source: rtems/c/src/lib/libbsp/powerpc/shared/bootloader/mm.c @ 116633f

/*
 *  mm.c -- Crude memory management for early boot.
 *
 *  Copyright (C) 1998, 1999 Gabriel Paubert, paubert@iram.es
 *
 *  Modified to compile in RTEMS development environment
 *  by Eric Valette
 *
 *  Copyright (C) 1999 Eric Valette. valette@crf.canon.fr
 *
 *  The license and distribution terms for this file may be
 *  found in found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 * $Id$
 */

/* This code is a crude memory manager for early boot for LinuxPPC.
 * As such, it does not try to perform many optimiztions depending
 * on the processor, it only uses features which are common to
 * all processors (no BATs...).
 *
 * On PreP platorms (the only ones on which it works for now),
 * it maps 1:1 all RAM/ROM and I/O space as claimed by the
 * residual data. The holes between these areas can be virtually
 * remapped to any of these, since for some functions it is very handy
 * to have virtually contiguous but physically discontiguous memory.
 * 
 * Physical memory allocation is also very crude, since it's only
 * designed to manage a small number of large chunks. For valloc/vfree
 * and palloc/pfree, the unit of allocation is the 4kB page.
 * 
 * The salloc/sfree has been added after tracing gunzip and seeing
 * how it performed a very large number of small allocations.
 * For these the unit of allocation is 8 bytes (the s stands for
 * small or subpage). This memory is cleared when allocated. 
 * 
 */

#include <rtems/bspIo.h>

#include <sys/types.h>
#include <libcpu/spr.h>
#include "bootldr.h"
#include <libcpu/mmu.h>
#include <libcpu/page.h>
#include <limits.h>

/* We use our own kind of simple memory areas for the loader, but
 * we want to avoid potential clashes with kernel includes.
 * Here a map maps contiguous areas from base to end,
 * the firstpte entry corresponds to physical address and has the low
 * order bits set for caching and permission. 
 */

typedef struct _map {
        struct _map *next;
        u_long base;
        u_long end;
        u_long firstpte;
} map;

/* The LSB of the firstpte entries on map lists other than mappings
 * are constants which can be checked for debugging. All these constants
 * have bit of weight 4 set, this bit is zero in the mappings list entries.
 * Actually firstpte&7 value is:
 * - 0 or 1 should not happen
 * - 2 for RW actual virtual->physical mappings
 * - 3 for RO actual virtual->physical mappings
 * - 6 for free areas to be suballocated by salloc
 * - 7 for salloc'ated areas
 * - 4 or 5 for all others, in this case firtpte & 63 is
 *   - 4 for unused maps (on the free list)
 *   - 12 for free physical memory
 *   - 13 for physical memory in use
 *   - 20 for free virtual address space
 *   - 21 for allocated virtual address space
 *   - 28 for physical memory space suballocated by salloc
 *   - 29 for physical memory that can't be freed
 */

#define MAP_FREE_SUBS 6
#define MAP_USED_SUBS 7

#define MAP_FREE 4      
#define MAP_FREE_PHYS 12
#define MAP_USED_PHYS 13
#define MAP_FREE_VIRT 20
#define MAP_USED_VIRT 21
#define MAP_SUBS_PHYS 28
#define MAP_PERM_PHYS 29

SPR_RW(SDR1);
SPR_RO(DSISR);
SPR_RO(DAR);

/* We need a few statically allocated free maps to bootstrap the
 * memory managment */
static map free_maps[4] = {{free_maps+1, 0, 0, MAP_FREE},
                           {free_maps+2, 0, 0, MAP_FREE},
                           {free_maps+3, 0, 0, MAP_FREE},
                           {NULL, 0, 0, MAP_FREE}};
struct _mm_private {
        void *sdr1;
        u_long hashmask;
        map *freemaps;     /* Pool of unused map structs */
        map *mappings;     /* Sorted list of virtual->physical mappings */
        map *physavail;    /* Unallocated physical address space */
        map *physused;     /* Allocated physical address space */
        map *physperm;     /* Permanently allocated physical space */
        map *virtavail;    /* Unallocated virtual address space */
        map *virtused;     /* Allocated virtual address space */
        map *sallocfree;   /* Free maps for salloc */
        map *sallocused;   /* Used maps for salloc */
        map *sallocphys;   /* Physical areas used by salloc */
        u_int hashcnt;     /* Used to cycle in PTEG when they overflow */
} mm_private = {hashmask: 0xffc0, 
                freemaps: free_maps+0};

