arch/m68k/sun3/mmu_emu.c

   1 /*
   2 ** Tablewalk MMU emulator
   3 **
   4 ** by Toshiyasu Morita
   5 **
   6 ** Started 1/16/98 @ 2:22 am
   7 */
   8
   9 #include <linux/mman.h>
  10 #include <linux/mm.h>
  11 #include <linux/kernel.h>
  12 #include <linux/ptrace.h>
  13 #include <linux/delay.h>
  14 #include <linux/bootmem.h>
  15 #include <linux/bitops.h>
  16 #include <linux/module.h>
  17
  18 #include <asm/setup.h>
  19 #include <asm/traps.h>
  20 #include <asm/system.h>
  21 #include <asm/uaccess.h>
  22 #include <asm/page.h>
  23 #include <asm/pgtable.h>
  24 #include <asm/sun3mmu.h>
  25 #include <asm/segment.h>
  26 #include <asm/oplib.h>
  27 #include <asm/mmu_context.h>
  28 #include <asm/dvma.h>
  29
  30 extern void prom_reboot (char *) __attribute__ ((__noreturn__));
  31
  32 #undef DEBUG_MMU_EMU
  33 #define DEBUG_PROM_MAPS
  34
  35 /*
  36 ** Defines
  37 */
  38
  39 #define CONTEXTS_NUM            8
  40 #define SEGMAPS_PER_CONTEXT_NUM 2048
  41 #define PAGES_PER_SEGMENT       16
  42 #define PMEGS_NUM               256
  43 #define PMEG_MASK               0xFF
  44
  45 /*
  46 ** Globals
  47 */
  48
  49 unsigned long vmalloc_end;
  50 EXPORT_SYMBOL(vmalloc_end);
  51
  52 unsigned long pmeg_vaddr[PMEGS_NUM];
  53 unsigned char pmeg_alloc[PMEGS_NUM];
  54 unsigned char pmeg_ctx[PMEGS_NUM];
  55
  56 /* pointers to the mm structs for each task in each
  57    context. 0xffffffff is a marker for kernel context */
  58 struct mm_struct *ctx_alloc[CONTEXTS_NUM] = {
  59     [0] = (struct mm_struct *)0xffffffff
  60 };
  61
  62 /* has this context been mmdrop'd? */
  63 static unsigned char ctx_avail = CONTEXTS_NUM-1;
  64
  65 /* array of pages to be marked off for the rom when we do mem_init later */
  66 /* 256 pages lets the rom take up to 2mb of physical ram..  I really
  67    hope it never wants mote than that. */
  68 unsigned long rom_pages[256];
  69
  70 /* Print a PTE value in symbolic form. For debugging. */
  71 void print_pte (pte_t pte)
  72 {
  73 #if 0
  74         /* Verbose version. */
  75         unsigned long val = pte_val (pte);
  76         printk (" pte=%lx [addr=%lx",
  77                 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT);
  78         if (val & SUN3_PAGE_VALID)      printk (" valid");
  79         if (val & SUN3_PAGE_WRITEABLE)  printk (" write");
  80         if (val & SUN3_PAGE_SYSTEM)     printk (" sys");
  81         if (val & SUN3_PAGE_NOCACHE)    printk (" nocache");
  82         if (val & SUN3_PAGE_ACCESSED)   printk (" accessed");
  83         if (val & SUN3_PAGE_MODIFIED)   printk (" modified");
  84         switch (val & SUN3_PAGE_TYPE_MASK) {
  85                 case SUN3_PAGE_TYPE_MEMORY: printk (" memory"); break;
  86                 case SUN3_PAGE_TYPE_IO:     printk (" io");     break;
  87                 case SUN3_PAGE_TYPE_VME16:  printk (" vme16");  break;
  88                 case SUN3_PAGE_TYPE_VME32:  printk (" vme32");  break;
  89         }
  90         printk ("]\n");
  91 #else
  92         /* Terse version. More likely to fit on a line. */
  93         unsigned long val = pte_val (pte);
  94         char flags[7], *type;
  95
  96         flags[0] = (val & SUN3_PAGE_VALID)     ? 'v' : '-';
  97         flags[1] = (val & SUN3_PAGE_WRITEABLE) ? 'w' : '-';
  98         flags[2] = (val & SUN3_PAGE_SYSTEM)    ? 's' : '-';
  99         flags[3] = (val & SUN3_PAGE_NOCACHE)   ? 'x' : '-';
 100         flags[4] = (val & SUN3_PAGE_ACCESSED)  ? 'a' : '-';
 101         flags[5] = (val & SUN3_PAGE_MODIFIED)  ? 'm' : '-';
 102         flags[6] = '\0';
 103
 104         switch (val & SUN3_PAGE_TYPE_MASK) {
 105                 case SUN3_PAGE_TYPE_MEMORY: type = "memory"; break;
 106                 case SUN3_PAGE_TYPE_IO:     type = "io"    ; break;
 107                 case SUN3_PAGE_TYPE_VME16:  type = "vme16" ; break;
 108                 case SUN3_PAGE_TYPE_VME32:  type = "vme32" ; break;
 109                 default: type = "unknown?"; break;
 110         }
 111
 112         printk (" pte=%08lx [%07lx %s %s]\n",
 113                 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT, flags, type);
 114 #endif
 115 }
 116
 117 /* Print the PTE value for a given virtual address. For debugging. */
 118 void print_pte_vaddr (unsigned long vaddr)
 119 {
 120         printk (" vaddr=%lx [%02lx]", vaddr, sun3_get_segmap (vaddr));
 121         print_pte (__pte (sun3_get_pte (vaddr)));
 122 }
 123
 124 /*
 125  * Initialise the MMU emulator.
