arch/x86/entry/vdso/vma.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright 2007 Andi Kleen, SUSE Labs.
  *
  * This contains most of the x86 vDSO kernel-side code.
  */
 #include <linux/mm.h>
 #include <linux/err.h>
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/random.h>
 #include <linux/elf.h>
 #include <linux/cpu.h>
 #include <linux/ptrace.h>
 #include <linux/time_namespace.h>

 #include <asm/pvclock.h>
 #include <asm/vgtod.h>
 #include <asm/proto.h>
 #include <asm/vdso.h>
 #include <asm/vvar.h>
 #include <asm/tlb.h>
 #include <asm/page.h>
 #include <asm/desc.h>
 #include <asm/cpufeature.h>
 #include <clocksource/hyperv_timer.h>

 #undef _ASM_X86_VVAR_H
 #define EMIT_VVAR(name, offset)	\
 	const size_t name ## _offset = offset;
 #include <asm/vvar.h>

 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 {
 	return (struct vdso_data *)(vvar_page + _vdso_data_offset);
 }
 #undef EMIT_VVAR

 unsigned int vclocks_used __read_mostly;

 #if defined(CONFIG_X86_64)
 unsigned int __read_mostly vdso64_enabled = 1;
 #endif

 void __init init_vdso_image(const struct vdso_image *image)
 {
 	BUG_ON(image->size % PAGE_SIZE != 0);

 	apply_alternatives((struct alt_instr *)(image->data + image->alt),
 			   (struct alt_instr *)(image->data + image->alt +
 						image->alt_len));
 }

 static const struct vm_special_mapping vvar_mapping;
 struct linux_binprm;

 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
 		      struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	const struct vdso_image *image = vma->vm_mm->context.vdso_image;

 	if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size)
 		return VM_FAULT_SIGBUS;

 	vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
 	get_page(vmf->page);
 	return 0;
 }

 static void vdso_fix_landing(const struct vdso_image *image,
 		struct vm_area_struct *new_vma)
 {
 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 	if (in_ia32_syscall() && image == &vdso_image_32) {
 		struct pt_regs *regs = current_pt_regs();
 		unsigned long vdso_land = image->sym_int80_landing_pad;
 		unsigned long old_land_addr = vdso_land +
 			(unsigned long)current->mm->context.vdso;

 		/* Fixing userspace landing - look at do_fast_syscall_32 */
 		if (regs->ip == old_land_addr)
 			regs->ip = new_vma->vm_start + vdso_land;
 	}
 #endif
 }

 static int vdso_mremap(const struct vm_special_mapping *sm,
 		struct vm_area_struct *new_vma)
 {
 	const struct vdso_image *image = current->mm->context.vdso_image;

 	vdso_fix_landing(image, new_vma);
 	current->mm->context.vdso = (void __user *)new_vma->vm_start;

 	return 0;
 }

 #ifdef CONFIG_TIME_NS
 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;
 }

 /*
  * The vvar page layout depends on whether a task belongs to the root or
  * non-root time namespace. Whenever a task changes its namespace, the VVAR
  * page tables are cleared and then they will re-faulted with a
  * corresponding layout.
  * See also the comment near timens_setup_vdso_data() for details.
  */
 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, &vvar_mapping))
 			zap_page_range(vma, vma->vm_start, size);
 	}

 	mmap_read_unlock(mm);
 	return 0;
 }
 #else
 static inline 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)
 {
 	const struct vdso_image *image = vma->vm_mm->context.vdso_image;
 	unsigned long pfn;
 	long sym_offset;

 	if (!image)
 		return VM_FAULT_SIGBUS;

 	sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +
 		image->sym_vvar_start;

 	/*
 	 * Sanity check: a symbol offset of zero means that the page
 	 * does not exist for this vdso image, not that the page is at
 	 * offset zero relative to the text mapping.  This should be
 	 * impossible here, because sym_offset should only be zero for
 	 * the page past the end of the vvar mapping.
 	 */
 	if (sym_offset == 0)
 		return VM_FAULT_SIGBUS;

 	if (sym_offset == image->sym_vvar_page) {
 		struct page *timens_page = find_timens_vvar_page(vma);

 		pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;

 		/*
 		 * If a task belongs to a time namespace then a namespace
 		 * specific VVAR is mapped with the sym_vvar_page offset and
 		 * the real VVAR page is mapped with the sym_timens_page
 		 * offset.
 		 * See also the comment near timens_setup_vdso_data().
 		 */
 		if (timens_page) {
 			unsigned long addr;
 			vm_fault_t err;