/* A simplified hash table entry declaration */
typedef struct _hash_entry {
        int key;
        u_long rpn;
} hash_entry;

void print_maps(map *, const char *);

/* The handler used for all exceptions although for now it is only 
 * designed to properly handle MMU interrupts to fill the hash table.
 */


void _handler(int vec, ctxt *p) {
        map *area;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        u_long vaddr, cause;
        if (vec==4 || vec==7) { /* ISI exceptions are different */
                vaddr = p->nip;
                cause = p->msr;
        } else { /* Valid for DSI and alignment exceptions */
                vaddr = _read_DAR();
                cause = _read_DSISR();
        }

        if (vec==3 || vec==4) {
                /* Panic if the fault is not PTE not found. */
                if (!(cause & 0x40000000)) {
                        MMUon();
                        printk("\nPanic: vector=%x, cause=%lx\n", vec, cause);
                        hang("Memory protection violation at ", vaddr, p);
                }
                
                for(area=mm->mappings; area; area=area->next) {
                        if(area->base<=vaddr && vaddr<=area->end) break;
                }

                if (area) {
                        u_long hash, vsid, rpn;
                        hash_entry volatile *hte, *_hte1;
                        u_int i, alt=0, flushva;
                
                        vsid = _read_SR((void *)vaddr);
                        rpn = (vaddr&PAGE_MASK)-area->base+area->firstpte;
                        hash = vsid<<6;
                        hash ^= (vaddr>>(PAGE_SHIFT-6))&0x3fffc0;
                        hash &= mm->hashmask;
                        /* Find an empty entry in the PTEG, else 
                         * replace a random one.
                         */
                        hte = (hash_entry *) ((u_long)(mm->sdr1)+hash);
                        for (i=0; i<8; i++) {
                                if (hte[i].key>=0) goto found;
                        }
                        hash ^= mm->hashmask;
                        alt = 0x40; _hte1 = hte;
                        hte = (hash_entry *) ((u_long)(mm->sdr1)+hash);
                        
                        for (i=0; i<8; i++) {
                                if (hte[i].key>=0) goto found;
                        }
                        alt = 0;
                        hte = _hte1;
                        /* Chose a victim entry and replace it. There might be
                         * better policies to choose the victim, but in a boot 
                         * loader we want simplicity as long as it works.
                         *
                         * We would not need to invalidate the TLB entry since
                         * the mapping is still valid. But this would be a mess
                         * when unmapping so we make sure that the TLB is a
                         * subset of the hash table under all circumstances.
                         */
                        i = mm->hashcnt;
                        mm->hashcnt = (mm->hashcnt+1)%8;
                        /* Note that the hash is already complemented here ! */
                        flushva = (~(hash<<9)^((hte[i].key)<<5)) &0x3ff000;
                        if (hte[i].key&0x40) flushva^=0x3ff000;
                        flushva |= ((hte[i].key<<21)&0xf0000000)
                          | ((hte[i].key<<22)&0x0fc00000);
                        hte[i].key=0;
                        asm volatile("sync; tlbie %0; sync" : : "r" (flushva));
                found:
                        hte[i].rpn = rpn;
                        asm volatile("eieio": : );
                        hte[i].key = 0x80000000|(vsid<<7)|alt|
                          ((vaddr>>22)&0x3f);
                        return;
                } else {
                        MMUon();
                        printk("\nPanic: vector=%x, cause=%lx\n", vec, cause);
                        hang("\nInvalid memory access attempt at ", vaddr, p);
                }
        } else {
          MMUon();
          printk("\nPanic: vector=%x, dsisr=%lx, faultaddr =%lx, msr=%lx opcode=%lx\n", vec, 
                 cause, p->nip, p->msr, * ((unsigned int*) p->nip) );
          if (vec == 7) {
            unsigned int* ptr = ((unsigned int*) p->nip) - 4 * 10;
            for (; ptr <= (((unsigned int*) p->nip) + 4 * 10); ptr ++)
              printk("Hexdecimal code at address %x = %x\n", ptr, *ptr);
          }
          hang("Program or alignment exception at ", vaddr, p);
        }
}

