2 ** Tablewalk MMU emulator
6 ** Started 1/16/98 @ 2:22 am
9 #include <linux/mman.h>
11 #include <linux/kernel.h>
12 #include <linux/ptrace.h>
13 #include <linux/delay.h>
14 #include <linux/bootmem.h>
16 #include <asm/setup.h>
17 #include <asm/traps.h>
18 #include <asm/system.h>
19 #include <asm/uaccess.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>
29 extern void prom_reboot (char *) __attribute__ ((__noreturn__));
32 #define DEBUG_PROM_MAPS
38 #define CONTEXTS_NUM 8
39 #define SEGMAPS_PER_CONTEXT_NUM 2048
40 #define PAGES_PER_SEGMENT 16
42 #define PMEG_MASK 0xFF
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];
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
58 /* has this context been mmdrop'd? */
59 static unsigned char ctx_avail = CONTEXTS_NUM-1;
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];
66 /* Print a PTE value in symbolic form. For debugging. */
67 void print_pte (pte_t pte)
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;
88 /* Terse version. More likely to fit on a line. */
89 unsigned long val = pte_val (pte);
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' : '-';
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;
108 printk (" pte=%08lx [%07lx %s %s]\n",
109 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT, flags, type);
113 /* Print the PTE value for a given virtual address. For debugging. */
114 void print_pte_vaddr (unsigned long vaddr)
116 printk (" vaddr=%lx [%02lx]", vaddr, sun3_get_segmap (vaddr));
117 print_pte (__pte (sun3_get_pte (vaddr)));
121 * Initialise the MMU emulator.
123 void mmu_emu_init(unsigned long bootmem_end)
125 unsigned long seg, num;
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));
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;
137 /* mark all of the pmegs used thus far as reserved */
138 for (i=0; i < __pa(bootmem_end) / SUN3_PMEG_SIZE ; ++i)
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++)
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);
154 print_pte_vaddr (seg);
156 sun3_put_segmap(seg, SUN3_INVALID_PMEG);
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++) {
166 print_pte_vaddr (seg + (i*PAGE_SIZE));
170 // the lowest mapping here is the end of our
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;
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);
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);
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 */
205 void clear_context(unsigned long context)
207 unsigned char oldctx;
211 if(!ctx_alloc[context])
212 panic("clear_context: context not allocated\n");
214 ctx_alloc[context]->context = SUN3_INVALID_CONTEXT;
215 ctx_alloc[context] = (struct mm_struct *)0;
219 oldctx = sun3_get_context();
221 sun3_put_context(context);
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);
232 sun3_put_context(oldctx);
235 /* gets an empty context. if full, kills the next context listed to
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 */
241 unsigned long get_free_context(struct mm_struct *mm)
243 unsigned long new = 1;
244 static unsigned char next_to_die = 1;
247 /* kill someone to get our context */
250 next_to_die = (next_to_die + 1) & 0x7;
254 while(new < CONTEXTS_NUM) {
260 // check to make sure one was really free...
261 if(new == CONTEXTS_NUM)
262 panic("get_free_context: failed to find free context");
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.
276 //todo: better allocation scheme? but is extra complexity worthwhile?
277 //todo: only clear old entries if necessary? how to tell?
279 inline void mmu_emu_map_pmeg (int context, int vaddr)
281 static unsigned char curr_pmeg = 128;
284 /* Round address to PMEG boundary. */
285 vaddr &= ~SUN3_PMEG_MASK;
287 /* Find a spare one. */
288 while (pmeg_alloc[curr_pmeg] == 2)
293 printk("mmu_emu_map_pmeg: pmeg %x to context %d vaddr %x\n",
294 curr_pmeg, context, vaddr);
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);
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 */
310 for(i = 0; i < CONTEXTS_NUM; i++) {
312 sun3_put_segmap (vaddr, curr_pmeg);
314 sun3_put_context(context);
315 pmeg_alloc[curr_pmeg] = 2;
316 pmeg_ctx[curr_pmeg] = 0;
320 pmeg_alloc[curr_pmeg] = 1;
321 pmeg_ctx[curr_pmeg] = context;
322 sun3_put_segmap (vaddr, curr_pmeg);
325 pmeg_vaddr[curr_pmeg] = vaddr;
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);
331 /* Consider a different one next time. */
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.
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> ?
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.
351 int mmu_emu_handle_fault (unsigned long vaddr, int read_flag, int kernel_fault)
353 unsigned long segment, offset;
354 unsigned char context;
358 if(current->mm == NULL) {
359 crp = swapper_pg_dir;
362 context = current->mm->context;
364 crp = swapper_pg_dir;
366 crp = current->mm->pgd;
370 printk ("mmu_emu_handle_fault: vaddr=%lx type=%s crp=%p\n",
371 vaddr, read_flag ? "read" : "write", crp);
374 segment = (vaddr >> SUN3_PMEG_SIZE_BITS) & 0x7FF;
375 offset = (vaddr >> SUN3_PTE_SIZE_BITS) & 0xF;
378 printk ("mmu_emu_handle_fault: segment=%lx offset=%lx\n", segment, offset);
381 pte = (pte_t *) pgd_val (*(crp + segment));
383 //todo: next line should check for valid pmd properly.
385 // printk ("mmu_emu_handle_fault: invalid pmd\n");
389 pte = (pte_t *) __va ((unsigned long)(pte + offset));
391 /* Make sure this is a valid page */
392 if (!(pte_val (*pte) & SUN3_PAGE_VALID))
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);
399 /* Write the pte value to hardware MMU */
400 sun3_put_pte (vaddr&PAGE_MASK, pte_val (*pte));
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
408 if (pte_val (*pte) & SUN3_PAGE_WRITEABLE)
409 pte_val (*pte) |= (SUN3_PAGE_ACCESSED
410 | SUN3_PAGE_MODIFIED);
412 return 0; /* Write-protect error. */
414 pte_val (*pte) |= SUN3_PAGE_ACCESSED;
417 printk ("seg:%d crp:%p ->", get_fs().seg, crp);
418 print_pte_vaddr (vaddr);