arch/powerpc/mm/mem.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  PowerPC version
  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
  *
  *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
  *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
  *    Copyright (C) 1996 Paul Mackerras
  *  PPC44x/36-bit changes by Matt Porter (mporter@mvista.com)
  *
  *  Derived from "arch/i386/mm/init.c"
  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  */

 #include <linux/memblock.h>
 #include <linux/highmem.h>
 #include <linux/suspend.h>
 #include <linux/dma-direct.h>

 #include <asm/machdep.h>
 #include <asm/rtas.h>
 #include <asm/kasan.h>
 #include <asm/sparsemem.h>
 #include <asm/svm.h>

 #include <mm/mmu_decl.h>

 unsigned long long memory_limit;
 bool init_mem_is_free;

 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
 EXPORT_SYMBOL(empty_zero_page);

 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
 {
 	if (ppc_md.phys_mem_access_prot)
 		return ppc_md.phys_mem_access_prot(file, pfn, size, vma_prot);

 	if (!page_is_ram(pfn))
 		vma_prot = pgprot_noncached(vma_prot);

 	return vma_prot;
 }
 EXPORT_SYMBOL(phys_mem_access_prot);

 #ifdef CONFIG_MEMORY_HOTPLUG
 static DEFINE_MUTEX(linear_mapping_mutex);

 #ifdef CONFIG_NUMA
 int memory_add_physaddr_to_nid(u64 start)
 {
 	return hot_add_scn_to_nid(start);
 }
 #endif

 int __weak create_section_mapping(unsigned long start, unsigned long end,
 				  int nid, pgprot_t prot)
 {
 	return -ENODEV;
 }

 int __weak remove_section_mapping(unsigned long start, unsigned long end)
 {
 	return -ENODEV;
 }

 int __ref arch_create_linear_mapping(int nid, u64 start, u64 size,
 				     struct mhp_params *params)
 {
 	int rc;

 	start = (unsigned long)__va(start);
 	mutex_lock(&linear_mapping_mutex);
 	rc = create_section_mapping(start, start + size, nid,
 				    params->pgprot);
 	mutex_unlock(&linear_mapping_mutex);
 	if (rc) {
 		pr_warn("Unable to create linear mapping for 0x%llx..0x%llx: %d\n",
 			start, start + size, rc);
 		return -EFAULT;
 	}
 	return 0;
 }

 void __ref arch_remove_linear_mapping(u64 start, u64 size)
 {
 	int ret;

 	/* Remove htab bolted mappings for this section of memory */
 	start = (unsigned long)__va(start);

 	mutex_lock(&linear_mapping_mutex);
 	ret = remove_section_mapping(start, start + size);
 	mutex_unlock(&linear_mapping_mutex);
 	if (ret)
 		pr_warn("Unable to remove linear mapping for 0x%llx..0x%llx: %d\n",
 			start, start + size, ret);

 	/* Ensure all vmalloc mappings are flushed in case they also
 	 * hit that section of memory
 	 */
 	vm_unmap_aliases();
 }

 int __ref arch_add_memory(int nid, u64 start, u64 size,
 			  struct mhp_params *params)
 {
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int rc;

 	rc = arch_create_linear_mapping(nid, start, size, params);
 	if (rc)
 		return rc;
 	rc = __add_pages(nid, start_pfn, nr_pages, params);
 	if (rc)
 		arch_remove_linear_mapping(start, size);
 	return rc;
 }

 void __ref arch_remove_memory(int nid, u64 start, u64 size,
 			      struct vmem_altmap *altmap)
 {
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;

 	__remove_pages(start_pfn, nr_pages, altmap);
 	arch_remove_linear_mapping(start, size);
 }
 #endif

 #ifndef CONFIG_NUMA
 void __init mem_topology_setup(void)
 {
 	max_low_pfn = max_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
 	min_low_pfn = MEMORY_START >> PAGE_SHIFT;
 #ifdef CONFIG_HIGHMEM
 	max_low_pfn = lowmem_end_addr >> PAGE_SHIFT;
 #endif