/* Generic routines for map handling.
 */

static inline
void free_map(map *p) {
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        if (!p) return;
        p->next=mm->freemaps;
        mm->freemaps=p;
        p->firstpte=MAP_FREE;
}

/* Sorted insertion in linked list */
static
int insert_map(map **head, map *p) {
        map *q = *head;
        if (!p) return 0;
        if (q && (q->base < p->base)) {
                for(;q->next && q->next->base<p->base; q = q->next);
                if ((q->end >= p->base) ||
                    (q->next && p->end>=q->next->base)) {
                        free_map(p);
                        printk("Overlapping areas!\n");
                        return 1;
                }
                p->next = q->next;
                q->next = p;
        } else { /* Insert at head */
                if (q && (p->end >= q->base)) {
                        free_map(p);
                        printk("Overlapping areas!\n");
                        return 1;
                }
                p->next = q;
                *head = p;
        }
        return 0;
}


/* Removal from linked list */

static
map *remove_map(map **head, map *p) {
        map *q = *head;

        if (!p || !q) return NULL;
        if (q==p) {
                *head = q->next;
                return p;
        }
        for(;q && q->next!=p; q=q->next);
        if (q) {
                q->next=p->next;
                return p;
        } else {
                return NULL;
        }
}

static
map *remove_map_at(map **head, void * vaddr) {
        map *p, *q = *head;

        if (!vaddr || !q) return NULL;
        if (q->base==(u_long)vaddr) {
                *head = q->next;
                return q;
        }
        while (q->next && q->next->base != (u_long)vaddr) q=q->next;
        p=q->next;
        if (p) q->next=p->next;
        return p;
}

static inline
map * alloc_map_page(void) {
        map *from, *p;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;

        /* printk("Allocating new map page !"); */
        /* Get the highest page */
        for (from=mm->physavail; from && from->next; from=from->next);
        if (!from) return NULL;

        from->end -= PAGE_SIZE;
        
        mm->freemaps = (map *) (from->end+1);
        
        for(p=mm->freemaps; p<mm->freemaps+PAGE_SIZE/sizeof(map)-1; p++) {
                p->next = p+1;
                p->firstpte = MAP_FREE;
        }  
        (p-1)->next=0;

        /* Take the last one as pointer to self and insert
         * the map into the permanent map list.
         */

        p->firstpte = MAP_PERM_PHYS;
        p->base=(u_long) mm->freemaps;
        p->end = p->base+PAGE_SIZE-1;
        
        insert_map(&mm->physperm, p);
        
        if (from->end+1 == from->base) 
                free_map(remove_map(&mm->physavail, from));
        
        return mm->freemaps;
}

static
map * alloc_map(void) {
        map *p;
        struct _mm_private * mm = (struct _mm_private *) bd->mm_private;

        p = mm->freemaps;
        if (!p) {
                p=alloc_map_page();
        }

        if(p) mm->freemaps=p->next;

        return p;
}

static
void coalesce_maps(map *p) {
        while(p) {
                if (p->next && (p->end+1 == p->next->base)) {
                        map *q=p->next;
                        p->end=q->end;
                        p->next=q->next;
                        free_map(q);
                } else {
                        p = p->next;
                }
        }
}

/* These routines are used to find the free memory zones to avoid
 * overlapping destructive copies when initializing.
 * They work from the top because of the way we want to boot. 
 * In the following the term zone refers to the memory described
 * by one or several contiguous so called segments in the
 * residual data.
 */
#define STACK_PAGES 2
static inline u_long 
find_next_zone(RESIDUAL *res, u_long lowpage, u_long flags) {
        u_long i, newmin=0, size=0;
        for(i=0; i<res->ActualNumMemSegs; i++) {
                if (res->Segs[i].Usage & flags
                    && res->Segs[i].BasePage<lowpage
                    && res->Segs[i].BasePage>newmin) {
                        newmin=res->Segs[i].BasePage;
                        size=res->Segs[i].PageCount;
                }
        }
        return newmin+size;
}

static inline u_long 
find_zone_start(RESIDUAL *res, u_long highpage, u_long flags) {
        u_long i;
        int progress;
        do {
                progress=0;
                for (i=0; i<res->ActualNumMemSegs; i++) {
                        if ( (res->Segs[i].BasePage+res->Segs[i].PageCount 
                              == highpage)
                             && res->Segs[i].Usage & flags) {
                                highpage=res->Segs[i].BasePage;
                                progress=1;
                        }
                }
        } while(progress);
        return highpage;
}

