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/memblock.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/sun3mmu.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 pr_cont(" pte=%lx [addr=%lx",
76 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT);
77 if (val & SUN3_PAGE_VALID) pr_cont(" valid");
78 if (val & SUN3_PAGE_WRITEABLE) pr_cont(" write");
79 if (val & SUN3_PAGE_SYSTEM) pr_cont(" sys");
80 if (val & SUN3_PAGE_NOCACHE) pr_cont(" nocache");
81 if (val & SUN3_PAGE_ACCESSED) pr_cont(" accessed");
82 if (val & SUN3_PAGE_MODIFIED) pr_cont(" modified");
83 switch (val & SUN3_PAGE_TYPE_MASK) {
84 case SUN3_PAGE_TYPE_MEMORY: pr_cont(" memory"); break;
85 case SUN3_PAGE_TYPE_IO: pr_cont(" io"); break;
86 case SUN3_PAGE_TYPE_VME16: pr_cont(" vme16"); break;
87 case SUN3_PAGE_TYPE_VME32: pr_cont(" vme32"); break;
88 }
89 pr_cont("]\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 pr_cont(" 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 pr_cont(" 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 __init 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 pr_info("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 pr_info("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_fc(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_fc(USER_DATA);
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 */
clear_context(unsigned long context)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("%s: context not allocated\n", __func__);
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 */
get_free_context(struct mm_struct * mm)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("%s: failed to find free context", __func__);
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
mmu_emu_map_pmeg(int context,int vaddr)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 pr_info("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
mmu_emu_handle_fault(unsigned long vaddr,int read_flag,int kernel_fault)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 pr_info("%s: vaddr=%lx type=%s crp=%p\n", __func__, vaddr,
373 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 pr_info("%s: segment=%lx offset=%lx\n", __func__, 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 // pr_info("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 pr_info("seg:%ld crp:%p ->", get_fs().seg, crp);
420 print_pte_vaddr (vaddr);
421 pr_cont("\n");
422 #endif
423
424 return 1;
425 }
426