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/uaccess.h> 21 #include <asm/page.h> 22 #include <asm/pgtable.h> 23 #include <asm/sun3mmu.h> 24 #include <asm/segment.h> 25 #include <asm/oplib.h> 26 #include <asm/mmu_context.h> 27 #include <asm/dvma.h> 28 29 30 #undef DEBUG_MMU_EMU 31 #define DEBUG_PROM_MAPS 32 33 /* 34 ** Defines 35 */ 36 37 #define CONTEXTS_NUM 8 38 #define SEGMAPS_PER_CONTEXT_NUM 2048 39 #define PAGES_PER_SEGMENT 16 40 #define PMEGS_NUM 256 41 #define PMEG_MASK 0xFF 42 43 /* 44 ** Globals 45 */ 46 47 unsigned long m68k_vmalloc_end; 48 EXPORT_SYMBOL(m68k_vmalloc_end); 49 50 unsigned long pmeg_vaddr[PMEGS_NUM]; 51 unsigned char pmeg_alloc[PMEGS_NUM]; 52 unsigned char pmeg_ctx[PMEGS_NUM]; 53 54 /* pointers to the mm structs for each task in each 55 context. 0xffffffff is a marker for kernel context */ 56 static struct mm_struct *ctx_alloc[CONTEXTS_NUM] = { 57 [0] = (struct mm_struct *)0xffffffff 58 }; 59 60 /* has this context been mmdrop'd? */ 61 static unsigned char ctx_avail = CONTEXTS_NUM-1; 62 63 /* array of pages to be marked off for the rom when we do mem_init later */ 64 /* 256 pages lets the rom take up to 2mb of physical ram.. I really 65 hope it never wants mote than that. */ 66 unsigned long rom_pages[256]; 67 68 /* Print a PTE value in symbolic form. For debugging. */ 69 void print_pte (pte_t pte) 70 { 71 #if 0 72 /* Verbose version. */ 73 unsigned long val = pte_val (pte); 74 printk (" pte=%lx [addr=%lx", 75 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT); 76 if (val & SUN3_PAGE_VALID) printk (" valid"); 77 if (val & SUN3_PAGE_WRITEABLE) printk (" write"); 78 if (val & SUN3_PAGE_SYSTEM) printk (" sys"); 79 if (val & SUN3_PAGE_NOCACHE) printk (" nocache"); 80 if (val & SUN3_PAGE_ACCESSED) printk (" accessed"); 81 if (val & SUN3_PAGE_MODIFIED) printk (" modified"); 82 switch (val & SUN3_PAGE_TYPE_MASK) { 83 case SUN3_PAGE_TYPE_MEMORY: printk (" memory"); break; 84 case SUN3_PAGE_TYPE_IO: printk (" io"); break; 85 case SUN3_PAGE_TYPE_VME16: printk (" vme16"); break; 86 case SUN3_PAGE_TYPE_VME32: printk (" vme32"); break; 87 } 88 printk ("]\n"); 89 #else 90 /* Terse version. More likely to fit on a line. */ 91 unsigned long val = pte_val (pte); 92 char flags[7], *type; 93 94 flags[0] = (val & SUN3_PAGE_VALID) ? 'v' : '-'; 95 flags[1] = (val & SUN3_PAGE_WRITEABLE) ? 'w' : '-'; 96 flags[2] = (val & SUN3_PAGE_SYSTEM) ? 's' : '-'; 97 flags[3] = (val & SUN3_PAGE_NOCACHE) ? 'x' : '-'; 98 flags[4] = (val & SUN3_PAGE_ACCESSED) ? 'a' : '-'; 99 flags[5] = (val & SUN3_PAGE_MODIFIED) ? 'm' : '-'; 100 flags[6] = '\0'; 101 102 switch (val & SUN3_PAGE_TYPE_MASK) { 103 case SUN3_PAGE_TYPE_MEMORY: type = "memory"; break; 104 case SUN3_PAGE_TYPE_IO: type = "io" ; break; 105 case SUN3_PAGE_TYPE_VME16: type = "vme16" ; break; 106 case SUN3_PAGE_TYPE_VME32: type = "vme32" ; break; 107 default: type = "unknown?"; break; 108 } 109 110 printk (" pte=%08lx [%07lx %s %s]\n", 111 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT, flags, type); 112 #endif 113 } 114 115 /* Print the PTE value for a given virtual address. For debugging. */ 116 void print_pte_vaddr (unsigned long vaddr) 117 { 118 printk (" vaddr=%lx [%02lx]", vaddr, sun3_get_segmap (vaddr)); 119 print_pte (__pte (sun3_get_pte (vaddr))); 120 } 121 122 /* 123 * Initialise the MMU emulator. 