/* The Motorola NT firmware does not provide any setting in the residual
 * data about memory segment usage. The following table provides enough
 * info so that this bootloader can work.
 */
MEM_MAP seg_fix[] = {
    { 0x2000, 0xFFF00, 0x00100 },
    { 0x0020, 0x02000, 0x7E000 },
    { 0x0008, 0x00800, 0x00168 },
    { 0x0004, 0x00000, 0x00005 },
    { 0x0001, 0x006F1, 0x0010F },
    { 0x0002, 0x006AD, 0x00044 },
    { 0x0010, 0x00005, 0x006A8 },
    { 0x0010, 0x00968, 0x00698 },
    { 0x0800, 0xC0000, 0x3F000 },
    { 0x0600, 0xBF800, 0x00800 },
    { 0x0500, 0x81000, 0x3E800 },
    { 0x0480, 0x80800, 0x00800 },
    { 0x0440, 0x80000, 0x00800 } };


/* The Motorola NT firmware does not set up all required info in the residual
 * data. This routine changes some things in a way that the bootloader and
 * linux are happy.
 */
void
fix_residual( RESIDUAL *res )
{
#if 0
    PPC_DEVICE *hostbridge;
#endif
    int i;

    /* Missing memory segment information */
    res->ActualNumMemSegs = sizeof(seg_fix)/sizeof(MEM_MAP);
    for (i=0; i<res->ActualNumMemSegs; i++) {
        res->Segs[i].Usage = seg_fix[i].Usage;
        res->Segs[i].BasePage = seg_fix[i].BasePage;
        res->Segs[i].PageCount = seg_fix[i].PageCount;
    }
    /* The following should be fixed in the current version of the 
     * kernel and of the bootloader. 
     */
#if 0
    /* PPCBug has this zero */
    res->VitalProductData.CacheLineSize = 0;
    /* Motorola NT firmware sets TimeBaseDivisor to 0 */
    if ( res->VitalProductData.TimeBaseDivisor == 0 ) {
        res->VitalProductData.TimeBaseDivisor = 4000;
    }

    /* Motorola NT firmware records the PCIBridge as a "PCIDEVICE" and
     * sets "PCIBridgeDirect". This bootloader and linux works better if
     * BusId = "PROCESSORDEVICE" and Interface = "PCIBridgeIndirect".
     */
    hostbridge=residual_find_device(PCIDEVICE, NULL,
                                        BridgeController,
                                        PCIBridge, -1, 0);
    if (hostbridge) {
        hostbridge->DeviceId.BusId = PROCESSORDEVICE;
        hostbridge->DeviceId.Interface = PCIBridgeIndirect;
    }
#endif
}

/* This routine is the first C code called with very little stack space!
 * Its goal is to find where the boot image can be moved. This will
 * be the highest address with enough room. 
 */
int early_setup(u_long image_size) {
        register RESIDUAL *res = bd->residual; 
        u_long minpages = PAGE_ALIGN(image_size)>>PAGE_SHIFT;

        /* Fix residual if we are loaded by Motorola NT firmware */
        if ( res && res->VitalProductData.FirmwareSupplier == 0x10000 )
            fix_residual( res );

        /* FIXME: if OF we should do something different */
        if( !bd->of_entry && res &&
           res->ResidualLength <= sizeof(RESIDUAL) && res->Version == 0 ) {
                u_long lowpage=ULONG_MAX, highpage; 
                u_long imghigh=0, stkhigh=0;
                /* Find the highest and large enough contiguous zone 
                   consisting of free and BootImage sections. */
                /* Find 3 free areas of memory, one for the main image, one 
                 * for the stack (STACK_PAGES), and page one to put the map  
                 * structures. They are allocated from the top of memory. 
                 * In most cases the stack will be put just below the image.
                 */
                while((highpage = 
                       find_next_zone(res, lowpage, BootImage|Free))) {
                        lowpage=find_zone_start(res, highpage, BootImage|Free);
                        if ((highpage-lowpage)>minpages && 
                            highpage>imghigh) {
                                imghigh=highpage;
                                highpage -=minpages;
                        }
                        if ((highpage-lowpage)>STACK_PAGES &&
                            highpage>stkhigh) {
                                stkhigh=highpage;
                                highpage-=STACK_PAGES;
                        }
                }

                bd->image = (void *)((imghigh-minpages)<<PAGE_SHIFT);
                bd->stack=(void *) (stkhigh<<PAGE_SHIFT);

