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;
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 [0] = (struct mm_struct *)0xffffffff
59 /* has this context been mmdrop'd? */
60 static unsigned char ctx_avail = CONTEXTS_NUM-1;
62 /* array of pages to be marked off for the rom when we do mem_init later */
63 /* 256 pages lets the rom take up to 2mb of physical ram.. I really
64 hope it never wants mote than that. */
65 unsigned long rom_pages[256];
67 /* Print a PTE value in symbolic form. For debugging. */
68 void print_pte (pte_t pte)
71 /* Verbose version. */
72 unsigned long val = pte_val (pte);
73 printk (" pte=%lx [addr=%lx",
74 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT);
75 if (val & SUN3_PAGE_VALID) printk (" valid");
76 if (val & SUN3_PAGE_WRITEABLE) printk (" write");
77 if (val & SUN3_PAGE_SYSTEM) printk (" sys");
78 if (val & SUN3_PAGE_NOCACHE) printk (" nocache");
79 if (val & SUN3_PAGE_ACCESSED) printk (" accessed");
80 if (val & SUN3_PAGE_MODIFIED) printk (" modified");
81 switch (val & SUN3_PAGE_TYPE_MASK) {
82 case SUN3_PAGE_TYPE_MEMORY: printk (" memory"); break;
83 case SUN3_PAGE_TYPE_IO: printk (" io"); break;
84 case SUN3_PAGE_TYPE_VME16: printk (" vme16"); break;
85 case SUN3_PAGE_TYPE_VME32: printk (" vme32"); break;
89 /* Terse version. More likely to fit on a line. */
90 unsigned long val = pte_val (pte);
93 flags[0] = (val & SUN3_PAGE_VALID) ? 'v' : '-';
94 flags[1] = (val & SUN3_PAGE_WRITEABLE) ? 'w' : '-';
95 flags[2] = (val & SUN3_PAGE_SYSTEM) ? 's' : '-';
96 flags[3] = (val & SUN3_PAGE_NOCACHE) ? 'x' : '-';
97 flags[4] = (val & SUN3_PAGE_ACCESSED) ? 'a' : '-';
98 flags[5] = (val & SUN3_PAGE_MODIFIED) ? 'm' : '-';
101 switch (val & SUN3_PAGE_TYPE_MASK) {
102 case SUN3_PAGE_TYPE_MEMORY: type = "memory"; break;
103 case SUN3_PAGE_TYPE_IO: type = "io" ; break;
104 case SUN3_PAGE_TYPE_VME16: type = "vme16" ; break;
105 case SUN3_PAGE_TYPE_VME32: type = "vme32" ; break;
106 default: type = "unknown?"; break;
109 printk (" pte=%08lx [%07lx %s %s]\n",
110 val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT, flags, type);
114 /* Print the PTE value for a given virtual address. For debugging. */
115 void print_pte_vaddr (unsigned long vaddr)
117 printk (" vaddr=%lx [%02lx]", vaddr, sun3_get_segmap (vaddr));
118 print_pte (__pte (sun3_get_pte (vaddr)));
122 * Initialise the MMU emulator.
124 void mmu_emu_init(unsigned long bootmem_end)
126 unsigned long seg, num;
129 memset(rom_pages, 0, sizeof(rom_pages));
130 memset(pmeg_vaddr, 0, sizeof(pmeg_vaddr));
131 memset(pmeg_alloc, 0, sizeof(pmeg_alloc));
132 memset(pmeg_ctx, 0, sizeof(pmeg_ctx));
134 /* pmeg align the end of bootmem, adding another pmeg,
135 * later bootmem allocations will likely need it */
136 bootmem_end = (bootmem_end + (2 * SUN3_PMEG_SIZE)) & ~SUN3_PMEG_MASK;
138 /* mark all of the pmegs used thus far as reserved */
139 for (i=0; i < __pa(bootmem_end) / SUN3_PMEG_SIZE ; ++i)
143 /* I'm thinking that most of the top pmeg's are going to be
144 used for something, and we probably shouldn't risk it */
145 for(num = 0xf0; num <= 0xff; num++)
148 /* liberate all existing mappings in the rest of kernel space */
149 for(seg = bootmem_end; seg < 0x0f800000; seg += SUN3_PMEG_SIZE) {
150 i = sun3_get_segmap(seg);
155 print_pte_vaddr (seg);
157 sun3_put_segmap(seg, SUN3_INVALID_PMEG);
162 for (num=0, seg=0x0F800000; seg<0x10000000; seg+=16*PAGE_SIZE) {
163 if (sun3_get_segmap (seg) != SUN3_INVALID_PMEG) {
164 #ifdef DEBUG_PROM_MAPS
165 for(i = 0; i < 16; i++) {
167 print_pte_vaddr (seg + (i*PAGE_SIZE));
171 // the lowest mapping here is the end of our
176 // mark the segmap alloc'd, and reserve any
177 // of the first 0xbff pages the hardware is
178 // already using... does any sun3 support > 24mb?
