/* * linux/mm/nommu.c * * Replacement code for mm functions to support CPU's that don't * have any form of memory management unit (thus no virtual memory). * * See Documentation/nommu-mmap.txt * * Copyright (c) 2004-2008 David Howells <dhowells@redhat.com> * Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com> * Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org> * Copyright (c) 2002 Greg Ungerer <gerg@snapgear.com> * Copyright (c) 2007-2009 Paul Mundt <lethal@linux-sh.org> */ #include <linux/module.h> #include <linux/mm.h> #include <linux/mman.h> #include <linux/swap.h> #include <linux/file.h> #include <linux/highmem.h> #include <linux/pagemap.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/tracehook.h> #include <linux/blkdev.h> #include <linux/backing-dev.h> #include <linux/mount.h> #include <linux/personality.h> #include <linux/security.h> #include <linux/syscalls.h> #include <asm/uaccess.h> #include <asm/tlb.h> #include <asm/tlbflush.h> #include <asm/mmu_context.h> #include "internal.h" static inline __attribute__((format(printf, 1, 2))) void no_printk(const char *fmt, ...) { } #if 0 #define kenter(FMT, ...) \ printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__) #define kleave(FMT, ...) \ printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__) #define kdebug(FMT, ...) \ printk(KERN_DEBUG "xxx" FMT"yyy\n", ##__VA_ARGS__) #else #define kenter(FMT, ...) \ no_printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__) #define kleave(FMT, ...) \ no_printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__) #define kdebug(FMT, ...) \ no_printk(KERN_DEBUG FMT"\n", ##__VA_ARGS__) #endif void *high_memory; struct page *mem_map; unsigned long max_mapnr; unsigned long num_physpages; struct percpu_counter vm_committed_as; int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */ int sysctl_overcommit_ratio = 50; /* default is 50% */ int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT; int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS; int heap_stack_gap = 0; atomic_long_t mmap_pages_allocated; EXPORT_SYMBOL(mem_map); EXPORT_SYMBOL(num_physpages); /* list of mapped, potentially shareable regions */ static struct kmem_cache *vm_region_jar; struct rb_root nommu_region_tree = RB_ROOT; DECLARE_RWSEM(nommu_region_sem); struct vm_operations_struct generic_file_vm_ops = { }; /* * Handle all mappings that got truncated by a "truncate()" * system call. * * NOTE! We have to be ready to update the memory sharing * between the file and the memory map for a potential last * incomplete page. Ugly, but necessary. */ int vmtruncate(struct inode *inode, loff_t offset) { struct address_space *mapping = inode->i_mapping; unsigned long limit; if (inode->i_size < offset) goto do_expand; i_size_write(inode, offset); truncate_inode_pages(mapping, offset); goto out_truncate; do_expand: limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; if (limit != RLIM_INFINITY && offset > limit) goto out_sig; if (offset > inode->i_sb->s_maxbytes) goto out; i_size_write(inode, offset); out_truncate: if (inode->i_op->truncate) inode->i_op->truncate(inode); return 0; out_sig: send_sig(SIGXFSZ, current, 0); out: return -EFBIG; } EXPORT_SYMBOL(vmtruncate); /* * Return the total memory allocated for this pointer, not * just what the caller asked for. * * Doesn't have to be accurate, i.e. may have races. */ unsigned int kobjsize(const void *objp) { struct page *page; /* * If the object we have should not have ksize performed on it, * return size of 0 */ if (!objp || !virt_addr_valid(objp)) return 0; page = virt_to_head_page(objp); /* * If the allocator sets PageSlab, we know the pointer came from * kmalloc(). */ if (PageSlab(page)) return ksize(objp); /* * If it's not a compound page, see if we have a matching VMA * region. This test is intentionally done in reverse order, * so if there's no VMA, we still fall through and hand back * PAGE_SIZE for 0-order pages. */ if (!PageCompound(page)) { struct vm_area_struct *vma; vma = find_vma(current->mm, (unsigned long)objp); if (vma) return vma->vm_end - vma->vm_start; } /* * The ksize() function is only guaranteed to work for pointers * returned by kmalloc(). So handle arbitrary pointers here. */ return PAGE_SIZE << compound_order(page); } int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, int nr_pages, int foll_flags, struct page **pages, struct vm_area_struct **vmas) { struct vm_area_struct *vma; unsigned long vm_flags; int i; /* calculate required read or write permissions. * If FOLL_FORCE is set, we only require the "MAY" flags. */ vm_flags = (foll_flags & FOLL_WRITE) ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD); vm_flags &= (foll_flags & FOLL_FORCE) ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE); for (i = 0; i < nr_pages; i++) { vma = find_vma(mm, start); if (!vma) goto finish_or_fault; /* protect what we can, including chardevs */ if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) || !