 126  */
 127 void mmu_emu_init(unsigned long bootmem_end)
 128 {
 129         unsigned long seg, num;
 130         int i,j;
 131
 132         memset(rom_pages, 0, sizeof(rom_pages));
 133         memset(pmeg_vaddr, 0, sizeof(pmeg_vaddr));
 134         memset(pmeg_alloc, 0, sizeof(pmeg_alloc));
 135         memset(pmeg_ctx, 0, sizeof(pmeg_ctx));
 136
 137         /* pmeg align the end of bootmem, adding another pmeg,
 138          * later bootmem allocations will likely need it */
 139         bootmem_end = (bootmem_end + (2 * SUN3_PMEG_SIZE)) & ~SUN3_PMEG_MASK;
 140
 141         /* mark all of the pmegs used thus far as reserved */
 142         for (i=0; i < __pa(bootmem_end) / SUN3_PMEG_SIZE ; ++i)
 143                 pmeg_alloc[i] = 2;
 144
 145
 146         /* I'm thinking that most of the top pmeg's are going to be
 147            used for something, and we probably shouldn't risk it */
 148         for(num = 0xf0; num <= 0xff; num++)
 149                 pmeg_alloc[num] = 2;
 150
 151         /* liberate all existing mappings in the rest of kernel space */
 152         for(seg = bootmem_end; seg < 0x0f800000; seg += SUN3_PMEG_SIZE) {
 153                 i = sun3_get_segmap(seg);
 154
 155                 if(!pmeg_alloc[i]) {
 156 #ifdef DEBUG_MMU_EMU
 157                         printk("freed: ");
 158                         print_pte_vaddr (seg);
 159 #endif
 160                         sun3_put_segmap(seg, SUN3_INVALID_PMEG);
 161                 }
 162         }
 163
 164         j = 0;
 165         for (num=0, seg=0x0F800000; seg<0x10000000; seg+=16*PAGE_SIZE) {
 166                 if (sun3_get_segmap (seg) != SUN3_INVALID_PMEG) {
 167 #ifdef DEBUG_PROM_MAPS
 168                         for(i = 0; i < 16; i++) {
 169                                 printk ("mapped:");
 170                                 print_pte_vaddr (seg + (i*PAGE_SIZE));
 171                                 break;
 172                         }
 173 #endif
 174                         // the lowest mapping here is the end of our
 175                         // vmalloc region
 176                         if(!vmalloc_end)
 177                                 vmalloc_end = seg;
 178
 179                         // mark the segmap alloc'd, and reserve any
 180                         // of the first 0xbff pages the hardware is
 181                         // already using...  does any sun3 support > 24mb?
