1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 ** Tablewalk MMU emulator 4 ** 5 ** by Toshiyasu Morita 6 ** 7 ** Started 1/16/98 @ 2:22 am 8 */ 9 10 #include <linux/init.h> 11 #include <linux/mman.h> 12 #include <linux/mm.h> 13 #include <linux/kernel.h> 14 #include <linux/ptrace.h> 15 #include <linux/delay.h> 16 #include <linux/bootmem.h> 17 #include <linux/bitops.h> 18 #include <linux/module.h> 19 #include <linux/sched/mm.h> 20 21 #include <asm/setup.h> 22 #include <asm/traps.h> 23 #include <linux/uaccess.h> 24 #include <asm/page.h> 25 #include <asm/pgtable.h> 26 #include <asm/sun3mmu.h> 27 #include <asm/segment.h> 28 #include <asm/oplib.h> 29 #include <asm/mmu_context.h> 30 #include <asm/dvma.h> 31 32 33 #undef DEBUG_MMU_EMU 34 #define DEBUG_PROM_MAPS 35 36 /* 37 ** Defines 38 */ 39 40 #define CONTEXTS_NUM 8 41 #define SEGMAPS_PER_CONTEXT_NUM 2048 42 #define PAGES_PER_SEGMENT 16 43 #define PMEGS_NUM 256 44 #define PMEG_MASK 0xFF 45 46 /* 47 ** Globals 48 */ 49 50 unsigned long m68k_vmalloc_end; 51 EXPORT_SYMBOL(m68k_vmalloc_end); 52 53 unsigned long pmeg_vaddr[PMEGS_NUM]; 54 unsigned char pmeg_alloc[PMEGS_NUM]; 55 unsigned char pmeg_ctx[PMEGS_NUM]; 56 57 /* pointers to the mm structs for each task in each 58 context. 0xffffffff is a marker for kernel context */ 59 static struct mm_struct *ctx_alloc[CONTEXTS_NUM] = { 60 [0] = (struct mm_struct *)0xffffffff 61 }; 62 63 /* has this context been mmdrop'd? */ 64 static unsigned char ctx_avail = CONTEXTS_NUM-1; 65 66 /* array of pages to be marked off for the rom when we do mem_init later */ 67 /* 256 pages lets the rom take up to 2mb of physical ram.. I really 68 hope it never wants mote than that. */ 69 unsigned long rom_pages[256]; 70 71 /* Print a PTE value in symbolic form. For debugging. */ 72 void print_pte (pte_t pte) 73 { 74 #if 0 75 /* Verbose version. */ 76 unsigned long val = pte_val (pte); 77 pr_cont(" pte=%lx [addr=%lx", 78 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT); 79 if (val & SUN3_PAGE_VALID) pr_cont(" valid"); 80 if (val & SUN3_PAGE_WRITEABLE) pr_cont(" write"); 81 if (val & SUN3_PAGE_SYSTEM) pr_cont(" sys"); 82 if (val & SUN3_PAGE_NOCACHE) pr_cont(" nocache"); 83 if (val & SUN3_PAGE_ACCESSED) pr_cont(" accessed"); 84 if (val & SUN3_PAGE_MODIFIED) pr_cont(" modified"); 85 switch (val & SUN3_PAGE_TYPE_MASK) { 86 case SUN3_PAGE_TYPE_MEMORY: pr_cont(" memory"); break; 87 case SUN3_PAGE_TYPE_IO: pr_cont(" io"); break; 88 case SUN3_PAGE_TYPE_VME16: pr_cont(" vme16"); break; 89 case SUN3_PAGE_TYPE_VME32: pr_cont(" vme32"); break; 90 } 91 pr_cont("]\n"); 92 #else 93 /* Terse version. More likely to fit on a line. */ 94 unsigned long val = pte_val (pte); 95 char flags[7], *type; 96 97 flags[0] = (val & SUN3_PAGE_VALID) ? 'v' : '-'; 98 flags[1] = (val & SUN3_PAGE_WRITEABLE) ? 'w' : '-'; 99 flags[2] = (val & SUN3_PAGE_SYSTEM) ? 's' : '-'; 100 flags[3] = (val & SUN3_PAGE_NOCACHE) ? 'x' : '-'; 101 flags[4] = (val & SUN3_PAGE_ACCESSED) ? 'a' : '-'; 102 flags[5] = (val & SUN3_PAGE_MODIFIED) ? 