arch/sparc/vdso/vma.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Set up the VMAs to tell the VM about the vDSO.
  * Copyright 2007 Andi Kleen, SUSE Labs.
  */

 /*
  * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
  */

 #include <linux/mm.h>
 #include <linux/err.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/linkage.h>
 #include <linux/random.h>
 #include <linux/elf.h>
 #include <asm/cacheflush.h>
 #include <asm/spitfire.h>
 #include <asm/vdso.h>
 #include <asm/vvar.h>
 #include <asm/page.h>

 unsigned int __read_mostly vdso_enabled = 1;

 static struct vm_special_mapping vvar_mapping = {
 	.name = "[vvar]"
 };

 #ifdef	CONFIG_SPARC64
 static struct vm_special_mapping vdso_mapping64 = {
 	.name = "[vdso]"
 };
 #endif

 #ifdef CONFIG_COMPAT
 static struct vm_special_mapping vdso_mapping32 = {
 	.name = "[vdso]"
 };
 #endif

 struct vvar_data *vvar_data;

 struct vdso_elfinfo32 {
 	Elf32_Ehdr	*hdr;
 	Elf32_Sym	*dynsym;
 	unsigned long	dynsymsize;
 	const char	*dynstr;
 	unsigned long	text;
 };

 struct vdso_elfinfo64 {
 	Elf64_Ehdr	*hdr;
 	Elf64_Sym	*dynsym;
 	unsigned long	dynsymsize;
 	const char	*dynstr;
 	unsigned long	text;
 };

 struct vdso_elfinfo {
 	union {
 		struct vdso_elfinfo32 elf32;
 		struct vdso_elfinfo64 elf64;
 	} u;
 };

 static void *one_section64(struct vdso_elfinfo64 *e, const char *name,
 			   unsigned long *size)
 {
 	const char *snames;
 	Elf64_Shdr *shdrs;
 	unsigned int i;

 	shdrs = (void *)e->hdr + e->hdr->e_shoff;
 	snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
 	for (i = 1; i < e->hdr->e_shnum; i++) {
 		if (!strcmp(snames+shdrs[i].sh_name, name)) {
 			if (size)
 				*size = shdrs[i].sh_size;
 			return (void *)e->hdr + shdrs[i].sh_offset;
 		}
 	}
 	return NULL;
 }

 static int find_sections64(const struct vdso_image *image, struct vdso_elfinfo *_e)
 {
 	struct vdso_elfinfo64 *e = &_e->u.elf64;

 	e->hdr = image->data;
 	e->dynsym = one_section64(e, ".dynsym", &e->dynsymsize);
 	e->dynstr = one_section64(e, ".dynstr", NULL);

 	if (!e->dynsym || !e->dynstr) {
 		pr_err("VDSO64: Missing symbol sections.\n");
 		return -ENODEV;
 	}
 	return 0;
 }

 static Elf64_Sym *find_sym64(const struct vdso_elfinfo64 *e, const char *name)
 {
 	unsigned int i;

 	for (i = 0; i < (e->dynsymsize / sizeof(Elf64_Sym)); i++) {
 		Elf64_Sym *s = &e->dynsym[i];
 		if (s->st_name == 0)
 			continue;
 		if (!strcmp(e->dynstr + s->st_name, name))
 			return s;
 	}
 	return NULL;
 }

 static int patchsym64(struct vdso_elfinfo *_e, const char *orig,
 		      const char *new)
 {
 	struct vdso_elfinfo64 *e = &_e->u.elf64;
 	Elf64_Sym *osym = find_sym64(e, orig);
 	Elf64_Sym *nsym = find_sym64(e, new);

 	if (!nsym || !osym) {
 		pr_err("VDSO64: Missing symbols.\n");
 		return -ENODEV;
 	}
 	osym->st_value = nsym->st_value;
 	osym->st_size = nsym->st_size;
 	osym->st_info = nsym->st_info;
 	osym->st_other = nsym->st_other;
 	osym->st_shndx = nsym->st_shndx;

 	return 0;
 }

 static void *one_section32(struct vdso_elfinfo32 *e, const char *name,
 			   unsigned long *size)
 {
 	const char *snames;
 	Elf32_Shdr *shdrs;
 	unsigned int i;

