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