// SPDX-License-Identifier: GPL-2.0 /* * linux/drivers/char/mem.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Added devfs support. * Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu> * Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com> */ #include <linux/mm.h> #include <linux/miscdevice.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/mman.h> #include <linux/random.h> #include <linux/init.h> #include <linux/tty.h> #include <linux/capability.h> #include <linux/ptrace.h> #include <linux/device.h> #include <linux/highmem.h> #include <linux/backing-dev.h> #include <linux/shmem_fs.h> #include <linux/splice.h> #include <linux/pfn.h> #include <linux/export.h> #include <linux/io.h> #include <linux/uio.h> #include <linux/uaccess.h> #include <linux/security.h> #ifdef CONFIG_IA64 # include <linux/efi.h> #endif #define DEVMEM_MINOR 1 #define DEVPORT_MINOR 4 static inline unsigned long size_inside_page(unsigned long start, unsigned long size) { unsigned long sz; sz = PAGE_SIZE - (start & (PAGE_SIZE - 1)); return min(sz, size); } #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE static inline int valid_phys_addr_range(phys_addr_t addr, size_t count) { return addr + count <= __pa(high_memory); } static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) { return 1; } #endif #ifdef CONFIG_STRICT_DEVMEM static inline int page_is_allowed(unsigned long pfn) { return devmem_is_allowed(pfn); } static inline int range_is_allowed(unsigned long pfn, unsigned long size) { u64 from = ((u64)pfn) << PAGE_SHIFT; u64 to = from + size; u64 cursor = from; while (cursor < to) { if (!devmem_is_allowed(pfn)) return 0; cursor += PAGE_SIZE; pfn++; } return 1; } #else static inline int page_is_allowed(unsigned long pfn) { return 1; } static inline int range_is_allowed(unsigned long pfn, unsigned long size) { return 1; } #endif #ifndef unxlate_dev_mem_ptr #define unxlate_dev_mem_ptr unxlate_dev_mem_ptr void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr) { } #endif static inline bool should_stop_iteration(void) { if (need_resched()) cond_resched(); return signal_pending(current); } /* * This funcion reads the *physical* memory. The f_pos points directly to the * memory location. */ static ssize_t read_mem(struct file *file, char __user *buf, size_t count, loff_t *ppos) { phys_addr_t p = *ppos; ssize_t read, sz; void *ptr; char *bounce; int err; if (p != *ppos) return 0; if (!valid_phys_addr_range(p, count)) return -EFAULT; read = 0; #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED /* we don't have page 0 mapped on sparc and m68k.. */ if (p < PAGE_SIZE) { sz = size_inside_page(p, count); if (sz > 0) { if (clear_user(buf, sz)) return -EFAULT; buf += sz; p += sz; count -= sz; read += sz; } } #endif bounce = kmalloc(PAGE_SIZE, GFP_KERNEL); if (!bounce) return -ENOMEM; while (count > 0) { unsigned long remaining; int allowed, probe; sz = size_inside_page(p, count); err = -EPERM; allowed = page_is_allowed(p >> PAGE_SHIFT); if (!allowed) goto failed; err = -EFAULT; if (allowed == 2) { /* Show zeros for restricted memory. */ remaining = clear_user(buf, sz); } else { /* * On ia64 if a page has been mapped somewhere as * uncached, then it must also be accessed uncached * by the kernel or data corruption may occur. */ ptr = xlate_dev_mem_ptr(p); if (!ptr) goto failed; probe = copy_from_kernel_nofault(bounce, ptr, sz); unxlate_dev_mem_ptr(p, ptr); if (probe) goto failed; remaining = copy_to_user(buf, bounce, sz); } if (remaining) goto failed; buf += sz; p += sz; count -= sz; read += sz; if (should_stop_iteration()) break; } kfree(bounce); *ppos += read; return read; failed: kfree(bounce); return err; } static ssize_t write_mem(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { phys_addr_t p = *ppos; ssize_t written, sz; unsigned long copied; void *ptr; if (p != *ppos) return -EFBIG; if (!valid_phys_addr_range(p, count)) return -EFAULT; written = 0; #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED /* we don't have page 0 mapped on sparc and m68k.. */ if (p < PAGE_SIZE) { sz = size_inside_page(p, count); /* Hmm. Do something? */ buf += sz; p += sz; count -= sz; written += sz; } #endif while (count > 0) { int allowed; sz = size_inside_page(p, count); allowed = page_is_allowed(p >> PAGE_SHIFT); if (!allowed) return -EPERM; /* Skip actual writing when a page is marked as restricted. */ if (allowed == 1) { /* * On ia64 if a page has been mapped somewhere as * uncached, then it must also be accessed uncached * by the kernel or data corruption may occur. */ ptr = xlate_dev_mem_ptr(p); if (!ptr) { if (written) break; return -EFAULT; } copied = copy_from_user(ptr, buf, sz); unxlate_dev_mem_ptr(p, ptr); if (copied) { written += sz - copied; if (written) break; return -EFAULT; } } buf += sz; p += sz; count -= sz; written += sz; if (should_stop_iteration()) break; } *ppos += written; return written; } int __weak phys_mem_access_prot_allowed(struct file *file, unsigned long pfn, unsigned long size, pgprot_t *vma_prot) { return 1; } #ifndef __HAVE_PHYS_MEM_ACCESS_PROT /* * Architectures vary in how they handle caching for addresses * outside of main memory. * */ #ifdef pgprot_noncached static int uncached_access(struct file *file, phys_addr_t addr) { #if defined(CONFIG_IA64) /* * On ia64, we ignore O_DSYNC because we cannot tolerate memory * attribute aliases. */ return !(efi_mem_attributes(addr) & EFI_MEMORY_WB); #else /* * Accessing memory above the top the kernel knows about or through a * file pointer * that was marked O_DSYNC will be done non-cached. */ if (file->f_flags & O_DSYNC) return 1; return addr >= __pa(high_memory); #endif } #endif static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, unsigned long size, pgprot_t vma_prot) { #ifdef pgprot_noncached phys_addr_t offset = pfn << PAGE_SHIFT; if (uncached_access(file, offset)) return pgprot_noncached(vma_prot); #endif return vma_prot; } #endif #ifndef CONFIG_MMU static unsigned long get_unmapped_area_mem(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { if (!valid_mmap_phys_addr_range(pgoff, len)) return (unsigned long) -EINVAL; return pgoff << PAGE_SHIFT; } /* permit direct mmap, for read, write or exec */ static unsigned memory_mmap_capabilities(struct file *file) { return NOMMU_MAP_DIRECT | NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC; } static unsigned zero_mmap_capabilities(struct file *file) { return NOMMU_MAP_COPY; } /* can't do an in-place private mapping if there's no MMU */ static inline int private_mapping_ok(struct vm_area_struct *vma) { return vma->vm_flags & VM_MAYSHARE; } #else static inline int private_mapping_ok(struct vm_area_struct *vma) { return 1; } #endif static const struct vm_operations_struct mmap_mem_ops = { #ifdef CONFIG_HAVE_IOREMAP_PROT .access = generic_access_phys #endif }; static int mmap_mem(struct file *file, struct vm_area_struct *vma) { size_t size = vma->vm_end - vma->vm_start; phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT; /* Does it even fit in phys_addr_t? */ if (offset >> PAGE_SHIFT != vma->vm_pgoff) return -EINVAL; /* It's illegal to wrap around the end of the physical address space. */ if (offset + (phys_addr_t)size - 1 < offset) return -EINVAL; if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size)) return -EINVAL; if (!private_mapping_ok(vma)) return -ENOSYS; if (!range_is_allowed(vma->vm_pgoff, size)) return -EPERM; if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size, &vma->vm_page_prot)) return -EINVAL; vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff, size, vma->vm_page_prot); vma->vm_ops = &mmap_mem_ops; /* Remap-pfn-range will mark the range VM_IO */ if (remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff, size, vma->vm_page_prot)) { return -EAGAIN; } return 0; } static ssize_t read_port(struct file *file, char __user *buf, size_t count, loff_t *ppos) { unsigned long i = *ppos; char __user *tmp = buf; if (!access_ok(buf, count)) return -EFAULT; while (count-- > 0 && i < 65536) { if (__put_user(inb(i), tmp) < 0) return -EFAULT; i++; tmp++; } *ppos = i; return tmp-buf; } static ssize_t write_port(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { unsigned long i = *ppos; const char __user *tmp = buf; if (!access_ok(buf, count)) return -EFAULT; while (count-- > 0 && i < 65536) { char c; if (__get_user(c, tmp)) { if (tmp > buf) break; return -EFAULT; } outb(c, i); i++; tmp++; } *ppos = i; return tmp-buf; } static ssize_t read_null(struct file *file, char __user *buf, size_t count, loff_t *ppos) { return 0; } static ssize_t write_null(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { return count; } static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to) { return 0; } static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from) { size_t count = iov_iter_count(from); iov_iter_advance(from, count); return count; } static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf, struct splice_desc *sd) { return sd->len; } static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null); } static int uring_cmd_null(struct io_uring_cmd *ioucmd, unsigned int issue_flags) { return 0; } static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter) { size_t written = 0; while (iov_iter_count(iter)) { size_t chunk = iov_iter_count(iter), n; if (chunk > PAGE_SIZE) chunk = PAGE_SIZE; /* Just for latency reasons */ n = iov_iter_zero(chunk, iter); if (!n && iov_iter_count(iter)) return written ? written : -EFAULT; written += n; if (signal_pending(current)) return written ? written : -ERESTARTSYS; if (!need_resched()) continue; if (iocb->ki_flags & IOCB_NOWAIT) return written ? written : -EAGAIN; cond_resched(); } return written; } static ssize_t read_zero(struct file *file, char __user *buf, size_t count, loff_t *ppos) { size_t cleared = 0; while (count) { size_t chunk = min_t(size_t, count, PAGE_SIZE); size_t left; left = clear_user(buf + cleared, chunk); if (unlikely(left)) { cleared += (chunk - left); if (!cleared) return -EFAULT; break; } cleared += chunk; count -= chunk; if (signal_pending(current)) break; cond_resched(); } return cleared; } static int mmap_zero(struct file *file, struct vm_area_struct *vma) { #ifndef CONFIG_MMU return -ENOSYS; #endif if (vma->vm_flags & VM_SHARED) return shmem_zero_setup(vma); vma_set_anonymous(vma); return 0; } static unsigned long get_unmapped_area_zero(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { #ifdef CONFIG_MMU if (flags & MAP_SHARED) { /* * mmap_zero() will call shmem_zero_setup() to create a file, * so use shmem's get_unmapped_area in case it can be huge; * and pass NULL for file as in mmap.c's get_unmapped_area(), * so as not to confuse shmem with our handle on "/dev/zero". */ return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags); } /* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */ return current->mm->get_unmapped_area(file, addr, len, pgoff, flags); #else return -ENOSYS; #endif } static ssize_t write_full(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { return -ENOSPC; } /* * Special lseek() function for /dev/null and /dev/zero. Most notably, you * can fopen() both devices with "a" now. This was previously impossible. * -- SRB. */ static loff_t null_lseek(struct file *file, loff_t offset, int orig) { return file->f_pos = 0; } /* * The memory devices use the full 32/64 bits of the offset, and so we cannot * check against negative addresses: they are ok. The return value is weird, * though, in that case (0). * * also note that seeking relative to the "end of file" isn't supported: * it has no meaning, so it returns -EINVAL. */ static loff_t memory_lseek(struct file *file, loff_t offset, int orig) { loff_t ret; inode_lock(file_inode(file)); switch (orig) { case