 			/*
 			 * Optimization: inside time namespace pre-fault
 			 * VVAR page too. As on timens page there are only
 			 * offsets for clocks on VVAR, it'll be faulted
 			 * shortly by VDSO code.
 			 */
 			addr = vmf->address + (image->sym_timens_page - sym_offset);
 			err = vmf_insert_pfn(vma, addr, pfn);
 			if (unlikely(err & VM_FAULT_ERROR))
 				return err;

 			pfn = page_to_pfn(timens_page);
 		}

 		return vmf_insert_pfn(vma, vmf->address, pfn);
 	} else if (sym_offset == image->sym_pvclock_page) {
 		struct pvclock_vsyscall_time_info *pvti =
 			pvclock_get_pvti_cpu0_va();
 		if (pvti && vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)) {
 			return vmf_insert_pfn_prot(vma, vmf->address,
 					__pa(pvti) >> PAGE_SHIFT,
 					pgprot_decrypted(vma->vm_page_prot));
 		}
 	} else if (sym_offset == image->sym_hvclock_page) {
 		struct ms_hyperv_tsc_page *tsc_pg = hv_get_tsc_page();

 		if (tsc_pg && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK))
 			return vmf_insert_pfn(vma, vmf->address,
 					virt_to_phys(tsc_pg) >> PAGE_SHIFT);
 	} else if (sym_offset == image->sym_timens_page) {
 		struct page *timens_page = find_timens_vvar_page(vma);

 		if (!timens_page)
 			return VM_FAULT_SIGBUS;

 		pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
 		return vmf_insert_pfn(vma, vmf->address, pfn);
 	}

 	return VM_FAULT_SIGBUS;
 }

 static const struct vm_special_mapping vdso_mapping = {
 	.name = "[vdso]",
 	.fault = vdso_fault,
 	.mremap = vdso_mremap,
 };
 static const struct vm_special_mapping vvar_mapping = {
 	.name = "[vvar]",
 	.fault = vvar_fault,
 };

 /*
  * Add vdso and vvar mappings to current process.
  * @image          - blob to map
  * @addr           - request a specific address (zero to map at free addr)
  */
 static int map_vdso(const struct vdso_image *image, unsigned long addr)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long text_start;
 	int ret = 0;

 	if (mmap_write_lock_killable(mm))
 		return -EINTR;

 	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;

 	/*
 	 * 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|VM_IO|VM_DONTDUMP|
 				       VM_PFNMAP,
 				       &vvar_mapping);

 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		do_munmap(mm, text_start, image->size, NULL);
 	} else {
 		current->mm->context.vdso = (void __user *)text_start;
 		current->mm->context.vdso_image = image;
 	}

 up_fail:
 	mmap_write_unlock(mm);
 	return ret;
 }

 #ifdef CONFIG_X86_64
 /*
  * Put the vdso above the (randomized) stack with another randomized
  * offset.  This way there is no hole in the middle of address space.
  * To save memory make sure it is still in the same PTE as the stack
  * top.  This doesn't give that many random bits.
  *
  * Note that this algorithm is imperfect: the distribution of the vdso
  * start address within a PMD is biased toward the end.
  *
  * Only used for the 64-bit and x32 vdsos.
  */
 static unsigned long vdso_addr(unsigned long start, unsigned len)
 {
 	unsigned long addr, end;
 	unsigned offset;

 	/*
 	 * Round up the start address.  It can start out unaligned as a result
 	 * of stack start randomization.
 	 */
 	start = PAGE_ALIGN(start);

 	/* Round the lowest possible end address up to a PMD boundary. */
 	end = (start + len + PMD_SIZE - 1) & PMD_MASK;
 	if (end >= TASK_SIZE_MAX)
 		end = TASK_SIZE_MAX;
 	end -= len;

 	if (end > start) {
 		offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
 		addr = start + (offset << PAGE_SHIFT);
 	} else {
 		addr = start;
 	}

 	/*
 	 * Forcibly align the final address in case we have a hardware
 	 * issue that requires alignment for performance reasons.
 	 */
 	addr = align_vdso_addr(addr);

 	return addr;
 }

 static int map_vdso_randomized(const struct vdso_image *image)
 {
 	unsigned long addr = vdso_addr(current->mm->start_stack, image->size-image->sym_vvar_start);

 	return map_vdso(image, addr);
 }
 #endif

 int map_vdso_once(const struct vdso_image *image, unsigned long addr)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;

