPL_MASK;
 136                         break;
 137         }
 138 
 139 /*
 140  * Save old state, set default return value (%eax) to 0
 141  */
 142         pt_regs->eax = 0;
 143         current->saved_kernel_stack = current->tss.esp0;
 144         current->tss.esp0 = (unsigned long) pt_regs;
 145         current->tss.vm86_info = v86;
 146 
 147         current->tss.screen_bitmap = info.screen_bitmap;
 148         if (info.flags & VM86_SCREEN_BITMAP)
 149                 mark_screen_rdonly(current);
 150         __asm__ __volatile__("movl %0,%%esp\n\t"
 151                 "jmp ret_from_sys_call"
 152                 : /* no outputs */
 153                 :"r" (&info.regs));
 154         return 0;
 155 }
 156 
 157 static inline void return_to_32bit(struct vm86_regs * regs16, int retval)
     /* [previous][next][first][last][top][bottom][index][help] */
 158 {
 159         struct pt_regs * regs32;
 160 
 161         regs32 = save_v86_state(regs16);
 162         regs32->eax = retval;
 163         __asm__ __volatile__("movl %0,%%esp\n\t"
 164                 "jmp ret_from_sys_call"
 165                 : : "r" (regs32));
 166 }
 167 
 168 static inline void set_IF(struct vm86_regs * regs)
     /* [previous][next][first][last][top][bottom][index][help] */
 169 {
 170         VEFLAGS |= VIF_MASK;
 171         if (VEFLAGS & VIP_MASK)
 172                 return_to_32bit(regs, VM86_STI);
 173 }
 174 
 175 static inline void clear_IF(struct vm86_regs * regs)
     /* [previous][next][first][last][top][bottom][index][help] */
 176 {
 177         VEFLAGS &= ~VIF_MASK;
 178 }
 179 
 180 static inline void clear_TF(struct vm86_regs * regs)
     /* [previous][next][first][last][top][bottom][index][help] */
 181 {
 182         regs->eflags &= ~TF_MASK;
 183 }
 184 
 185 static inline void set_vflags_long(unsigned long eflags, struct vm86_regs * regs)
     /* [previous][next][first][last][top][bottom][index][help] */
 186 {
 187         set_flags(VEFLAGS, eflags, current->tss.v86mask);
 188         set_flags(regs->eflags, eflags, SAFE_MASK);
 189         if (eflags & IF_MASK)
 190                 set_IF(regs);
 191 }
 192 
 193 static inline void set_vflags_short(unsigned short flags, struct vm86_regs * regs)
     /* [previous][next][first][last][top][bottom][index][help] */
 194 {
 195         set_flags(VFLAGS, flags, current->tss.v86mask);
 196         set_flags(regs->eflags, flags, SAFE_MASK);
 197         if (flags & IF_MASK)
 198                 set_IF(regs);
 199 }
 200 
 201 static inline unsigned long get_vflags(struct vm86_regs * regs)
     /* [previous][next][first][last][top][bottom][index][help] */
 202 {
 203         unsigned long flags = regs->eflags & RETURN_MASK;
 204 
 205         if (VEFLAGS & VIF_MASK)
 206                 flags |= IF_MASK;
 207         return flags | (VEFLAGS & current->tss.v86mask);
 208 }
 209 
 210 static inline int is_revectored(int nr, struct revectored_struct * bitmap)
     /* [previous][next][first][last][top][bottom][index][help] */
 211 {
 212         __asm__ __volatile__("btl %2,%%fs:%1\n\tsbbl %0,%0"
 213                 :"=r" (nr)
 214                 :"m" (*bitmap),"r" (nr));
 215         return nr;
 216 }
 217 
 218 /*
 219  * Boy are these ugly, but we need to do the correct 16-bit arithmetic.
 220  * Gcc makes a mess of it, so we do it inline and use non-obvious calling
 221  * conventions..
 222  */
 223 #define pushb(base, ptr, val) \
 224 __asm__ __volatile__( \
 225         "decw %w0\n\t" \
 226         "movb %2,%%fs:0(%1,%0)" \
 227         : "=r" (ptr) \
 228         : "r" (base), "q" (val), "0" (ptr))
 229 
 230 #define pushw(base, ptr, val) \
 231 __asm__ __volatile__( \
 232         "decw %w0\n\t" \
 233         "movb %h2,%%fs:0(%1,%0)\n\t" \
 234         "decw %w0\n\t" \
 235         "movb %b2,%%fs:0(%1,%0)" \
 236         : "=r" (ptr) \
 237         : "r" (base), "q" (val), "0" (ptr))
 238 
 239 #define pushl(base, ptr, val) \
 240 __asm__ __volatile__( \
 241         "decw %w0\n\t" \
 242         "rorl $16,%2\n\t" \
 243         "movb %h2,%%fs:0(%1,%0)\n\t" \
 244         "decw %w0\n\t" \
 245         "movb %b2,%%fs:0(%1,%0)\n\t" \
 246         "decw %w0\n\t" \
 247         "rorl $16,%2\n\t" \
 248         "movb %h2,%%fs:0(%1,%0)\n\t" \
 249         "decw %w0\n\t" \
 250         "movb %b2,%%fs:0(%1,%0)" \
 251         : "=r" (ptr) \
 252         : "r" (base), "q" (val), "0" (ptr))
 253 
 254 #define popb(base, ptr) \
 255 ({ unsigned long __res; \
 256 __asm__ __volatile__( \
 257         "movb %%fs:0(%1,%0),%b2\n\t" \
 258         "incw %w0" \
 259         : "=r" (ptr), "=r" (base), "=q" (__res) \
 260         : "0" (ptr), "1" (base), "2" (0)); \
 261 __res; })
 262 
 263 #define popw(base, ptr) \
 264 ({ unsigned long __res; \
 265 __asm__ __volatile__( \
 266         "movb %%fs:0(%1,%0),%b2\n\t" \
 267         "incw %w0\n\t" \
 268         "movb %%fs:0(%1,%0),%h2\n\t" \