                /* The code mover is put at the lowest possible place
                 * of free memory. If this corresponds to the loaded boot
                 * partition image it does not matter because it overrides 
                 * the unused part of it (x86 code). 
                 */
                bd->mover=(void *) (lowpage<<PAGE_SHIFT);

                /* Let us flush the caches in all cases. After all it should 
                 * not harm even on 601 and we don't care about performance. 
                 * Right now it's easy since all processors have a line size 
                 * of 32 bytes. Once again residual data has proved unreliable.
                 */
                bd->cache_lsize = 32;
        }
        /* For now we always assume that it's succesful, we should
         * handle better the case of insufficient memory.
         */
        return 0;
}

void * valloc(u_long size) {
        map *p, *q;
        struct _mm_private * mm = (struct _mm_private *) bd->mm_private;

        if (size==0) return NULL;
        size=PAGE_ALIGN(size)-1;
        for (p=mm->virtavail; p; p=p->next) {
                if (p->base+size <= p->end) break;
        }
        if(!p) return NULL;
        q=alloc_map();
        q->base=p->base;
        q->end=q->base+size;
        q->firstpte=MAP_USED_VIRT;
        insert_map(&mm->virtused, q);
        if (q->end==p->end) free_map(remove_map(&mm->virtavail, p));
        else p->base += size+1;
        return (void *)q->base;
}

static 
void vflush(map *virtmap) {
        struct _mm_private * mm = (struct _mm_private *) bd->mm_private;
        u_long i, limit=(mm->hashmask>>3)+8;
        hash_entry volatile *p=(hash_entry *) mm->sdr1;

        /* PTE handling is simple since the processor never update
         * the entries. Writable pages always have the C bit set and 
         * all valid entries have the R bit set. From the processor
         * point of view the hash table is read only.
         */
        for (i=0; i<limit; i++) {
                if (p[i].key<0) {
                        u_long va;
                        va = ((i<<9)^((p[i].key)<<5)) &0x3ff000;
                        if (p[i].key&0x40) va^=0x3ff000;
                        va |= ((p[i].key<<21)&0xf0000000)
                          | ((p[i].key<<22)&0x0fc00000);
                        if (va>=virtmap->base && va<=virtmap->end) {
                                p[i].key=0;
                                asm volatile("sync; tlbie %0; sync" : :
                                             "r" (va));
                        }
                }
        }
}

void vfree(void *vaddr) {
        map *physmap, *virtmap; /* Actual mappings pertaining to this vm */
        struct _mm_private * mm = (struct _mm_private *) bd->mm_private;
        
        /* Flush memory queues */
        asm volatile("sync": : : "memory");

        virtmap = remove_map_at(&mm->virtused, vaddr);
        if (!virtmap) return;

        /* Remove mappings corresponding to virtmap */
        for (physmap=mm->mappings; physmap; ) {
                map *nextmap=physmap->next;
                if (physmap->base>=virtmap->base 
                    && physmap->base<virtmap->end) {
                        free_map(remove_map(&mm->mappings, physmap));
                }
                physmap=nextmap;
        }

        vflush(virtmap);

        virtmap->firstpte= MAP_FREE_VIRT;
        insert_map(&mm->virtavail, virtmap); 
        coalesce_maps(mm->virtavail);
}

void vunmap(void *vaddr) {
        map *physmap, *virtmap; /* Actual mappings pertaining to this vm */
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        
        /* Flush memory queues */
        asm volatile("sync": : : "memory");

