/*
 *      linux/mm/mmap.c
 *
 * Written by obz.
 */
#include <linux/stat.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/shm.h>
#include <linux/errno.h>
#include <linux/mman.h>
#include <linux/string.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>

#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/pgtable.h>

/* description of effects of mapping type and prot in current implementation.
 * this is due to the limited x86 page protection hardware.  The expected
 * behavior is in parens:
 *
 * map_type     prot
 *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
 * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
 *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 *              
 * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
 *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 *
 */
pgprot_t protection_map[16] = {
        __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
        __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
};

/* SLAB cache for vm_area_struct's. */
kmem_cache_t *vm_area_cachep;

int sysctl_overcommit_memory;

/* Check that a process has enough memory to allocate a
 * new virtual mapping.
 */
static inline int vm_enough_memory(long pages)
{
        /* Stupid algorithm to decide if we have enough memory: while
         * simple, it hopefully works in most obvious cases.. Easy to
         * fool it, but this should catch most mistakes.
         */
        long freepages;
        
        /* Sometimes we want to use more memory than we have. */
        if (sysctl_overcommit_memory)
            return 1;

        freepages = buffermem >> PAGE_SHIFT;
        freepages += page_cache_size;
        freepages >>= 1;
        freepages += nr_free_pages;
        freepages += nr_swap_pages;
        freepages -= num_physpages >> 4;
        return freepages > pages;
}

/* Remove one vm structure from the inode's i_mmap ring. */
static inline void remove_shared_vm_struct(struct vm_area_struct *vma)
{
        struct dentry * dentry = vma->vm_dentry;

        if (dentry) {
                if (vma->vm_flags & VM_DENYWRITE)
                        dentry->d_inode->i_writecount++;
                if(vma->vm_next_share)
                        vma->vm_next_share->vm_pprev_share = vma->vm_pprev_share;
                *vma->vm_pprev_share = vma->vm_next_share;
        }
}

asmlinkage unsigned long sys_brk(unsigned long brk)
{
        unsigned long rlim, retval;
        unsigned long newbrk, oldbrk;
        struct mm_struct *mm = current->mm;

        lock_kernel();
        retval = mm->brk;
        if (brk < mm->end_code)
                goto out;
        newbrk = PAGE_ALIGN(brk);
        oldbrk = PAGE_ALIGN(mm->brk);
        if (oldbrk == newbrk) {
                retval = mm->brk = brk;
                goto out;
        }

        /* Always allow shrinking brk. */
        if (brk <= mm->brk) {
                retval = mm->brk = brk;
                do_munmap(newbrk, oldbrk-newbrk);
                goto out;
        }

        /* Check against rlimit and stack.. */
        retval = mm->brk;
        rlim = current->rlim[RLIMIT_DATA].rlim_cur;
        if (rlim >= RLIM_INFINITY)
                rlim = ~0;
        if (brk - mm->end_code > rlim)
                goto out;

        /* Check against existing mmap mappings. */
        if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
                goto out;

        /* Check if we have enough memory.. */
        if (!vm_enough_memory((newbrk-oldbrk) >> PAGE_SHIFT))
                goto out;

        /* Ok, looks good - let it rip. */
        if(do_mmap(NULL, oldbrk, newbrk-oldbrk,
                   PROT_READ|PROT_WRITE|PROT_EXEC,
                   MAP_FIXED|MAP_PRIVATE, 0) == oldbrk)
                mm->brk = brk;
        retval = mm->brk;
out:
        unlock_kernel();
        return retval;
}

/* Combine the mmap "prot" and "flags" argument into one "vm_flags" used
 * internally. Essentially, translate the "PROT_xxx" and "MAP_xxx" bits
 * into "VM_xxx".
 */
static inline unsigned long vm_flags(unsigned long prot, unsigned long flags)
{
#define _trans(x,bit1,bit2) \
((bit1==bit2)?(x&bit1):(x&bit1)?bit2:0)

        unsigned long prot_bits, flag_bits;
        prot_bits =
                _trans(prot, PROT_READ, VM_READ) |
                _trans(prot, PROT_WRITE, VM_WRITE) |
                _trans(prot, PROT_EXEC, VM_EXEC);
        flag_bits =
                _trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN) |
                _trans(flags, MAP_DENYWRITE, VM_DENYWRITE) |
                _trans(flags, MAP_EXECUTABLE, VM_EXECUTABLE);
        return prot_bits | flag_bits;
#undef _trans
}

unsigned long do_mmap(struct file * file, unsigned long addr, unsigned long len,
        unsigned long prot, unsigned long flags, unsigned long off)
{
        struct mm_struct * mm = current->mm;
        struct vm_area_struct * vma;
        int correct_wcount = 0;

        if ((len = PAGE_ALIGN(len)) == 0)
                return addr;

        if (len > TASK_SIZE || addr > TASK_SIZE-len)
                return -EINVAL;

