427 lines
12 KiB
C
427 lines
12 KiB
C
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/*
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** Tablewalk MMU emulator
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**
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** by Toshiyasu Morita
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**
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** Started 1/16/98 @ 2:22 am
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*/
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#include <linux/init.h>
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#include <linux/mman.h>
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#include <linux/mm.h>
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#include <linux/kernel.h>
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#include <linux/ptrace.h>
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#include <linux/delay.h>
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#include <linux/bootmem.h>
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#include <linux/bitops.h>
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#include <linux/module.h>
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#include <asm/setup.h>
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#include <asm/traps.h>
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#include <asm/uaccess.h>
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#include <asm/page.h>
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#include <asm/pgtable.h>
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#include <asm/sun3mmu.h>
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#include <asm/segment.h>
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#include <asm/oplib.h>
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#include <asm/mmu_context.h>
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#include <asm/dvma.h>
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#undef DEBUG_MMU_EMU
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#define DEBUG_PROM_MAPS
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/*
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** Defines
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*/
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#define CONTEXTS_NUM 8
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#define SEGMAPS_PER_CONTEXT_NUM 2048
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#define PAGES_PER_SEGMENT 16
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#define PMEGS_NUM 256
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#define PMEG_MASK 0xFF
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/*
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** Globals
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*/
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unsigned long m68k_vmalloc_end;
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EXPORT_SYMBOL(m68k_vmalloc_end);
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unsigned long pmeg_vaddr[PMEGS_NUM];
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unsigned char pmeg_alloc[PMEGS_NUM];
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unsigned char pmeg_ctx[PMEGS_NUM];
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/* pointers to the mm structs for each task in each
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context. 0xffffffff is a marker for kernel context */
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static struct mm_struct *ctx_alloc[CONTEXTS_NUM] = {
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[0] = (struct mm_struct *)0xffffffff
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};
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/* has this context been mmdrop'd? */
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static unsigned char ctx_avail = CONTEXTS_NUM-1;
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/* array of pages to be marked off for the rom when we do mem_init later */
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/* 256 pages lets the rom take up to 2mb of physical ram.. I really
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hope it never wants mote than that. */
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unsigned long rom_pages[256];
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/* Print a PTE value in symbolic form. For debugging. */
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void print_pte (pte_t pte)
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{
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#if 0
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/* Verbose version. */
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unsigned long val = pte_val (pte);
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printk (" pte=%lx [addr=%lx",
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val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT);
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if (val & SUN3_PAGE_VALID) printk (" valid");
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if (val & SUN3_PAGE_WRITEABLE) printk (" write");
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if (val & SUN3_PAGE_SYSTEM) printk (" sys");
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if (val & SUN3_PAGE_NOCACHE) printk (" nocache");
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if (val & SUN3_PAGE_ACCESSED) printk (" accessed");
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if (val & SUN3_PAGE_MODIFIED) printk (" modified");
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switch (val & SUN3_PAGE_TYPE_MASK) {
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case SUN3_PAGE_TYPE_MEMORY: printk (" memory"); break;
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case SUN3_PAGE_TYPE_IO: printk (" io"); break;
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case SUN3_PAGE_TYPE_VME16: printk (" vme16"); break;
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case SUN3_PAGE_TYPE_VME32: printk (" vme32"); break;
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}
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printk ("]\n");
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#else
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/* Terse version. More likely to fit on a line. */
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unsigned long val = pte_val (pte);
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char flags[7], *type;
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flags[0] = (val & SUN3_PAGE_VALID) ? 'v' : '-';
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flags[1] = (val & SUN3_PAGE_WRITEABLE) ? 'w' : '-';
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flags[2] = (val & SUN3_PAGE_SYSTEM) ? 's' : '-';
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flags[3] = (val & SUN3_PAGE_NOCACHE) ? 'x' : '-';
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flags[4] = (val & SUN3_PAGE_ACCESSED) ? 'a' : '-';
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flags[5] = (val & SUN3_PAGE_MODIFIED) ? 'm' : '-';
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flags[6] = '\0';
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switch (val & SUN3_PAGE_TYPE_MASK) {
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case SUN3_PAGE_TYPE_MEMORY: type = "memory"; break;
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case SUN3_PAGE_TYPE_IO: type = "io" ; break;
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case SUN3_PAGE_TYPE_VME16: type = "vme16" ; break;
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case SUN3_PAGE_TYPE_VME32: type = "vme32" ; break;
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default: type = "unknown?"; break;
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}
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printk (" pte=%08lx [%07lx %s %s]\n",
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val, (val & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT, flags, type);
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#endif
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}
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/* Print the PTE value for a given virtual address. For debugging. */
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void print_pte_vaddr (unsigned long vaddr)
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{
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printk (" vaddr=%lx [%02lx]", vaddr, sun3_get_segmap (vaddr));
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print_pte (__pte (sun3_get_pte (vaddr)));
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}
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/*
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* Initialise the MMU emulator.
