// 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>

#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);

}

#else

static inline int page_is_allowed(unsigned long pfn)

{

	return 1;

}

#endif

static inline bool should_stop_iteration(void)

{

	if (need_resched())

		cond_resched();

	return signal_pending(current);

}

/**

 * SPDX-Req-ID: a89784c55426aec4b8ba345f281a0ec478d43897a0a248618cb140c03c770c75

 * SPDX-Req-Text:

 * read_mem - read from physical memory (/dev/mem).

 * @file: struct file associated with /dev/mem.

 * @buf: user-space buffer to copy data to.

 * @count: number of bytes to read.

 * @ppos: pointer to the current file position, representing the physical

 *        address to read from.

 *

 * This function checks if the requested physical memory range is valid

 * and accessible by the user, then it copies data to the input

 * user-space buffer up to the requested number of bytes.

 *

 * Function's expectations:

 *

 * 1. This function shall check if the value pointed by ppos exceeds the

 *    maximum addressable physical address;

 *

 * 2. This function shall check if the physical address range to be read

 *    is valid (i.e. it falls within a memory block and if it can be mapped

 *    to the kernel address space);

 *

 * 3. For each memory page falling in the requested physical range

 *    [ppos, ppos + count - 1]:

 *   3.1. this function shall check if user space access is allowed (if

 *        config STRICT_DEVMEM is not set, access is always granted);

 *

 *   3.2. if access is allowed, the memory content from the page range falling

 *        within the requested physical range shall be copied to the user space

 *        buffer;

 *

 *   3.3. zeros shall be copied to the user space buffer (for the page range

 *        falling within the requested physical range):

 *     3.3.1. if access to the memory page is restricted or,

 *     3.2.2. if the current page is page 0 on HW architectures where page 0 is

 *            not mapped.

 *

 * 4. The file position '*ppos' shall be advanced by the number of bytes

 *    successfully copied to user space (including zeros).

 *

 * Context: process context.

 *

 * Return:

 * * the number of bytes copied to user on success

 * * %-EFAULT - the requested address range is not valid or a fault happened

 *   when copying to user-space (i.e. copy_from_kernel_nofault() failed)

 * * %-EPERM - access to any of the required physical pages is not allowed

 * * %-ENOMEM - out of memory error for auxiliary kernel buffers supporting

 *   the operation of copying content from the physical pages

 *

 * SPDX-Req-End

 */

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;

}

/**

 * SPDX-Req-ID: 6e16917c09ee583de5dc9e8a24a406e75bb229554699a501cfa8efdb308862d7

 * SPDX-Req-Text:

 * write_mem - write to physical memory (/dev/mem).

 * @file: struct file associated with /dev/mem.

 * @buf: user-space buffer containing the data to write.

 * @count: number of bytes to write.

 * @ppos: pointer to the current file position, representing the physical

 *        address to write to.

 *

 * This function checks if the target physical memory range is valid

 * and accessible by the user, then it writes data from the input

 * user-space buffer up to the requested number of bytes.

 *

 * Function's expectations:

 * 1. This function shall check if the value pointed by ppos exceeds the

 *    maximum addressable physical address;

 *

 * 2. This function shall check if the physical address range to be written

 *    is valid (i.e. it falls within a memory block and if it can be mapped

 *    to the kernel address space);

 *

 * 3. For each memory page falling in the physical range to be written

 *    [ppos, ppos + count - 1]:

 *   3.1. this function shall check if user space access is allowed (if

 *        config STRICT_DEVMEM is not set, access is always granted);

 *

 *   3.2. the content from the user space buffer shall be copied to the page

 *        range falling within the physical range to be written if access is

 *        allowed;

 *

 *   3.3. the data to be copied from the user space buffer (for the page range

 *        falling within the range to be written) shall be skipped:

 *     3.3.1. if access to the memory page is restricted or,

 *     3.3.2. if the current page is page 0 on HW architectures where page 0

 *            is not mapped.

 *

 * 4. The file position '*ppos' shall be advanced by the number of bytes

 *    successfully copied from user space (including skipped bytes).

 *

 * Context: process context.