(vm_flags & vma->vm_flags)) goto finish_or_fault; if (pages) { pages[i] = virt_to_page(start); if (pages[i]) page_cache_get(pages[i]); } if (vmas) vmas[i] = vma; start += PAGE_SIZE; } return i; finish_or_fault: return i ? : -EFAULT; } /* * get a list of pages in an address range belonging to the specified process * and indicate the VMA that covers each page * - this is potentially dodgy as we may end incrementing the page count of a * slab page or a secondary page from a compound page * - don't permit access to VMAs that don't support it, such as I/O mappings */ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, int nr_pages, int write, int force, struct page **pages, struct vm_area_struct **vmas) { int flags = 0; if (write) flags |= FOLL_WRITE; if (force) flags |= FOLL_FORCE; return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas); } EXPORT_SYMBOL(get_user_pages); /** * follow_pfn - look up PFN at a user virtual address * @vma: memory mapping * @address: user virtual address * @pfn: location to store found PFN * * Only IO mappings and raw PFN mappings are allowed. * * Returns zero and the pfn at @pfn on success, -ve otherwise. */ int follow_pfn(struct vm_area_struct *vma, unsigned long address, unsigned long *pfn) { if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) return -EINVAL; *pfn = address >> PAGE_SHIFT; return 0; } EXPORT_SYMBOL(follow_pfn); DEFINE_RWLOCK(vmlist_lock); struct vm_struct *vmlist; void vfree(const void *addr) { kfree(addr); } EXPORT_SYMBOL(vfree); void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot) { /* * You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc() * returns only a logical address. */ return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM); } EXPORT_SYMBOL(__vmalloc); void *vmalloc_user(unsigned long size) { void *ret; ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL); if (ret) { struct vm_area_struct *vma; down_write(¤t->mm->mmap_sem); vma = find_vma(current->mm, (unsigned long)ret); if (vma) vma->vm_flags |= VM_USERMAP; up_write(¤t->mm->mmap_sem); } return ret; } EXPORT_SYMBOL(vmalloc_user); struct page *vmalloc_to_page(const void *addr) { return virt_to_page(addr); } EXPORT_SYMBOL(vmalloc_to_page); unsigned long vmalloc_to_pfn(const void *addr) { return page_to_pfn(virt_to_page(addr)); } EXPORT_SYMBOL(vmalloc_to_pfn); long vread(char *buf, char *addr, unsigned long count) { memcpy(buf, addr, count); return count; } long vwrite(char *buf, char *addr, unsigned long count) { /* Don't allow overflow */ if ((unsigned long) addr + count < count) count = -(unsigned long) addr; memcpy(addr, buf, count); return(count); } /* * vmalloc - allocate virtually continguos memory * * @size: allocation size * * Allocate enough pages to cover @size from the page level * allocator and map them into continguos kernel virtual space. * * For tight control over page level allocator and protection flags * use __vmalloc() instead. */ void *vmalloc(unsigned long size) { return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL); } EXPORT_SYMBOL(vmalloc); void *vmalloc_node(unsigned long size, int node) { return vmalloc(size); } EXPORT_SYMBOL(vmalloc_node); #ifndef PAGE_KERNEL_EXEC # define PAGE_KERNEL_EXEC PAGE_KERNEL #endif /** * vmalloc_exec - allocate virtually contiguous, executable memory * @size: allocation size * * Kernel-internal function to allocate enough pages to cover @size * the page level allocator and map them into contiguous and * executable kernel virtual space. * * For tight control over page level allocator and protection flags * use __vmalloc() instead. */ void *vmalloc_exec(unsigned long size) { return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC); } /** * vmalloc_32 - allocate virtually contiguous memory (32bit addressable) * @size: allocation size * * Allocate enough 32bit PA addressable pages to cover @size from the * page level allocator and map them into continguos kernel virtual space. */ void *vmalloc_32(unsigned long size) { return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL); } EXPORT_SYMBOL(vmalloc_32); /** * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory * @size: allocation size * * The resulting memory area is 32bit addressable and zeroed so it can be * mapped to userspace without leaking data. * * VM_USERMAP is set on the corresponding VMA so that subsequent calls to * remap_vmalloc_range() are permissible. */ void *vmalloc_32_user(unsigned long size) { /* * We'll have to sort out the ZONE_DMA bits for 64-bit, * but for now this can simply use vmalloc_user() directly. */ return vmalloc_user(size); } EXPORT_SYMBOL(vmalloc_32_user); void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot) { BUG(); return NULL; } EXPORT_SYMBOL(vmap); void vunmap(const void *addr) { BUG(); } EXPORT_SYMBOL(vunmap); void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t prot) { BUG(); return NULL; } EXPORT_SYMBOL(vm_map_ram); void vm_unmap_ram(const void *mem, unsigned int count) { BUG(); } EXPORT_SYMBOL(vm_unmap_ram); void vm_unmap_aliases(void) { } EXPORT_SYMBOL_GPL(vm_unmap_aliases); /* * Implement a stub for vmalloc_sync_all() if the architecture chose not to * have one. */ void __attribute__((weak)) vmalloc_sync_all(void) { } int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, struct page *page) { return -EINVAL; } EXPORT_SYMBOL(vm_insert_page); /* * sys_brk() for the most part doesn't need the global kernel * lock, except when an application is doing something nasty * like trying to un-brk an area that has already been mapped * to a regular file. in this case, the unmapping will need * to invoke file system routines that need the global lock. */ SYSCALL_DEFINE1(brk, unsigned long, brk) { struct mm_struct *mm = current->mm; if (brk < mm->start_brk || brk > mm->context.end_brk) return mm->brk; if (mm->brk == brk) return mm->brk; /* * Always allow shrinking brk */ if (brk <= mm->brk) { mm->brk = brk; return brk; } /* * Ok, looks good - let it rip. */ return mm->brk = brk; } /* * initialise the VMA and region record slabs */ void __init mmap_init(void) { int ret; ret = percpu_counter_init(&vm_committed_as, 0); VM_BUG_ON(ret); vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC); } /* * validate the region tree * - the caller must hold the region lock */ #ifdef CONFIG_DEBUG_NOMMU_REGIONS static noinline void validate_nommu_regions(void) { struct vm_region *region, *last; struct rb_node *p, *lastp; lastp = rb_first(&nommu_region_tree); if (!lastp) return; last = rb_entry(lastp, struct vm_region, vm_rb); BUG_ON(unlikely(last->vm_end <= last->vm_start)); BUG_ON(unlikely(last->vm_top < last->vm_end)); while ((p = rb_next(lastp))) { region = rb_entry(p, struct vm_region, vm_rb); last = rb_entry(lastp, struct vm_region, vm_rb); BUG_ON(unlikely(region->vm_end <= region->vm_start)); BUG_ON(unlikely(region->vm_top < region->vm_end)); BUG_ON(unlikely(region->vm_start < last->vm_top)); lastp = p; } } #else static void validate_nommu_regions(void) { } #endif /* * add a region into the global tree */ static void add_nommu_region(struct vm_region *region) { struct vm_region *pregion; struct rb_node **p, *parent; validate_nommu_regions(); parent = NULL; p = &nommu_region_tree.rb_node; while (*p) { parent = *p; pregion = rb_entry(parent, struct vm_region, vm_rb); if (region->vm_start < pregion->vm_start) p = &(*p)->rb_left; else if (region->vm_start > pregion->vm_start) p = &(*p)->rb_right; else if (pregion == region) return; else BUG(); } rb_link_node(®ion->vm_rb, parent, p); rb_insert_color(®ion->vm_rb, &nommu_region_tree); validate_nommu_regions(); } /* * delete a region from the global tree */ static void delete_nommu_region(struct vm_region *region) { BUG_ON(!nommu_region_tree.rb_node); validate_nommu_regions(); rb_erase(®ion->vm_rb, &nommu_region_tree); validate_nommu_regions(); } /* * free a contiguous series of pages */ static void free_page_series(unsigned long from, unsigned long to) { for (; from < to; from += PAGE_SIZE) { struct page *page = virt_to_page(from); kdebug("- free %lx", from); atomic_long_dec(&mmap_pages_allocated); if (page_count(page) != 1) kdebug("free page %p: refcount not one: %d", page, page_count(page)); put_page(page); } } /* * release a reference to a region * - the caller must hold the region semaphore for writing, which this releases * - the region may not have been added to the tree yet, in which case vm_top * will equal vm_start */ static void __put_nommu_region(struct vm_region *region) __releases(nommu_region_sem) { kenter("%p{%d}", region, atomic_read(®ion->vm_usage)); BUG_ON(!nommu_region_tree.rb_node); if (atomic_dec_and_test(®ion->vm_usage)) { if (region->vm_top > region->vm_start) delete_nommu_region(region); up_write(&nommu_region_sem); if (region->vm_file) fput(region->vm_file); /* IO memory and memory shared directly out of the pagecache * from ramfs/tmpfs mustn't be released here */ if (region->vm_flags & VM_MAPPED_COPY) { kdebug("free series"); free_page_series(region->vm_start, region->vm_top); } kmem_cache_free(vm_region_jar, region); } else { up_write(&nommu_region_sem); } } /* * release a reference to a region */ static void put_nommu_region(struct vm_region *region) { down_write(&nommu_region_sem); __put_nommu_region(region); } /* * update protection on a vma */ static void protect_vma(struct vm_area_struct *vma, unsigned long flags) { #ifdef CONFIG_MPU struct mm_struct *mm = vma->vm_mm; long start = vma->vm_start & PAGE_MASK; while (start < vma->vm_end) { protect_page(mm, start, flags); start += PAGE_SIZE; } update_protections(mm); #endif } /* * add a VMA into a process's mm_struct in the appropriate place in the list * and tree and add to the address space's page tree also if not an anonymous * page * - should be called with mm->mmap_sem held writelocked */ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma) { struct vm_area_struct *pvma, **pp; struct address_space *mapping; struct rb_node **p, *parent; kenter(",%p", vma); BUG_ON(!vma->vm_region); mm->map_count++; vma->vm_mm = mm; protect_vma(vma, vma->vm_flags); /* add the VMA to the mapping */ if (vma->vm_file) { mapping = vma->vm_file->f_mapping; flush_dcache_mmap_lock(mapping); vma_prio_tree_insert(vma, &mapping->i_mmap); flush_dcache_mmap_unlock(mapping); } /* add the VMA to the tree */ parent = NULL; p = &mm->mm_rb.rb_node; while (*p) { parent = *p; pvma = rb_entry(parent, struct vm_area_struct, vm_rb); /* sort by: start addr, end addr, VMA struct addr in that order * (the latter is necessary as we may get identical VMAs) */ if (vma->vm_start < pvma->vm_start) p = &(*p)->rb_left; else if (vma->vm_start > pvma->vm_start) p = &(*p)->rb_right; else if (vma->vm_end < pvma->vm_end) p = &(*p)->rb_left; else if (vma->vm_end > pvma->vm_end) p = &(*p)->rb_right; else if (vma < pvma) p = &(*p)->rb_left; else if (vma > pvma) p = &(*p)->rb_right; else BUG(); } rb_link_node(&vma->vm_rb, parent, p); rb_insert_color(&vma->vm_rb, &mm->mm_rb); /* add VMA to the VMA list also */ for (pp = &mm->mmap; (pvma = *pp); pp = &(*pp)->vm_next) { if (pvma->vm_start > vma->vm_start) break; if (pvma->vm_start < vma->vm_start) continue; if (pvma->vm_end < vma->vm_end) break; } vma->vm_next = *pp; *pp = vma; } /* * delete a VMA from its owning mm_struct and address space */ static void delete_vma_from_mm(struct vm_area_struct *vma) { struct vm_area_struct **pp; struct address_space *mapping; struct mm_struct *mm = vma->vm_mm; kenter("%p", vma); protect_vma(vma, 0); mm->map_count--; if (mm->mmap_cache == vma) mm->mmap_cache = NULL; /* remove the VMA from the mapping */ if (vma->vm_file) { mapping = vma->vm_file->f_mapping; flush_dcache_mmap_lock(mapping); vma_prio_tree_remove(vma, &mapping->i_mmap); flush_dcache_mmap_unlock(mapping); } /* remove from the MM's tree and list */ rb_erase(&vma->vm_rb, &mm->mm_rb); for (pp = &mm->mmap; *pp; pp = &(*pp)->vm_next) { if (*pp == vma) { *pp = vma->vm_next; break; } } vma->vm_mm = NULL; } /* * destroy a VMA record */ static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma) { kenter("%p", vma); if (vma->vm_ops && vma->vm_ops->close) vma->vm_ops->close(vma); if (vma->vm_file) { fput(vma->vm_file); if (vma->vm_flags & VM_EXECUTABLE) removed_exe_file_vma(mm); } put_nommu_region(vma->vm_region); kmem_cache_free(vm_area_cachep, vma); } /* * look up the first VMA in which addr resides, NULL if none * - should be called with mm->mmap_sem at least held readlocked */ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) { struct vm_area_struct *vma; struct rb_node *n = mm->mm_rb.rb_node; /* check the cache first */ vma = mm->mmap_cache; if (vma && vma->vm_start <= addr && vma->vm_end > addr) return vma; /* trawl the tree (there may be multiple mappings in which addr * resides) */ for (n = rb_first(&mm->mm_rb); n; n = rb_next(n)) { vma = rb_entry(n, struct vm_area_struct, vm_rb); if (vma->vm_start > addr) return NULL; if (vma->vm_end > addr) { mm->mmap_cache = vma; return vma; } } return NULL; } EXPORT_SYMBOL(find_vma); /* * find a VMA * - we don't extend stack VMAs under NOMMU conditions */ struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr) { return find_vma(mm, addr); } /* * expand a stack to a given address * - not supported under NOMMU conditions */ int expand_stack(struct vm_area_struct *vma, unsigned long address) { return -ENOMEM; } /* * look up the first VMA exactly that exactly matches addr * - should be called with mm->mmap_sem at least held readlocked */ static struct vm_area_struct *find_vma_exact(struct mm_struct *mm, unsigned long addr, unsigned long len) { struct vm_area_struct *vma; struct rb_node *n = mm->mm_rb.rb_node; unsigned long end = addr + len; /* check the cache first */ vma = mm->mmap_cache; if (vma && vma->vm_start == addr && vma->vm_end == end) return vma; /* trawl the tree (there may be multiple mappings in which addr * resides) */ for (n = rb_first(&mm->mm_rb); n; n = rb_next(n)) { vma = rb_entry(n, struct vm_area_struct, vm_rb); if (vma->vm_start < addr) continue; if (vma->vm_start > addr) return NULL; if (vma->vm_end == end) { mm->mmap_cache = vma; return vma; } } return NULL; } /* * determine whether a mapping should be permitted and, if so, what sort of * mapping we're capable of supporting */ static int validate_mmap_request(struct file *file, unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, unsigned long pgoff, unsigned long *_capabilities) { unsigned long capabilities, rlen; unsigned long reqprot = prot; int ret; /* do the simple checks first */ if (flags & MAP_FIXED || addr) { printk(KERN_DEBUG "%d: Can't do fixed-address/overlay mmap of RAM\n", current->pid); return -EINVAL; } if ((flags & MAP_TYPE) != MAP_PRIVATE && (flags & MAP_TYPE) != MAP_SHARED) return -EINVAL; if (!len) return -EINVAL; /* Careful about overflows.. */ rlen = PAGE_ALIGN(len); if (!rlen || rlen > TASK_SIZE) return -ENOMEM; /* offset overflow? */ if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff) return -EOVERFLOW; if (file) { /* validate file mapping requests */ struct address_space *mapping; /* files must support mmap */ if (!file->f_op || !file->f_op->mmap) return -ENODEV; /* work out if what we've got could possibly be shared * - we support chardevs that provide their own "memory" * - we support files/blockdevs that are memory backed */ mapping = file->f_mapping; if (!mapping) mapping = file->f_path.dentry->d_inode->i_mapping; capabilities = 0; if (mapping && mapping->backing_dev_info) capabilities = mapping->backing_dev_info->capabilities; if (!capabilities) { /* no explicit capabilities set, so assume some * defaults */ switch (file->f_path.dentry->d_inode->i_mode & S_IFMT) { case S_IFREG: case S_IFBLK: capabilities = BDI_CAP_MAP_COPY; break; case S_IFCHR: capabilities = BDI_CAP_MAP_DIRECT | BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP; break; default: return -EINVAL; } } /* eliminate any capabilities that we can't support on this * device */ if (!file->f_op->get_unmapped_area) capabilities &= ~BDI_CAP_MAP_DIRECT; if (!file->f_op->read) capabilities &= ~BDI_CAP_MAP_COPY; /* The file shall have been opened with read permission. */ if (!(file->f_mode & FMODE_READ)) return -EACCES; if (flags & MAP_SHARED) { /* do checks for writing, appending and locking */ if ((prot & PROT_WRITE) && !(file->f_mode & FMODE_WRITE)) return -EACCES; if (IS_APPEND(file->f_path.dentry->d_inode) && (file->f_mode & FMODE_WRITE)) return -EACCES; if (locks_verify_locked(file->f_path.dentry->d_inode)) return -EAGAIN; if (!(capabilities & BDI_CAP_MAP_DIRECT)) return -ENODEV; if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) || ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) || ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP)) ) { printk("MAP_SHARED not completely supported on !MMU\n"); return -EINVAL; } /* we mustn't privatise shared mappings */ capabilities &= ~BDI_CAP_MAP_COPY; } else { /* we're going to read the file into private memory we * allocate */ if (!