 	mmap_write_lock(mm);
 	/*
 	 * Check if we have already mapped vdso blob - fail to prevent
 	 * abusing from userspace install_speciall_mapping, which may
 	 * not do accounting and rlimit right.
 	 * We could search vma near context.vdso, but it's a slowpath,
 	 * so let's explicitly check all VMAs to be completely sure.
 	 */
 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
 		if (vma_is_special_mapping(vma, &vdso_mapping) ||
 				vma_is_special_mapping(vma, &vvar_mapping)) {
 			mmap_write_unlock(mm);
 			return -EEXIST;
 		}
 	}
 	mmap_write_unlock(mm);

 	return map_vdso(image, addr);
 }

 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 static int load_vdso32(void)
 {
 	if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
 		return 0;

 	return map_vdso(&vdso_image_32, 0);
 }
 #endif

 #ifdef CONFIG_X86_64
 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
 	if (!vdso64_enabled)
 		return 0;

 	return map_vdso_randomized(&vdso_image_64);
 }

 #ifdef CONFIG_COMPAT
 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 				       int uses_interp, bool x32)
 {
 #ifdef CONFIG_X86_X32_ABI
 	if (x32) {
 		if (!vdso64_enabled)
 			return 0;
 		return map_vdso_randomized(&vdso_image_x32);
 	}
 #endif
 #ifdef CONFIG_IA32_EMULATION
 	return load_vdso32();
 #else
 	return 0;
 #endif
 }
 #endif
 #else
 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
 	return load_vdso32();
 }
 #endif

 bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
 {
 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 	const struct vdso_image *image = current->mm->context.vdso_image;
 	unsigned long vdso = (unsigned long) current->mm->context.vdso;

 	if (in_ia32_syscall() && image == &vdso_image_32) {
 		if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad ||
 		    regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad)
 			return true;
 	}
 #endif
 	return false;
 }

 #ifdef CONFIG_X86_64
 static __init int vdso_setup(char *s)
 {
 	vdso64_enabled = simple_strtoul(s, NULL, 0);
 	return 0;
 }
 __setup("vdso=", vdso_setup);

 static int __init init_vdso(void)
 {
 	BUILD_BUG_ON(VDSO_CLOCKMODE_MAX >= 32);

 	init_vdso_image(&vdso_image_64);

 #ifdef CONFIG_X86_X32_ABI
 	init_vdso_image(&vdso_image_x32);
 #endif

 	return 0;
 }
 subsys_initcall(init_vdso);
 #endif /* CONFIG_X86_64 */
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright 2007 Andi Kleen, SUSE Labs.
	*
	* This contains most of the x86 vDSO kernel-side code.
	*/
	#include <linux/mm.h>
	#include <linux/err.h>
	#include <linux/sched.h>
	#include <linux/sched/task_stack.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <linux/random.h>
	#include <linux/elf.h>
	#include <linux/cpu.h>
	#include <linux/ptrace.h>
	#include <linux/time_namespace.h>

	#include <asm/pvclock.h>
	#include <asm/vgtod.h>
	#include <asm/proto.h>
	#include <asm/vdso.h>
	#include <asm/vvar.h>
	#include <asm/tlb.h>
	#include <asm/page.h>
	#include <asm/desc.h>
	#include <asm/cpufeature.h>
	#include <clocksource/hyperv_timer.h>

	#undef _ASM_X86_VVAR_H
	#define EMIT_VVAR(name, offset) \
	const size_t name ## _offset = offset;
	#include <asm/vvar.h>

	struct vdso_data arch_get_vdso_data(void vvar_page)
	{
	return (struct vdso_data *)(vvar_page + _vdso_data_offset);
	}
	#undef EMIT_VVAR

	unsigned int vclocks_used __read_mostly;

	#if defined(CONFIG_X86_64)
	unsigned int __read_mostly vdso64_enabled = 1;
	#endif

	void __init init_vdso_image(const struct vdso_image *image)
	{
	BUG_ON(image->size % PAGE_SIZE != 0);

	apply_alternatives((struct alt_instr *)(image->data + image->alt),
	(struct alt_instr *)(image->data + image->alt +
	image->alt_len));
	}

	static const struct vm_special_mapping vvar_mapping;
	struct linux_binprm;

	static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
	struct vm_area_struct vma, struct vm_fault vmf)
	{
	const struct vdso_image *image = vma->vm_mm->context.vdso_image;

	if (!image \|\| (vmf->pgoff << PAGE_SHIFT) >= image->size)
	return VM_FAULT_SIGBUS;

	vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
	get_page(vmf->page);
	return 0;
	}

	static void vdso_fix_landing(const struct vdso_image *image,
	struct vm_area_struct *new_vma)
	{
	#if defined CONFIG_X86_32 \|\| defined CONFIG_IA32_EMULATION
	if (in_ia32_syscall() && image == &vdso_image_32) {
	struct pt_regs *regs = current_pt_regs();
	unsigned long vdso_land = image->sym_int80_landing_pad;
	unsigned long old_land_addr = vdso_land +
	(unsigned long)current->mm->context.vdso;