'm' : '-'; 103 flags[6] = '\0'; 104 105 switch (val & SUN3_PAGE_TYPE_MASK) { 106 case SUN3_PAGE_TYPE_MEMORY: type = "memory"; break; 107 case SUN3_PAGE_TYPE_IO: type = "io" ; break; 108 case SUN3_PAGE_TYPE_VME16: type = "vme16" ; break; 109 case SUN3_PAGE_TYPE_VME32: type = "vme32" ; break; 110 default: type = "unknown?"; break; 111 } 112 113 pr_cont(" pte=%08lx [%07lx %s %s]\n", 114 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT, flags, type); 115 #endif 116 } 117 118 /* Print the PTE value for a given virtual address. For debugging. */ 119 void print_pte_vaddr (unsigned long vaddr) 120 { 121 pr_cont(" vaddr=%lx [%02lx]", vaddr, sun3_get_segmap (vaddr)); 122 print_pte (__pte (sun3_get_pte (vaddr))); 123 } 124 125 /* 126 * Initialise the MMU emulator. 127 */ 128 void __init mmu_emu_init(unsigned long bootmem_end) 129 { 130 unsigned long seg, num; 131 int i,j; 132 133 memset(rom_pages, 0, sizeof(rom_pages)); 134 memset(pmeg_vaddr, 0, sizeof(pmeg_vaddr)); 135 memset(pmeg_alloc, 0, sizeof(pmeg_alloc)); 136 memset(pmeg_ctx, 0, sizeof(pmeg_ctx)); 137 138 /* pmeg align the end of bootmem, adding another pmeg, 139 * later bootmem allocations will likely need it */ 140 bootmem_end = (bootmem_end + (2 * SUN3_PMEG_SIZE)) & ~SUN3_PMEG_MASK; 141 142 /* mark all of the pmegs used thus far as reserved */ 143 for (i=0; i < __pa(bootmem_end) / SUN3_PMEG_SIZE ; ++i) 144 pmeg_alloc[i] = 2; 145 146 147 /* I'm thinking that most of the top pmeg's are going to be 148 used for something, and we probably shouldn't risk it */ 149 for(num = 0xf0; num <= 0xff; num++) 150 pmeg_alloc[num] = 2; 151 152 /* liberate all existing mappings in the rest of kernel space */ 153 for(seg = bootmem_end; seg < 0x0f800000; seg += SUN3_PMEG_SIZE) { 154 i = sun3_get_segmap(seg); 155 156 if(!pmeg_alloc[i]) { 157 #ifdef DEBUG_MMU_EMU 158 pr_info("freed:"); 159 print_pte_vaddr (seg); 160 #endif 161 sun3_put_segmap(seg, SUN3_INVALID_PMEG); 162 } 163 } 164 165 j = 0; 166 for (num=0, seg=0x0F800000; seg<0x10000000; seg+=16*PAGE_SIZE) { 167 if (sun3_get_segmap (seg) != SUN3_INVALID_PMEG) { 168 #ifdef DEBUG_PROM_MAPS 169 for(i = 0; i < 16; i++) { 170 pr_info("mapped:"); 171 print_pte_vaddr (seg + (i*PAGE_SIZE)); 172 break; 173 } 174 #endif 175 // the lowest mapping here is the end of our 176 // vmalloc region 177 if (!m68k_vmalloc_end) 178 m68k_vmalloc_end = seg; 179 180 // mark the segmap alloc'd, and reserve any 181 // of the first 0xbff pages the hardware is 182 // already using... does any sun3 support > 24mb? 183 pmeg_alloc[sun3_get_segmap(seg)] = 2; 184 } 185 } 186 187 dvma_init(); 188 189 190 /* blank everything below the kernel, and we've got the base 191 mapping to start all the contexts off with... */ 192 for(seg = 0; seg < PAGE_OFFSET; seg += SUN3_PMEG_SIZE) 193 sun3_put_segmap(seg, SUN3_INVALID_PMEG); 194 195 set_fs(MAKE_MM_SEG(3)); 196 for(seg = 0; seg < 0x10000000; seg += SUN3_PMEG_SIZE) { 197 i = sun3_get_segmap(seg); 198 for(j = 1; j < CONTEXTS_NUM; j++) 199 (*(romvec->pv_setctxt))(j, (void *)seg, i); 200 } 201 set_fs(KERNEL_DS); 202 203 } 204 205 /* erase the mappings for a dead context. Uses the pg_dir for hints 206 as the pmeg tables proved somewhat unreliable, and unmapping all of 207 TASK_SIZE was much slower and no more stable. */ 208 /* todo: find a better way to keep track of the pmegs used by a 209 context for when they're cleared */ 210 void clear_context(unsigned long context) 211 { 212 unsigned char oldctx; 213 unsigned long i; 214 215 