 *

 * Return:

 * * the number of bytes copied from user-space on success

 * * %-EFBIG - the value pointed by ppos exceeds the maximum addressable

 *   physical address

 * * %-EFAULT - the physical address range is not valid or no bytes could

 *   be copied from user-space

 * * %-EPERM - access to any of the required pages is not allowed

 *

 * SPDX-Req-End

 */

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)

{

	/*

	 * 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

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 is_nommu_shared_mapping(vma->vm_flags);

}

#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

};

/**

 * SPDX-Req-ID: 032b3f1c9e61452bf826328d95fae043c4ea4b966ad6583a0377554d3c4f2d76

 * SPDX-Req-Text:

 * mmap_mem - map physical memory into user space (/dev/mem).

 * @file: file structure for the device.

 * @vma: virtual memory area structure describing the user mapping.

 *

 * This function checks if the requested physical memory range is valid

 * and accessible by the user, then it maps the physical memory range to

 * user-mode address space.

 *

 * Function's expectations:

 * 1. This function shall check if the requested physical address range to be

 *    mapped fits within the maximum addressable physical range;

 *

 * 2. This function shall check if the requested  physical range corresponds to

 *    a valid physical range and if access is allowed on it (if config STRICT_DEVMEM

 *    is not set, access is always allowed);

 *

 * 3. This function shall check if the input virtual memory area can be used for

 *    a private mapping (always OK if there is an MMU);

 *

 * 4. This function shall set the virtual memory area operations to

 *    &mmap_mem_ops;

 *

 * 5. This function shall establish a mapping between the user-space

 *    virtual memory area described by vma and the physical memory

 *    range specified by vma->vm_pgoff and size;

 *

 * Context: process context.

 *

 * Return:

 * * 0 on success

 * * %-EAGAIN - invalid or unsupported mapping requested (remap_pfn_range()

 *   fails)

 * * %-EINVAL - requested physical range to be mapped is not valid

 * * %-EPERM - no permission to access the requested physical range

 *

 * SPDX-Req-End

 */

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;

}

#ifdef CONFIG_DEVPORT

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;

}

#endif

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;

}

#ifndef CONFIG_MMU

static unsigned long get_unmapped_area_zero(struct file *file,

				unsigned long addr, unsigned long len,

				unsigned long pgoff, unsigned long flags)

{

	return -ENOSYS;

}

#else

static unsigned long get_unmapped_area_zero(struct file *file,

				unsigned long addr, unsigned long len,

				unsigned long pgoff, unsigned long flags)

{

	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,

	 * attempt to map aligned to huge page size if possible, otherwise we

	 * fall back to system page size mappings.

	 */

#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	return thp_get_unmapped_area(file, addr, len, pgoff, flags);

#else

	return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);

#endif

}

#endif /* CONFIG_MMU */

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;

}

/**

 * SPDX-Req-ID: feb4cb915f91d319078204293f6cf99eb50e775a8f670e478e30e84bd6979a14

 * SPDX-Req-Text:

 * memory_lseek - change the file position.

 * @file: file structure for the device.

 * @offset: file offset to seek to.

 * @orig: where to start seeking from (see whence in the llseek manpage).

 *

 * This function changes the file position according to the input offset

 * and orig parameters.

 *

 * Function's expectations:

 * 1. This function shall lock the semaphore of the inode corresponding to the

 *    input file before any operation and unlock it before returning.

 *

 * 2. This function shall check the orig value and accordingly:

 *   2.1. if it is equal to SEEK_CUR, the current file position shall be

 *        incremented by the input offset;

 *   2.2. if it is equal to SEEK_SET, the current file position shall be

 *        set to the input offset value;

 *   2.3. any other value shall result in an error condition.

 *

 * 3. Before writing the current file position, the new position value

 *    shall be checked to not overlap with Linux ERRNO values.

 *

 * Assumptions of Use:

 * 1. the input file pointer is expected to be valid.

 *

 * Notes:

 * 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 passing orig equal to SEEK_END returns -EINVAL.

 *

 * Context: process context, locks/unlocks inode->i_rwsem

 *

 * Return:

 * * the new file position on success

 * * %-EOVERFLOW - the new position value equals or exceeds

 *   (unsigned long long) -MAX_ERRNO

 * * %-EINVAL - the orig parameter is invalid

 *

 * SPDX-Req-End

 */

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;

}