(capabilities & BDI_CAP_MAP_COPY)) return -ENODEV; /* we don't permit a private writable mapping to be * shared with the backing device */ if (prot & PROT_WRITE) capabilities &= ~BDI_CAP_MAP_DIRECT; } /* handle executable mappings and implied executable * mappings */ if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) { if (prot & PROT_EXEC) return -EPERM; } else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) { /* handle implication of PROT_EXEC by PROT_READ */ if (current->personality & READ_IMPLIES_EXEC) { if (capabilities & BDI_CAP_EXEC_MAP) prot |= PROT_EXEC; } } else if ((prot & PROT_READ) && (prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP) ) { /* backing file is not executable, try to copy */ capabilities &= ~BDI_CAP_MAP_DIRECT; } } else { /* anonymous mappings are always memory backed and can be * privately mapped */ capabilities = BDI_CAP_MAP_COPY; /* handle PROT_EXEC implication by PROT_READ */ if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) prot |= PROT_EXEC; } /* allow the security API to have its say */ ret = security_file_mmap(file, reqprot, prot, flags, addr, 0); if (ret < 0) return ret; /* looks okay */ *_capabilities = capabilities; return 0; } /* * we've determined that we can make the mapping, now translate what we * now know into VMA flags */ static unsigned long determine_vm_flags(struct file *file, unsigned long prot, unsigned long flags, unsigned long capabilities) { unsigned long vm_flags; vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags); vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; /* vm_flags |= mm->def_flags; */ if (!(capabilities & BDI_CAP_MAP_DIRECT)) { /* attempt to share read-only copies of mapped file chunks */ if (file && !(prot & PROT_WRITE)) vm_flags |= VM_MAYSHARE; } else { /* overlay a shareable mapping on the backing device or inode * if possible - used for chardevs, ramfs/tmpfs/shmfs and * romfs/cramfs */ if (flags & MAP_SHARED) vm_flags |= VM_MAYSHARE | VM_SHARED; else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0) vm_flags |= VM_MAYSHARE; } /* refuse to let anyone share private mappings with this process if * it's being traced - otherwise breakpoints set in it may interfere * with another untraced process */ if ((flags & MAP_PRIVATE) && tracehook_expect_breakpoints(current)) vm_flags &= ~VM_MAYSHARE; return vm_flags; } /* * set up a shared mapping on a file (the driver or filesystem provides and * pins the storage) */ static int do_mmap_shared_file(struct vm_area_struct *vma) { int ret; ret = vma->vm_file->f_op->mmap(vma->vm_file, vma); if (ret == 0) { vma->vm_region->vm_top = vma->vm_region->vm_end; return ret; } if (ret != -ENOSYS) return ret; /* getting an ENOSYS error indicates that direct mmap isn't * possible (as opposed to tried but failed) so we'll fall * through to making a private copy of the data and mapping * that if we can */ return -ENODEV; } /* * set up a private mapping or an anonymous shared mapping */ static int do_mmap_private(struct vm_area_struct *vma, struct vm_region *region, unsigned long len) { struct page *pages; unsigned long total, point, n, rlen; void *base; int ret, order; /* invoke the file's mapping function so that it can keep track of * shared mappings on devices or memory * - VM_MAYSHARE will be set if it may attempt to share */ if (vma->vm_file) { ret = vma->vm_file->f_op->mmap(vma->vm_file, vma); if (ret == 0) { /* shouldn't return success if we're not sharing */ BUG_ON(!(vma->vm_flags & VM_MAYSHARE)); vma->vm_region->vm_top = vma->vm_region->vm_end; return ret; } if (ret != -ENOSYS) return ret; /* getting an ENOSYS error indicates that direct mmap isn't * possible (as opposed to tried but failed) so we'll try to * make a private copy of the data and map that instead */ } rlen = PAGE_ALIGN(len); /* allocate some memory to hold the mapping * - note that this may not return a page-aligned address if the object * we're allocating is smaller than a page */ order = get_order(rlen); kdebug("alloc order %d for %lx", order, len); pages = alloc_pages(GFP_KERNEL, order); if (!pages) goto enomem; total = 1 << order; atomic_long_add(total, &mmap_pages_allocated); point = rlen >> PAGE_SHIFT; /* we allocated a power-of-2 sized page set, so we may want to trim off * the excess */ if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages) { while (total > point) { order = ilog2(total - point); n = 1 << order; kdebug("shave %lu/%lu @%lu", n, total - point, total); atomic_long_sub(n, &mmap_pages_allocated); total -= n; set_page_refcounted(pages + total); __free_pages(pages + total, order); } } for (point = 1; point < total; point++) set_page_refcounted(&pages[point]); base = page_address(pages); region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY; region->vm_start = (unsigned long) base; region->vm_end = region->vm_start + rlen; region->vm_top = region->vm_start + (total << PAGE_SHIFT); vma->vm_start = region->vm_start; vma->vm_end = region->vm_start + len; if (vma->vm_file) { /* read the contents of a file into the copy */ mm_segment_t old_fs; loff_t fpos; fpos = vma->vm_pgoff; fpos <<= PAGE_SHIFT; old_fs = get_fs(); set_fs(KERNEL_DS); ret = vma->vm_file->f_op->read(vma->vm_file, base, rlen, &fpos); set_fs(old_fs); if (ret < 0) goto error_free; /* clear the last little bit */ if (ret < rlen) memset(base + ret, 0, rlen - ret); } else { /* if it's an anonymous mapping, then just clear it */ memset(base, 0, rlen); } return 0; error_free: free_page_series(region->vm_start, region->vm_end); region->vm_start = vma->vm_start = 0; region->vm_end = vma->vm_end = 0; region->vm_top = 0; return ret; enomem: printk("Allocation of length %lu from process %d (%s) failed\n", len, current->pid, current->comm); show_free_areas(); return -ENOMEM; } /* * handle mapping creation for uClinux */ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, unsigned long pgoff) { struct vm_area_struct *vma; struct vm_region *region; struct rb_node *rb; unsigned long capabilities, vm_flags, result; int ret; kenter(",%lx,%lx,%lx,%lx,%lx", addr, len, prot, flags, pgoff); if (!