 	/* Place all memblock_regions in the same node and merge contiguous
 	 * memblock_regions
 	 */
 	memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
 }

 void __init initmem_init(void)
 {
 	sparse_init();
 }

 /* mark pages that don't exist as nosave */
 static int __init mark_nonram_nosave(void)
 {
 	unsigned long spfn, epfn, prev = 0;
 	int i;

 	for_each_mem_pfn_range(i, MAX_NUMNODES, &spfn, &epfn, NULL) {
 		if (prev && prev < spfn)
 			register_nosave_region(prev, spfn);

 		prev = epfn;
 	}

 	return 0;
 }
 #else /* CONFIG_NUMA */
 static int __init mark_nonram_nosave(void)
 {
 	return 0;
 }
 #endif

 /*
  * Zones usage:
  *
  * We setup ZONE_DMA to be 31-bits on all platforms and ZONE_NORMAL to be
  * everything else. GFP_DMA32 page allocations automatically fall back to
  * ZONE_DMA.
  *
  * By using 31-bit unconditionally, we can exploit zone_dma_bits to inform the
  * generic DMA mapping code.  32-bit only devices (if not handled by an IOMMU
  * anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
  * ZONE_DMA.
  */
 static unsigned long max_zone_pfns[MAX_NR_ZONES];

 /*
  * paging_init() sets up the page tables - in fact we've already done this.
  */
 void __init paging_init(void)
 {
 	unsigned long long total_ram = memblock_phys_mem_size();
 	phys_addr_t top_of_ram = memblock_end_of_DRAM();

 #ifdef CONFIG_HIGHMEM
 	unsigned long v = __fix_to_virt(FIX_KMAP_END);
 	unsigned long end = __fix_to_virt(FIX_KMAP_BEGIN);

 	for (; v < end; v += PAGE_SIZE)
 		map_kernel_page(v, 0, __pgprot(0)); /* XXX gross */

 	map_kernel_page(PKMAP_BASE, 0, __pgprot(0));	/* XXX gross */
 	pkmap_page_table = virt_to_kpte(PKMAP_BASE);
 #endif /* CONFIG_HIGHMEM */

 	printk(KERN_DEBUG "Top of RAM: 0x%llx, Total RAM: 0x%llx\n",
 	       (unsigned long long)top_of_ram, total_ram);
 	printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 	       (long int)((top_of_ram - total_ram) >> 20));

 	/*
 	 * Allow 30-bit DMA for very limited Broadcom wifi chips on many
 	 * powerbooks.
 	 */
 	if (IS_ENABLED(CONFIG_PPC32))
 		zone_dma_bits = 30;
 	else
 		zone_dma_bits = 31;

 #ifdef CONFIG_ZONE_DMA
 	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn,
 				      1UL << (zone_dma_bits - PAGE_SHIFT));
 #endif
 	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
 #ifdef CONFIG_HIGHMEM
 	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
 #endif

 	free_area_init(max_zone_pfns);

 	mark_nonram_nosave();
 }

 void __init mem_init(void)
 {
 	/*
 	 * book3s is limited to 16 page sizes due to encoding this in
 	 * a 4-bit field for slices.
 	 */
 	BUILD_BUG_ON(MMU_PAGE_COUNT > 16);

 #ifdef CONFIG_SWIOTLB
 	/*
 	 * Some platforms (e.g. 85xx) limit DMA-able memory way below
 	 * 4G. We force memblock to bottom-up mode to ensure that the
 	 * memory allocated in swiotlb_init() is DMA-able.
 	 * As it's the last memblock allocation, no need to reset it
 	 * back to to-down.
 	 */
 	memblock_set_bottom_up(true);
 	if (is_secure_guest())
 		svm_swiotlb_init();
 	else
 		swiotlb_init(0);
 #endif

 	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
 	set_max_mapnr(max_pfn);

 	kasan_late_init();

 	memblock_free_all();

