arch/arm64/kernel/vdso.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * VDSO implementations.
  *
  * Copyright (C) 2012 ARM Limited
  *
  * Author: Will Deacon <will.deacon@arm.com>
  */

 #include <linux/cache.h>
 #include <linux/clocksource.h>
 #include <linux/elf.h>
 #include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/gfp.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/signal.h>
 #include <linux/slab.h>
 #include <linux/time_namespace.h>
 #include <linux/timekeeper_internal.h>
 #include <linux/vmalloc.h>
 #include <vdso/datapage.h>
 #include <vdso/helpers.h>
 #include <vdso/vsyscall.h>

 #include <asm/cacheflush.h>
 #include <asm/signal32.h>
 #include <asm/vdso.h>

 extern char vdso_start[], vdso_end[];
 extern char vdso32_start[], vdso32_end[];

 enum vdso_abi {
 	VDSO_ABI_AA64,
 	VDSO_ABI_AA32,
 };

 enum vvar_pages {
 	VVAR_DATA_PAGE_OFFSET,
 	VVAR_TIMENS_PAGE_OFFSET,
 	VVAR_NR_PAGES,
 };

 struct vdso_abi_info {
 	const char *name;
 	const char *vdso_code_start;
 	const char *vdso_code_end;
 	unsigned long vdso_pages;
 	/* Data Mapping */
 	struct vm_special_mapping *dm;
 	/* Code Mapping */
 	struct vm_special_mapping *cm;
 };

 static struct vdso_abi_info vdso_info[] __ro_after_init = {
 	[VDSO_ABI_AA64] = {
 		.name = "vdso",
 		.vdso_code_start = vdso_start,
 		.vdso_code_end = vdso_end,
 	},
 #ifdef CONFIG_COMPAT_VDSO
 	[VDSO_ABI_AA32] = {
 		.name = "vdso32",
 		.vdso_code_start = vdso32_start,
 		.vdso_code_end = vdso32_end,
 	},
 #endif /* CONFIG_COMPAT_VDSO */
 };

 /*
  * The vDSO data page.
  */
 static union {
 	struct vdso_data	data[CS_BASES];
 	u8			page[PAGE_SIZE];
 } vdso_data_store __page_aligned_data;
 struct vdso_data *vdso_data = vdso_data_store.data;

 static int __vdso_remap(enum vdso_abi abi,
 			const struct vm_special_mapping *sm,
 			struct vm_area_struct *new_vma)
 {
 	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
 	unsigned long vdso_size = vdso_info[abi].vdso_code_end -
 				  vdso_info[abi].vdso_code_start;

 	if (vdso_size != new_size)
 		return -EINVAL;

 	current->mm->context.vdso = (void *)new_vma->vm_start;

 	return 0;
 }

 static int __vdso_init(enum vdso_abi abi)
 {
 	int i;
 	struct page **vdso_pagelist;
 	unsigned long pfn;

 	if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
 		pr_err("vDSO is not a valid ELF object!\n");
 		return -EINVAL;
 	}

 	vdso_info[abi].vdso_pages = (
 			vdso_info[abi].vdso_code_end -
 			vdso_info[abi].vdso_code_start) >>
 			PAGE_SHIFT;

 	vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
 				sizeof(struct page *),
 				GFP_KERNEL);
 	if (vdso_pagelist == NULL)
 		return -ENOMEM;

 	/* Grab the vDSO code pages. */
 	pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);

 	for (i = 0; i < vdso_info[abi].vdso_pages; i++)
 		vdso_pagelist[i] = pfn_to_page(pfn + i);

 	vdso_info[abi].cm->pages = vdso_pagelist;

 	return 0;
 }

 #ifdef CONFIG_TIME_NS
 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 {
 	return (struct vdso_data *)(vvar_page);
 }

 /*
  * The vvar mapping contains data for a specific time namespace, so when a task
  * changes namespace we must unmap its vvar data for the old namespace.
  * Subsequent faults will map in data for the new namespace.
  *
  * For more details see timens_setup_vdso_data().
  */
 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 {
 	struct mm_struct *mm = task->mm;
 	struct vm_area_struct *vma;

 	mmap_read_lock(mm);

 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
 		unsigned long size = vma->vm_end - vma->vm_start;