 182                         pmeg_alloc[sun3_get_segmap(seg)] = 2;
 183                 }
 184         }
 185
 186         dvma_init();
 187
 188
 189         /* blank everything below the kernel, and we've got the base
 190            mapping to start all the contexts off with... */
 191         for(seg = 0; seg < PAGE_OFFSET; seg += SUN3_PMEG_SIZE)
 192                 sun3_put_segmap(seg, SUN3_INVALID_PMEG);
 193
 194         set_fs(MAKE_MM_SEG(3));
 195         for(seg = 0; seg < 0x10000000; seg += SUN3_PMEG_SIZE) {
 196                 i = sun3_get_segmap(seg);
 197                 for(j = 1; j < CONTEXTS_NUM; j++)
 198                         (*(romvec->pv_setctxt))(j, (void *)seg, i);
 199         }
 200         set_fs(KERNEL_DS);
 201
 202 }
 203
 204 /* erase the mappings for a dead context.  Uses the pg_dir for hints
 205    as the pmeg tables proved somewhat unreliable, and unmapping all of
 206    TASK_SIZE was much slower and no more stable. */
 207 /* todo: find a better way to keep track of the pmegs used by a
 208    context for when they're cleared */
 209 void clear_context(unsigned long context)
 210 {
 211      unsigned char oldctx;
 212      unsigned long i;
 213
 214      if(context) {
 215              if(!ctx_alloc[context])
 216                      panic("clear_context: context not allocated\n");
 217
 218              ctx_alloc[context]->context = SUN3_INVALID_CONTEXT;
 219              ctx_alloc[context] = (struct mm_struct *)0;
 220              ctx_avail++;
 221      }
 222
 223      oldctx = sun3_get_context();
 224
 225      sun3_put_context(context);
 226
 227      for(i = 0; i < SUN3_INVALID_PMEG; i++) {
 228              if((pmeg_ctx[i] == context) && (pmeg_alloc[i] == 1)) {
 229                      sun3_put_segmap(pmeg_vaddr[i], SUN3_INVALID_PMEG);
 230                      pmeg_ctx[i] = 0;
 231                      pmeg_alloc[i] = 0;
 232                      pmeg_vaddr[i] = 0;
 233              }
 234      }
 235
 236      sun3_put_context(oldctx);
 237 }
 238
 239 /* gets an empty context.  if full, kills the next context listed to
 240    die first */
 241 /* This context invalidation scheme is, well, totally arbitrary, I'm
 242    sure it could be much more intellegent...  but it gets the job done
 243    for now without much overhead in making it's decision. */
 244 /* todo: come up with optimized scheme for flushing contexts */
 245 unsigned long get_free_context(struct mm_struct *mm)
 246 {
 247         unsigned long new = 1;
 248         static unsigned char next_to_die = 1;
 249
 250         if(!ctx_avail) {
 251                 /* kill someone to get our context */
 252                 new = next_to_die;
 253                 clear_context(new);
 254                 next_to_die = (next_to_die + 1) & 0x7;
 255                 if(!next_to_die)
 256                         next_to_die++;
 257         } else {
 258                 while(new < CONTEXTS_NUM) {
 259                         if(ctx_alloc[new])
 260                                 new++;
 261                         else
 262                                 break;
 263                 }
 264                 // check to make sure one was really free...
 265                 if(new == CONTEXTS_NUM)
 266                         panic("get_free_context: failed to find free context");
 267         }
 268
 269         ctx_alloc[new] = mm;
 270         ctx_avail--;
 271
 272         return new;
 273 }
 274
 275 /*
 276  * Dynamically select a `spare' PMEG and use it to map virtual `vaddr' in
 277  * `context'. Maintain internal PMEG management structures. This doesn't
 278  * actually map the physical address, but does clear the old mappings.
 279  */
 280 //todo: better allocation scheme? but is extra complexity worthwhile?
 281 //todo: only clear old entries if necessary? how to tell?
 282
 283 inline void mmu_emu_map_pmeg (int context, int vaddr)
 284 {
 285         static unsigned char curr_pmeg = 128;
 286         int i;
 287
 288         /* Round address to PMEG boundary. */
 289         vaddr &= ~SUN3_PMEG_MASK;
 290
 291         /* Find a spare one. */
 292         while (pmeg_alloc[curr_pmeg] == 2)
 293                 ++curr_pmeg;
 294
 295
 296 #ifdef DEBUG_MMU_EMU
 297 printk("mmu_emu_map_pmeg: pmeg %x to context %d vaddr %x\n",
 298        curr_pmeg, context, vaddr);
 299 #endif
 300
 301         /* Invalidate old mapping for the pmeg, if any */
 302         if (pmeg_alloc[curr_pmeg] == 1) {
 303                 sun3_put_context(pmeg_ctx[curr_pmeg]);
 304                 sun3_put_segmap (pmeg_vaddr[curr_pmeg], SUN3_INVALID_PMEG);
 305                 sun3_put_context(context);
 306         }
 307
 308         /* Update PMEG management structures. */
 309         // don't take pmeg's away from the kernel...
