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![Linus Torvalds](/assets/img/avatar_default.png)
This reverts commit 6f98a4bfee
.
It turns out we still can't do this. Way too many platforms that don't
have any real source of randomness at boot and no jitter entropy because
they don't even have a cycle counter.
As reported by Guenter Roeck:
"This causes a large number of qemu boot test failures for various
architectures (arm, m68k, microblaze, sparc32, xtensa are the ones I
observed).
Common denominator is that boot hangs at 'Saving random seed:'"
This isn't hugely unexpected - we tried it, it failed, so now we'll
revert it.
Link: https://lore.kernel.org/all/20220322155820.GA1745955@roeck-us.net/
Reported-and-bisected-by: Guenter Roeck <linux@roeck-us.net>
Cc: Jason Donenfeld <Jason@zx2c4.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
781 lines
16 KiB
C
781 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/drivers/char/mem.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* Added devfs support.
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* Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
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* Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
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*/
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#include <linux/mm.h>
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#include <linux/miscdevice.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/mman.h>
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#include <linux/random.h>
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#include <linux/init.h>
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#include <linux/tty.h>
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#include <linux/capability.h>
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#include <linux/ptrace.h>
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#include <linux/device.h>
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#include <linux/highmem.h>
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#include <linux/backing-dev.h>
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#include <linux/shmem_fs.h>
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#include <linux/splice.h>
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#include <linux/pfn.h>
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#include <linux/export.h>
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#include <linux/io.h>
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#include <linux/uio.h>
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#include <linux/uaccess.h>
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#include <linux/security.h>
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#ifdef CONFIG_IA64
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# include <linux/efi.h>
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#endif
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#define DEVMEM_MINOR 1
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#define DEVPORT_MINOR 4
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static inline unsigned long size_inside_page(unsigned long start,
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unsigned long size)
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{
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unsigned long sz;
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sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
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return min(sz, size);
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}
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#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
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static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
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{
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return addr + count <= __pa(high_memory);
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}
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static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
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{
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return 1;
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}
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#endif
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#ifdef CONFIG_STRICT_DEVMEM
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static inline int page_is_allowed(unsigned long pfn)
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{
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return devmem_is_allowed(pfn);
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}
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static inline int range_is_allowed(unsigned long pfn, unsigned long size)
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{
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u64 from = ((u64)pfn) << PAGE_SHIFT;
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u64 to = from + size;
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u64 cursor = from;
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while (cursor < to) {
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if (!devmem_is_allowed(pfn))
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return 0;
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cursor += PAGE_SIZE;
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pfn++;
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}
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return 1;
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}
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#else
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static inline int page_is_allowed(unsigned long pfn)
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{
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return 1;
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}
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static inline int range_is_allowed(unsigned long pfn, unsigned long size)
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{
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return 1;
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}
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#endif
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#ifndef unxlate_dev_mem_ptr
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#define unxlate_dev_mem_ptr unxlate_dev_mem_ptr
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void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
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{
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}
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#endif
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static inline bool should_stop_iteration(void)
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{
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if (need_resched())
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cond_resched();
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return fatal_signal_pending(current);
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}
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/*
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* This funcion reads the *physical* memory. The f_pos points directly to the
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* memory location.
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*/
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static ssize_t read_mem(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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phys_addr_t p = *ppos;
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ssize_t read, sz;
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void *ptr;
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char *bounce;
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int err;
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if (p != *ppos)
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return 0;
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if (!valid_phys_addr_range(p, count))
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return -EFAULT;
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read = 0;
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#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
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/* we don't have page 0 mapped on sparc and m68k.. */
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if (p < PAGE_SIZE) {
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sz = size_inside_page(p, count);
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if (sz > 0) {
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if (clear_user(buf, sz))
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return -EFAULT;
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buf += sz;
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p += sz;
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count -= sz;
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read += sz;
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}
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}
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#endif
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bounce = kmalloc(PAGE_SIZE, GFP_KERNEL);
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if (!bounce)
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return -ENOMEM;
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while (count > 0) {
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unsigned long remaining;
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int allowed, probe;
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sz = size_inside_page(p, count);
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err = -EPERM;
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allowed = page_is_allowed(p >> PAGE_SHIFT);
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if (!allowed)
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goto failed;
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err = -EFAULT;
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if (allowed == 2) {
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/* Show zeros for restricted memory. */
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remaining = clear_user(buf, sz);
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} else {
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/*
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* On ia64 if a page has been mapped somewhere as
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* uncached, then it must also be accessed uncached
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* by the kernel or data corruption may occur.