if(context) { 216 if(!ctx_alloc[context]) 217 panic("clear_context: context not allocated\n"); 218 219 ctx_alloc[context]->context = SUN3_INVALID_CONTEXT; 220 ctx_alloc[context] = (struct mm_struct *)0; 221 ctx_avail++; 222 } 223 224 oldctx = sun3_get_context(); 225 226 sun3_put_context(context); 227 228 for(i = 0; i < SUN3_INVALID_PMEG; i++) { 229 if((pmeg_ctx[i] == context) && (pmeg_alloc[i] == 1)) { 230 sun3_put_segmap(pmeg_vaddr[i], SUN3_INVALID_PMEG); 231 pmeg_ctx[i] = 0; 232 pmeg_alloc[i] = 0; 233 pmeg_vaddr[i] = 0; 234 } 235 } 236 237 sun3_put_context(oldctx); 238 } 239 240 /* gets an empty context. if full, kills the next context listed to 241 die first */ 242 /* This context invalidation scheme is, well, totally arbitrary, I'm 243 sure it could be much more intelligent... but it gets the job done 244 for now without much overhead in making it's decision. */ 245 /* todo: come up with optimized scheme for flushing contexts */ 246 unsigned long get_free_context(struct mm_struct *mm) 247 { 248 unsigned long new = 1; 249 static unsigned char next_to_die = 1; 250 251 if(!ctx_avail) { 252 /* kill someone to get our context */ 253 new = next_to_die; 254 clear_context(new); 255 next_to_die = (next_to_die + 1) & 0x7; 256 if(!next_to_die) 257 next_to_die++; 258 } else { 259 while(new < CONTEXTS_NUM) { 260 if(ctx_alloc[new]) 261 new++; 262 else 263 break; 264 } 265 // check to make sure one was really free... 266 if(new == CONTEXTS_NUM) 267 panic("get_free_context: failed to find free context"); 268 } 269 270 ctx_alloc[new] = mm; 271 ctx_avail--; 272 273 return new; 274 } 275 276 /* 277 * Dynamically select a `spare' PMEG and use it to map virtual `vaddr' in 278 * `context'. Maintain internal PMEG management structures. This doesn't 279 * actually map the physical address, but does clear the old mappings. 280 */ 281 //todo: better allocation scheme? but is extra complexity worthwhile? 282 //todo: only clear old entries if necessary? how to tell? 283 284 inline void mmu_emu_map_pmeg (int context, int vaddr) 285 { 286 static unsigned char curr_pmeg = 128; 287 int i; 288 289 /* Round address to PMEG boundary. */ 290 vaddr &= ~SUN3_PMEG_MASK; 291 292 /* Find a spare one. */ 293 while (pmeg_alloc[curr_pmeg] == 2) 294 ++curr_pmeg; 295 296 297 #ifdef DEBUG_MMU_EMU 298 pr_info("mmu_emu_map_pmeg: pmeg %x to context %d vaddr %x\n", 299 curr_pmeg, context, vaddr); 300 #endif 301 302 /* Invalidate old mapping for the pmeg, if any */ 303 if (pmeg_alloc[curr_pmeg] == 1) { 304 sun3_put_context(pmeg_ctx[curr_pmeg]); 305 sun3_put_segmap (pmeg_vaddr[curr_pmeg], SUN3_INVALID_PMEG); 306 sun3_put_context(context); 307 } 308 309 /* Update PMEG management structures. */ 310 // don't take pmeg's away from the kernel... 311 if(vaddr >= PAGE_OFFSET) { 312 /* map kernel pmegs into all contexts */ 313 unsigned char i; 314 315 for(i = 0; i < CONTEXTS_NUM; i++) { 316 sun3_put_context(i); 317 sun3_put_segmap (vaddr, curr_pmeg); 318 } 319 sun3_put_context(context); 320 pmeg_alloc[curr_pmeg] = 2; 321 pmeg_ctx[curr_pmeg] = 0; 322 323 } 324 else { 325 pmeg_alloc[curr_pmeg] = 1; 326 pmeg_ctx[curr_pmeg] = context; 327 sun3_put_segmap (vaddr, curr_pmeg); 328 329 } 330 pmeg_vaddr[curr_pmeg] = vaddr; 331 332 /* Set hardware mapping and clear