 #ifdef CONFIG_HIGHMEM
 	{
 		unsigned long pfn, highmem_mapnr;

 		highmem_mapnr = lowmem_end_addr >> PAGE_SHIFT;
 		for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
 			phys_addr_t paddr = (phys_addr_t)pfn << PAGE_SHIFT;
 			struct page *page = pfn_to_page(pfn);
 			if (!memblock_is_reserved(paddr))
 				free_highmem_page(page);
 		}
 	}
 #endif /* CONFIG_HIGHMEM */

 #if defined(CONFIG_PPC_FSL_BOOK3E) && !defined(CONFIG_SMP)
 	/*
 	 * If smp is enabled, next_tlbcam_idx is initialized in the cpu up
 	 * functions.... do it here for the non-smp case.
 	 */
 	per_cpu(next_tlbcam_idx, smp_processor_id()) =
 		(mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) - 1;
 #endif

 #ifdef CONFIG_PPC32
 	pr_info("Kernel virtual memory layout:\n");
 #ifdef CONFIG_KASAN
 	pr_info("  * 0x%08lx..0x%08lx  : kasan shadow mem\n",
 		KASAN_SHADOW_START, KASAN_SHADOW_END);
 #endif
 	pr_info("  * 0x%08lx..0x%08lx  : fixmap\n", FIXADDR_START, FIXADDR_TOP);
 #ifdef CONFIG_HIGHMEM
 	pr_info("  * 0x%08lx..0x%08lx  : highmem PTEs\n",
 		PKMAP_BASE, PKMAP_ADDR(LAST_PKMAP));
 #endif /* CONFIG_HIGHMEM */
 	if (ioremap_bot != IOREMAP_TOP)
 		pr_info("  * 0x%08lx..0x%08lx  : early ioremap\n",
 			ioremap_bot, IOREMAP_TOP);
 	pr_info("  * 0x%08lx..0x%08lx  : vmalloc & ioremap\n",
 		VMALLOC_START, VMALLOC_END);
 #ifdef MODULES_VADDR
 	pr_info("  * 0x%08lx..0x%08lx  : modules\n",
 		MODULES_VADDR, MODULES_END);
 #endif
 #endif /* CONFIG_PPC32 */
 }

 void free_initmem(void)
 {
 	ppc_md.progress = ppc_printk_progress;
 	mark_initmem_nx();
 	init_mem_is_free = true;
 	free_initmem_default(POISON_FREE_INITMEM);
 }

 /*
  * System memory should not be in /proc/iomem but various tools expect it
  * (eg kdump).
  */
 static int __init add_system_ram_resources(void)
 {
 	phys_addr_t start, end;
 	u64 i;

 	for_each_mem_range(i, &start, &end) {
 		struct resource *res;

 		res = kzalloc(sizeof(struct resource), GFP_KERNEL);
 		WARN_ON(!res);

 		if (res) {
 			res->name = "System RAM";
 			res->start = start;
 			/*
 			 * In memblock, end points to the first byte after
 			 * the range while in resourses, end points to the
 			 * last byte in the range.
 			 */
 			res->end = end - 1;
 			res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 			WARN_ON(request_resource(&iomem_resource, res) < 0);
 		}
 	}

 	return 0;
 }
 subsys_initcall(add_system_ram_resources);

 #ifdef CONFIG_STRICT_DEVMEM
 /*
  * devmem_is_allowed(): check to see if /dev/mem access to a certain address
  * is valid. The argument is a physical page number.
  *
  * Access has to be given to non-kernel-ram areas as well, these contain the
  * PCI mmio resources as well as potential bios/acpi data regions.
  */
 int devmem_is_allowed(unsigned long pfn)
 {
 	if (page_is_rtas_user_buf(pfn))
 		return 1;
 	if (iomem_is_exclusive(PFN_PHYS(pfn)))
 		return 0;
 	if (!page_is_ram(pfn))
 		return 1;
 	return 0;
 }
 #endif /* CONFIG_STRICT_DEVMEM */

 /*
  * This is defined in kernel/resource.c but only powerpc needs to export it, for
  * the EHEA driver. Drop this when drivers/net/ethernet/ibm/ehea is removed.
  */
 EXPORT_SYMBOL_GPL(walk_system_ram_range);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* PowerPC version
	* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
	*
	* Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
	* and Cort Dougan (PReP) (cort@cs.nmt.edu)
	* Copyright (C) 1996 Paul Mackerras
	* PPC44x/36-bit changes by Matt Porter (mporter@mvista.com)
	*
	* Derived from "arch/i386/mm/init.c"
	* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
	*/