        /* vaddr must be within one of the vm areas in use and
         * then must correspond to one of the physical areas 
         */
        for (virtmap=mm->virtused; virtmap; virtmap=virtmap->next) {
                if (virtmap->base<=(u_long)vaddr && 
                    virtmap->end>=(u_long)vaddr) break;
        }
        if (!virtmap) return;

        physmap = remove_map_at(&mm->mappings, vaddr);
        if(!physmap) return;
        vflush(physmap);
        free_map(physmap);
}

int vmap(void *vaddr, u_long p, u_long size) {
        map *q;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;

        size=PAGE_ALIGN(size);
        if(!size) return 1;
        /* Check that the requested area fits in one vm image */
        for (q=mm->virtused; q; q=q->next) {
                if ((q->base <= (u_long)vaddr) && 
                    (q->end>=(u_long)vaddr+size -1)) break;
        }
        if (!q) return 1;
        q= alloc_map();
        if (!q) return 1;
        q->base = (u_long)vaddr;
        q->end = (u_long)vaddr+size-1;
        q->firstpte = p;
        return insert_map(&mm->mappings, q);
}

static
void create_identity_mappings(int type, int attr) {
        u_long lowpage=ULONG_MAX, highpage;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        RESIDUAL * res=bd->residual;

        while((highpage = find_next_zone(res, lowpage, type))) {
                map *p;
                lowpage=find_zone_start(res, highpage, type);
                p=alloc_map();
                /* Do not map page 0 to catch null pointers */
                lowpage = lowpage ? lowpage : 1;
                p->base=lowpage<<PAGE_SHIFT;
                p->end=(highpage<<PAGE_SHIFT)-1;
                p->firstpte = (lowpage<<PAGE_SHIFT)|attr;
                insert_map(&mm->mappings, p);
        }
}

static inline
void add_free_map(u_long base, u_long end) {
        map *q=NULL;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;

        if (base<end) q=alloc_map();
        if (!q) return;
        q->base=base;
        q->end=end-1;
        q->firstpte=MAP_FREE_VIRT;
        insert_map(&mm->virtavail, q); 
}

static inline
void create_free_vm(void) {
        map *p;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;

        u_long vaddr=PAGE_SIZE; /* Never map vaddr 0 */
        for(p=mm->mappings; p; p=p->next) {
                add_free_map(vaddr, p->base);
                vaddr=p->end+1;
        }
        /* Special end of memory case */
        if (vaddr) add_free_map(vaddr,0);
}

/* Memory management initialization.
 * Set up the mapping lists. 
 */

static inline 
void add_perm_map(u_long start, u_long size) {
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        map *p=alloc_map();
        p->base = start;
        p->end = start + size - 1;
        p->firstpte = MAP_PERM_PHYS;
        insert_map(& mm->physperm , p);
}

void mm_init(u_long image_size) 
{
        u_long lowpage=ULONG_MAX, highpage;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        RESIDUAL * res=bd->residual;
        extern void (tlb_handlers)(void);
        extern void (_handler_glue)(void);
        int i;
        map *p;

        /* The checks are simplified by the fact that the image
         * and stack area are always allocated at the upper end
         * of a free block. 
         */
        while((highpage = find_next_zone(res, lowpage, BootImage|Free))) {
                lowpage=find_zone_start(res, highpage, BootImage|Free);
                if ( ( ((u_long)bd->image+PAGE_ALIGN(image_size))>>PAGE_SHIFT)
                     == highpage) {
                        highpage=(u_long)(bd->image)>>PAGE_SHIFT;
                        add_perm_map((u_long)bd->image, image_size);
                }
                if ( (( u_long)bd->stack>>PAGE_SHIFT) == highpage) {
                        highpage -= STACK_PAGES;
                        add_perm_map(highpage<<PAGE_SHIFT, 
                                     STACK_PAGES*PAGE_SIZE);
                }
                /* Protect the interrupt handlers that we need ! */
                if (lowpage<2) lowpage=2;
                /* Check for the special case of full area! */
                if (highpage>lowpage) {
                        p = alloc_map();
                        p->base = lowpage<<PAGE_SHIFT;
                        p->end = (highpage<<PAGE_SHIFT)-1;
                        p->firstpte=MAP_FREE_PHYS;
                        insert_map(&mm->physavail, p);
                }
        }

