mmu_emu.c

  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#include <linux/string_choices.h>
 21
 22#include <asm/setup.h>
 23#include <asm/traps.h>
 24#include <linux/uaccess.h>
 25#include <asm/page.h>
 26#include <asm/sun3mmu.h>
 27#include <asm/oplib.h>
 28#include <asm/mmu_context.h>
 29#include <asm/dvma.h>
 30
 31#include "sun3.h"
 32
 33#undef DEBUG_MMU_EMU
 34#define DEBUG_PROM_MAPS
 35
 36/*
 37** Defines
 38*/
 39
 40#define CONTEXTS_NUM		8
 41#define SEGMAPS_PER_CONTEXT_NUM 2048
 42#define PAGES_PER_SEGMENT	16
 43#define PMEGS_NUM		256
 44#define PMEG_MASK		0xFF
 45
 46/*
 47** Globals
 48*/
 49
 50unsigned long m68k_vmalloc_end;
 51EXPORT_SYMBOL(m68k_vmalloc_end);
 52
 53unsigned long pmeg_vaddr[PMEGS_NUM];
 54unsigned char pmeg_alloc[PMEGS_NUM];
 55unsigned char pmeg_ctx[PMEGS_NUM];
 56
 57/* pointers to the mm structs for each task in each
 58   context. 0xffffffff is a marker for kernel context */
 59static struct mm_struct *ctx_alloc[CONTEXTS_NUM] = {
 60    [0] = (struct mm_struct *)0xffffffff
 61};
 62
 63/* has this context been mmdrop'd? */
 64static unsigned char ctx_avail = CONTEXTS_NUM-1;
 65
 66/* array of pages to be marked off for the rom when we do mem_init later */
 67/* 256 pages lets the rom take up to 2mb of physical ram..  I really
 68   hope it never wants mote than that. */
 69unsigned long rom_pages[256];
 70
 71/* Print a PTE value in symbolic form. For debugging. */
 72static void print_pte(pte_t pte)
 73{
 74#if 0
 75	/* Verbose version. */
 76	unsigned long val = pte_val (pte);
 77	pr_cont(" pte=%lx [addr=%lx",
 78		val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT);
 79	if (val & SUN3_PAGE_VALID)	pr_cont(" valid");
 80	if (val & SUN3_PAGE_WRITEABLE)	pr_cont(" write");
 81	if (val & SUN3_PAGE_SYSTEM)	pr_cont(" sys");
 82	if (val & SUN3_PAGE_NOCACHE)	pr_cont(" nocache");
 83	if (val & SUN3_PAGE_ACCESSED)	pr_cont(" accessed");
 84	if (val & SUN3_PAGE_MODIFIED)	pr_cont(" modified");
 85	switch (val & SUN3_PAGE_TYPE_MASK) {
 86		case SUN3_PAGE_TYPE_MEMORY: pr_cont(" memory"); break;
 87		case SUN3_PAGE_TYPE_IO:     pr_cont(" io");     break;
 88		case SUN3_PAGE_TYPE_VME16:  pr_cont(" vme16");  break;
 89		case SUN3_PAGE_TYPE_VME32:  pr_cont(" vme32");  break;
 90	}
 91	pr_cont("]\n");
 92#else
 93	/* Terse version. More likely to fit on a line. */
 94	unsigned long val = pte_val (pte);
 95	char flags[7], *type;
 96
 97	flags[0] = (val & SUN3_PAGE_VALID)     ? 'v' : '-';
 98	flags[1] = (val & SUN3_PAGE_WRITEABLE) ? 'w' : '-';
 99	flags[2] = (val & SUN3_PAGE_SYSTEM)    ? 's' : '-';
100	flags[3] = (val & SUN3_PAGE_NOCACHE)   ? 'x' : '-';
101	flags[4] = (val & SUN3_PAGE_ACCESSED)  ? 'a' : '-';
102	flags[5] = (val & SUN3_PAGE_MODIFIED)  ? 'm' : '-';
103	flags[6] = '\0';
104
105	switch (val & SUN3_PAGE_TYPE_MASK) {
106		case SUN3_PAGE_TYPE_MEMORY: type = "memory"; break;
107		case SUN3_PAGE_TYPE_IO:     type = "io"    ; break;
108		case SUN3_PAGE_TYPE_VME16:  type = "vme16" ; break;
109		case SUN3_PAGE_TYPE_VME32:  type = "vme32" ; break;
110		default: type = "unknown?"; break;
111	}
112
113	pr_cont(" pte=%08lx [%07lx %s %s]\n",
114		val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT, flags, type);
115#endif
116}
117
118/* Print the PTE value for a given virtual address. For debugging. */
119void print_pte_vaddr (unsigned long vaddr)
120{
121	pr_cont(" vaddr=%lx [%02lx]", vaddr, sun3_get_segmap (vaddr));
122	print_pte (__pte (sun3_get_pte (vaddr)));
123}
124
125/*
126 * Initialise the MMU emulator.