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*/
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void __init mmu_emu_init(unsigned long bootmem_end)
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{
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unsigned long seg, num;
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int i,j;
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memset(rom_pages, 0, sizeof(rom_pages));
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memset(pmeg_vaddr, 0, sizeof(pmeg_vaddr));
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memset(pmeg_alloc, 0, sizeof(pmeg_alloc));
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memset(pmeg_ctx, 0, sizeof(pmeg_ctx));
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/* pmeg align the end of bootmem, adding another pmeg,
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* later bootmem allocations will likely need it */
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bootmem_end = (bootmem_end + (2 * SUN3_PMEG_SIZE)) & ~SUN3_PMEG_MASK;
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/* mark all of the pmegs used thus far as reserved */
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for (i=0; i < __pa(bootmem_end) / SUN3_PMEG_SIZE ; ++i)
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pmeg_alloc[i] = 2;
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/* I'm thinking that most of the top pmeg's are going to be
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used for something, and we probably shouldn't risk it */
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for(num = 0xf0; num <= 0xff; num++)
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pmeg_alloc[num] = 2;
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/* liberate all existing mappings in the rest of kernel space */
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for(seg = bootmem_end; seg < 0x0f800000; seg += SUN3_PMEG_SIZE) {
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i = sun3_get_segmap(seg);
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if(!pmeg_alloc[i]) {
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#ifdef DEBUG_MMU_EMU
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printk("freed: ");
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print_pte_vaddr (seg);
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#endif
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sun3_put_segmap(seg, SUN3_INVALID_PMEG);
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}
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}
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j = 0;
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for (num=0, seg=0x0F800000; seg<0x10000000; seg+=16*PAGE_SIZE) {
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if (sun3_get_segmap (seg) != SUN3_INVALID_PMEG) {
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#ifdef DEBUG_PROM_MAPS
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for(i = 0; i < 16; i++) {
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printk ("mapped:");
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print_pte_vaddr (seg + (i*PAGE_SIZE));
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break;
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}
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#endif
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// the lowest mapping here is the end of our
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// vmalloc region
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if (!m68k_vmalloc_end)
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m68k_vmalloc_end = seg;
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// mark the segmap alloc'd, and reserve any
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// of the first 0xbff pages the hardware is
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// already using... does any sun3 support > 24mb?
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pmeg_alloc[sun3_get_segmap(seg)] = 2;
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}
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}
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dvma_init();
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/* blank everything below the kernel, and we've got the base
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mapping to start all the contexts off with... */
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for(seg = 0; seg < PAGE_OFFSET; seg += SUN3_PMEG_SIZE)
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sun3_put_segmap(seg, SUN3_INVALID_PMEG);
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set_fs(MAKE_MM_SEG(3));
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for(seg = 0; seg < 0x10000000; seg += SUN3_PMEG_SIZE) {
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i = sun3_get_segmap(seg);
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for(j = 1; j < CONTEXTS_NUM; j++)
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(*(romvec->pv_setctxt))(j, (void *)seg, i);
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}
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set_fs(KERNEL_DS);
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}
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/* erase the mappings for a dead context. Uses the pg_dir for hints
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as the pmeg tables proved somewhat unreliable, and unmapping all of
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TASK_SIZE was much slower and no more stable. */
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/* todo: find a better way to keep track of the pmegs used by a
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context for when they're cleared */
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void clear_context(unsigned long context)
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{
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unsigned char oldctx;
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unsigned long i;
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if(context) {
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if(!ctx_alloc[context])
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panic("clear_context: context not allocated\n");
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ctx_alloc[context]->context = SUN3_INVALID_CONTEXT;
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ctx_alloc[context] = (struct mm_struct *)0;
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ctx_avail++;
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}
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oldctx = sun3_get_context();
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sun3_put_context(context);
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for(i = 0; i < SUN3_INVALID_PMEG; i++) {
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if((pmeg_ctx[i] == context) && (pmeg_alloc[i] == 1)) {
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sun3_put_segmap(pmeg_vaddr[i], SUN3_INVALID_PMEG);
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pmeg_ctx[i] = 0;
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pmeg_alloc[i] = 0;
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pmeg_vaddr[i] = 0;
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}
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}
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sun3_put_context(oldctx);