124 */ 125 void mmu_emu_init(unsigned long bootmem_end) 126 { 127 unsigned long seg, num; 128 int i,j; 129 130 memset(rom_pages, 0, sizeof(rom_pages)); 131 memset(pmeg_vaddr, 0, sizeof(pmeg_vaddr)); 132 memset(pmeg_alloc, 0, sizeof(pmeg_alloc)); 133 memset(pmeg_ctx, 0, sizeof(pmeg_ctx)); 134 135 /* pmeg align the end of bootmem, adding another pmeg, 136 * later bootmem allocations will likely need it */ 137 bootmem_end = (bootmem_end + (2 * SUN3_PMEG_SIZE)) & ~SUN3_PMEG_MASK; 138 139 /* mark all of the pmegs used thus far as reserved */ 140 for (i=0; i < __pa(bootmem_end) / SUN3_PMEG_SIZE ; ++i) 141 pmeg_alloc[i] = 2; 142 143 144 /* I'm thinking that most of the top pmeg's are going to be 145 used for something, and we probably shouldn't risk it */ 146 for(num = 0xf0; num <= 0xff; num++) 147 pmeg_alloc[num] = 2; 148 149 /* liberate all existing mappings in the rest of kernel space */ 150 for(seg = bootmem_end; seg < 0x0f800000; seg += SUN3_PMEG_SIZE) { 151 i = sun3_get_segmap(seg); 152 153 if(!pmeg_alloc[i]) { 154 #ifdef DEBUG_MMU_EMU 155 printk("freed: "); 156 print_pte_vaddr (seg); 157 #endif 158 sun3_put_segmap(seg, SUN3_INVALID_PMEG); 159 } 160 } 161 162 j = 0; 163 for (num=0, seg=0x0F800000; seg<0x10000000; seg+=16*PAGE_SIZE) { 164 if (sun3_get_segmap (seg) != SUN3_INVALID_PMEG) { 165 #ifdef DEBUG_PROM_MAPS 166 for(i = 0; i < 16; i++) { 167 printk ("mapped:"); 168 print_pte_vaddr (seg + (i*PAGE_SIZE)); 169 break; 170 } 171 #endif 172 // the lowest mapping here is the end of our 173 // vmalloc region 174 if (!m68k_vmalloc_end) 175 m68k_vmalloc_end = seg; 176 177 // mark the segmap alloc'd, and reserve any 178 // of the first 0xbff pages the hardware is 179 // already using... does any sun3 support > 24mb? 180 pmeg_alloc[sun3_get_segmap(seg)] = 2; 181 } 182 } 183 184 dvma_init(); 185 186 187 /* blank everything below the kernel, and we've got the base 188 mapping to start all the contexts off with... */ 189 for(seg = 0; seg < PAGE_OFFSET; seg += SUN3_PMEG_SIZE) 190 sun3_put_segmap(seg, SUN3_INVALID_PMEG); 191 192 set_fs(MAKE_MM_SEG(3)); 193 for(seg = 0; seg < 0x10000000; seg += SUN3_PMEG_SIZE) { 194 i = sun3_get_segmap(seg); 195 for(j = 1; j < CONTEXTS_NUM; j++) 196 (*(romvec->pv_setctxt))(j, (void *)seg, i); 197 } 198 set_fs(KERNEL_DS); 199 200 } 201 202 /* erase the mappings for a dead context. Uses the pg_dir for hints 203 as the pmeg tables proved somewhat unreliable, and unmapping all of 204 TASK_SIZE was much slower and no more stable. */ 205 /* todo: find a better way to keep track of the pmegs used by a 206 context for when they're cleared */ 207 void clear_context(unsigned long context) 208 { 209 unsigned char oldctx; 210 unsigned long i; 211 212 if(context) { 213 if(!ctx_alloc[context]) 214 panic("clear_context: context not allocated\n"); 215 216 ctx_alloc[context]->context = SUN3_INVALID_CONTEXT; 217 ctx_alloc[context] = (struct mm_struct *)0; 218 ctx_avail++; 219 } 220 221 