 	shdrs = (void *)e->hdr + e->hdr->e_shoff;
 	snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
 	for (i = 1; i < e->hdr->e_shnum; i++) {
 		if (!strcmp(snames+shdrs[i].sh_name, name)) {
 			if (size)
 				*size = shdrs[i].sh_size;
 			return (void *)e->hdr + shdrs[i].sh_offset;
 		}
 	}
 	return NULL;
 }

 static int find_sections32(const struct vdso_image *image, struct vdso_elfinfo *_e)
 {
 	struct vdso_elfinfo32 *e = &_e->u.elf32;

 	e->hdr = image->data;
 	e->dynsym = one_section32(e, ".dynsym", &e->dynsymsize);
 	e->dynstr = one_section32(e, ".dynstr", NULL);

 	if (!e->dynsym || !e->dynstr) {
 		pr_err("VDSO32: Missing symbol sections.\n");
 		return -ENODEV;
 	}
 	return 0;
 }

 static Elf32_Sym *find_sym32(const struct vdso_elfinfo32 *e, const char *name)
 {
 	unsigned int i;

 	for (i = 0; i < (e->dynsymsize / sizeof(Elf32_Sym)); i++) {
 		Elf32_Sym *s = &e->dynsym[i];
 		if (s->st_name == 0)
 			continue;
 		if (!strcmp(e->dynstr + s->st_name, name))
 			return s;
 	}
 	return NULL;
 }

 static int patchsym32(struct vdso_elfinfo *_e, const char *orig,
 		      const char *new)
 {
 	struct vdso_elfinfo32 *e = &_e->u.elf32;
 	Elf32_Sym *osym = find_sym32(e, orig);
 	Elf32_Sym *nsym = find_sym32(e, new);

 	if (!nsym || !osym) {
 		pr_err("VDSO32: Missing symbols.\n");
 		return -ENODEV;
 	}
 	osym->st_value = nsym->st_value;
 	osym->st_size = nsym->st_size;
 	osym->st_info = nsym->st_info;
 	osym->st_other = nsym->st_other;
 	osym->st_shndx = nsym->st_shndx;

 	return 0;
 }

 static int find_sections(const struct vdso_image *image, struct vdso_elfinfo *e,
 			 bool elf64)
 {
 	if (elf64)
 		return find_sections64(image, e);
 	else
 		return find_sections32(image, e);
 }

 static int patch_one_symbol(struct vdso_elfinfo *e, const char *orig,
 			    const char *new_target, bool elf64)
 {
 	if (elf64)
 		return patchsym64(e, orig, new_target);
 	else
 		return patchsym32(e, orig, new_target);
 }

 static int stick_patch(const struct vdso_image *image, struct vdso_elfinfo *e, bool elf64)
 {
 	int err;

 	err = find_sections(image, e, elf64);
 	if (err)
 		return err;

 	err = patch_one_symbol(e,
 			       "__vdso_gettimeofday",
 			       "__vdso_gettimeofday_stick", elf64);
 	if (err)
 		return err;

 	return patch_one_symbol(e,
 				"__vdso_clock_gettime",
 				"__vdso_clock_gettime_stick", elf64);
 	return 0;
 }

 /*
  * Allocate pages for the vdso and vvar, and copy in the vdso text from the
  * kernel image.
  */
 int __init init_vdso_image(const struct vdso_image *image,
 			   struct vm_special_mapping *vdso_mapping, bool elf64)
 {
 	int cnpages = (image->size) / PAGE_SIZE;
 	struct page *dp, **dpp = NULL;
 	struct page *cp, **cpp = NULL;
 	struct vdso_elfinfo ei;
 	int i, dnpages = 0;

 	if (tlb_type != spitfire) {
 		int err = stick_patch(image, &ei, elf64);
 		if (err)
 			return err;
 	}

 	/*
 	 * First, the vdso text.  This is initialied data, an integral number of
 	 * pages long.
 	 */
 	if (WARN_ON(image->size % PAGE_SIZE != 0))
 		goto oom;

 	cpp = kcalloc(cnpages, sizeof(struct page *), GFP_KERNEL);
 	vdso_mapping->pages = cpp;

 	if (!cpp)
 		goto oom;

 	for (i = 0; i < cnpages; i++) {
 		cp = alloc_page(GFP_KERNEL);
 		if (!cp)
 			goto oom;
 		cpp[i] = cp;
 		copy_page(page_address(cp), image->data + i * PAGE_SIZE);
 	}