        /* Allocate the hash table */
        mm->sdr1=__palloc(0x10000, PA_PERM|16);
        _write_SDR1((u_long)mm->sdr1);
        memset(mm->sdr1, 0, 0x10000);
        mm->hashmask = 0xffc0;

        /* Setup the segment registers as we want them */
        for (i=0; i<16; i++) _write_SR(i, (void *)(i<<28));
        /* Create the maps for the physical memory, firwmarecode does not
         * seem to be necessary. ROM is mapped read-only to reduce the risk 
         * of reprogramming it because it's often Flash and some are 
         * amazingly easy to overwrite.
         */
        create_identity_mappings(BootImage|Free|FirmwareCode|FirmwareHeap|
                                 FirmwareStack, PTE_RAM);
        create_identity_mappings(SystemROM, PTE_ROM);
        create_identity_mappings(IOMemory|SystemIO|SystemRegs|
                                 PCIAddr|PCIConfig|ISAAddr, PTE_IO);

        create_free_vm();
        
        /* Install our own MMU and trap handlers. */
        codemove((void *) 0x300, _handler_glue, 0x100, bd->cache_lsize); 
        codemove((void *) 0x400, _handler_glue, 0x100, bd->cache_lsize); 
        codemove((void *) 0x600, _handler_glue, 0x100, bd->cache_lsize); 
        codemove((void *) 0x700, _handler_glue, 0x100, bd->cache_lsize); 
}
  
void * salloc(u_long size) {
        map *p, *q;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;

        if (size==0) return NULL;

        size = (size+7)&~7;

        for (p=mm->sallocfree; p; p=p->next) {
                if (p->base+size <= p->end) break;
        }
        if(!p) {
                void *m;
                m = __palloc(size, PA_SUBALLOC);
                p = alloc_map();
                if (!m && !p) return NULL;
                p->base = (u_long) m;
                p->firstpte = MAP_FREE_SUBS;
                p->end = (u_long)m+PAGE_ALIGN(size)-1;
                insert_map(&mm->sallocfree, p);
                coalesce_maps(mm->sallocfree);
                coalesce_maps(mm->sallocphys);
        };
        q=alloc_map();
        q->base=p->base;
        q->end=q->base+size-1;
        q->firstpte=MAP_USED_SUBS;
        insert_map(&mm->sallocused, q);
        if (q->end==p->end) free_map(remove_map(&mm->sallocfree, p));
        else p->base += size;
        memset((void *)q->base, 0, size);
        return (void *)q->base;
}

void sfree(void *p) {
        map *q;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;

        q=remove_map_at(&mm->sallocused, p);
        if (!q) return;
        q->firstpte=MAP_FREE_SUBS;
        insert_map(&mm->sallocfree, q);
        coalesce_maps(mm->sallocfree);
}

/* first/last area fit, flags is a power of 2 indicating the required
 * alignment. The algorithms are stupid because we expect very little 
 * fragmentation of the areas, if any. The unit of allocation is the page.
 * The allocation is by default performed from higher addresses down,
 * unless flags&PA_LOW is true. 
 */

void * __palloc(u_long size, int flags) 
{
        u_long mask = ((1<<(flags&PA_ALIGN_MASK))-1);
        map *newmap, *frommap, *p, *splitmap=0;
        map **queue; 
        u_long qflags;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;

        /* Asking for a size which is not a multiple of the alignment
           is likely to be an error. */

        if (size & mask) return NULL;
        size = PAGE_ALIGN(size);
        if(!size) return NULL;

        if (flags&PA_SUBALLOC) {
                queue = &mm->sallocphys;
                qflags = MAP_SUBS_PHYS;
        } else if (flags&PA_PERM) {
                queue = &mm->physperm;
                qflags = MAP_PERM_PHYS;
        } else {
                queue = &mm->physused;
                qflags = MAP_USED_PHYS;
        }
        /* We need to allocate that one now so no two allocations may attempt
         * to take the same memory simultaneously. Alloc_map_page does
         * not call back here to avoid infinite recursion in alloc_map. 
         */

        if (mask&PAGE_MASK) {
                splitmap=alloc_map();
                if (!splitmap) return NULL;
        }

        for (p=mm->physavail, frommap=NULL; p; p=p->next) {
                u_long high = p->end;
                u_long limit  = ((p->base+mask)&~mask) + size-1;
                if (high>=limit && ((p->base+mask)&~mask)+size>p->base) {
                        frommap = p;
                        if (flags&PA_LOW) break;
                }
        }

        if (!frommap) {
                if (splitmap) free_map(splitmap);
                return NULL;  
        }
        
        newmap=alloc_map();
        
        if (flags&PA_LOW) {
                newmap->base = (frommap->base+mask)&~mask;
        } else {
                newmap->base = (frommap->end +1 - size) & ~mask;
        }

        newmap->end = newmap->base+size-1;
        newmap->firstpte = qflags;