        /* offset overflow? */
        if (off + len < off)
                return -EINVAL;

        /* mlock MCL_FUTURE? */
        if (mm->def_flags & VM_LOCKED) {
                unsigned long locked = mm->locked_vm << PAGE_SHIFT;
                locked += len;
                if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
                        return -EAGAIN;
        }

        /* Do simple checking here so the lower-level routines won't have
         * to. we assume access permissions have been handled by the open
         * of the memory object, so we don't do any here.
         */
        if (file != NULL) {
                switch (flags & MAP_TYPE) {
                case MAP_SHARED:
                        if ((prot & PROT_WRITE) && !(file->f_mode & 2))
                                return -EACCES;

                        /* make sure there are no mandatory locks on the file. */
                        if (locks_verify_locked(file->f_dentry->d_inode))
                                return -EAGAIN;
                        /* fall through */
                case MAP_PRIVATE:
                        if (!(file->f_mode & 1))
                                return -EACCES;
                        break;

                default:
                        return -EINVAL;
                }
        } else if ((flags & MAP_TYPE) != MAP_PRIVATE)
                return -EINVAL;

        /* Obtain the address to map to. we verify (or select) it and ensure
         * that it represents a valid section of the address space.
         */
        if (flags & MAP_FIXED) {
                if (addr & ~PAGE_MASK)
                        return -EINVAL;
        } else {
                addr = get_unmapped_area(addr, len);
                if (!addr)
                        return -ENOMEM;
        }

        /* Determine the object being mapped and call the appropriate
         * specific mapper. the address has already been validated, but
         * not unmapped, but the maps are removed from the list.
         */
        if (file && (!file->f_op || !file->f_op->mmap))
                return -ENODEV;

        vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
        if (!vma)
                return -ENOMEM;

        vma->vm_mm = mm;
        vma->vm_start = addr;
        vma->vm_end = addr + len;
        vma->vm_flags = vm_flags(prot,flags) | mm->def_flags;

        if (file) {
                if (file->f_mode & 1)
                        vma->vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
                if (flags & MAP_SHARED) {
                        vma->vm_flags |= VM_SHARED | VM_MAYSHARE;

                        /* This looks strange, but when we don't have the file open
                         * for writing, we can demote the shared mapping to a simpler
                         * private mapping. That also takes care of a security hole
                         * with ptrace() writing to a shared mapping without write
                         * permissions.
                         *
                         * We leave the VM_MAYSHARE bit on, just to get correct output
                         * from /proc/xxx/maps..
                         */
                        if (!(file->f_mode & 2))
                                vma->vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
                }
        } else
                vma->vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
        vma->vm_page_prot = protection_map[vma->vm_flags & 0x0f];
        vma->vm_ops = NULL;
        vma->vm_offset = off;
        vma->vm_dentry = NULL;
        vma->vm_pte = 0;

        do_munmap(addr, len);   /* Clear old maps */

        /* Check against address space limit. */
        if ((mm->total_vm << PAGE_SHIFT) + len
            > current->rlim[RLIMIT_AS].rlim_cur) {
                kmem_cache_free(vm_area_cachep, vma);
                return -ENOMEM;
        }

        /* Private writable mapping? Check memory availability.. */
        if ((vma->vm_flags & (VM_SHARED | VM_WRITE)) == VM_WRITE) {
                if (!(flags & MAP_NORESERVE) &&
                    !vm_enough_memory(len >> PAGE_SHIFT)) {
                        kmem_cache_free(vm_area_cachep, vma);
                        return -ENOMEM;
                }
        }

        if (file) {
                int error = 0;
                if (vma->vm_flags & VM_DENYWRITE) {
                        if (file->f_dentry->d_inode->i_writecount > 0)
                                error = -ETXTBSY;
                        else {
                                /* f_op->mmap might possibly sleep
                                 * (generic_file_mmap doesn't, but other code
                                 * might). In any case, this takes care of any
                                 * race that this might cause.
                                 */
                                file->f_dentry->d_inode->i_writecount--;
                                correct_wcount = 1;
                        }
                }
                if (!error)
                        error = file->f_op->mmap(file, vma);
        
                if (error) {
                        if (correct_wcount)
                                file->f_dentry->d_inode->i_writecount++;
                        kmem_cache_free(vm_area_cachep, vma);
                        return error;
                }
        }

        flags = vma->vm_flags;
        insert_vm_struct(mm, vma);
        if (correct_wcount)
                file->f_dentry->d_inode->i_writecount++;
        merge_segments(mm, vma->vm_start, vma->vm_end);
        
        addr = vma->vm_start;