 		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
 			zap_page_range(vma, vma->vm_start, size);
 #ifdef CONFIG_COMPAT_VDSO
 		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
 			zap_page_range(vma, vma->vm_start, size);
 #endif
 	}

 	mmap_read_unlock(mm);
 	return 0;
 }

 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 {
 	if (likely(vma->vm_mm == current->mm))
 		return current->nsproxy->time_ns->vvar_page;

 	/*
 	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
 	 * through interfaces like /proc/$pid/mem or
 	 * process_vm_{readv,writev}() as long as there's no .access()
 	 * in special_mapping_vmops.
 	 * For more details check_vma_flags() and __access_remote_vm()
 	 */
 	WARN(1, "vvar_page accessed remotely");

 	return NULL;
 }
 #else
 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 {
 	return NULL;
 }
 #endif

 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 			     struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct page *timens_page = find_timens_vvar_page(vma);
 	unsigned long pfn;

 	switch (vmf->pgoff) {
 	case VVAR_DATA_PAGE_OFFSET:
 		if (timens_page)
 			pfn = page_to_pfn(timens_page);
 		else
 			pfn = sym_to_pfn(vdso_data);
 		break;
 #ifdef CONFIG_TIME_NS
 	case VVAR_TIMENS_PAGE_OFFSET:
 		/*
 		 * If a task belongs to a time namespace then a namespace
 		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 		 * offset.
 		 * See also the comment near timens_setup_vdso_data().
 		 */
 		if (!timens_page)
 			return VM_FAULT_SIGBUS;
 		pfn = sym_to_pfn(vdso_data);
 		break;
 #endif /* CONFIG_TIME_NS */
 	default:
 		return VM_FAULT_SIGBUS;
 	}

 	return vmf_insert_pfn(vma, vmf->address, pfn);
 }

 static int vvar_mremap(const struct vm_special_mapping *sm,
 		       struct vm_area_struct *new_vma)
 {
 	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;

 	if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
 		return -EINVAL;

 	return 0;
 }

 static int __setup_additional_pages(enum vdso_abi abi,
 				    struct mm_struct *mm,
 				    struct linux_binprm *bprm,
 				    int uses_interp)
 {
 	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 	unsigned long gp_flags = 0;
 	void *ret;

 	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);

 	vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
 	/* Be sure to map the data page */
 	vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;

 	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 	if (IS_ERR_VALUE(vdso_base)) {
 		ret = ERR_PTR(vdso_base);
 		goto up_fail;
 	}

 	ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 				       VM_READ|VM_MAYREAD|VM_PFNMAP,
 				       vdso_info[abi].dm);
 	if (IS_ERR(ret))
 		goto up_fail;

 	if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
 		gp_flags = VM_ARM64_BTI;

 	vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 	mm->context.vdso = (void *)vdso_base;
 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 				       VM_READ|VM_EXEC|gp_flags|
 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 				       vdso_info[abi].cm);
 	if (IS_ERR(ret))
 		goto up_fail;

 	return 0;

 up_fail:
 	mm->context.vdso = NULL;
 	return PTR_ERR(ret);
 }

 #ifdef CONFIG_COMPAT
 /*
  * Create and map the vectors page for AArch32 tasks.
  */
 static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
 		struct vm_area_struct *new_vma)
 {
 	return __vdso_remap(VDSO_ABI_AA32, sm, new_vma);
 }

 enum aarch32_map {
 	AA32_MAP_VECTORS, /* kuser helpers */
 	AA32_MAP_SIGPAGE,
 	AA32_MAP_VVAR,
 	AA32_MAP_VDSO,
 };

 static struct page *aarch32_vectors_page __ro_after_init;
 static struct page *aarch32_sig_page __ro_after_init;

 static struct vm_special_mapping aarch32_vdso_maps[] = {
 	[AA32_MAP_VECTORS] = {
 		.name	= "[vectors]", /* ABI */
 		.pages	= &aarch32_vectors_page,
 	},
 	[AA32_MAP_SIGPAGE] = {
 		.name	= "[sigpage]", /* ABI */
 		.pages	= &aarch32_sig_page,
 	},
 	[AA32_MAP_VVAR] = {
 		.name = "[vvar]",
 		.fault = vvar_fault,
 		.mremap = vvar_mremap,
 	},
 	[AA32_MAP_VDSO] = {
 		.name = "[vdso]",
 		.mremap = aarch32_vdso_mremap,
 	},
 };

 static int aarch32_alloc_kuser_vdso_page(void)
 {
 	extern char __kuser_helper_start[], __kuser_helper_end[];
 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
 	unsigned long vdso_page;