179 pmeg_alloc[sun3_get_segmap(seg)] = 2;
186 /* blank everything below the kernel, and we've got the base
187 mapping to start all the contexts off with... */
188 for(seg = 0; seg < PAGE_OFFSET; seg += SUN3_PMEG_SIZE)
189 sun3_put_segmap(seg, SUN3_INVALID_PMEG);
191 set_fs(MAKE_MM_SEG(3));
192 for(seg = 0; seg < 0x10000000; seg += SUN3_PMEG_SIZE) {
193 i = sun3_get_segmap(seg);
194 for(j = 1; j < CONTEXTS_NUM; j++)
195 (*(romvec->pv_setctxt))(j, (void *)seg, i);
201 /* erase the mappings for a dead context. Uses the pg_dir for hints
202 as the pmeg tables proved somewhat unreliable, and unmapping all of
203 TASK_SIZE was much slower and no more stable. */
204 /* todo: find a better way to keep track of the pmegs used by a
205 context for when they're cleared */
206 void clear_context(unsigned long context)
208 unsigned char oldctx;
212 if(!ctx_alloc[context])
213 panic("clear_context: context not allocated\n");
215 ctx_alloc[context]->context = SUN3_INVALID_CONTEXT;
216 ctx_alloc[context] = (struct mm_struct *)0;
220 oldctx = sun3_get_context();
222 sun3_put_context(context);
224 for(i = 0; i < SUN3_INVALID_PMEG; i++) {
225 if((pmeg_ctx[i] == context) && (pmeg_alloc[i] == 1)) {
226 sun3_put_segmap(pmeg_vaddr[i], SUN3_INVALID_PMEG);
233 sun3_put_context(oldctx);
236 /* gets an empty context. if full, kills the next context listed to
238 /* This context invalidation scheme is, well, totally arbitrary, I'm
239 sure it could be much more intellegent... but it gets the job done
240 for now without much overhead in making it's decision. */
241 /* todo: come up with optimized scheme for flushing contexts */
242 unsigned long get_free_context(struct mm_struct *mm)
244 unsigned long new = 1;
245 static unsigned char next_to_die = 1;
248 /* kill someone to get our context */
251 next_to_die = (next_to_die + 1) & 0x7;
255 while(new < CONTEXTS_NUM) {
261 // check to make sure one was really free...
262 if(new == CONTEXTS_NUM)
263 panic("get_free_context: failed to find free context");
273 * Dynamically select a `spare' PMEG and use it to map virtual `vaddr' in
274 * `context'. Maintain internal PMEG management structures. This doesn't
275 * actually map the physical address, but does clear the old mappings.
277 //todo: better allocation scheme? but is extra complexity worthwhile?
278 //todo: only clear old entries if necessary? how to tell?
280 inline void mmu_emu_map_pmeg (int context, int vaddr)
282 static unsigned char curr_pmeg = 128;
285 /* Round address to PMEG boundary. */
286 vaddr &= ~SUN3_PMEG_MASK;
288 /* Find a spare one. */
289 while (pmeg_alloc[curr_pmeg] == 2)
294 printk("mmu_emu_map_pmeg: pmeg %x to context %d vaddr %x\n",
295 curr_pmeg, context, vaddr);
298 /* Invalidate old mapping for the pmeg, if any */
299 if (pmeg_alloc[curr_pmeg] == 1) {
300 sun3_put_context(pmeg_ctx[curr_pmeg]);
301 sun3_put_segmap (pmeg_vaddr[curr_pmeg], SUN3_INVALID_PMEG);
302 sun3_put_context(context);
305 /* Update PMEG management structures. */
306 // don't take pmeg's away from the kernel...