 269         "incw %w0" \
 270         : "=r" (ptr), "=r" (base), "=q" (__res) \
 271         : "0" (ptr), "1" (base), "2" (0)); \
 272 __res; })
 273 
 274 #define popl(base, ptr) \
 275 ({ unsigned long __res; \
 276 __asm__ __volatile__( \
 277         "movb %%fs:0(%1,%0),%b2\n\t" \
 278         "incw %w0\n\t" \
 279         "movb %%fs:0(%1,%0),%h2\n\t" \
 280         "incw %w0\n\t" \
 281         "rorl $16,%2\n\t" \
 282         "movb %%fs:0(%1,%0),%b2\n\t" \
 283         "incw %w0\n\t" \
 284         "movb %%fs:0(%1,%0),%h2\n\t" \
 285         "incw %w0\n\t" \
 286         "rorl $16,%2" \
 287         : "=r" (ptr), "=r" (base), "=q" (__res) \
 288         : "0" (ptr), "1" (base)); \
 289 __res; })
 290 
 291 static void do_int(struct vm86_regs *regs, int i, unsigned char * ssp, unsigned long sp)
     /* [previous][next][first][last][top][bottom][index][help] */
 292 {
 293         unsigned short seg = get_fs_word((void *) ((i<<2)+2));
 294 
 295         if (seg == BIOSSEG || regs->cs == BIOSSEG ||
 296             is_revectored(i, &current->tss.vm86_info->int_revectored))
 297                 return_to_32bit(regs, VM86_INTx + (i << 8));
 298         if (i==0x21 && is_revectored(AH(regs),&current->tss.vm86_info->int21_revectored))
 299                 return_to_32bit(regs, VM86_INTx + (i << 8));
 300         pushw(ssp, sp, get_vflags(regs));
 301         pushw(ssp, sp, regs->cs);
 302         pushw(ssp, sp, IP(regs));
 303         regs->cs = seg;
 304         SP(regs) -= 6;
 305         IP(regs) = get_fs_word((void *) (i<<2));
 306         clear_TF(regs);
 307         clear_IF(regs);
 308         return;
 309 }
 310 
 311 void handle_vm86_debug(struct vm86_regs * regs, long error_code)
     /* [previous][next][first][last][top][bottom][index][help] */
 312 {
 313 #if 0
 314         do_int(regs, 1, (unsigned char *) (regs->ss << 4), SP(regs));
 315 #else
 316         if (current->flags & PF_PTRACED)
 317                 current->blocked &= ~(1 << (SIGTRAP-1));
 318         send_sig(SIGTRAP, current, 1);
 319         current->tss.trap_no = 1;
 320         current->tss.error_code = error_code;
 321 #endif
 322 }
 323 
 324 void handle_vm86_fault(struct vm86_regs * regs, long error_code)
     /* [previous][next][first][last][top][bottom][index][help] */
 325 {
 326         unsigned char *csp, *ssp;
 327         unsigned long ip, sp;
 328 
 329         csp = (unsigned char *) (regs->cs << 4);
 330         ssp = (unsigned char *) (regs->ss << 4);
 331         sp = SP(regs);
 332         ip = IP(regs);
 333 
 334         switch (popb(csp, ip)) {
 335 
 336         /* operand size override */
 337         case 0x66:
 338                 switch (popb(csp, ip)) {
 339 
 340                 /* pushfd */
 341                 case 0x9c:
 342                         SP(regs) -= 4;
 343                         IP(regs) += 2;
 344                         pushl(ssp, sp, get_vflags(regs));
 345                         return;
 346 
 347                 /* popfd */
 348                 case 0x9d:
 349                         SP(regs) += 4;
 350                         IP(regs) += 2;
 351                         set_vflags_long(popl(ssp, sp), regs);
 352                         return;
 353                 }
 354 
 355         /* pushf */
 356         case 0x9c:
 357                 SP(regs) -= 2;
 358                 IP(regs)++;
 359                 pushw(ssp, sp, get_vflags(regs));
 360                 return;
 361 
 362         /* popf */
 363         case 0x9d:
 364                 SP(regs) += 2;
 365                 IP(regs)++;
 366                 set_vflags_short(popw(ssp, sp), regs);
 367                 return;
 368 
 369         /* int xx */
 370         case 0xcd:
 371                 IP(regs) += 2;
 372                 do_int(regs, popb(csp, ip), ssp, sp);
 373                 return;
 374 
 375         /* iret */
 376         case 0xcf:
 377                 SP(regs) += 6;
 378                 IP(regs) = popw(ssp, sp);
 379                 regs->cs = popw(ssp, sp);
 380                 set_vflags_short(popw(ssp, sp), regs);
 381                 return;
 382 
 383         /* cli */
 384         case 0xfa:
 385                 IP(regs)++;
 386                 clear_IF(regs);
 387                 return;
 388 
 389         /* sti */
 390         /*
 391          * Damn. This is incorrect: the 'sti' instruction should actually
 392          * enable interrupts after the /next/ instruction. Not good.
 393          *
 394          * Probably needs some horsing around with the TF flag. Aiee..
 395          */
 396         case 0xfb:
 397                 IP(regs)++;
 398                 set_IF(regs);
 399                 return;
 400 
 401         default:
 402                 return_to_32bit(regs, VM86_UNKNOWN);
 403         }
 404 }

/* [previous][next][first][last][top][bottom][index][help] */