arch/x86/vdso/vdso32-setup.c - fp2-dev/kernel/msm - Gitiles

 /*
  * (C) Copyright 2002 Linus Torvalds
  * Portions based on the vdso-randomization code from exec-shield:
  * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
  *
  * This file contains the needed initializations to support sysenter.
  */

 #include <linux/init.h>
 #include <linux/smp.h>
 #include <linux/thread_info.h>
 #include <linux/sched.h>
 #include <linux/gfp.h>
 #include <linux/string.h>
 #include <linux/elf.h>
 #include <linux/mm.h>
 #include <linux/err.h>
 #include <linux/module.h>

 #include <asm/cpufeature.h>
 #include <asm/msr.h>
 #include <asm/pgtable.h>
 #include <asm/unistd.h>
 #include <asm/elf.h>
 #include <asm/tlbflush.h>
 #include <asm/vdso.h>
 #include <asm/proto.h>

 enum {
 	VDSO_DISABLED = 0,
 	VDSO_ENABLED = 1,
 	VDSO_COMPAT = 2,
 };

 #ifdef CONFIG_COMPAT_VDSO
 #define VDSO_DEFAULT	VDSO_COMPAT
 #else
 #define VDSO_DEFAULT	VDSO_ENABLED
 #endif

 #ifdef CONFIG_X86_64
 #define vdso_enabled			sysctl_vsyscall32
 #define arch_setup_additional_pages	syscall32_setup_pages
 #endif

 /*
  * This is the difference between the prelinked addresses in the vDSO images
  * and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
  * in the user address space.
  */
 #define VDSO_ADDR_ADJUST	(VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)

 /*
  * Should the kernel map a VDSO page into processes and pass its
  * address down to glibc upon exec()?
  */
 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;

 static int __init vdso_setup(char *s)
 {
 	vdso_enabled = simple_strtoul(s, NULL, 0);

 	return 1;
 }

 /*
  * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
  * behavior on both 64-bit and 32-bit kernels.
  * On 32-bit kernels, vdso=[012] means the same thing.
  */
 __setup("vdso32=", vdso_setup);

 #ifdef CONFIG_X86_32
 __setup_param("vdso=", vdso32_setup, vdso_setup, 0);

 EXPORT_SYMBOL_GPL(vdso_enabled);
 #endif

 static __init void reloc_symtab(Elf32_Ehdr *ehdr,
 				unsigned offset, unsigned size)
 {
 	Elf32_Sym *sym = (void *)ehdr + offset;
 	unsigned nsym = size / sizeof(*sym);
 	unsigned i;

 	for(i = 0; i < nsym; i++, sym++) {
 		if (sym->st_shndx == SHN_UNDEF ||
 		    sym->st_shndx == SHN_ABS)
 			continue;  /* skip */

 		if (sym->st_shndx > SHN_LORESERVE) {
 			printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
 			       sym->st_shndx);
 			continue;
 		}

 		switch(ELF_ST_TYPE(sym->st_info)) {
 		case STT_OBJECT:
 		case STT_FUNC:
 		case STT_SECTION:
 		case STT_FILE:
 			sym->st_value += VDSO_ADDR_ADJUST;
 		}
 	}
 }

 static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
 {
 	Elf32_Dyn *dyn = (void *)ehdr + offset;

 	for(; dyn->d_tag != DT_NULL; dyn++)
 		switch(dyn->d_tag) {
 		case DT_PLTGOT:
 		case DT_HASH:
 		case DT_STRTAB:
 		case DT_SYMTAB:
 		case DT_RELA:
 		case DT_INIT:
 		case DT_FINI:
 		case DT_REL:
 		case DT_DEBUG:
 		case DT_JMPREL:
 		case DT_VERSYM:
 		case DT_VERDEF:
 		case DT_VERNEED:
 		case DT_ADDRRNGLO ... DT_ADDRRNGHI:
 			/* definitely pointers needing relocation */
 			dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
 			break;

 		case DT_ENCODING ... OLD_DT_LOOS-1:
 		case DT_LOOS ... DT_HIOS-1:
 			/* Tags above DT_ENCODING are pointers if
 			   they're even */
 			if (dyn->d_tag >= DT_ENCODING &&
 			    (dyn->d_tag & 1) == 0)
 				dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
 			break;

 		case DT_VERDEFNUM:
 		case DT_VERNEEDNUM:
 		case DT_FLAGS_1:
 		case DT_RELACOUNT:
 		case DT_RELCOUNT:
 		case DT_VALRNGLO ... DT_VALRNGHI:
 			/* definitely not pointers */
 			break;

 		case OLD_DT_LOOS ... DT_LOOS-1:
 		case DT_HIOS ... DT_VALRNGLO-1:
 		default:
 			if (dyn->d_tag > DT_ENCODING)
 				printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
 				       dyn->d_tag);
 			break;
 		}
 }

 static __init void relocate_vdso(Elf32_Ehdr *ehdr)
 {
 	Elf32_Phdr *phdr;
 	Elf32_Shdr *shdr;
 	int i;

 	BUG_ON(memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0 ||
 	       !elf_check_arch_ia32(ehdr) ||
 	       ehdr->e_type != ET_DYN);

 	ehdr->e_entry += VDSO_ADDR_ADJUST;