 	/*
 	 * Now the vvar page.  This is uninitialized data.
 	 */

 	if (vvar_data == NULL) {
 		dnpages = (sizeof(struct vvar_data) / PAGE_SIZE) + 1;
 		if (WARN_ON(dnpages != 1))
 			goto oom;
 		dpp = kcalloc(dnpages, sizeof(struct page *), GFP_KERNEL);
 		vvar_mapping.pages = dpp;

 		if (!dpp)
 			goto oom;

 		dp = alloc_page(GFP_KERNEL);
 		if (!dp)
 			goto oom;

 		dpp[0] = dp;
 		vvar_data = page_address(dp);
 		memset(vvar_data, 0, PAGE_SIZE);

 		vvar_data->seq = 0;
 	}

 	return 0;
  oom:
 	if (cpp != NULL) {
 		for (i = 0; i < cnpages; i++) {
 			if (cpp[i] != NULL)
 				__free_page(cpp[i]);
 		}
 		kfree(cpp);
 		vdso_mapping->pages = NULL;
 	}

 	if (dpp != NULL) {
 		for (i = 0; i < dnpages; i++) {
 			if (dpp[i] != NULL)
 				__free_page(dpp[i]);
 		}
 		kfree(dpp);
 		vvar_mapping.pages = NULL;
 	}

 	pr_warn("Cannot allocate vdso\n");
 	vdso_enabled = 0;
 	return -ENOMEM;
 }

 static int __init init_vdso(void)
 {
 	int err = 0;
 #ifdef CONFIG_SPARC64
 	err = init_vdso_image(&vdso_image_64_builtin, &vdso_mapping64, true);
 	if (err)
 		return err;
 #endif

 #ifdef CONFIG_COMPAT
 	err = init_vdso_image(&vdso_image_32_builtin, &vdso_mapping32, false);
 #endif
 	return err;

 }
 subsys_initcall(init_vdso);

 struct linux_binprm;

 /* Shuffle the vdso up a bit, randomly. */
 static unsigned long vdso_addr(unsigned long start, unsigned int len)
 {
 	unsigned int offset;

 	/* This loses some more bits than a modulo, but is cheaper */
 	offset = get_random_int() & (PTRS_PER_PTE - 1);
 	return start + (offset << PAGE_SHIFT);
 }

 static int map_vdso(const struct vdso_image *image,
 		struct vm_special_mapping *vdso_mapping)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long text_start, addr = 0;
 	int ret = 0;

 	down_write(&mm->mmap_sem);

 	/*
 	 * First, get an unmapped region: then randomize it, and make sure that
 	 * region is free.
 	 */
 	if (current->flags & PF_RANDOMIZE) {
 		addr = get_unmapped_area(NULL, 0,
 					 image->size - image->sym_vvar_start,
 					 0, 0);
 		if (IS_ERR_VALUE(addr)) {
 			ret = addr;
 			goto up_fail;
 		}
 		addr = vdso_addr(addr, image->size - image->sym_vvar_start);
 	}
 	addr = get_unmapped_area(NULL, addr,
 				 image->size - image->sym_vvar_start, 0, 0);
 	if (IS_ERR_VALUE(addr)) {
 		ret = addr;
 		goto up_fail;
 	}

 	text_start = addr - image->sym_vvar_start;
 	current->mm->context.vdso = (void __user *)text_start;

 	/*
 	 * MAYWRITE to allow gdb to COW and set breakpoints
 	 */
 	vma = _install_special_mapping(mm,
 				       text_start,
 				       image->size,
 				       VM_READ|VM_EXEC|
 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 				       vdso_mapping);

 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		goto up_fail;
 	}

 	vma = _install_special_mapping(mm,
 				       addr,
 				       -image->sym_vvar_start,
 				       VM_READ|VM_MAYREAD,
 				       &vvar_mapping);

 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		do_munmap(mm, text_start, image->size, NULL);
 	}

 up_fail:
 	if (ret)
 		current->mm->context.vdso = NULL;

 	up_write(&mm->mmap_sem);
 	return ret;
 }

 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {

 	if (!vdso_enabled)
 		return 0;

 #if defined CONFIG_COMPAT
 	if (!(is_32bit_task()))
 		return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
 	else
 		return map_vdso(&vdso_image_32_builtin, &vdso_mapping32);
 #else
 	return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
 #endif

