physmem.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  4 */
  5
  6#include <linux/module.h>
  7#include <linux/memblock.h>
  8#include <linux/mm.h>
  9#include <linux/pfn.h>
 10#include <asm/page.h>
 11#include <asm/sections.h>
 12#include <as-layout.h>
 13#include <init.h>
 14#include <kern.h>
 15#include <kern_util.h>
 16#include <mem_user.h>
 17#include <os.h>
 18
 19static int physmem_fd = -1;
 20
 21/* Changed during early boot */
 22unsigned long high_physmem;
 23EXPORT_SYMBOL(high_physmem);
 24
 25void map_memory(unsigned long virt, unsigned long phys, unsigned long len,
 26		int r, int w, int x)
 27{
 28	__u64 offset;
 29	int fd, err;
 30
 31	fd = phys_mapping(phys, &offset);
 32	err = os_map_memory((void *) virt, fd, offset, len, r, w, x);
 33	if (err) {
 34		if (err == -ENOMEM)
 35			printk(KERN_ERR "try increasing the host's "
 36			       "/proc/sys/vm/max_map_count to <physical "
 37			       "memory size>/4096\n");
 38		panic("map_memory(0x%lx, %d, 0x%llx, %ld, %d, %d, %d) failed, "
 39		      "err = %d\n", virt, fd, offset, len, r, w, x, err);
 40	}
 41}
 42
 43/**
 44 * setup_physmem() - Setup physical memory for UML
 45 * @start:	Start address of the physical kernel memory,
 46 *		i.e start address of the executable image.
 47 * @reserve_end:	end address of the physical kernel memory.
 48 * @len:	Length of total physical memory that should be mapped/made
 49 *		available, in bytes.
 50 *
 51 * Creates an unlinked temporary file of size (len) and memory maps
 52 * it on the last executable image address (uml_reserved).
 53 *
 54 * The offset is needed as the length of the total physical memory
 55 * (len) includes the size of the memory used be the executable image,
 56 * but the mapped-to address is the last address of the executable image
 57 * (uml_reserved == end address of executable image).
 58 *
 59 * The memory mapped memory of the temporary file is used as backing memory
 60 * of all user space processes/kernel tasks.
 61 */
 62void __init setup_physmem(unsigned long start, unsigned long reserve_end,
 63			  unsigned long len)
 64{
 65	unsigned long reserve = reserve_end - start;
 66	unsigned long map_size = len - reserve;
 67	int err;
 68
 69	if (len <= reserve) {
 70		os_warn("Too few physical memory! Needed=%lu, given=%lu\n",
 71			reserve, len);
 72		exit(1);
 73	}
 74
 75	physmem_fd = create_mem_file(len);
 76
 77	err = os_map_memory((void *) reserve_end, physmem_fd, reserve,
 78			    map_size, 1, 1, 1);
 79	if (err < 0) {
 80		os_warn("setup_physmem - mapping %lu bytes of memory at 0x%p "
 81			"failed - errno = %d\n", map_size,
 82			(void *) reserve_end, err);
 83		exit(1);
 84	}
 85
 86	/*
 87	 * Special kludge - This page will be mapped in to userspace processes
 88	 * from physmem_fd, so it needs to be written out there.
 89	 */
 90	os_seek_file(physmem_fd, __pa(__syscall_stub_start));
 91	os_write_file(physmem_fd, __syscall_stub_start, PAGE_SIZE);
 92
 93	memblock_add(__pa(start), len);
 94	memblock_reserve(__pa(start), reserve);
 95
 96	min_low_pfn = PFN_UP(__pa(reserve_end));
 97	max_low_pfn = min_low_pfn + (map_size >> PAGE_SHIFT);
 98}
 99
100int phys_mapping(unsigned long phys, unsigned long long *offset_out)
101{
102	int fd = -1;
103
104	if (phys < physmem_size) {
105		fd = physmem_fd;
106		*offset_out = phys;
107	}
108
109	return fd;
110}
111EXPORT_SYMBOL(phys_mapping);
112
113static int __init uml_mem_setup(char *line, int *add)
114{
115	char *retptr;
116
117	*add = 0;
118	physmem_size = memparse(line,&retptr);
119	return 0;
120}
121__uml_setup("mem=", uml_mem_setup,
122"mem=<Amount of desired ram>\n"
123"    This controls how much \"physical\" memory the kernel allocates\n"
124"    for the system. The size is specified as a number followed by\n"
125"    one of 'k', 'K', 'm', 'M', which have the obvious meanings.\n"
126"    This is not related to the amount of memory in the host.  It can\n"
127"    be more, and the excess, if it's ever used, will just be swapped out.\n"
128"	Example: mem=64M\n\n"
129);