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