 }

 static __init int vdso_setup(char *s)
 {
 	int err;
 	unsigned long val;

 	err = kstrtoul(s, 10, &val);
 	if (err)
 		return err;
 	vdso_enabled = val;
 	return 0;
 }
 __setup("vdso=", vdso_setup);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Set up the VMAs to tell the VM about the vDSO.
	* Copyright 2007 Andi Kleen, SUSE Labs.
	*/

	/*
	* Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
	*/

	#include <linux/mm.h>
	#include <linux/err.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <linux/linkage.h>
	#include <linux/random.h>
	#include <linux/elf.h>
	#include <asm/cacheflush.h>
	#include <asm/spitfire.h>
	#include <asm/vdso.h>
	#include <asm/vvar.h>
	#include <asm/page.h>

	unsigned int __read_mostly vdso_enabled = 1;

	static struct vm_special_mapping vvar_mapping = {
	.name = "[vvar]"
	};

	#ifdef CONFIG_SPARC64
	static struct vm_special_mapping vdso_mapping64 = {
	.name = "[vdso]"
	};
	#endif

	#ifdef CONFIG_COMPAT
	static struct vm_special_mapping vdso_mapping32 = {
	.name = "[vdso]"
	};
	#endif

	struct vvar_data *vvar_data;

	struct vdso_elfinfo32 {
	Elf32_Ehdr *hdr;
	Elf32_Sym *dynsym;
	unsigned long dynsymsize;
	const char *dynstr;
	unsigned long text;
	};

	struct vdso_elfinfo64 {
	Elf64_Ehdr *hdr;
	Elf64_Sym *dynsym;
	unsigned long dynsymsize;
	const char *dynstr;
	unsigned long text;
	};

	struct vdso_elfinfo {
	union {
	struct vdso_elfinfo32 elf32;
	struct vdso_elfinfo64 elf64;
	} u;
	};

	static void one_section64(struct vdso_elfinfo64 e, const char *name,
	unsigned long *size)
	{
	const char *snames;
	Elf64_Shdr *shdrs;
	unsigned int i;

	shdrs = (void *)e->hdr + e->hdr->e_shoff;
	snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
	for (i = 1; i < e->hdr->e_shnum; i++) {
	if (!strcmp(snames+shdrs[i].sh_name, name)) {
	if (size)
	*size = shdrs[i].sh_size;
	return (void *)e->hdr + shdrs[i].sh_offset;
	}
	}
	return NULL;
	}

	static int find_sections64(const struct vdso_image image, struct vdso_elfinfo _e)
	{
	struct vdso_elfinfo64 *e = &_e->u.elf64;

	e->hdr = image->data;
	e->dynsym = one_section64(e, ".dynsym", &e->dynsymsize);
	e->dynstr = one_section64(e, ".dynstr", NULL);

	if (!e->dynsym \|\| !e->dynstr) {
	pr_err("VDSO64: Missing symbol sections.\n");
	return -ENODEV;
	}
	return 0;
	}

	static Elf64_Sym find_sym64(const struct vdso_elfinfo64 e, const char *name)
	{
	unsigned int i;

	for (i = 0; i < (e->dynsymsize / sizeof(Elf64_Sym)); i++) {
	Elf64_Sym *s = &e->dynsym[i];
	if (s->st_name == 0)
	continue;
	if (!strcmp(e->dynstr + s->st_name, name))
	return s;
	}
	return NULL;
	}

	static int patchsym64(struct vdso_elfinfo _e, const char orig,
	const char *new)
	{
	struct vdso_elfinfo64 *e = &_e->u.elf64;
	Elf64_Sym *osym = find_sym64(e, orig);
	Elf64_Sym *nsym = find_sym64(e, new);

	if (!nsym \|\| !osym) {
	pr_err("VDSO64: Missing symbols.\n");
	return -ENODEV;
	}
	osym->st_value = nsym->st_value;
	osym->st_size = nsym->st_size;
	osym->st_info = nsym->st_info;
	osym->st_other = nsym->st_other;
	osym->st_shndx = nsym->st_shndx;

	return 0;
	}

	static void one_section32(struct vdso_elfinfo32 e, const char *name,
	unsigned long *size)
	{
	const char *snames;
	Elf32_Shdr *shdrs;
	unsigned int i;