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}
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/* gets an empty context. if full, kills the next context listed to
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die first */
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/* This context invalidation scheme is, well, totally arbitrary, I'm
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sure it could be much more intelligent... but it gets the job done
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for now without much overhead in making it's decision. */
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/* todo: come up with optimized scheme for flushing contexts */
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unsigned long get_free_context(struct mm_struct *mm)
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{
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unsigned long new = 1;
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static unsigned char next_to_die = 1;
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if(!ctx_avail) {
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/* kill someone to get our context */
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new = next_to_die;
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clear_context(new);
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next_to_die = (next_to_die + 1) & 0x7;
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if(!next_to_die)
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next_to_die++;
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} else {
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while(new < CONTEXTS_NUM) {
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if(ctx_alloc[new])
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new++;
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else
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break;
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}
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// check to make sure one was really free...
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if(new == CONTEXTS_NUM)
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panic("get_free_context: failed to find free context");
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}
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ctx_alloc[new] = mm;
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ctx_avail--;
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return new;
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}
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/*
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* Dynamically select a `spare' PMEG and use it to map virtual `vaddr' in
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* `context'. Maintain internal PMEG management structures. This doesn't
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* actually map the physical address, but does clear the old mappings.
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*/
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//todo: better allocation scheme? but is extra complexity worthwhile?
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//todo: only clear old entries if necessary? how to tell?
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inline void mmu_emu_map_pmeg (int context, int vaddr)
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{
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static unsigned char curr_pmeg = 128;
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int i;
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/* Round address to PMEG boundary. */
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vaddr &= ~SUN3_PMEG_MASK;
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/* Find a spare one. */
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while (pmeg_alloc[curr_pmeg] == 2)
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++curr_pmeg;
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#ifdef DEBUG_MMU_EMU
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printk("mmu_emu_map_pmeg: pmeg %x to context %d vaddr %x\n",
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curr_pmeg, context, vaddr);
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#endif
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/* Invalidate old mapping for the pmeg, if any */
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if (pmeg_alloc[curr_pmeg] == 1) {
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sun3_put_context(pmeg_ctx[curr_pmeg]);
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sun3_put_segmap (pmeg_vaddr[curr_pmeg], SUN3_INVALID_PMEG);
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sun3_put_context(context);
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}
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/* Update PMEG management structures. */
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// don't take pmeg's away from the kernel...
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if(vaddr >= PAGE_OFFSET) {
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/* map kernel pmegs into all contexts */
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unsigned char i;
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for(i = 0; i < CONTEXTS_NUM; i++) {
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sun3_put_context(i);
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sun3_put_segmap (vaddr, curr_pmeg);
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}
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sun3_put_context(context);
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pmeg_alloc[curr_pmeg] = 2;
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pmeg_ctx[curr_pmeg] = 0;
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}
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else {
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pmeg_alloc[curr_pmeg] = 1;
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pmeg_ctx[curr_pmeg] = context;
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sun3_put_segmap (vaddr, curr_pmeg);
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}
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pmeg_vaddr[curr_pmeg] = vaddr;
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/* Set hardware mapping and clear the old PTE entries. */
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for (i=0; i<SUN3_PMEG_SIZE; i+=SUN3_PTE_SIZE)
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sun3_put_pte (vaddr + i, SUN3_PAGE_SYSTEM);
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/* Consider a different one next time. */
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++curr_pmeg;
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}
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/*
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* Handle a pagefault at virtual address `vaddr'; check if there should be a
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* page there (specifically, whether the software pagetables indicate that
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* there is). This is necessary due to the limited size of the second-level
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* Sun3 hardware pagetables (256 groups of 16 pages). If there should be a
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* mapping present, we select a `spare' PMEG and use it to create a mapping.