        /* merge_segments might have merged our vma, so we can't use it any more */
        mm->total_vm += len >> PAGE_SHIFT;
        if ((flags & VM_LOCKED) && !(flags & VM_IO)) {
                unsigned long start = addr;
                mm->locked_vm += len >> PAGE_SHIFT;
                do {
                        char c;
                        get_user(c,(char *) start);
                        len -= PAGE_SIZE;
                        start += PAGE_SIZE;
                        __asm__ __volatile__("": :"r" (c));
                } while (len > 0);
        }
        return addr;
}

/* Get an address range which is currently unmapped.
 * For mmap() without MAP_FIXED and shmat() with addr=0.
 * Return value 0 means ENOMEM.
 */
unsigned long get_unmapped_area(unsigned long addr, unsigned long len)
{
        struct vm_area_struct * vmm;

        if (len > TASK_SIZE)
                return 0;
        if (!addr)
                addr = TASK_UNMAPPED_BASE;
        addr = PAGE_ALIGN(addr);

        for (vmm = find_vma(current->mm, addr); ; vmm = vmm->vm_next) {
                /* At this point:  (!vmm || addr < vmm->vm_end). */
                if (TASK_SIZE - len < addr)
                        return 0;
                if (!vmm || addr + len <= vmm->vm_start)
                        return addr;
                addr = vmm->vm_end;
        }
}

/* Normal function to fix up a mapping
 * This function is the default for when an area has no specific
 * function.  This may be used as part of a more specific routine.
 * This function works out what part of an area is affected and
 * adjusts the mapping information.  Since the actual page
 * manipulation is done in do_mmap(), none need be done here,
 * though it would probably be more appropriate.
 *
 * By the time this function is called, the area struct has been
 * removed from the process mapping list, so it needs to be
 * reinserted if necessary.
 *
 * The 4 main cases are:
 *    Unmapping the whole area
 *    Unmapping from the start of the segment to a point in it
 *    Unmapping from an intermediate point to the end
 *    Unmapping between to intermediate points, making a hole.
 *
 * Case 4 involves the creation of 2 new areas, for each side of
 * the hole.  If possible, we reuse the existing area rather than
 * allocate a new one, and the return indicates whether the old
 * area was reused.
 */
static int unmap_fixup(struct vm_area_struct *area, unsigned long addr,
                         size_t len, struct vm_area_struct **extra)
{
        struct vm_area_struct *mpnt;
        unsigned long end = addr + len;

        area->vm_mm->total_vm -= len >> PAGE_SHIFT;
        if (area->vm_flags & VM_LOCKED)
                area->vm_mm->locked_vm -= len >> PAGE_SHIFT;

        /* Unmapping the whole area. */
        if (addr == area->vm_start && end == area->vm_end) {
                if (area->vm_ops && area->vm_ops->close)
                        area->vm_ops->close(area);
                if (area->vm_dentry)
                        dput(area->vm_dentry);
                return 0;
        }

        /* Work out to one of the ends. */
        if (end == area->vm_end)
                area->vm_end = addr;
        else if (addr == area->vm_start) {
                area->vm_offset += (end - area->vm_start);
                area->vm_start = end;
        } else {
        /* Unmapping a hole: area->vm_start < addr <= end < area->vm_end */
                /* Add end mapping -- leave beginning for below */
                mpnt = *extra;
                *extra = NULL;

                mpnt->vm_mm = area->vm_mm;
                mpnt->vm_start = end;
                mpnt->vm_end = area->vm_end;
                mpnt->vm_page_prot = area->vm_page_prot;
                mpnt->vm_flags = area->vm_flags;
                mpnt->vm_ops = area->vm_ops;
                mpnt->vm_offset = area->vm_offset + (end - area->vm_start);
                mpnt->vm_dentry = dget(area->vm_dentry);
                if (mpnt->vm_ops && mpnt->vm_ops->open)
                        mpnt->vm_ops->open(mpnt);
                area->vm_end = addr;    /* Truncate area */
                insert_vm_struct(current->mm, mpnt);
        }