	/* Fixing userspace landing - look at do_fast_syscall_32 */
	if (regs->ip == old_land_addr)
	regs->ip = new_vma->vm_start + vdso_land;
	}
	#endif
	}

	static int vdso_mremap(const struct vm_special_mapping *sm,
	struct vm_area_struct *new_vma)
	{
	const struct vdso_image *image = current->mm->context.vdso_image;

	vdso_fix_landing(image, new_vma);
	current->mm->context.vdso = (void __user *)new_vma->vm_start;

	return 0;
	}

	#ifdef CONFIG_TIME_NS
	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;
	}

	/*
	* The vvar page layout depends on whether a task belongs to the root or
	* non-root time namespace. Whenever a task changes its namespace, the VVAR
	* page tables are cleared and then they will re-faulted with a
	* corresponding layout.
	* See also the comment near timens_setup_vdso_data() for details.
	*/
	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, &vvar_mapping))
	zap_page_range(vma, vma->vm_start, size);
	}

	mmap_read_unlock(mm);
	return 0;
	}
	#else
	static inline 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)
	{
	const struct vdso_image *image = vma->vm_mm->context.vdso_image;
	unsigned long pfn;
	long sym_offset;

	if (!image)
	return VM_FAULT_SIGBUS;

	sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +
	image->sym_vvar_start;

	/*
	* Sanity check: a symbol offset of zero means that the page
	* does not exist for this vdso image, not that the page is at
	* offset zero relative to the text mapping. This should be
	* impossible here, because sym_offset should only be zero for
	* the page past the end of the vvar mapping.
	*/
	if (sym_offset == 0)
	return VM_FAULT_SIGBUS;

	if (sym_offset == image->sym_vvar_page) {
	struct page *timens_page = find_timens_vvar_page(vma);

	pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;

	/*
	* If a task belongs to a time namespace then a namespace
	* specific VVAR is mapped with the sym_vvar_page offset and
	* the real VVAR page is mapped with the sym_timens_page
	* offset.
	* See also the comment near timens_setup_vdso_data().
	*/
	if (timens_page) {
	unsigned long addr;
	vm_fault_t err;

	/*
	* Optimization: inside time namespace pre-fault
	* VVAR page too. As on timens page there are only
	* offsets for clocks on VVAR, it'll be faulted
	* shortly by VDSO code.
	*/
	addr = vmf->address + (image->sym_timens_page - sym_offset);
	err = vmf_insert_pfn(vma, addr, pfn);
	if (unlikely(err & VM_FAULT_ERROR))
	return err;

	pfn = page_to_pfn(timens_page);
	}

	return vmf_insert_pfn(vma, vmf->address, pfn);
	} else if (sym_offset == image->sym_pvclock_page) {
	struct pvclock_vsyscall_time_info *pvti =
	pvclock_get_pvti_cpu0_va();
	if (pvti && vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)) {
	return vmf_insert_pfn_prot(vma, vmf->address,
	__pa(pvti) >> PAGE_SHIFT,
	pgprot_decrypted(vma->vm_page_prot));
	}
	} else if (sym_offset == image->sym_hvclock_page) {
	struct ms_hyperv_tsc_page *tsc_pg = hv_get_tsc_page();

	if (tsc_pg && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK))
	return vmf_insert_pfn(vma, vmf->address,
	virt_to_phys(tsc_pg) >> PAGE_SHIFT);
	} else if (sym_offset == image->sym_timens_page) {
	struct page *timens_page = find_timens_vvar_page(vma);

	if (!timens_page)
	return VM_FAULT_SIGBUS;

	pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
	return vmf_insert_pfn(vma, vmf->address, pfn);
	}

	return VM_FAULT_SIGBUS;
	}

	static const struct vm_special_mapping vdso_mapping = {
	.name = "[vdso]",
	.fault = vdso_fault,
	.mremap = vdso_mremap,
	};
	static const struct vm_special_mapping vvar_mapping = {
	.name = "[vvar]",
	.fault = vvar_fault,
	};

	/*
	* Add vdso and vvar mappings to current process.
	* @image - blob to map
	* @addr - request a specific address (zero to map at free addr)
	*/
	static int map_vdso(const struct vdso_image *image, unsigned long addr)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long text_start;
	int ret = 0;

	if (mmap_write_lock_killable(mm))
	return -EINTR;

	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;

