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 static 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 intelligent... 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 } 428