(flags & MAP_FIXED)) addr = round_hint_to_min(addr); /* decide whether we should attempt the mapping, and if so what sort of * mapping */ ret = validate_mmap_request(file, addr, len, prot, flags, pgoff, &capabilities); if (ret < 0) { kleave(" = %d [val]", ret); return ret; } /* we've determined that we can make the mapping, now translate what we * now know into VMA flags */ vm_flags = determine_vm_flags(file, prot, flags, capabilities); /* we're going to need to record the mapping */ region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL); if (!region) goto error_getting_region; vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); if (!vma) goto error_getting_vma; atomic_set(®ion->vm_usage, 1); region->vm_flags = vm_flags; region->vm_pgoff = pgoff; INIT_LIST_HEAD(&vma->anon_vma_node); vma->vm_flags = vm_flags; vma->vm_pgoff = pgoff; if (file) { region->vm_file = file; get_file(file); vma->vm_file = file; get_file(file); if (vm_flags & VM_EXECUTABLE) { added_exe_file_vma(current->mm); vma->vm_mm = current->mm; } } down_write(&nommu_region_sem); /* if we want to share, we need to check for regions created by other * mmap() calls that overlap with our proposed mapping * - we can only share with a superset match on most regular files * - shared mappings on character devices and memory backed files are * permitted to overlap inexactly as far as we are concerned for in * these cases, sharing is handled in the driver or filesystem rather * than here */ if (vm_flags & VM_MAYSHARE) { struct vm_region *pregion; unsigned long pglen, rpglen, pgend, rpgend, start; pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; pgend = pgoff + pglen; for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) { pregion = rb_entry(rb, struct vm_region, vm_rb); if (!(pregion->vm_flags & VM_MAYSHARE)) continue; /* search for overlapping mappings on the same file */ if (pregion->vm_file->f_path.dentry->d_inode != file->f_path.dentry->d_inode) continue; if (pregion->vm_pgoff >= pgend) continue; rpglen = pregion->vm_end - pregion->vm_start; rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT; rpgend = pregion->vm_pgoff + rpglen; if (pgoff >= rpgend) continue; /* handle inexactly overlapping matches between * mappings */ if ((pregion->vm_pgoff != pgoff || rpglen != pglen) && !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) { /* new mapping is not a subset of the region */ if (!(capabilities & BDI_CAP_MAP_DIRECT)) goto sharing_violation; continue; } /* we've found a region we can share */ atomic_inc(&pregion->vm_usage); vma->vm_region = pregion; start = pregion->vm_start; start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT; vma->vm_start = start; vma->vm_end = start + len; if (pregion->vm_flags & VM_MAPPED_COPY) { kdebug("share copy"); vma->vm_flags |= VM_MAPPED_COPY; } else { kdebug("share mmap"); ret = do_mmap_shared_file(vma); if (ret < 0) { vma->vm_region = NULL; vma->vm_start = 0; vma->vm_end = 0; atomic_dec(&pregion->vm_usage); pregion = NULL; goto error_just_free; } } fput(region->vm_file); kmem_cache_free(vm_region_jar, region); region = pregion; result = start; goto share; } /* obtain the address at which to make a shared mapping * - this is the hook for quasi-memory character devices to * tell us the location of a shared mapping */ if (file && file->f_op->get_unmapped_area) { addr = file->f_op->get_unmapped_area(file, addr, len, pgoff, flags); if (IS_ERR((void *) addr)) { ret = addr; if (ret != (unsigned long) -ENOSYS) goto error_just_free; /* the driver refused to tell us where to site * the mapping so we'll have to attempt to copy * it */ ret = (unsigned long) -ENODEV; if (!(capabilities & BDI_CAP_MAP_COPY)) goto error_just_free; capabilities &= ~BDI_CAP_MAP_DIRECT; } else { vma->vm_start = region->vm_start = addr; vma->vm_end = region->vm_end = addr + len; } } } vma->vm_region = region; add_nommu_region(region); /* set up the mapping */ if (file && vma->vm_flags & VM_SHARED) ret = do_mmap_shared_file(vma); else ret = do_mmap_private(vma, region, len); if (ret < 0) goto error_put_region; /* okay... we have a mapping; now we have to register it */ result = vma->vm_start; current->mm->total_vm += len >> PAGE_SHIFT; share: add_vma_to_mm(current->mm, vma); up_write(&nommu_region_sem); if (prot & PROT_EXEC) flush_icache_range(result, result + len); kleave(" = %lx", result); return result; error_put_region: __put_nommu_region(region); if (vma) { if (vma->vm_file) { fput(vma->vm_file); if (vma->vm_flags & VM_EXECUTABLE) removed_exe_file_vma(vma->vm_mm); } kmem_cache_free(vm_area_cachep, vma); } kleave(" = %d [pr]", ret); return ret; error_just_free: up_write(&nommu_region_sem); error: fput(region->vm_file); kmem_cache_free(vm_region_jar, region); fput(vma->vm_file); if (vma->vm_flags & VM_EXECUTABLE) removed_exe_file_vma(vma->vm_mm); kmem_cache_free(vm_area_cachep, vma); kleave(" = %d", ret); return ret; sharing_violation: up_write(&nommu_region_sem); printk(KERN_WARNING "Attempt to share mismatched mappings\n"); ret = -EINVAL; goto error; error_getting_vma: kmem_cache_free(vm_region_jar, region); printk(KERN_WARNING "Allocation of vma for %lu byte allocation" " from process %d