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 m68k_vmalloc_end;
49 EXPORT_SYMBOL(m68k_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. */
print_pte(pte_t pte)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. */
print_pte_vaddr(unsigned long vaddr)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 */
mmu_emu_init(unsigned long bootmem_end)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 (!m68k_vmalloc_end)
176 m68k_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 */
clear_context(unsigned long context)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 */
get_free_context(struct mm_struct * mm)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
mmu_emu_map_pmeg(int context,int vaddr)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
mmu_emu_handle_fault(unsigned long vaddr,int read_flag,int kernel_fault)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 }
427