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*/
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ptr = xlate_dev_mem_ptr(p);
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if (!ptr)
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goto failed;
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probe = copy_from_kernel_nofault(bounce, ptr, sz);
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unxlate_dev_mem_ptr(p, ptr);
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if (probe)
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goto failed;
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remaining = copy_to_user(buf, bounce, sz);
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}
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if (remaining)
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goto failed;
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buf += sz;
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p += sz;
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count -= sz;
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read += sz;
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if (should_stop_iteration())
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break;
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}
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kfree(bounce);
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*ppos += read;
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return read;
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failed:
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kfree(bounce);
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return err;
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}
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static ssize_t write_mem(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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phys_addr_t p = *ppos;
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ssize_t written, sz;
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unsigned long copied;
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void *ptr;
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if (p != *ppos)
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return -EFBIG;
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if (!valid_phys_addr_range(p, count))
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return -EFAULT;
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written = 0;
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#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
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/* we don't have page 0 mapped on sparc and m68k.. */
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if (p < PAGE_SIZE) {
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sz = size_inside_page(p, count);
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/* Hmm. Do something? */
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buf += sz;
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p += sz;
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count -= sz;
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written += sz;
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}
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#endif
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while (count > 0) {
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int allowed;
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sz = size_inside_page(p, count);
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allowed = page_is_allowed(p >> PAGE_SHIFT);
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if (!allowed)
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return -EPERM;
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/* Skip actual writing when a page is marked as restricted. */
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if (allowed == 1) {
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/*
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* On ia64 if a page has been mapped somewhere as
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* uncached, then it must also be accessed uncached
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* by the kernel or data corruption may occur.
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*/
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ptr = xlate_dev_mem_ptr(p);
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if (!ptr) {
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if (written)
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break;
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return -EFAULT;
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}
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copied = copy_from_user(ptr, buf, sz);
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unxlate_dev_mem_ptr(p, ptr);
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if (copied) {
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written += sz - copied;
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if (written)
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break;
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return -EFAULT;
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}
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}
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buf += sz;
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p += sz;
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count -= sz;
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written += sz;
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if (should_stop_iteration())
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break;
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}
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*ppos += written;
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return written;
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}
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int __weak phys_mem_access_prot_allowed(struct file *file,
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unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
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{
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return 1;
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}
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#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
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/*
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* Architectures vary in how they handle caching for addresses
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* outside of main memory.
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*
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*/
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#ifdef pgprot_noncached
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static int uncached_access(struct file *file, phys_addr_t addr)
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{
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#if defined(CONFIG_IA64)
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/*
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* On ia64, we ignore O_DSYNC because we cannot tolerate memory
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* attribute aliases.
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*/
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return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
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#else
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/*
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* Accessing memory above the top the kernel knows about or through a
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* file pointer
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* that was marked O_DSYNC will be done non-cached.
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*/
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if (file->f_flags & O_DSYNC)
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return 1;
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return addr >= __pa(high_memory);
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#endif
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}
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#endif
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static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
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unsigned long size, pgprot_t vma_prot)
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{
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#ifdef pgprot_noncached
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phys_addr_t offset = pfn << PAGE_SHIFT;
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if (uncached_access(file, offset))
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return pgprot_noncached(vma_prot);
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#endif
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return vma_prot;
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}
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#endif
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#ifndef CONFIG_MMU
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static unsigned long get_unmapped_area_mem(struct file *file,
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unsigned long addr,
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unsigned long len,
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unsigned long pgoff,
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unsigned long flags)
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{
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if (!valid_mmap_phys_addr_range(pgoff, len))
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return (unsigned long) -EINVAL;
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return pgoff << PAGE_SHIFT;
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}
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/* permit direct mmap, for read, write or exec */
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static unsigned memory_mmap_capabilities(struct file *file)
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{
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return NOMMU_MAP_DIRECT |
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NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
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}
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static unsigned zero_mmap_capabilities(struct file *file)
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{
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return NOMMU_MAP_COPY;
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}
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/* can't do an in-place private mapping if there's no MMU */
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static inline int private_mapping_ok(struct vm_area_struct *vma)
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{
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return vma->vm_flags & VM_MAYSHARE;
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}
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#else
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static inline int private_mapping_ok(struct vm_area_struct *vma)
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{
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return 1;
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}
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#endif