	shdrs = (void *)e->hdr + e->hdr->e_shoff;
	snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
	for (i = 1; i < e->hdr->e_shnum; i++) {
	if (!strcmp(snames+shdrs[i].sh_name, name)) {
	if (size)
	*size = shdrs[i].sh_size;
	return (void *)e->hdr + shdrs[i].sh_offset;
	}
	}
	return NULL;
	}

	static int find_sections32(const struct vdso_image image, struct vdso_elfinfo _e)
	{
	struct vdso_elfinfo32 *e = &_e->u.elf32;

	e->hdr = image->data;
	e->dynsym = one_section32(e, ".dynsym", &e->dynsymsize);
	e->dynstr = one_section32(e, ".dynstr", NULL);

	if (!e->dynsym \|\| !e->dynstr) {
	pr_err("VDSO32: Missing symbol sections.\n");
	return -ENODEV;
	}
	return 0;
	}

	static Elf32_Sym find_sym32(const struct vdso_elfinfo32 e, const char *name)
	{
	unsigned int i;

	for (i = 0; i < (e->dynsymsize / sizeof(Elf32_Sym)); i++) {
	Elf32_Sym *s = &e->dynsym[i];
	if (s->st_name == 0)
	continue;
	if (!strcmp(e->dynstr + s->st_name, name))
	return s;
	}
	return NULL;
	}

	static int patchsym32(struct vdso_elfinfo _e, const char orig,
	const char *new)
	{
	struct vdso_elfinfo32 *e = &_e->u.elf32;
	Elf32_Sym *osym = find_sym32(e, orig);
	Elf32_Sym *nsym = find_sym32(e, new);

	if (!nsym \|\| !osym) {
	pr_err("VDSO32: Missing symbols.\n");
	return -ENODEV;
	}
	osym->st_value = nsym->st_value;
	osym->st_size = nsym->st_size;
	osym->st_info = nsym->st_info;
	osym->st_other = nsym->st_other;
	osym->st_shndx = nsym->st_shndx;

	return 0;
	}

	static int find_sections(const struct vdso_image image, struct vdso_elfinfo e,
	bool elf64)
	{
	if (elf64)
	return find_sections64(image, e);
	else
	return find_sections32(image, e);
	}

	static int patch_one_symbol(struct vdso_elfinfo e, const char orig,
	const char *new_target, bool elf64)
	{
	if (elf64)
	return patchsym64(e, orig, new_target);
	else
	return patchsym32(e, orig, new_target);
	}

	static int stick_patch(const struct vdso_image image, struct vdso_elfinfo e, bool elf64)
	{
	int err;

	err = find_sections(image, e, elf64);
	if (err)
	return err;

	err = patch_one_symbol(e,
	"__vdso_gettimeofday",
	"__vdso_gettimeofday_stick", elf64);
	if (err)
	return err;

	return patch_one_symbol(e,
	"__vdso_clock_gettime",
	"__vdso_clock_gettime_stick", elf64);
	return 0;
	}

	/*
	* Allocate pages for the vdso and vvar, and copy in the vdso text from the
	* kernel image.
	*/
	int __init init_vdso_image(const struct vdso_image *image,
	struct vm_special_mapping *vdso_mapping, bool elf64)
	{
	int cnpages = (image->size) / PAGE_SIZE;
	struct page dp, *dpp = NULL;
	struct page cp, *cpp = NULL;
	struct vdso_elfinfo ei;
	int i, dnpages = 0;

	if (tlb_type != spitfire) {
	int err = stick_patch(image, &ei, elf64);
	if (err)
	return err;
	}

	/*
	* First, the vdso text. This is initialied data, an integral number of
	* pages long.
	*/
	if (WARN_ON(image->size % PAGE_SIZE != 0))
	goto oom;

	cpp = kcalloc(cnpages, sizeof(struct page *), GFP_KERNEL);
	vdso_mapping->pages = cpp;

	if (!cpp)
	goto oom;

	for (i = 0; i < cnpages; i++) {
	cp = alloc_page(GFP_KERNEL);
	if (!cp)
	goto oom;
	cpp[i] = cp;
	copy_page(page_address(cp), image->data + i * PAGE_SIZE);
	}