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* `read_flag' is nonzero for a read fault; zero for a write. Returns nonzero
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* if we successfully handled the fault.
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*/
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//todo: should we bump minor pagefault counter? if so, here or in caller?
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//todo: possibly inline this into bus_error030 in <asm/buserror.h> ?
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// kernel_fault is set when a kernel page couldn't be demand mapped,
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// and forces another try using the kernel page table. basically a
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// hack so that vmalloc would work correctly.
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int mmu_emu_handle_fault (unsigned long vaddr, int read_flag, int kernel_fault)
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{
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unsigned long segment, offset;
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unsigned char context;
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pte_t *pte;
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|
pgd_t * crp;
|
||
|
|
|
||
|
|
if(current->mm == NULL) {
|
||
|
|
crp = swapper_pg_dir;
|
||
|
|
context = 0;
|
||
|
|
} else {
|
||
|
|
context = current->mm->context;
|
||
|
|
if(kernel_fault)
|
||
|
|
crp = swapper_pg_dir;
|
||
|
|
else
|
||
|
|
crp = current->mm->pgd;
|
||
|
|
}
|
||
|
|
|
||
|
|
#ifdef DEBUG_MMU_EMU
|
||
|
|
printk ("mmu_emu_handle_fault: vaddr=%lx type=%s crp=%p\n",
|
||
|
|
vaddr, read_flag ? "read" : "write", crp);
|
||
|
|
#endif
|
||
|
|
|
||
|
|
segment = (vaddr >> SUN3_PMEG_SIZE_BITS) & 0x7FF;
|
||
|
|
offset = (vaddr >> SUN3_PTE_SIZE_BITS) & 0xF;
|
||
|
|
|
||
|
|
#ifdef DEBUG_MMU_EMU
|
||
|
|
printk ("mmu_emu_handle_fault: segment=%lx offset=%lx\n", segment, offset);
|
||
|
|
#endif
|
||
|
|
|
||
|
|
pte = (pte_t *) pgd_val (*(crp + segment));
|
||
|
|
|
||
|
|
//todo: next line should check for valid pmd properly.
|
||
|
|
if (!pte) {
|
||
|
|
// printk ("mmu_emu_handle_fault: invalid pmd\n");
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
pte = (pte_t *) __va ((unsigned long)(pte + offset));
|
||
|
|
|
||
|
|
/* Make sure this is a valid page */
|
||
|
|
if (!(pte_val (*pte) & SUN3_PAGE_VALID))
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
/* Make sure there's a pmeg allocated for the page */
|
||
|
|
if (sun3_get_segmap (vaddr&~SUN3_PMEG_MASK) == SUN3_INVALID_PMEG)
|
||
|
|
mmu_emu_map_pmeg (context, vaddr);
|
||
|
|
|
||
|
|
/* Write the pte value to hardware MMU */
|
||
|
|
sun3_put_pte (vaddr&PAGE_MASK, pte_val (*pte));
|
||
|
|
|
||
|
|
/* Update software copy of the pte value */
|
||
|
|
// I'm not sure this is necessary. If this is required, we ought to simply
|
||
|
|
// copy this out when we reuse the PMEG or at some other convenient time.
|
||
|
|
// Doing it here is fairly meaningless, anyway, as we only know about the
|
||
|
|
// first access to a given page. --m
|
||
|
|
if (!read_flag) {
|
||
|
|
if (pte_val (*pte) & SUN3_PAGE_WRITEABLE)
|
||
|
|
pte_val (*pte) |= (SUN3_PAGE_ACCESSED
|
||
|
|
| SUN3_PAGE_MODIFIED);
|
||
|
|
else
|
||
|
|
return 0; /* Write-protect error. */
|
||
|
|
} else
|
||
|
|
pte_val (*pte) |= SUN3_PAGE_ACCESSED;
|
||
|
|
|
||
|
|
#ifdef DEBUG_MMU_EMU
|
||
|
|
printk ("seg:%d crp:%p ->", get_fs().seg, crp);
|
||
|
|
print_pte_vaddr (vaddr);
|
||
|
|
printk ("\n");
|
||
|
|
#endif
|
||
|
|
|
||
|
|
return 1;
|
||
|
|
}
|