        /* Add a fragment if we don't allocate until the end. */
        
        if (splitmap) {
                splitmap->base=newmap->base+size;
                splitmap->end=frommap->end;
                splitmap->firstpte= MAP_FREE_PHYS;
                frommap->end=newmap->base-1;
        } else if (flags & PA_LOW) {
                frommap->base=newmap->base+size;
        } else {
                frommap->end=newmap->base-1;
        }

        /* Remove a fragment if it becomes empty. */
        if (frommap->base == frommap->end+1) {
                free_map(remove_map(&mm->physavail, frommap));
        }

        if (splitmap) {
                if (splitmap->base == splitmap->end+1) {
                        free_map(remove_map(&mm->physavail, splitmap));
                } else {
                        insert_map(&mm->physavail, splitmap);  
                }
        }

        insert_map(queue, newmap);
        return (void *) newmap->base;
                
}

void pfree(void * p) {
        map *q;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        q=remove_map_at(&mm->physused, p);
        if (!q) return;
        q->firstpte=MAP_FREE_PHYS;
        insert_map(&mm->physavail, q);
        coalesce_maps(mm->physavail);
}

#ifdef DEBUG 
/* Debugging functions */
void print_maps(map *chain, const char *s) {
        map *p;
        printk("%s",s);
        for(p=chain; p; p=p->next) {
                printk("    %08lx-%08lx: %08lx\n", 
                       p->base, p->end, p->firstpte);
        }
}

void print_all_maps(const char * s) {
        u_long freemaps;
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        map *free;
        printk("%s",s);
        print_maps(mm->mappings, "  Currently defined mappings:\n");
        print_maps(mm->physavail, "  Currently available physical areas:\n");
        print_maps(mm->physused, "  Currently used physical areas:\n");
        print_maps(mm->virtavail, "  Currently available virtual areas:\n");
        print_maps(mm->virtused, "  Currently used virtual areas:\n");
        print_maps(mm->physperm, "  Permanently used physical areas:\n");
        print_maps(mm->sallocphys, "  Physical memory used for salloc:\n");
        print_maps(mm->sallocfree, "  Memory available for salloc:\n");
        print_maps(mm->sallocused, "  Memory allocated through salloc:\n");
        for (freemaps=0, free=mm->freemaps; free; freemaps++, free=free->next);
        printk("  %ld free maps.\n", freemaps);
}

void print_hash_table(void) {
        struct _mm_private *mm = (struct _mm_private *) bd->mm_private;
        hash_entry *p=(hash_entry *) mm->sdr1;
        u_int i, valid=0;
        for (i=0; i<((mm->hashmask)>>3)+8; i++) {
                if (p[i].key<0) valid++;
        }
        printk("%u valid hash entries on pass 1.\n", valid);
        valid = 0;
        for (i=0; i<((mm->hashmask)>>3)+8; i++) {
                if (p[i].key<0) valid++;
        }
        printk("%u valid hash entries on pass 2.\n"
               "     vpn:rpn_attr, p/s, pteg.i\n", valid);
        for (i=0; i<((mm->hashmask)>>3)+8; i++) {
                if (p[i].key<0) {
                        u_int pteg=(i>>3);
                        u_long vpn;
                        vpn = (pteg^((p[i].key)>>7)) &0x3ff;
                        if (p[i].key&0x40) vpn^=0x3ff;
                        vpn |= ((p[i].key<<9)&0xffff0000)
                          | ((p[i].key<<10)&0xfc00);
                        printk("%08lx:%08lx, %s, %5d.%d\n",
                               vpn,  p[i].rpn, p[i].key&0x40 ? "sec" : "pri",
                               pteg, i%8);
                }
        }
}

#endif