	#include <linux/memblock.h>
	#include <linux/highmem.h>
	#include <linux/suspend.h>
	#include <linux/dma-direct.h>

	#include <asm/machdep.h>
	#include <asm/rtas.h>
	#include <asm/kasan.h>
	#include <asm/sparsemem.h>
	#include <asm/svm.h>

	#include <mm/mmu_decl.h>

	unsigned long long memory_limit;
	bool init_mem_is_free;

	unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
	EXPORT_SYMBOL(empty_zero_page);

	pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
	unsigned long size, pgprot_t vma_prot)
	{
	if (ppc_md.phys_mem_access_prot)
	return ppc_md.phys_mem_access_prot(file, pfn, size, vma_prot);

	if (!page_is_ram(pfn))
	vma_prot = pgprot_noncached(vma_prot);

	return vma_prot;
	}
	EXPORT_SYMBOL(phys_mem_access_prot);

	#ifdef CONFIG_MEMORY_HOTPLUG
	static DEFINE_MUTEX(linear_mapping_mutex);

	#ifdef CONFIG_NUMA
	int memory_add_physaddr_to_nid(u64 start)
	{
	return hot_add_scn_to_nid(start);
	}
	#endif

	int __weak create_section_mapping(unsigned long start, unsigned long end,
	int nid, pgprot_t prot)
	{
	return -ENODEV;
	}

	int __weak remove_section_mapping(unsigned long start, unsigned long end)
	{
	return -ENODEV;
	}

	int __ref arch_create_linear_mapping(int nid, u64 start, u64 size,
	struct mhp_params *params)
	{
	int rc;

	start = (unsigned long)__va(start);
	mutex_lock(&linear_mapping_mutex);
	rc = create_section_mapping(start, start + size, nid,
	params->pgprot);
	mutex_unlock(&linear_mapping_mutex);
	if (rc) {
	pr_warn("Unable to create linear mapping for 0x%llx..0x%llx: %d\n",
	start, start + size, rc);
	return -EFAULT;
	}
	return 0;
	}

	void __ref arch_remove_linear_mapping(u64 start, u64 size)
	{
	int ret;

	/* Remove htab bolted mappings for this section of memory */
	start = (unsigned long)__va(start);

	mutex_lock(&linear_mapping_mutex);
	ret = remove_section_mapping(start, start + size);
	mutex_unlock(&linear_mapping_mutex);
	if (ret)
	pr_warn("Unable to remove linear mapping for 0x%llx..0x%llx: %d\n",
	start, start + size, ret);

	/* Ensure all vmalloc mappings are flushed in case they also
	* hit that section of memory
	*/
	vm_unmap_aliases();
	}

	int __ref arch_add_memory(int nid, u64 start, u64 size,
	struct mhp_params *params)
	{
	unsigned long start_pfn = start >> PAGE_SHIFT;
	unsigned long nr_pages = size >> PAGE_SHIFT;
	int rc;

	rc = arch_create_linear_mapping(nid, start, size, params);
	if (rc)
	return rc;
	rc = __add_pages(nid, start_pfn, nr_pages, params);
	if (rc)
	arch_remove_linear_mapping(start, size);
	return rc;
	}

	void __ref arch_remove_memory(int nid, u64 start, u64 size,
	struct vmem_altmap *altmap)
	{
	unsigned long start_pfn = start >> PAGE_SHIFT;
	unsigned long nr_pages = size >> PAGE_SHIFT;

	__remove_pages(start_pfn, nr_pages, altmap);
	arch_remove_linear_mapping(start, size);
	}
	#endif

	#ifndef CONFIG_NUMA
	void __init mem_topology_setup(void)
	{
	max_low_pfn = max_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
	min_low_pfn = MEMORY_START >> PAGE_SHIFT;
	#ifdef CONFIG_HIGHMEM
	max_low_pfn = lowmem_end_addr >> PAGE_SHIFT;
	#endif