	/*
	* 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\|VM_IO\|VM_DONTDUMP\|
	VM_PFNMAP,
	&vvar_mapping);

	if (IS_ERR(vma)) {
	ret = PTR_ERR(vma);
	do_munmap(mm, text_start, image->size, NULL);
	} else {
	current->mm->context.vdso = (void __user *)text_start;
	current->mm->context.vdso_image = image;
	}

	up_fail:
	mmap_write_unlock(mm);
	return ret;
	}

	#ifdef CONFIG_X86_64
	/*
	* Put the vdso above the (randomized) stack with another randomized
	* offset. This way there is no hole in the middle of address space.
	* To save memory make sure it is still in the same PTE as the stack
	* top. This doesn't give that many random bits.
	*
	* Note that this algorithm is imperfect: the distribution of the vdso
	* start address within a PMD is biased toward the end.
	*
	* Only used for the 64-bit and x32 vdsos.
	*/
	static unsigned long vdso_addr(unsigned long start, unsigned len)
	{
	unsigned long addr, end;
	unsigned offset;

	/*
	* Round up the start address. It can start out unaligned as a result
	* of stack start randomization.
	*/
	start = PAGE_ALIGN(start);

	/* Round the lowest possible end address up to a PMD boundary. */
	end = (start + len + PMD_SIZE - 1) & PMD_MASK;
	if (end >= TASK_SIZE_MAX)
	end = TASK_SIZE_MAX;
	end -= len;

	if (end > start) {
	offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
	addr = start + (offset << PAGE_SHIFT);
	} else {
	addr = start;
	}

	/*
	* Forcibly align the final address in case we have a hardware
	* issue that requires alignment for performance reasons.
	*/
	addr = align_vdso_addr(addr);

	return addr;
	}

	static int map_vdso_randomized(const struct vdso_image *image)
	{
	unsigned long addr = vdso_addr(current->mm->start_stack, image->size-image->sym_vvar_start);

	return map_vdso(image, addr);
	}
	#endif

	int map_vdso_once(const struct vdso_image *image, unsigned long addr)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;

	mmap_write_lock(mm);
	/*
	* Check if we have already mapped vdso blob - fail to prevent
	* abusing from userspace install_speciall_mapping, which may
	* not do accounting and rlimit right.
	* We could search vma near context.vdso, but it's a slowpath,
	* so let's explicitly check all VMAs to be completely sure.
	*/
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
	if (vma_is_special_mapping(vma, &vdso_mapping) \|\|
	vma_is_special_mapping(vma, &vvar_mapping)) {
	mmap_write_unlock(mm);
	return -EEXIST;
	}
	}
	mmap_write_unlock(mm);

	return map_vdso(image, addr);
	}

	#if defined(CONFIG_X86_32) \|\| defined(CONFIG_IA32_EMULATION)
	static int load_vdso32(void)
	{
	if (vdso32_enabled != 1) /* Other values all mean "disabled" */
	return 0;

	return map_vdso(&vdso_image_32, 0);
	}
	#endif

	#ifdef CONFIG_X86_64
	int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
	{
	if (!vdso64_enabled)
	return 0;

	return map_vdso_randomized(&vdso_image_64);
	}

	#ifdef CONFIG_COMPAT
	int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
	int uses_interp, bool x32)
	{
	#ifdef CONFIG_X86_X32_ABI
	if (x32) {
	if (!vdso64_enabled)
	return 0;
	return map_vdso_randomized(&vdso_image_x32);
	}
	#endif
	#ifdef CONFIG_IA32_EMULATION
	return load_vdso32();
	#else
	return 0;
	#endif
	}
	#endif
	#else
	int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
	{
	return load_vdso32();
	}
	#endif

	bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
	{
	#if defined(CONFIG_X86_32) \|\| defined(CONFIG_IA32_EMULATION)
	const struct vdso_image *image = current->mm->context.vdso_image;
	unsigned long vdso = (unsigned long) current->mm->context.vdso;

	if (in_ia32_syscall() && image == &vdso_image_32) {
	if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad \|\|
	regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad)
	return true;
	}
	#endif
	return false;
	}

	#ifdef CONFIG_X86_64
	static __init int vdso_setup(char *s)
	{
	vdso64_enabled = simple_strtoul(s, NULL, 0);
	return 0;
	}
	__setup("vdso=", vdso_setup);

	static int __init init_vdso(void)
	{
	BUILD_BUG_ON(VDSO_CLOCKMODE_MAX >= 32);

	init_vdso_image(&vdso_image_64);

	#ifdef CONFIG_X86_X32_ABI
	init_vdso_image(&vdso_image_x32);
	#endif

	return 0;
	}
	subsys_initcall(init_vdso);
	#endif /* CONFIG_X86_64 */