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