 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 		return 0;

 	vdso_page = get_zeroed_page(GFP_ATOMIC);
 	if (!vdso_page)
 		return -ENOMEM;

 	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
 	       kuser_sz);
 	aarch32_vectors_page = virt_to_page(vdso_page);
 	flush_dcache_page(aarch32_vectors_page);
 	return 0;
 }

 static int aarch32_alloc_sigpage(void)
 {
 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
 	unsigned long sigpage;

 	sigpage = get_zeroed_page(GFP_ATOMIC);
 	if (!sigpage)
 		return -ENOMEM;

 	memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
 	aarch32_sig_page = virt_to_page(sigpage);
 	flush_dcache_page(aarch32_sig_page);
 	return 0;
 }

 static int __aarch32_alloc_vdso_pages(void)
 {

 	if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
 		return 0;

 	vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 	vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];

 	return __vdso_init(VDSO_ABI_AA32);
 }

 static int __init aarch32_alloc_vdso_pages(void)
 {
 	int ret;

 	ret = __aarch32_alloc_vdso_pages();
 	if (ret)
 		return ret;

 	ret = aarch32_alloc_sigpage();
 	if (ret)
 		return ret;

 	return aarch32_alloc_kuser_vdso_page();
 }
 arch_initcall(aarch32_alloc_vdso_pages);

 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 {
 	void *ret;

 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 		return 0;

 	/*
 	 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
 	 * not safe to CoW the page containing the CPU exception vectors.
 	 */
 	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
 				       VM_READ | VM_EXEC |
 				       VM_MAYREAD | VM_MAYEXEC,
 				       &aarch32_vdso_maps[AA32_MAP_VECTORS]);

 	return PTR_ERR_OR_ZERO(ret);
 }

 static int aarch32_sigreturn_setup(struct mm_struct *mm)
 {
 	unsigned long addr;
 	void *ret;

 	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 	if (IS_ERR_VALUE(addr)) {
 		ret = ERR_PTR(addr);
 		goto out;
 	}

 	/*
 	 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
 	 * set breakpoints.
 	 */
 	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 				       VM_READ | VM_EXEC | VM_MAYREAD |
 				       VM_MAYWRITE | VM_MAYEXEC,
 				       &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
 	if (IS_ERR(ret))
 		goto out;

 	mm->context.sigpage = (void *)addr;

 out:
 	return PTR_ERR_OR_ZERO(ret);
 }

 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	int ret;

 	if (mmap_write_lock_killable(mm))
 		return -EINTR;

 	ret = aarch32_kuser_helpers_setup(mm);
 	if (ret)
 		goto out;

 	if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
 		ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
 					       uses_interp);
 		if (ret)
 			goto out;
 	}

 	ret = aarch32_sigreturn_setup(mm);
 out:
 	mmap_write_unlock(mm);
 	return ret;
 }
 #endif /* CONFIG_COMPAT */

 static int vdso_mremap(const struct vm_special_mapping *sm,
 		struct vm_area_struct *new_vma)
 {
 	return __vdso_remap(VDSO_ABI_AA64, sm, new_vma);
 }

 enum aarch64_map {
 	AA64_MAP_VVAR,
 	AA64_MAP_VDSO,
 };

 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 	[AA64_MAP_VVAR] = {
 		.name	= "[vvar]",
 		.fault = vvar_fault,
 		.mremap = vvar_mremap,
 	},
 	[AA64_MAP_VDSO] = {
 		.name	= "[vdso]",
 		.mremap = vdso_mremap,
 	},
 };

 static int __init vdso_init(void)
 {
 	vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
 	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];

 	return __vdso_init(VDSO_ABI_AA64);
 }
 arch_initcall(vdso_init);

 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	int ret;

 	if (mmap_write_lock_killable(mm))
 		return -EINTR;

 	ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
 	mmap_write_unlock(mm);

 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* VDSO implementations.
	*
	* Copyright (C) 2012 ARM Limited
	*
	* Author: Will Deacon <will.deacon@arm.com>
	*/