	/*
	* Now the vvar page. This is uninitialized data.
	*/

	if (vvar_data == NULL) {
	dnpages = (sizeof(struct vvar_data) / PAGE_SIZE) + 1;
	if (WARN_ON(dnpages != 1))
	goto oom;
	dpp = kcalloc(dnpages, sizeof(struct page *), GFP_KERNEL);
	vvar_mapping.pages = dpp;

	if (!dpp)
	goto oom;

	dp = alloc_page(GFP_KERNEL);
	if (!dp)
	goto oom;

	dpp[0] = dp;
	vvar_data = page_address(dp);
	memset(vvar_data, 0, PAGE_SIZE);

	vvar_data->seq = 0;
	}

	return 0;
	oom:
	if (cpp != NULL) {
	for (i = 0; i < cnpages; i++) {
	if (cpp[i] != NULL)
	__free_page(cpp[i]);
	}
	kfree(cpp);
	vdso_mapping->pages = NULL;
	}

	if (dpp != NULL) {
	for (i = 0; i < dnpages; i++) {
	if (dpp[i] != NULL)
	__free_page(dpp[i]);
	}
	kfree(dpp);
	vvar_mapping.pages = NULL;
	}

	pr_warn("Cannot allocate vdso\n");
	vdso_enabled = 0;
	return -ENOMEM;
	}

	static int __init init_vdso(void)
	{
	int err = 0;
	#ifdef CONFIG_SPARC64
	err = init_vdso_image(&vdso_image_64_builtin, &vdso_mapping64, true);
	if (err)
	return err;
	#endif

	#ifdef CONFIG_COMPAT
	err = init_vdso_image(&vdso_image_32_builtin, &vdso_mapping32, false);
	#endif
	return err;

	}
	subsys_initcall(init_vdso);

	struct linux_binprm;

	/* Shuffle the vdso up a bit, randomly. */
	static unsigned long vdso_addr(unsigned long start, unsigned int len)
	{
	unsigned int offset;

	/* This loses some more bits than a modulo, but is cheaper */
	offset = get_random_int() & (PTRS_PER_PTE - 1);
	return start + (offset << PAGE_SHIFT);
	}

	static int map_vdso(const struct vdso_image *image,
	struct vm_special_mapping *vdso_mapping)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long text_start, addr = 0;
	int ret = 0;

	down_write(&mm->mmap_sem);

	/*
	* First, get an unmapped region: then randomize it, and make sure that
	* region is free.
	*/
	if (current->flags & PF_RANDOMIZE) {
	addr = get_unmapped_area(NULL, 0,
	image->size - image->sym_vvar_start,
	0, 0);
	if (IS_ERR_VALUE(addr)) {
	ret = addr;
	goto up_fail;
	}
	addr = vdso_addr(addr, image->size - image->sym_vvar_start);
	}
	addr = get_unmapped_area(NULL, addr,
	image->size - image->sym_vvar_start, 0, 0);
	if (IS_ERR_VALUE(addr)) {
	ret = addr;
	goto up_fail;
	}

	text_start = addr - image->sym_vvar_start;
	current->mm->context.vdso = (void __user *)text_start;

	/*
	* MAYWRITE to allow gdb to COW and set breakpoints
	*/
	vma = _install_special_mapping(mm,
	text_start,
	image->size,
	VM_READ\|VM_EXEC\|
	VM_MAYREAD\|VM_MAYWRITE\|VM_MAYEXEC,
	vdso_mapping);

	if (IS_ERR(vma)) {
	ret = PTR_ERR(vma);
	goto up_fail;
	}

	vma = _install_special_mapping(mm,
	addr,
	-image->sym_vvar_start,
	VM_READ\|VM_MAYREAD,
	&vvar_mapping);

	if (IS_ERR(vma)) {
	ret = PTR_ERR(vma);
	do_munmap(mm, text_start, image->size, NULL);
	}

	up_fail:
	if (ret)
	current->mm->context.vdso = NULL;

	up_write(&mm->mmap_sem);
	return ret;
	}

	int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
	{

	if (!vdso_enabled)
	return 0;

	#if defined CONFIG_COMPAT
	if (!(is_32bit_task()))
	return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
	else
	return map_vdso(&vdso_image_32_builtin, &vdso_mapping32);
	#else
	return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
	#endif

	}

	static __init int vdso_setup(char *s)
	{
	int err;
	unsigned long val;

	err = kstrtoul(s, 10, &val);
	if (err)
	return err;
	vdso_enabled = val;
	return 0;
	}
	__setup("vdso=", vdso_setup);