	/* Place all memblock_regions in the same node and merge contiguous
	* memblock_regions
	*/
	memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
	}

	void __init initmem_init(void)
	{
	sparse_init();
	}

	/* mark pages that don't exist as nosave */
	static int __init mark_nonram_nosave(void)
	{
	unsigned long spfn, epfn, prev = 0;
	int i;

	for_each_mem_pfn_range(i, MAX_NUMNODES, &spfn, &epfn, NULL) {
	if (prev && prev < spfn)
	register_nosave_region(prev, spfn);

	prev = epfn;
	}

	return 0;
	}
	#else /* CONFIG_NUMA */
	static int __init mark_nonram_nosave(void)
	{
	return 0;
	}
	#endif

	/*
	* Zones usage:
	*
	* We setup ZONE_DMA to be 31-bits on all platforms and ZONE_NORMAL to be
	* everything else. GFP_DMA32 page allocations automatically fall back to
	* ZONE_DMA.
	*
	* By using 31-bit unconditionally, we can exploit zone_dma_bits to inform the
	* generic DMA mapping code. 32-bit only devices (if not handled by an IOMMU
	* anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
	* ZONE_DMA.
	*/
	static unsigned long max_zone_pfns[MAX_NR_ZONES];

	/*
	* paging_init() sets up the page tables - in fact we've already done this.
	*/
	void __init paging_init(void)
	{
	unsigned long long total_ram = memblock_phys_mem_size();
	phys_addr_t top_of_ram = memblock_end_of_DRAM();

	#ifdef CONFIG_HIGHMEM
	unsigned long v = __fix_to_virt(FIX_KMAP_END);
	unsigned long end = __fix_to_virt(FIX_KMAP_BEGIN);

	for (; v < end; v += PAGE_SIZE)
	map_kernel_page(v, 0, __pgprot(0)); /* XXX gross */

	map_kernel_page(PKMAP_BASE, 0, __pgprot(0)); /* XXX gross */
	pkmap_page_table = virt_to_kpte(PKMAP_BASE);
	#endif /* CONFIG_HIGHMEM */

	printk(KERN_DEBUG "Top of RAM: 0x%llx, Total RAM: 0x%llx\n",
	(unsigned long long)top_of_ram, total_ram);
	printk(KERN_DEBUG "Memory hole size: %ldMB\n",
	(long int)((top_of_ram - total_ram) >> 20));

	/*
	* Allow 30-bit DMA for very limited Broadcom wifi chips on many
	* powerbooks.
	*/
	if (IS_ENABLED(CONFIG_PPC32))
	zone_dma_bits = 30;
	else
	zone_dma_bits = 31;

	#ifdef CONFIG_ZONE_DMA
	max_zone_pfns[ZONE_DMA] = min(max_low_pfn,
	1UL << (zone_dma_bits - PAGE_SHIFT));
	#endif
	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
	#ifdef CONFIG_HIGHMEM
	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
	#endif

	free_area_init(max_zone_pfns);

	mark_nonram_nosave();
	}

	void __init mem_init(void)
	{
	/*
	* book3s is limited to 16 page sizes due to encoding this in
	* a 4-bit field for slices.
	*/
	BUILD_BUG_ON(MMU_PAGE_COUNT > 16);

	#ifdef CONFIG_SWIOTLB
	/*
	* Some platforms (e.g. 85xx) limit DMA-able memory way below
	* 4G. We force memblock to bottom-up mode to ensure that the
	* memory allocated in swiotlb_init() is DMA-able.
	* As it's the last memblock allocation, no need to reset it
	* back to to-down.
	*/
	memblock_set_bottom_up(true);
	if (is_secure_guest())
	svm_swiotlb_init();
	else
	swiotlb_init(0);
	#endif

	high_memory = (void ) __va(max_low_pfn PAGE_SIZE);
	set_max_mapnr(max_pfn);

	kasan_late_init();

	memblock_free_all();