 310         if(vaddr >= PAGE_OFFSET) {
 311                 /* map kernel pmegs into all contexts */
 312                 unsigned char i;
 313
 314                 for(i = 0; i < CONTEXTS_NUM; i++) {
 315                         sun3_put_context(i);
 316                         sun3_put_segmap (vaddr, curr_pmeg);
 317                 }
 318                 sun3_put_context(context);
 319                 pmeg_alloc[curr_pmeg] = 2;
 320                 pmeg_ctx[curr_pmeg] = 0;
 321
 322         }
 323         else {
 324                 pmeg_alloc[curr_pmeg] = 1;
 325                 pmeg_ctx[curr_pmeg] = context;
 326                 sun3_put_segmap (vaddr, curr_pmeg);
 327
 328         }
 329         pmeg_vaddr[curr_pmeg] = vaddr;
 330
 331         /* Set hardware mapping and clear the old PTE entries. */
 332         for (i=0; i<SUN3_PMEG_SIZE; i+=SUN3_PTE_SIZE)
 333                 sun3_put_pte (vaddr + i, SUN3_PAGE_SYSTEM);
 334
 335         /* Consider a different one next time. */
 336         ++curr_pmeg;
 337 }
 338
 339 /*
 340  * Handle a pagefault at virtual address `vaddr'; check if there should be a
 341  * page there (specifically, whether the software pagetables indicate that
 342  * there is). This is necessary due to the limited size of the second-level
 343  * Sun3 hardware pagetables (256 groups of 16 pages). If there should be a
 344  * mapping present, we select a `spare' PMEG and use it to create a mapping.
 345  * `read_flag' is nonzero for a read fault; zero for a write. Returns nonzero
 346  * if we successfully handled the fault.
 347  */
 348 //todo: should we bump minor pagefault counter? if so, here or in caller?
 349 //todo: possibly inline this into bus_error030 in <asm/buserror.h> ?
 350
 351 // kernel_fault is set when a kernel page couldn't be demand mapped,
 352 // and forces another try using the kernel page table.  basically a
 353 // hack so that vmalloc would work correctly.
 354
 355 int mmu_emu_handle_fault (unsigned long vaddr, int read_flag, int kernel_fault)
 356 {
 357         unsigned long segment, offset;
 358         unsigned char context;
 359         pte_t *pte;
 360         pgd_t * crp;
 361
 362         if(current->mm == NULL) {
 363                 crp = swapper_pg_dir;
 364                 context = 0;
 365         } else {
 366                 context = current->mm->context;
 367                 if(kernel_fault)
 368                         crp = swapper_pg_dir;
 369                 else
 370                         crp = current->mm->pgd;
 371         }
 372
 373 #ifdef DEBUG_MMU_EMU
 374         printk ("mmu_emu_handle_fault: vaddr=%lx type=%s crp=%p\n",
 375                 vaddr, read_flag ? "read" : "write", crp);
 376 #endif
 377
 378         segment = (vaddr >> SUN3_PMEG_SIZE_BITS) & 0x7FF;
 379         offset  = (vaddr >> SUN3_PTE_SIZE_BITS) & 0xF;
 380
 381 #ifdef DEBUG_MMU_EMU
 382         printk ("mmu_emu_handle_fault: segment=%lx offset=%lx\n", segment, offset);
 383 #endif
 384
 385         pte = (pte_t *) pgd_val (*(crp + segment));
 386
 387 //todo: next line should check for valid pmd properly.
 388         if (!pte) {
 389 //                printk ("mmu_emu_handle_fault: invalid pmd\n");
 390                 return 0;
 391         }
 392
 393         pte = (pte_t *) __va ((unsigned long)(pte + offset));
 394
 395         /* Make sure this is a valid page */
 396         if (!(pte_val (*pte) & SUN3_PAGE_VALID))
 397                 return 0;
 398
 399         /* Make sure there's a pmeg allocated for the page */
 400         if (sun3_get_segmap (vaddr&~SUN3_PMEG_MASK) == SUN3_INVALID_PMEG)
 401                 mmu_emu_map_pmeg (context, vaddr);
 402
 403         /* Write the pte value to hardware MMU */
 404         sun3_put_pte (vaddr&PAGE_MASK, pte_val (*pte));
 405
 406         /* Update software copy of the pte value */
 407 // I'm not sure this is necessary. If this is required, we ought to simply
 408 // copy this out when we reuse the PMEG or at some other convenient time.
 409 // Doing it here is fairly meaningless, anyway, as we only know about the
 410 // first access to a given page. --m
 411         if (!read_flag) {
 412                 if (pte_val (*pte) & SUN3_PAGE_WRITEABLE)
 413                         pte_val (*pte) |= (SUN3_PAGE_ACCESSED
 414                                            | SUN3_PAGE_MODIFIED);
 415                 else
 416                         return 0;       /* Write-protect error. */
 417         } else
 418                 pte_val (*pte) |= SUN3_PAGE_ACCESSED;
 419
 420 #ifdef DEBUG_MMU_EMU
 421         printk ("seg:%d crp:%p ->", get_fs().seg, crp);
 422         print_pte_vaddr (vaddr);
 423         printk ("\n");
 424 #endif
 425
 426         return 1;
 427 }