	#include <linux/cache.h>
	#include <linux/clocksource.h>
	#include <linux/elf.h>
	#include <linux/err.h>
	#include <linux/errno.h>
	#include <linux/gfp.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/sched.h>
	#include <linux/signal.h>
	#include <linux/slab.h>
	#include <linux/time_namespace.h>
	#include <linux/timekeeper_internal.h>
	#include <linux/vmalloc.h>
	#include <vdso/datapage.h>
	#include <vdso/helpers.h>
	#include <vdso/vsyscall.h>

	#include <asm/cacheflush.h>
	#include <asm/signal32.h>
	#include <asm/vdso.h>

	extern char vdso_start[], vdso_end[];
	extern char vdso32_start[], vdso32_end[];

	enum vdso_abi {
	VDSO_ABI_AA64,
	VDSO_ABI_AA32,
	};

	enum vvar_pages {
	VVAR_DATA_PAGE_OFFSET,
	VVAR_TIMENS_PAGE_OFFSET,
	VVAR_NR_PAGES,
	};

	struct vdso_abi_info {
	const char *name;
	const char *vdso_code_start;
	const char *vdso_code_end;
	unsigned long vdso_pages;
	/* Data Mapping */
	struct vm_special_mapping *dm;
	/* Code Mapping */
	struct vm_special_mapping *cm;
	};

	static struct vdso_abi_info vdso_info[] __ro_after_init = {
	[VDSO_ABI_AA64] = {
	.name = "vdso",
	.vdso_code_start = vdso_start,
	.vdso_code_end = vdso_end,
	},
	#ifdef CONFIG_COMPAT_VDSO
	[VDSO_ABI_AA32] = {
	.name = "vdso32",
	.vdso_code_start = vdso32_start,
	.vdso_code_end = vdso32_end,
	},
	#endif /* CONFIG_COMPAT_VDSO */
	};

	/*
	* The vDSO data page.
	*/
	static union {
	struct vdso_data data[CS_BASES];
	u8 page[PAGE_SIZE];
	} vdso_data_store __page_aligned_data;
	struct vdso_data *vdso_data = vdso_data_store.data;

	static int __vdso_remap(enum vdso_abi abi,
	const struct vm_special_mapping *sm,
	struct vm_area_struct *new_vma)
	{
	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
	unsigned long vdso_size = vdso_info[abi].vdso_code_end -
	vdso_info[abi].vdso_code_start;

	if (vdso_size != new_size)
	return -EINVAL;

	current->mm->context.vdso = (void *)new_vma->vm_start;

	return 0;
	}

	static int __vdso_init(enum vdso_abi abi)
	{
	int i;
	struct page **vdso_pagelist;
	unsigned long pfn;

	if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
	pr_err("vDSO is not a valid ELF object!\n");
	return -EINVAL;
	}

	vdso_info[abi].vdso_pages = (
	vdso_info[abi].vdso_code_end -
	vdso_info[abi].vdso_code_start) >>
	PAGE_SHIFT;

	vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
	sizeof(struct page *),
	GFP_KERNEL);
	if (vdso_pagelist == NULL)
	return -ENOMEM;

	/* Grab the vDSO code pages. */
	pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);

	for (i = 0; i < vdso_info[abi].vdso_pages; i++)
	vdso_pagelist[i] = pfn_to_page(pfn + i);

	vdso_info[abi].cm->pages = vdso_pagelist;

	return 0;
	}

	#ifdef CONFIG_TIME_NS
	struct vdso_data arch_get_vdso_data(void vvar_page)
	{
	return (struct vdso_data *)(vvar_page);
	}

	/*
	* The vvar mapping contains data for a specific time namespace, so when a task
	* changes namespace we must unmap its vvar data for the old namespace.
	* Subsequent faults will map in data for the new namespace.
	*
	* For more details see timens_setup_vdso_data().
	*/
	int vdso_join_timens(struct task_struct task, struct time_namespace ns)
	{
	struct mm_struct *mm = task->mm;
	struct vm_area_struct *vma;

	mmap_read_lock(mm);

	for (vma = mm->mmap; vma; vma = vma->vm_next) {
	unsigned long size = vma->vm_end - vma->vm_start;

	if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
	zap_page_range(vma, vma->vm_start, size);
	#ifdef CONFIG_COMPAT_VDSO
	if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
	zap_page_range(vma, vma->vm_start, size);
	#endif
	}

	mmap_read_unlock(mm);
	return 0;
	}

	static struct page find_timens_vvar_page(struct vm_area_struct vma)
	{
	if (likely(vma->vm_mm == current->mm))
	return current->nsproxy->time_ns->vvar_page;