        /* Close the current area ... */
        if (area->vm_ops && area->vm_ops->close) {
                end = area->vm_end; /* save new end */
                area->vm_end = area->vm_start;
                area->vm_ops->close(area);
                area->vm_end = end;
        }
        /* ... then reopen and reinsert. */
        if (area->vm_ops && area->vm_ops->open)
                area->vm_ops->open(area);
        insert_vm_struct(current->mm, area);
        return 1;
}

asmlinkage int sys_munmap(unsigned long addr, size_t len)
{
        int ret;

        lock_kernel();
        ret = do_munmap(addr, len);
        unlock_kernel();
        return ret;
}

/* Munmap is split into 2 main parts -- this part which finds
 * what needs doing, and the areas themselves, which do the
 * work.  This now handles partial unmappings.
 * Jeremy Fitzhardine <jeremy@sw.oz.au>
 */
int do_munmap(unsigned long addr, size_t len)
{
        struct vm_area_struct *mpnt, *next, *free, *extra;
        int freed;

        if ((addr & ~PAGE_MASK) || addr > TASK_SIZE || len > TASK_SIZE-addr)
                return -EINVAL;

        if ((len = PAGE_ALIGN(len)) == 0)
                return 0;

        /* Check if this memory area is ok - put it on the temporary
         * list if so..  The checks here are pretty simple --
         * every area affected in some way (by any overlap) is put
         * on the list.  If nothing is put on, nothing is affected.
         */
        mpnt = current->mm->mmap;
        while(mpnt && mpnt->vm_end <= addr)
                mpnt = mpnt->vm_next;
        if (!mpnt)
                return 0;

        /*
         * We may need one additional vma to fix up the mappings ... 
         * and this is the last chance for an easy error exit.
         */
        extra = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
        if (!extra)
                return -ENOMEM;

        next = mpnt->vm_next;

        /* we have mpnt->vm_next = next and addr < mpnt->vm_end */
        free = NULL;
        for ( ; mpnt && mpnt->vm_start < addr+len; ) {
                struct vm_area_struct *next = mpnt->vm_next;

                if(mpnt->vm_next)
                        mpnt->vm_next->vm_pprev = mpnt->vm_pprev;
                *mpnt->vm_pprev = mpnt->vm_next;

                mpnt->vm_next = free;
                free = mpnt;
                mpnt = next;
        }

        /* Ok - we have the memory areas we should free on the 'free' list,
         * so release them, and unmap the page range..
         * If the one of the segments is only being partially unmapped,
         * it will put new vm_area_struct(s) into the address space.
         */
        freed = 0;
        while ((mpnt = free) != NULL) {
                unsigned long st, end, size;

                free = free->vm_next;
                freed = 1;

                remove_shared_vm_struct(mpnt);

                st = addr < mpnt->vm_start ? mpnt->vm_start : addr;
                end = addr+len;
                end = end > mpnt->vm_end ? mpnt->vm_end : end;
                size = end - st;

                if (mpnt->vm_ops && mpnt->vm_ops->unmap)
                        mpnt->vm_ops->unmap(mpnt, st, size);

                flush_cache_range(current->mm, st, end);
                zap_page_range(current->mm, st, size);
                flush_tlb_range(current->mm, st, end);

                /*
                 * Fix the mapping, and free the old area if it wasn't reused.
                 */
                if (!unmap_fixup(mpnt, st, size, &extra))
                        kmem_cache_free(vm_area_cachep, mpnt);
        }

        /* Release the extra vma struct if it wasn't used */
        if (extra)
                kmem_cache_free(vm_area_cachep, extra);

        if (freed)
                current->mm->mmap_cache = NULL; /* Kill the cache. */
        return 0;
}

/* Release all mmaps. */
void exit_mmap(struct mm_struct * mm)
{
        struct vm_area_struct * mpnt;

        mpnt = mm->mmap;
        mm->mmap = mm->mmap_cache = NULL;
        mm->rss = 0;
        mm->total_vm = 0;
        mm->locked_vm = 0;
        while (mpnt) {
                struct vm_area_struct * next = mpnt->vm_next;
                unsigned long start = mpnt->vm_start;
                unsigned long end = mpnt->vm_end;
                unsigned long size = end - start;

                if (mpnt->vm_ops) {
                        if (mpnt->vm_ops->unmap)
                                mpnt->vm_ops->unmap(mpnt, start, size);
                        if (mpnt->vm_ops->close)
                                mpnt->vm_ops->close(mpnt);
                }
                remove_shared_vm_struct(mpnt);
                zap_page_range(mm, start, size);
                if (mpnt->vm_dentry)
                        dput(mpnt->vm_dentry);
                kmem_cache_free(vm_area_cachep, mpnt);
                mpnt = next;
        }
}