127 */
128void __init mmu_emu_init(unsigned long bootmem_end)
129{
130	unsigned long seg, num;
131	int i,j;
132
133	memset(rom_pages, 0, sizeof(rom_pages));
134	memset(pmeg_vaddr, 0, sizeof(pmeg_vaddr));
135	memset(pmeg_alloc, 0, sizeof(pmeg_alloc));
136	memset(pmeg_ctx, 0, sizeof(pmeg_ctx));
137
138	/* pmeg align the end of bootmem, adding another pmeg,
139	 * later bootmem allocations will likely need it */
140	bootmem_end = (bootmem_end + (2 * SUN3_PMEG_SIZE)) & ~SUN3_PMEG_MASK;
141
142	/* mark all of the pmegs used thus far as reserved */
143	for (i=0; i < __pa(bootmem_end) / SUN3_PMEG_SIZE ; ++i)
144		pmeg_alloc[i] = 2;
145
146
147	/* I'm thinking that most of the top pmeg's are going to be
148	   used for something, and we probably shouldn't risk it */
149	for(num = 0xf0; num <= 0xff; num++)
150		pmeg_alloc[num] = 2;
151
152	/* liberate all existing mappings in the rest of kernel space */
153	for(seg = bootmem_end; seg < 0x0f800000; seg += SUN3_PMEG_SIZE) {
154		i = sun3_get_segmap(seg);
155
156		if(!pmeg_alloc[i]) {
157#ifdef DEBUG_MMU_EMU
158			pr_info("freed:");
159			print_pte_vaddr (seg);
160#endif
161			sun3_put_segmap(seg, SUN3_INVALID_PMEG);
162		}
163	}
164
165	j = 0;
166	for (num=0, seg=0x0F800000; seg<0x10000000; seg+=16*PAGE_SIZE) {
167		if (sun3_get_segmap (seg) != SUN3_INVALID_PMEG) {
168#ifdef DEBUG_PROM_MAPS
169			for(i = 0; i < 16; i++) {
170				pr_info("mapped:");
171				print_pte_vaddr (seg + (i*PAGE_SIZE));
172				break;
173			}
174#endif
175			// the lowest mapping here is the end of our
176			// vmalloc region
177			if (!m68k_vmalloc_end)
178				m68k_vmalloc_end = seg;
179
180			// mark the segmap alloc'd, and reserve any
181			// of the first 0xbff pages the hardware is
182			// already using...  does any sun3 support > 24mb?
183			pmeg_alloc[sun3_get_segmap(seg)] = 2;
184		}
185	}
186
187	dvma_init();
188
189
190	/* blank everything below the kernel, and we've got the base
191	   mapping to start all the contexts off with... */
192	for(seg = 0; seg < PAGE_OFFSET; seg += SUN3_PMEG_SIZE)
193		sun3_put_segmap(seg, SUN3_INVALID_PMEG);
194
195	set_fc(3);
196	for(seg = 0; seg < 0x10000000; seg += SUN3_PMEG_SIZE) {
197		i = sun3_get_segmap(seg);
198		for(j = 1; j < CONTEXTS_NUM; j++)
199			(*(romvec->pv_setctxt))(j, (void *)seg, i);
200	}
201	set_fc(USER_DATA);
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 */
209void 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("%s: context not allocated\n", __func__);
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 */
245unsigned 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("%s: failed to find free context", __func__);
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
283inline 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
355int 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("%s: vaddr=%lx type=%s crp=%px\n", __func__, vaddr,
375		str_read_write(read_flag), 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("%s: segment=%lx offset=%lx\n", __func__, segment, offset);
383#endif
384
385	pte = (pte_t *) pgd_val (*(crp + segment));
386
387//todo: next line should check for valid pmd properly.
388	if (!pte) {
389//                pr_info("mmu_emu_handle_fault: invalid pmd\n");
390                return 0;
391        }
392
393	pte = (pte_t *) __va ((unsigned long)(pte + offset));
394
395	/* Make sure this is a valid page */
396	if (!(pte_val (*pte) & SUN3_PAGE_VALID))
397		return 0;
398
399	/* Make sure there's a pmeg allocated for the page */
400	if (sun3_get_segmap (vaddr&~SUN3_PMEG_MASK) == SUN3_INVALID_PMEG)
401		mmu_emu_map_pmeg (context, vaddr);
402
403	/* Write the pte value to hardware MMU */
404	sun3_put_pte (vaddr&PAGE_MASK, pte_val (*pte));
405
406	/* Update software copy of the pte value */
407// I'm not sure this is necessary. If this is required, we ought to simply
408// copy this out when we reuse the PMEG or at some other convenient time.
409// Doing it here is fairly meaningless, anyway, as we only know about the
410// first access to a given page. --m
411	if (!read_flag) {
412		if (pte_val (*pte) & SUN3_PAGE_WRITEABLE)
413			pte_val (*pte) |= (SUN3_PAGE_ACCESSED
414					   | SUN3_PAGE_MODIFIED);
415		else
416			return 0;	/* Write-protect error. */
417	} else
418		pte_val (*pte) |= SUN3_PAGE_ACCESSED;
419
420#ifdef DEBUG_MMU_EMU
421	pr_info("seg:%ld crp:%px ->", get_fc(), crp);
422	print_pte_vaddr (vaddr);
423	pr_cont("\n");
424#endif
425
426	return 1;
427}