	/*
	* VM_PFNMAP \| VM_IO protect .fault() handler from being called
	* through interfaces like /proc/$pid/mem or
	* process_vm_{readv,writev}() as long as there's no .access()
	* in special_mapping_vmops.
	* For more details check_vma_flags() and __access_remote_vm()
	*/
	WARN(1, "vvar_page accessed remotely");

	return NULL;
	}
	#else
	static struct page find_timens_vvar_page(struct vm_area_struct vma)
	{
	return NULL;
	}
	#endif

	static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
	struct vm_area_struct vma, struct vm_fault vmf)
	{
	struct page *timens_page = find_timens_vvar_page(vma);
	unsigned long pfn;

	switch (vmf->pgoff) {
	case VVAR_DATA_PAGE_OFFSET:
	if (timens_page)
	pfn = page_to_pfn(timens_page);
	else
	pfn = sym_to_pfn(vdso_data);
	break;
	#ifdef CONFIG_TIME_NS
	case VVAR_TIMENS_PAGE_OFFSET:
	/*
	* If a task belongs to a time namespace then a namespace
	* specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
	* the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
	* offset.
	* See also the comment near timens_setup_vdso_data().
	*/
	if (!timens_page)
	return VM_FAULT_SIGBUS;
	pfn = sym_to_pfn(vdso_data);
	break;
	#endif /* CONFIG_TIME_NS */
	default:
	return VM_FAULT_SIGBUS;
	}

	return vmf_insert_pfn(vma, vmf->address, pfn);
	}

	static int vvar_mremap(const struct vm_special_mapping *sm,
	struct vm_area_struct *new_vma)
	{
	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;

	if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
	return -EINVAL;

	return 0;
	}

	static int __setup_additional_pages(enum vdso_abi abi,
	struct mm_struct *mm,
	struct linux_binprm *bprm,
	int uses_interp)
	{
	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
	unsigned long gp_flags = 0;
	void *ret;

	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);

	vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
	/* Be sure to map the data page */
	vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;

	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
	if (IS_ERR_VALUE(vdso_base)) {
	ret = ERR_PTR(vdso_base);
	goto up_fail;
	}

	ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
	VM_READ\|VM_MAYREAD\|VM_PFNMAP,
	vdso_info[abi].dm);
	if (IS_ERR(ret))
	goto up_fail;

	if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
	gp_flags = VM_ARM64_BTI;

	vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
	mm->context.vdso = (void *)vdso_base;
	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
	VM_READ\|VM_EXEC\|gp_flags\|
	VM_MAYREAD\|VM_MAYWRITE\|VM_MAYEXEC,
	vdso_info[abi].cm);
	if (IS_ERR(ret))
	goto up_fail;

	return 0;

	up_fail:
	mm->context.vdso = NULL;
	return PTR_ERR(ret);
	}

	#ifdef CONFIG_COMPAT
	/*
	* Create and map the vectors page for AArch32 tasks.
	*/
	static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
	struct vm_area_struct *new_vma)
	{
	return __vdso_remap(VDSO_ABI_AA32, sm, new_vma);
	}

	enum aarch32_map {
	AA32_MAP_VECTORS, /* kuser helpers */
	AA32_MAP_SIGPAGE,
	AA32_MAP_VVAR,
	AA32_MAP_VDSO,
	};

	static struct page *aarch32_vectors_page __ro_after_init;
	static struct page *aarch32_sig_page __ro_after_init;

	static struct vm_special_mapping aarch32_vdso_maps[] = {
	[AA32_MAP_VECTORS] = {
	.name = "[vectors]", /* ABI */
	.pages = &aarch32_vectors_page,
	},
	[AA32_MAP_SIGPAGE] = {
	.name = "[sigpage]", /* ABI */
	.pages = &aarch32_sig_page,
	},
	[AA32_MAP_VVAR] = {
	.name = "[vvar]",
	.fault = vvar_fault,
	.mremap = vvar_mremap,
	},
	[AA32_MAP_VDSO] = {
	.name = "[vdso]",
	.mremap = aarch32_vdso_mremap,
	},
	};

	static int aarch32_alloc_kuser_vdso_page(void)
	{
	extern char __kuser_helper_start[], __kuser_helper_end[];
	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
	unsigned long vdso_page;