oldctx = sun3_get_context(); 222 223 sun3_put_context(context); 224 225 for(i = 0; i < SUN3_INVALID_PMEG; i++) { 226 if((pmeg_ctx[i] == context) && (pmeg_alloc[i] == 1)) { 227 sun3_put_segmap(pmeg_vaddr[i], SUN3_INVALID_PMEG); 228 pmeg_ctx[i] = 0; 229 pmeg_alloc[i] = 0; 230 pmeg_vaddr[i] = 0; 231 } 232 } 233 234 sun3_put_context(oldctx); 235 } 236 237 /* gets an empty context. if full, kills the next context listed to 238 die first */ 239 /* This context invalidation scheme is, well, totally arbitrary, I'm 240 sure it could be much more intelligent... but it gets the job done 241 for now without much overhead in making it's decision. */ 242 /* todo: come up with optimized scheme for flushing contexts */ 243 unsigned long get_free_context(struct mm_struct *mm) 244 { 245 unsigned long new = 1; 246 static unsigned char next_to_die = 1; 247 248 if(!ctx_avail) { 249 /* kill someone to get our context */ 250 new = next_to_die; 251 clear_context(new); 252 next_to_die = (next_to_die + 1) & 0x7; 253 if(!next_to_die) 254 next_to_die++; 255 } else { 256 while(new < CONTEXTS_NUM) { 257 if(ctx_alloc[new]) 258 new++; 259 else 260 break; 261 } 262 // check to make sure one was really free... 263 if(new == CONTEXTS_NUM) 264 panic("get_free_context: failed to find free context"); 265 } 266 267 ctx_alloc[new] = mm; 268 ctx_avail--; 269 270 return new; 271 } 272 273 /* 274 * Dynamically select a `spare' PMEG and use it to map virtual `vaddr' in 275 * `context'. Maintain internal PMEG management structures. This doesn't 276 * actually map the physical address, but does clear the old mappings. 277 */ 278 //todo: better allocation scheme? but is extra complexity worthwhile? 279 //todo: only clear old entries if necessary? how to tell? 280 281 inline void mmu_emu_map_pmeg (int context, int vaddr) 282 { 283 static unsigned char curr_pmeg = 128; 284 int i; 285 286 /* Round address to PMEG boundary. */ 287 vaddr &= ~SUN3_PMEG_MASK; 288 289 /* Find a spare one. */ 290 while (pmeg_alloc[curr_pmeg] == 2) 291 ++curr_pmeg; 292 293 294 #ifdef DEBUG_MMU_EMU 295 printk("mmu_emu_map_pmeg: pmeg %x to context %d vaddr %x\n", 296 curr_pmeg, context, vaddr); 297 #endif 298 299 /* Invalidate old mapping for the pmeg, if any */ 300 if (pmeg_alloc[curr_pmeg] == 1) { 301 sun3_put_context(pmeg_ctx[curr_pmeg]); 302 sun3_put_segmap (pmeg_vaddr[curr_pmeg], SUN3_INVALID_PMEG); 303 sun3_put_context(context); 304 } 305 306 /* Update PMEG management structures. */ 307 // don't take pmeg's away from the kernel... 308 if(vaddr >= PAGE_OFFSET) { 309 /* map kernel pmegs into all contexts */ 310 unsigned char i; 311 312 for(i = 0; i < CONTEXTS_NUM; i++) { 313 sun3_put_context(i); 314 sun3_put_segmap (vaddr, curr_pmeg); 315 } 316 sun3_put_context(context); 317 pmeg_alloc[curr_pmeg] = 2; 318 pmeg_ctx[curr_pmeg] = 0; 319 320 } 321 else { 322 pmeg_alloc[curr_pmeg] = 1; 323 pmeg_ctx[curr_pmeg] = context; 324 sun3_put_segmap (vaddr, curr_pmeg); 325 326 } 327 pmeg_vaddr[curr_pmeg] = vaddr; 328 329 /* Set hardware mapping and clear the old PTE entries. */ 330 for (i=0; i<SUN3_PMEG_SIZE; i+=SUN3_PTE_SIZE) 331 sun3_put_pte (vaddr + i, SUN3_PAGE_SYSTEM); 