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static const struct vm_operations_struct mmap_mem_ops = {
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#ifdef CONFIG_HAVE_IOREMAP_PROT
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.access = generic_access_phys
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#endif
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};
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static int mmap_mem(struct file *file, struct vm_area_struct *vma)
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{
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size_t size = vma->vm_end - vma->vm_start;
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phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
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/* Does it even fit in phys_addr_t? */
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if (offset >> PAGE_SHIFT != vma->vm_pgoff)
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return -EINVAL;
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/* It's illegal to wrap around the end of the physical address space. */
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if (offset + (phys_addr_t)size - 1 < offset)
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return -EINVAL;
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if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
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return -EINVAL;
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if (!private_mapping_ok(vma))
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return -ENOSYS;
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if (!range_is_allowed(vma->vm_pgoff, size))
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return -EPERM;
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if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
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&vma->vm_page_prot))
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return -EINVAL;
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vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
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size,
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vma->vm_page_prot);
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vma->vm_ops = &mmap_mem_ops;
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/* Remap-pfn-range will mark the range VM_IO */
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if (remap_pfn_range(vma,
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vma->vm_start,
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vma->vm_pgoff,
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size,
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vma->vm_page_prot)) {
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return -EAGAIN;
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}
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return 0;
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}
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static ssize_t read_port(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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unsigned long i = *ppos;
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char __user *tmp = buf;
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if (!access_ok(buf, count))
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return -EFAULT;
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while (count-- > 0 && i < 65536) {
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if (__put_user(inb(i), tmp) < 0)
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return -EFAULT;
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i++;
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tmp++;
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}
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*ppos = i;
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return tmp-buf;
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}
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static ssize_t write_port(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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unsigned long i = *ppos;
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const char __user *tmp = buf;
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if (!access_ok(buf, count))
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return -EFAULT;
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while (count-- > 0 && i < 65536) {
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char c;
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if (__get_user(c, tmp)) {
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if (tmp > buf)
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break;
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return -EFAULT;
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}
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outb(c, i);
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i++;
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tmp++;
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}
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*ppos = i;
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return tmp-buf;
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}
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static ssize_t read_null(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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return 0;
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}
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static ssize_t write_null(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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return count;
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}
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static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
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{
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return 0;
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}
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static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
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{
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size_t count = iov_iter_count(from);
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iov_iter_advance(from, count);
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return count;
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}
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static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
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struct splice_desc *sd)
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{
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return sd->len;
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}
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static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
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loff_t *ppos, size_t len, unsigned int flags)
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{
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return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
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}
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static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
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{
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size_t written = 0;
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while (iov_iter_count(iter)) {
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size_t chunk = iov_iter_count(iter), n;
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if (chunk > PAGE_SIZE)
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chunk = PAGE_SIZE; /* Just for latency reasons */
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n = iov_iter_zero(chunk, iter);
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if (!n && iov_iter_count(iter))
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return written ? written : -EFAULT;
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written += n;
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if (signal_pending(current))
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return written ? written : -ERESTARTSYS;
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if (!need_resched())
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continue;
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if (iocb->ki_flags & IOCB_NOWAIT)
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return written ? written : -EAGAIN;
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cond_resched();
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}
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return written;
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}
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static ssize_t read_zero(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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size_t cleared = 0;
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while (count) {
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size_t chunk = min_t(size_t, count, PAGE_SIZE);
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size_t left;
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left = clear_user(buf + cleared, chunk);
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if (unlikely(left)) {
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cleared += (chunk - left);
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if (!cleared)
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return -EFAULT;
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break;
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}
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cleared += chunk;
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count -= chunk;
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if (signal_pending(current))
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break;
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cond_resched();
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}
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return cleared;
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}
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static int mmap_zero(struct file *file, struct vm_area_struct *vma)
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{
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#ifndef CONFIG_MMU
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return -ENOSYS;
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#endif
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if (vma->vm_flags & VM_SHARED)
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return shmem_zero_setup(vma);
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vma_set_anonymous(vma);
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return 0;
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}
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static unsigned long get_unmapped_area_zero(struct file *file,
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unsigned long addr, unsigned long len,
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unsigned long pgoff, unsigned long flags)
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{
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|
#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,
|
|
};
|
|
|
|
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, 0 },
|
|
[9] = { "urandom", 0666, &urandom_fops, 0 },
|
|
#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);
|