SEEK_CUR: offset += file->f_pos; fallthrough; case SEEK_SET: /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */ if ((unsigned long long)offset >= -MAX_ERRNO) { ret = -EOVERFLOW; break; } file->f_pos = offset; ret = file->f_pos; force_successful_syscall_return(); break; default: ret = -EINVAL; } inode_unlock(file_inode(file)); return ret; } static int open_port(struct inode *inode, struct file *filp) { int rc; if (!capable(CAP_SYS_RAWIO)) return -EPERM; rc = security_locked_down(LOCKDOWN_DEV_MEM); if (rc) return rc; if (iminor(inode) != DEVMEM_MINOR) return 0; /* * Use a unified address space to have a single point to manage * revocations when drivers want to take over a /dev/mem mapped * range. */ filp->f_mapping = iomem_get_mapping(); return 0; } #define zero_lseek null_lseek #define full_lseek null_lseek #define write_zero write_null #define write_iter_zero write_iter_null #define open_mem open_port static const struct file_operations __maybe_unused mem_fops = { .llseek = memory_lseek, .read = read_mem, .write = write_mem, .mmap = mmap_mem, .open = open_mem, #ifndef CONFIG_MMU .get_unmapped_area = get_unmapped_area_mem, .mmap_capabilities = memory_mmap_capabilities, #endif }; static const struct file_operations null_fops = { .llseek = null_lseek, .read = read_null, .write = write_null, .read_iter = read_iter_null, .write_iter = write_iter_null, .splice_write = splice_write_null, .uring_cmd = uring_cmd_null, }; static const struct file_operations __maybe_unused port_fops = { .llseek = memory_lseek, .read = read_port, .write = write_port, .open = open_port, }; static const struct file_operations zero_fops = { .llseek = zero_lseek, .write = write_zero, .read_iter = read_iter_zero, .read = read_zero, .write_iter = write_iter_zero, .mmap = mmap_zero, .get_unmapped_area = get_unmapped_area_zero, #ifndef CONFIG_MMU .mmap_capabilities = zero_mmap_capabilities, #endif }; static const struct file_operations full_fops = { .llseek = full_lseek, .read_iter = read_iter_zero, .write = write_full, }; static const struct memdev { const char *name; umode_t mode; const struct file_operations *fops; fmode_t fmode; } devlist[] = { #ifdef CONFIG_DEVMEM [DEVMEM_MINOR] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET }, #endif [3] = { "null", 0666, &null_fops, FMODE_NOWAIT }, #ifdef CONFIG_DEVPORT [4] = { "port", 0, &port_fops, 0 }, #endif [5] = { "zero", 0666, &zero_fops, FMODE_NOWAIT }, [7] = { "full", 0666, &full_fops, 0 }, [8] = { "random", 0666, &random_fops, FMODE_NOWAIT }, [9] = { "urandom", 0666, &urandom_fops, FMODE_NOWAIT }, #ifdef CONFIG_PRINTK [11] = { "kmsg", 0644, &kmsg_fops, 0 }, #endif }; static int memory_open(struct inode *inode, struct file *filp) { int minor; const struct memdev *dev; minor = iminor(inode); if (minor >= ARRAY_SIZE(devlist)) return -ENXIO; dev = &devlist[minor]; if (!dev->fops) return -ENXIO; filp->f_op = dev->fops; filp->f_mode |= dev->fmode; if (dev->fops->open) return dev->fops->open(inode, filp); return 0; } static const struct file_operations memory_fops = { .open = memory_open, .llseek = noop_llseek, }; static char *mem_devnode(struct device *dev, umode_t *mode) { if (mode && devlist[MINOR(dev->devt)].mode) *mode = devlist[MINOR(dev->devt)].mode; return NULL; } static struct class *mem_class; static int __init chr_dev_init(void) { int minor; if (register_chrdev(MEM_MAJOR, "mem", &memory_fops)) printk("unable to get major %d for memory devs\n", MEM_MAJOR); mem_class = class_create(THIS_MODULE, "mem"); if (IS_ERR(mem_class)) return PTR_ERR(mem_class); mem_class->devnode = mem_devnode; for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) { if (!devlist[minor].name) continue; /* * Create /dev/port? */ if ((minor == DEVPORT_MINOR) && !arch_has_dev_port()) continue; device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor), NULL, devlist[minor].name); } return tty_init(); } fs_initcall(chr_dev_init);