	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
	return 0;

	vdso_page = get_zeroed_page(GFP_ATOMIC);
	if (!vdso_page)
	return -ENOMEM;

	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
	kuser_sz);
	aarch32_vectors_page = virt_to_page(vdso_page);
	flush_dcache_page(aarch32_vectors_page);
	return 0;
	}

	static int aarch32_alloc_sigpage(void)
	{
	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
	unsigned long sigpage;

	sigpage = get_zeroed_page(GFP_ATOMIC);
	if (!sigpage)
	return -ENOMEM;

	memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
	aarch32_sig_page = virt_to_page(sigpage);
	flush_dcache_page(aarch32_sig_page);
	return 0;
	}

	static int __aarch32_alloc_vdso_pages(void)
	{

	if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
	return 0;

	vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
	vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];

	return __vdso_init(VDSO_ABI_AA32);
	}

	static int __init aarch32_alloc_vdso_pages(void)
	{
	int ret;

	ret = __aarch32_alloc_vdso_pages();
	if (ret)
	return ret;

	ret = aarch32_alloc_sigpage();
	if (ret)
	return ret;

	return aarch32_alloc_kuser_vdso_page();
	}
	arch_initcall(aarch32_alloc_vdso_pages);

	static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
	{
	void *ret;

	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
	return 0;

	/*
	* Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
	* not safe to CoW the page containing the CPU exception vectors.
	*/
	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
	VM_READ \| VM_EXEC \|
	VM_MAYREAD \| VM_MAYEXEC,
	&aarch32_vdso_maps[AA32_MAP_VECTORS]);

	return PTR_ERR_OR_ZERO(ret);
	}

	static int aarch32_sigreturn_setup(struct mm_struct *mm)
	{
	unsigned long addr;
	void *ret;

	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
	if (IS_ERR_VALUE(addr)) {
	ret = ERR_PTR(addr);
	goto out;
	}

	/*
	* VM_MAYWRITE is required to allow gdb to Copy-on-Write and
	* set breakpoints.
	*/
	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
	VM_READ \| VM_EXEC \| VM_MAYREAD \|
	VM_MAYWRITE \| VM_MAYEXEC,
	&aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
	if (IS_ERR(ret))
	goto out;

	mm->context.sigpage = (void *)addr;

	out:
	return PTR_ERR_OR_ZERO(ret);
	}

	int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
	{
	struct mm_struct *mm = current->mm;
	int ret;

	if (mmap_write_lock_killable(mm))
	return -EINTR;

	ret = aarch32_kuser_helpers_setup(mm);
	if (ret)
	goto out;

	if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
	ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
	uses_interp);
	if (ret)
	goto out;
	}

	ret = aarch32_sigreturn_setup(mm);
	out:
	mmap_write_unlock(mm);
	return ret;
	}
	#endif /* CONFIG_COMPAT */

	static int vdso_mremap(const struct vm_special_mapping *sm,
	struct vm_area_struct *new_vma)
	{
	return __vdso_remap(VDSO_ABI_AA64, sm, new_vma);
	}

	enum aarch64_map {
	AA64_MAP_VVAR,
	AA64_MAP_VDSO,
	};

	static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
	[AA64_MAP_VVAR] = {
	.name = "[vvar]",
	.fault = vvar_fault,
	.mremap = vvar_mremap,
	},
	[AA64_MAP_VDSO] = {
	.name = "[vdso]",
	.mremap = vdso_mremap,
	},
	};

	static int __init vdso_init(void)
	{
	vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];

	return __vdso_init(VDSO_ABI_AA64);
	}
	arch_initcall(vdso_init);

	int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
	{
	struct mm_struct *mm = current->mm;
	int ret;

	if (mmap_write_lock_killable(mm))
	return -EINTR;

	ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
	mmap_write_unlock(mm);

	return ret;
	}