summaryrefslogtreecommitdiffstats
path: root/drivers/char/mem.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/char/mem.c')
-rw-r--r--drivers/char/mem.c787
1 files changed, 787 insertions, 0 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
new file mode 100644
index 000000000..5611d1273
--- /dev/null
+++ b/drivers/char/mem.c
@@ -0,0 +1,787 @@
+// 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);
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-28 06:06:47 +0000