307 if(vaddr >= PAGE_OFFSET) {
308 /* map kernel pmegs into all contexts */
311 for(i = 0; i < CONTEXTS_NUM; i++) {
313 sun3_put_segmap (vaddr, curr_pmeg);
315 sun3_put_context(context);
316 pmeg_alloc[curr_pmeg] = 2;
317 pmeg_ctx[curr_pmeg] = 0;
321 pmeg_alloc[curr_pmeg] = 1;
322 pmeg_ctx[curr_pmeg] = context;
323 sun3_put_segmap (vaddr, curr_pmeg);
326 pmeg_vaddr[curr_pmeg] = vaddr;
328 /* Set hardware mapping and clear the old PTE entries. */
329 for (i=0; i<SUN3_PMEG_SIZE; i+=SUN3_PTE_SIZE)
330 sun3_put_pte (vaddr + i, SUN3_PAGE_SYSTEM);
332 /* Consider a different one next time. */
337 * Handle a pagefault at virtual address `vaddr'; check if there should be a
338 * page there (specifically, whether the software pagetables indicate that
339 * there is). This is necessary due to the limited size of the second-level
340 * Sun3 hardware pagetables (256 groups of 16 pages). If there should be a
341 * mapping present, we select a `spare' PMEG and use it to create a mapping.
342 * `read_flag' is nonzero for a read fault; zero for a write. Returns nonzero
343 * if we successfully handled the fault.
345 //todo: should we bump minor pagefault counter? if so, here or in caller?
346 //todo: possibly inline this into bus_error030 in <asm/buserror.h> ?
348 // kernel_fault is set when a kernel page couldn't be demand mapped,
349 // and forces another try using the kernel page table. basically a
350 // hack so that vmalloc would work correctly.
352 int mmu_emu_handle_fault (unsigned long vaddr, int read_flag, int kernel_fault)
354 unsigned long segment, offset;
355 unsigned char context;
359 if(current->mm == NULL) {
360 crp = swapper_pg_dir;
363 context = current->mm->context;
365 crp = swapper_pg_dir;
367 crp = current->mm->pgd;
371 printk ("mmu_emu_handle_fault: vaddr=%lx type=%s crp=%p\n",
372 vaddr, read_flag ? "read" : "write", crp);
375 segment = (vaddr >> SUN3_PMEG_SIZE_BITS) & 0x7FF;
376 offset = (vaddr >> SUN3_PTE_SIZE_BITS) & 0xF;
379 printk ("mmu_emu_handle_fault: segment=%lx offset=%lx\n", segment, offset);
382 pte = (pte_t *) pgd_val (*(crp + segment));
384 //todo: next line should check for valid pmd properly.
386 // printk ("mmu_emu_handle_fault: invalid pmd\n");
390 pte = (pte_t *) __va ((unsigned long)(pte + offset));
392 /* Make sure this is a valid page */
393 if (!(pte_val (*pte) & SUN3_PAGE_VALID))
396 /* Make sure there's a pmeg allocated for the page */
397 if (sun3_get_segmap (vaddr&~SUN3_PMEG_MASK) == SUN3_INVALID_PMEG)
398 mmu_emu_map_pmeg (context, vaddr);
400 /* Write the pte value to hardware MMU */
401 sun3_put_pte (vaddr&PAGE_MASK, pte_val (*pte));
403 /* Update software copy of the pte value */
404 // I'm not sure this is necessary. If this is required, we ought to simply
405 // copy this out when we reuse the PMEG or at some other convenient time.
406 // Doing it here is fairly meaningless, anyway, as we only know about the
407 // first access to a given page. --m
409 if (pte_val (*pte) & SUN3_PAGE_WRITEABLE)
410 pte_val (*pte) |= (SUN3_PAGE_ACCESSED
411 | SUN3_PAGE_MODIFIED);
413 return 0; /* Write-protect error. */
415 pte_val (*pte) |= SUN3_PAGE_ACCESSED;
418 printk ("seg:%d crp:%p ->", get_fs().seg, crp);
419 print_pte_vaddr (vaddr);