failed\n", len, current->pid); show_free_areas(); return -ENOMEM; error_getting_region: printk(KERN_WARNING "Allocation of vm region for %lu byte allocation" " from process %d failed\n", len, current->pid); show_free_areas(); return -ENOMEM; } EXPORT_SYMBOL(do_mmap_pgoff); /* * split a vma into two pieces at address 'addr', a new vma is allocated either * for the first part or the tail. */ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, int new_below) { struct vm_area_struct *new; struct vm_region *region; unsigned long npages; kenter(""); /* we're only permitted to split anonymous regions that have a single * owner */ if (vma->vm_file || atomic_read(&vma->vm_region->vm_usage) != 1) return -ENOMEM; if (mm->map_count >= sysctl_max_map_count) return -ENOMEM; region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL); if (!region) return -ENOMEM; new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); if (!new) { kmem_cache_free(vm_region_jar, region); return -ENOMEM; } /* most fields are the same, copy all, and then fixup */ *new = *vma; *region = *vma->vm_region; new->vm_region = region; npages = (addr - vma->vm_start) >> PAGE_SHIFT; if (new_below) { region->vm_top = region->vm_end = new->vm_end = addr; } else { region->vm_start = new->vm_start = addr; region->vm_pgoff = new->vm_pgoff += npages; } if (new->vm_ops && new->vm_ops->open) new->vm_ops->open(new); delete_vma_from_mm(vma); down_write(&nommu_region_sem); delete_nommu_region(vma->vm_region); if (new_below) { vma->vm_region->vm_start = vma->vm_start = addr; vma->vm_region->vm_pgoff = vma->vm_pgoff += npages; } else { vma->vm_region->vm_end = vma->vm_end = addr; vma->vm_region->vm_top = addr; } add_nommu_region(vma->vm_region); add_nommu_region(new->vm_region); up_write(&nommu_region_sem); add_vma_to_mm(mm, vma); add_vma_to_mm(mm, new); return 0; } /* * shrink a VMA by removing the specified chunk from either the beginning or * the end */ static int shrink_vma(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long from, unsigned long to) { struct vm_region *region; kenter(""); /* adjust the VMA's pointers, which may reposition it in the MM's tree * and list */ delete_vma_from_mm(vma); if (from > vma->vm_start) vma->vm_end = from; else vma->vm_start = to; add_vma_to_mm(mm, vma); /* cut the backing region down to size */ region = vma->vm_region; BUG_ON(atomic_read(®ion->vm_usage) != 1); down_write(&nommu_region_sem); delete_nommu_region(region); if (from > region->vm_start) { to = region->vm_top; region->vm_top = region->vm_end = from; } else { region->vm_start = to; } add_nommu_region(region); up_write(&nommu_region_sem); free_page_series(from, to); return 0; } /* * release a mapping * - under NOMMU conditions the chunk to be unmapped must be backed by a single * VMA, though it need not cover the whole VMA */ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) { struct vm_area_struct *vma; struct rb_node *rb; unsigned long end = start + len; int ret; kenter(",%lx,%zx", start, len); if (len == 0) return -EINVAL; /* find the first potentially overlapping VMA */ vma = find_vma(mm, start); if (!vma) { static int limit = 0; if (limit < 5) { printk(KERN_WARNING "munmap of memory not mmapped by process %d" " (%s): 0x%lx-0x%lx\n", current->pid, current->comm, start, start + len - 1); limit++; } return -EINVAL; } /* we're allowed to split an anonymous VMA but not a file-backed one */ if (vma->vm_file) { do { if (start > vma->vm_start) { kleave(" = -EINVAL [miss]"); return -EINVAL; } if (end == vma->vm_end) goto erase_whole_vma; rb = rb_next(&vma->vm_rb); vma = rb_entry(rb, struct vm_area_struct, vm_rb); } while (rb); kleave(" = -EINVAL [split file]"); return -EINVAL; } else { /* the chunk must be a subset of the VMA found */ if (start == vma->vm_start && end == vma->vm_end) goto erase_whole_vma; if (start < vma->vm_start || end > vma->vm_end) { kleave(" = -EINVAL [superset]"); return -EINVAL; } if (start & ~PAGE_MASK) { kleave(" = -EINVAL [unaligned start]"); return -EINVAL; } if (end != vma->vm_end && end & ~PAGE_MASK) { kleave(" = -EINVAL [unaligned split]"); return -EINVAL; } if (start != vma->vm_start && end != vma->vm_end) { ret = split_vma(mm, vma, start, 1); if (ret < 0) { kleave(" = %d [split]", ret); return ret; } } return shrink_vma(mm, vma, start, end); } erase_whole_vma: delete_vma_from_mm(vma); delete_vma(mm, vma); kleave(" = 0"); return 0; } EXPORT_SYMBOL(do_munmap); SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) { int ret; struct mm_struct *mm = current->mm; down_write(&mm->mmap_sem); ret = do_munmap(mm, addr, len); up_write(&mm->mmap_sem); return ret; } /* * release all the mappings made in a process's VM space */ void exit_mmap(struct mm_struct *mm) { struct vm_area_struct *vma; if (!mm) return; kenter(""); mm->total_vm = 0; while ((vma = mm->mmap)) { mm->mmap = vma->vm_next; delete_vma_from_mm(vma); delete_vma(mm, vma); } kleave(""); } unsigned long do_brk(unsigned long addr, unsigned long len) { return -ENOMEM; } /* * expand (or shrink) an existing mapping, potentially moving it at the same * time (controlled by the MREMAP_MAYMOVE flag and available VM space) * * under NOMMU conditions, we only permit changing a mapping's size, and only * as long as it stays within the region allocated by do_mmap_private() and the * block is not shareable * * MREMAP_FIXED is not supported under NOMMU conditions */ unsigned long do_mremap(unsigned long addr, unsigned long old_len, unsigned long new_len, unsigned long flags, unsigned long new_addr) { struct vm_area_struct *vma; /* insanity checks first */ if (old_len == 0 || new_len == 0) return (unsigned long) -EINVAL; if (addr & ~PAGE_MASK) return -EINVAL; if (flags & MREMAP_FIXED && new_addr != addr) return (unsigned long) -EINVAL; vma = find_vma_exact(current->mm, addr, old_len); if (!vma) return (unsigned long) -EINVAL; if (vma->vm_end != vma->vm_start + old_len) return (unsigned long) -EFAULT; if (vma->vm_flags & VM_MAYSHARE) return (unsigned long) -EPERM; if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start) return (unsigned long) -ENOMEM; /* all checks complete - do it */ vma->vm_end = vma->vm_start + new_len; return vma->vm_start; } EXPORT_SYMBOL(do_mremap); SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, unsigned long, new_len, unsigned long, flags, unsigned long, new_addr) { unsigned long ret; down_write(¤t->mm->mmap_sem); ret = do_mremap(addr, old_len, new_len, flags, new_addr); up_write(¤t->mm->mmap_sem); return ret; } struct page *follow_page(struct vm_area_struct *vma, unsigned long address, unsigned int foll_flags) { return NULL; } int remap_pfn_range(struct vm_area_struct *vma, unsigned long from, unsigned long to, unsigned long size, pgprot_t prot) { vma->vm_start = vma->vm_pgoff << PAGE_SHIFT; return 0; } EXPORT_SYMBOL(remap_pfn_range); int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, unsigned long pgoff) { unsigned int size = vma->vm_end - vma->vm_start; if (!(vma->vm_flags & VM_USERMAP)) return -EINVAL; vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT)); vma->vm_end = vma->vm_start + size; return 0; } EXPORT_SYMBOL(remap_vmalloc_range); void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page) { } unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { return -ENOMEM; } void arch_unmap_area(struct mm_struct *mm, unsigned long addr) { } void unmap_mapping_range(struct address_space *mapping, loff_t const holebegin, loff_t const holelen, int even_cows) { } EXPORT_SYMBOL(unmap_mapping_range); /* * ask for an unmapped area at which to create a mapping on a file */ unsigned long get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { unsigned long (*get_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); get_area = current->mm->get_unmapped_area; if (file && file->f_op && file->f_op->get_unmapped_area) get_area = file->f_op->get_unmapped_area; if (!get_area) return -ENOSYS; return get_area(file, addr, len, pgoff, flags); } EXPORT_SYMBOL(get_unmapped_area); /* * Check that a process has enough memory to allocate a new virtual * mapping. 0 means there is enough memory for the allocation to * succeed and -ENOMEM implies there is not. * * We currently support three overcommit policies, which are set via the * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting * * Strict overcommit modes added 2002 Feb 26 by Alan Cox. * Additional code 2002 Jul 20 by Robert Love. * * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise. * * Note this is a helper function intended to be used by LSMs which * wish to use this logic. */ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) { unsigned long free, allowed; vm_acct_memory(pages); /* * Sometimes we want to use more memory than we have */ if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS) return 0; if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) { unsigned long n; free = global_page_state(NR_FILE_PAGES); free += nr_swap_pages; /* * Any slabs which are created with the * SLAB_RECLAIM_ACCOUNT flag claim to have contents * which are reclaimable, under pressure. The dentry * cache and most inode caches should fall into this */ free += global_page_state(NR_SLAB_RECLAIMABLE); /* * Leave the last 3% for root */ if (!cap_sys_admin) free -= free / 32; if (free > pages) return 0; /* * nr_free_pages() is very expensive on large systems, * only call if we're about to fail. */ n = nr_free_pages(); /* * Leave reserved pages. The pages are not for anonymous pages. */ if (n <= totalreserve_pages) goto error; else n -= totalreserve_pages; /* * Leave the last 3% for root */ if (!cap_sys_admin) n -= n / 32; free += n; if (free > pages) return 0; goto error; } allowed = totalram_pages * sysctl_overcommit_ratio / 100; /* * Leave the last 3% for root */ if (!cap_sys_admin) allowed -= allowed / 32; allowed += total_swap_pages; /* Don't let a single process grow too big: leave 3% of the size of this process for other processes */ if (mm) allowed -= mm->total_vm / 32; if (percpu_counter_read_positive(&vm_committed_as) < allowed) return 0; error: vm_unacct_memory(pages); return -ENOMEM; } int in_gate_area_no_task(unsigned long addr) { return 0; } int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { BUG(); return 0; } EXPORT_SYMBOL(filemap_fault); /* * Access another process' address space. * - source/target buffer must be kernel space */ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write) { struct vm_area_struct *vma; struct mm_struct *mm; if (addr + len < addr) return 0; mm = get_task_mm(tsk); if (!mm) return 0; down_read(&mm->mmap_sem); /* the access must start within one of the target process's mappings */ vma = find_vma(mm, addr); if (vma) { /* don't overrun this mapping */ if (addr + len >= vma->vm_end) len = vma->vm_end - addr; /* only read or write mappings where it is permitted */ if (write && vma->vm_flags & VM_MAYWRITE) len -= copy_to_user((void *) addr, buf, len); else if (!write && vma->vm_flags & VM_MAYREAD) len -= copy_from_user(buf, (void *) addr, len); else len = 0; } else { len = 0; } up_read(&mm->mmap_sem); mmput(mm); return len; }