/* Insert vm structure into process list sorted by address
 * and into the inode's i_mmap ring.
 */
void insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vmp)
{
        struct vm_area_struct **pprev = &mm->mmap;
        struct dentry * dentry;

        /* Find where to link it in. */
        while(*pprev && (*pprev)->vm_start <= vmp->vm_start)
                pprev = &(*pprev)->vm_next;

        /* Insert it. */
        if((vmp->vm_next = *pprev) != NULL)
                (*pprev)->vm_pprev = &vmp->vm_next;
        *pprev = vmp;
        vmp->vm_pprev = pprev;

        dentry = vmp->vm_dentry;
        if (dentry) {
                struct inode * inode = dentry->d_inode;
                if (vmp->vm_flags & VM_DENYWRITE)
                        inode->i_writecount--;
      
                /* insert vmp into inode's share list */
                if((vmp->vm_next_share = inode->i_mmap) != NULL)
                        inode->i_mmap->vm_pprev_share = &vmp->vm_next_share;
                inode->i_mmap = vmp;
                vmp->vm_pprev_share = &inode->i_mmap;
        }
}

/* Merge the list of memory segments if possible.
 * Redundant vm_area_structs are freed.
 * This assumes that the list is ordered by address.
 * We don't need to traverse the entire list, only those segments
 * which intersect or are adjacent to a given interval.
 */
void merge_segments (struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)
{
        struct vm_area_struct *prev, *mpnt, *next;

        down(&mm->mmap_sem);

        prev = NULL;
        mpnt = mm->mmap;
        while(mpnt && mpnt->vm_end <= start_addr) {
                prev = mpnt;
                mpnt = mpnt->vm_next;
        }
        if (!mpnt)
                goto no_vma;

        next = mpnt->vm_next;

        /* we have prev->vm_next == mpnt && mpnt->vm_next = next */
        if (!prev) {
                prev = mpnt;
                mpnt = next;
        }

        /* prev and mpnt cycle through the list, as long as
         * start_addr < mpnt->vm_end && prev->vm_start < end_addr
         */
        for ( ; mpnt && prev->vm_start < end_addr ; prev = mpnt, mpnt = next) {
                next = mpnt->vm_next;

                /* To share, we must have the same dentry, operations.. */
                if ((mpnt->vm_dentry != prev->vm_dentry)||
                    (mpnt->vm_pte != prev->vm_pte)      ||
                    (mpnt->vm_ops != prev->vm_ops)      ||
                    (mpnt->vm_flags != prev->vm_flags)  ||
                    (prev->vm_end != mpnt->vm_start))
                        continue;

                /*
                 * If we have a dentry or it's a shared memory area
                 * the offsets must be contiguous..
                 */
                if ((mpnt->vm_dentry != NULL) || (mpnt->vm_flags & VM_SHM)) {
                        unsigned long off = prev->vm_offset+prev->vm_end-prev->vm_start;
                        if (off != mpnt->vm_offset)
                                continue;
                }

                /* merge prev with mpnt and set up pointers so the new
                 * big segment can possibly merge with the next one.
                 * The old unused mpnt is freed.
                 */
                if(mpnt->vm_next)
                        mpnt->vm_next->vm_pprev = mpnt->vm_pprev;
                *mpnt->vm_pprev = mpnt->vm_next;

                prev->vm_end = mpnt->vm_end;
                if (mpnt->vm_ops && mpnt->vm_ops->close) {
                        mpnt->vm_offset += mpnt->vm_end - mpnt->vm_start;
                        mpnt->vm_start = mpnt->vm_end;
                        mpnt->vm_ops->close(mpnt);
                }
                remove_shared_vm_struct(mpnt);
                if (mpnt->vm_dentry)
                        dput(mpnt->vm_dentry);
                kmem_cache_free(vm_area_cachep, mpnt);
                mpnt = prev;
        }
        mm->mmap_cache = NULL;          /* Kill the cache. */
no_vma:
        up(&mm->mmap_sem);
}

__initfunc(void vma_init(void))
{
        vm_area_cachep = kmem_cache_create("vm_area_struct",
                                           sizeof(struct vm_area_struct),
                                           0, SLAB_HWCACHE_ALIGN,
                                           NULL, NULL);
        if(!vm_area_cachep)
                panic("vma_init: Cannot alloc vm_area_struct cache.");

        mm_cachep = kmem_cache_create("mm_struct",
                                      sizeof(struct mm_struct),
                                      0, SLAB_HWCACHE_ALIGN,
                                      NULL, NULL);
        if(!mm_cachep)
                panic("vma_init: Cannot alloc mm_struct cache.");
}