	#ifdef CONFIG_HIGHMEM
	{
	unsigned long pfn, highmem_mapnr;

	highmem_mapnr = lowmem_end_addr >> PAGE_SHIFT;
	for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
	phys_addr_t paddr = (phys_addr_t)pfn << PAGE_SHIFT;
	struct page *page = pfn_to_page(pfn);
	if (!memblock_is_reserved(paddr))
	free_highmem_page(page);
	}
	}
	#endif /* CONFIG_HIGHMEM */

	#if defined(CONFIG_PPC_FSL_BOOK3E) && !defined(CONFIG_SMP)
	/*
	* If smp is enabled, next_tlbcam_idx is initialized in the cpu up
	* functions.... do it here for the non-smp case.
	*/
	per_cpu(next_tlbcam_idx, smp_processor_id()) =
	(mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) - 1;
	#endif

	#ifdef CONFIG_PPC32
	pr_info("Kernel virtual memory layout:\n");
	#ifdef CONFIG_KASAN
	pr_info(" * 0x%08lx..0x%08lx : kasan shadow mem\n",
	KASAN_SHADOW_START, KASAN_SHADOW_END);
	#endif
	pr_info(" * 0x%08lx..0x%08lx : fixmap\n", FIXADDR_START, FIXADDR_TOP);
	#ifdef CONFIG_HIGHMEM
	pr_info(" * 0x%08lx..0x%08lx : highmem PTEs\n",
	PKMAP_BASE, PKMAP_ADDR(LAST_PKMAP));
	#endif /* CONFIG_HIGHMEM */
	if (ioremap_bot != IOREMAP_TOP)
	pr_info(" * 0x%08lx..0x%08lx : early ioremap\n",
	ioremap_bot, IOREMAP_TOP);
	pr_info(" * 0x%08lx..0x%08lx : vmalloc & ioremap\n",
	VMALLOC_START, VMALLOC_END);
	#ifdef MODULES_VADDR
	pr_info(" * 0x%08lx..0x%08lx : modules\n",
	MODULES_VADDR, MODULES_END);
	#endif
	#endif /* CONFIG_PPC32 */
	}

	void free_initmem(void)
	{
	ppc_md.progress = ppc_printk_progress;
	mark_initmem_nx();
	init_mem_is_free = true;
	free_initmem_default(POISON_FREE_INITMEM);
	}

	/*
	* System memory should not be in /proc/iomem but various tools expect it
	* (eg kdump).
	*/
	static int __init add_system_ram_resources(void)
	{
	phys_addr_t start, end;
	u64 i;

	for_each_mem_range(i, &start, &end) {
	struct resource *res;

	res = kzalloc(sizeof(struct resource), GFP_KERNEL);
	WARN_ON(!res);

	if (res) {
	res->name = "System RAM";
	res->start = start;
	/*
	* In memblock, end points to the first byte after
	* the range while in resourses, end points to the
	* last byte in the range.
	*/
	res->end = end - 1;
	res->flags = IORESOURCE_SYSTEM_RAM \| IORESOURCE_BUSY;
	WARN_ON(request_resource(&iomem_resource, res) < 0);
	}
	}

	return 0;
	}
	subsys_initcall(add_system_ram_resources);

	#ifdef CONFIG_STRICT_DEVMEM
	/*
	* devmem_is_allowed(): check to see if /dev/mem access to a certain address
	* is valid. The argument is a physical page number.
	*
	* Access has to be given to non-kernel-ram areas as well, these contain the
	* PCI mmio resources as well as potential bios/acpi data regions.
	*/
	int devmem_is_allowed(unsigned long pfn)
	{
	if (page_is_rtas_user_buf(pfn))
	return 1;
	if (iomem_is_exclusive(PFN_PHYS(pfn)))
	return 0;
	if (!page_is_ram(pfn))
	return 1;
	return 0;
	}
	#endif /* CONFIG_STRICT_DEVMEM */

	/*
	* This is defined in kernel/resource.c but only powerpc needs to export it, for
	* the EHEA driver. Drop this when drivers/net/ethernet/ibm/ehea is removed.
	*/
	EXPORT_SYMBOL_GPL(walk_system_ram_range);