332 333 /* Consider a different one next time. */ 334 ++curr_pmeg; 335 } 336 337 /* 338 * Handle a pagefault at virtual address `vaddr'; check if there should be a 339 * page there (specifically, whether the software pagetables indicate that 340 * there is). This is necessary due to the limited size of the second-level 341 * Sun3 hardware pagetables (256 groups of 16 pages). If there should be a 342 * mapping present, we select a `spare' PMEG and use it to create a mapping. 343 * `read_flag' is nonzero for a read fault; zero for a write. Returns nonzero 344 * if we successfully handled the fault. 345 */ 346 //todo: should we bump minor pagefault counter? if so, here or in caller? 347 //todo: possibly inline this into bus_error030 in <asm/buserror.h> ? 348 349 // kernel_fault is set when a kernel page couldn't be demand mapped, 350 // and forces another try using the kernel page table. basically a 351 // hack so that vmalloc would work correctly. 352 353 int mmu_emu_handle_fault (unsigned long vaddr, int read_flag, int kernel_fault) 354 { 355 unsigned long segment, offset; 356 unsigned char context; 357 pte_t *pte; 358 pgd_t * crp; 359 360 if(current->mm == NULL) { 361 crp = swapper_pg_dir; 362 context = 0; 363 } else { 364 context = current->mm->context; 365 if(kernel_fault) 366 crp = swapper_pg_dir; 367 else 368 crp = current->mm->pgd; 369 } 370 371 #ifdef DEBUG_MMU_EMU 372 printk ("mmu_emu_handle_fault: vaddr=%lx type=%s crp=%p\n", 373 vaddr, read_flag ? "read" : "write", crp); 374 #endif 375 376 segment = (vaddr >> SUN3_PMEG_SIZE_BITS) & 0x7FF; 377 offset = (vaddr >> SUN3_PTE_SIZE_BITS) & 0xF; 378 379 #ifdef DEBUG_MMU_EMU 380 printk ("mmu_emu_handle_fault: segment=%lx offset=%lx\n", segment, offset); 381 #endif 382 383 pte = (pte_t *) pgd_val (*(crp + segment)); 384 385 //todo: next line should check for valid pmd properly. 386 if (!pte) { 387 // printk ("mmu_emu_handle_fault: invalid pmd\n"); 388 return 0; 389 } 390 391 pte = (pte_t *) __va ((unsigned long)(pte + offset)); 392 393 /* Make sure this is a valid page */ 394 if (!(pte_val (*pte) & SUN3_PAGE_VALID)) 395 return 0; 396 397 /* Make sure there's a pmeg allocated for the page */ 398 if (sun3_get_segmap (vaddr&~SUN3_PMEG_MASK) == SUN3_INVALID_PMEG) 399 mmu_emu_map_pmeg (context, vaddr); 400 401 /* Write the pte value to hardware MMU */ 402 sun3_put_pte (vaddr&PAGE_MASK, pte_val (*pte)); 403 404 /* Update software copy of the pte value */ 405 // I'm not sure this is necessary. If this is required, we ought to simply 406 // copy this out when we reuse the PMEG or at some other convenient time. 407 // Doing it here is fairly meaningless, anyway, as we only know about the 408 // first access to a given page. --m 409 if (!read_flag) { 410 if (pte_val (*pte) & SUN3_PAGE_WRITEABLE) 411 pte_val (*pte) |= (SUN3_PAGE_ACCESSED 412 | SUN3_PAGE_MODIFIED); 413 else 414 return 0; /* Write-protect error. */ 415 } else 416 pte_val (*pte) |= SUN3_PAGE_ACCESSED; 417 418 #ifdef DEBUG_MMU_EMU 419 printk ("seg:%d crp:%p ->", get_fs().seg, crp); 420 print_pte_vaddr (vaddr); 421 printk ("\n"); 422 #endif 423 424 return 1; 425 } 426