the old PTE entries. */ 333 for (i=0; i<SUN3_PMEG_SIZE; i+=SUN3_PTE_SIZE) 334 sun3_put_pte (vaddr + i, SUN3_PAGE_SYSTEM); 335 336 /* Consider a different one next time. */ 337 ++curr_pmeg; 338 } 339 340 /* 341 * Handle a pagefault at virtual address `vaddr'; check if there should be a 342 * page there (specifically, whether the software pagetables indicate that 343 * there is). This is necessary due to the limited size of the second-level 344 * Sun3 hardware pagetables (256 groups of 16 pages). If there should be a 345 * mapping present, we select a `spare' PMEG and use it to create a mapping. 346 * `read_flag' is nonzero for a read fault; zero for a write. Returns nonzero 347 * if we successfully handled the fault. 348 */ 349 //todo: should we bump minor pagefault counter? if so, here or in caller? 350 //todo: possibly inline this into bus_error030 in <asm/buserror.h> ? 351 352 // kernel_fault is set when a kernel page couldn't be demand mapped, 353 // and forces another try using the kernel page table. basically a 354 // hack so that vmalloc would work correctly. 355 356 int mmu_emu_handle_fault (unsigned long vaddr, int read_flag, int kernel_fault) 357 { 358 unsigned long segment, offset; 359 unsigned char context; 360 pte_t *pte; 361 pgd_t * crp; 362 363 if(current->mm == NULL) { 364 crp = swapper_pg_dir; 365 context = 0; 366 } else { 367 context = current->mm->context; 368 if(kernel_fault) 369 crp = swapper_pg_dir; 370 else 371 crp = current->mm->pgd; 372 } 373 374 #ifdef DEBUG_MMU_EMU 375 pr_info("mmu_emu_handle_fault: vaddr=%lx type=%s crp=%p\n", 376 vaddr, read_flag ? "read" : "write", crp); 377 #endif 378 379 segment = (vaddr >> SUN3_PMEG_SIZE_BITS) & 0x7FF; 380 offset = (vaddr >> SUN3_PTE_SIZE_BITS) & 0xF; 381 382 #ifdef DEBUG_MMU_EMU 383 pr_info("mmu_emu_handle_fault: segment=%lx offset=%lx\n", segment, 384 offset); 385 #endif 386 387 pte = (pte_t *) pgd_val (*(crp + segment)); 388 389 //todo: next line should check for valid pmd properly. 390 if (!pte) { 391 // pr_info("mmu_emu_handle_fault: invalid pmd\n"); 392 return 0; 393 } 394 395 pte = (pte_t *) __va ((unsigned long)(pte + offset)); 396 397 /* Make sure this is a valid page */ 398 if (!(pte_val (*pte) & SUN3_PAGE_VALID)) 399 return 0; 400 401 /* Make sure there's a pmeg allocated for the page */ 402 if (sun3_get_segmap (vaddr&~SUN3_PMEG_MASK) == SUN3_INVALID_PMEG) 403 mmu_emu_map_pmeg (context, vaddr); 404 405 /* Write the pte value to hardware MMU */ 406 sun3_put_pte (vaddr&PAGE_MASK, pte_val (*pte)); 407 408 /* Update software copy of the pte value */ 409 // I'm not sure this is necessary. If this is required, we ought to simply 410 // copy this out when we reuse the PMEG or at some other convenient time. 411 // Doing it here is fairly meaningless, anyway, as we only know about the 412 // first access to a given page. --m 413 if (!read_flag) { 414 if (pte_val (*pte) & SUN3_PAGE_WRITEABLE) 415 pte_val (*pte) |= (SUN3_PAGE_ACCESSED 416 | SUN3_PAGE_MODIFIED); 417 else 418 return 0; /* Write-protect error. */ 419 } else 420 pte_val (*pte) |= SUN3_PAGE_ACCESSED; 421 422 #ifdef DEBUG_MMU_EMU 423 pr_info("seg:%ld crp:%p ->", get_fs().seg, crp); 424 print_pte_vaddr (vaddr); 425 pr_cont("\n"); 426 #endif 427 428 return 1; 429 } 430