// 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 <[email protected]> * Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <[email protected]> */ #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 … #define DEVPORT_MINOR … static inline unsigned long size_inside_page(unsigned long start, unsigned long 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) { … } static inline int range_is_allowed(unsigned long pfn, unsigned long size) { … } #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 static inline bool should_stop_iteration(void) { … } /* * 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) { … } static ssize_t write_mem(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { … } int __weak phys_mem_access_prot_allowed(struct file *file, unsigned long pfn, unsigned long size, pgprot_t *vma_prot) { … } #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) { … } #endif static const struct vm_operations_struct mmap_mem_ops = …; static int mmap_mem(struct file *file, struct vm_area_struct *vma) { … } #ifdef CONFIG_DEVPORT static ssize_t read_port(struct file *file, char __user *buf, size_t count, loff_t *ppos) { … } static ssize_t write_port(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { … } #endif static ssize_t read_null(struct file *file, char __user *buf, size_t count, loff_t *ppos) { … } static ssize_t write_null(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { … } static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to) { … } static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from) { … } static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf, struct splice_desc *sd) { … } static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { … } static int uring_cmd_null(struct io_uring_cmd *ioucmd, unsigned int issue_flags) { … } static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter) { … } static ssize_t read_zero(struct file *file, char __user *buf, size_t count, loff_t *ppos) { … } static int mmap_zero(struct file *file, struct vm_area_struct *vma) { … } static unsigned long get_unmapped_area_zero(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { … } static ssize_t write_full(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { … } /* * 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) { … } /* * 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) { … } static int open_port(struct inode *inode, struct file *filp) { … } #define zero_lseek … #define full_lseek … #define write_zero … #define write_iter_zero … #define splice_write_zero … #define open_mem … static const struct file_operations __maybe_unused mem_fops = …; static const struct file_operations null_fops = …; #ifdef CONFIG_DEVPORT static const struct file_operations port_fops = …; #endif static const struct file_operations zero_fops = …; static const struct file_operations full_fops = …; static const struct memdev { … } devlist[] = …; static int memory_open(struct inode *inode, struct file *filp) { … } static const struct file_operations memory_fops = …; static char *mem_devnode(const struct device *dev, umode_t *mode) { … } static const struct class mem_class = …; static int __init chr_dev_init(void) { … } fs_initcall(chr_dev_init);
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