 	/* rebase phdrs */
 	phdr = (void *)ehdr + ehdr->e_phoff;
 	for (i = 0; i < ehdr->e_phnum; i++) {
 		phdr[i].p_vaddr += VDSO_ADDR_ADJUST;

 		/* relocate dynamic stuff */
 		if (phdr[i].p_type == PT_DYNAMIC)
 			reloc_dyn(ehdr, phdr[i].p_offset);
 	}

 	/* rebase sections */
 	shdr = (void *)ehdr + ehdr->e_shoff;
 	for(i = 0; i < ehdr->e_shnum; i++) {
 		if (!(shdr[i].sh_flags & SHF_ALLOC))
 			continue;

 		shdr[i].sh_addr += VDSO_ADDR_ADJUST;

 		if (shdr[i].sh_type == SHT_SYMTAB ||
 		    shdr[i].sh_type == SHT_DYNSYM)
 			reloc_symtab(ehdr, shdr[i].sh_offset,
 				     shdr[i].sh_size);
 	}
 }

 /*
  * These symbols are defined by vdso32.S to mark the bounds
  * of the ELF DSO images included therein.
  */
 extern const char vdso32_default_start, vdso32_default_end;
 extern const char vdso32_sysenter_start, vdso32_sysenter_end;
 static struct page *vdso32_pages[1];

 #ifdef CONFIG_X86_64

 static int use_sysenter __read_mostly = -1;

 #define	vdso32_sysenter()	(use_sysenter > 0)

 /* May not be __init: called during resume */
 void syscall32_cpu_init(void)
 {
 	if (use_sysenter < 0) {
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
 			use_sysenter = 1;
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR)
 			use_sysenter = 1;
 	}

 	/* Load these always in case some future AMD CPU supports
 	   SYSENTER from compat mode too. */
 	checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 	checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 	checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);

 	wrmsrl(MSR_CSTAR, ia32_cstar_target);
 }

 #define compat_uses_vma		1

 static inline void map_compat_vdso(int map)
 {
 }

 #else  /* CONFIG_X86_32 */

 #define vdso32_sysenter()	(boot_cpu_has(X86_FEATURE_SEP))

 void enable_sep_cpu(void)
 {
 	int cpu = get_cpu();
 	struct tss_struct *tss = &per_cpu(init_tss, cpu);

 	if (!boot_cpu_has(X86_FEATURE_SEP)) {
 		put_cpu();
 		return;
 	}

 	tss->x86_tss.ss1 = __KERNEL_CS;
 	tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
 	wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 	wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
 	wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
 	put_cpu();
 }

 static struct vm_area_struct gate_vma;

 static int __init gate_vma_init(void)
 {
 	gate_vma.vm_mm = NULL;
 	gate_vma.vm_start = FIXADDR_USER_START;
 	gate_vma.vm_end = FIXADDR_USER_END;
 	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
 	gate_vma.vm_page_prot = __P101;
 	/*
 	 * Make sure the vDSO gets into every core dump.
 	 * Dumping its contents makes post-mortem fully interpretable later
 	 * without matching up the same kernel and hardware config to see
 	 * what PC values meant.
 	 */
 	gate_vma.vm_flags |= VM_ALWAYSDUMP;
 	return 0;
 }

 #define compat_uses_vma		0

 static void map_compat_vdso(int map)
 {
 	static int vdso_mapped;

 	if (map == vdso_mapped)
 		return;

 	vdso_mapped = map;

 	__set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
 		     map ? PAGE_READONLY_EXEC : PAGE_NONE);

 	/* flush stray tlbs */
 	flush_tlb_all();
 }

 #endif	/* CONFIG_X86_64 */

 int __init sysenter_setup(void)
 {
 	void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 	const void *vsyscall;
 	size_t vsyscall_len;

 	vdso32_pages[0] = virt_to_page(syscall_page);

 #ifdef CONFIG_X86_32
 	gate_vma_init();
 #endif

 	if (!vdso32_sysenter()) {
 		vsyscall = &vdso32_default_start;
 		vsyscall_len = &vdso32_default_end - &vdso32_default_start;
 	} else {
 		vsyscall = &vdso32_sysenter_start;
 		vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
 	}

 	memcpy(syscall_page, vsyscall, vsyscall_len);
 	relocate_vdso(syscall_page);

 	return 0;
 }

 /* Setup a VMA at program startup for the vsyscall page */
 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long addr;
 	int ret = 0;
 	bool compat;

 	if (vdso_enabled == VDSO_DISABLED)
 		return 0;

 	down_write(&mm->mmap_sem);

 	/* Test compat mode once here, in case someone
 	   changes it via sysctl */
 	compat = (vdso_enabled == VDSO_COMPAT);

 	map_compat_vdso(compat);

 	if (compat)
 		addr = VDSO_HIGH_BASE;
 	else {
 		addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 		if (IS_ERR_VALUE(addr)) {
 			ret = addr;
 			goto up_fail;
 		}
 	}

 	if (compat_uses_vma || !compat) {
 		/*
 		 * MAYWRITE to allow gdb to COW and set breakpoints
 		 *
 		 * Make sure the vDSO gets into every core dump.
 		 * Dumping its contents makes post-mortem fully
 		 * interpretable later without matching up the same
 		 * kernel and hardware config to see what PC values
 		 * meant.
 		 */
 		ret = install_special_mapping(mm, addr, PAGE_SIZE,
 					      VM_READ|VM_EXEC|
 					      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
 					      VM_ALWAYSDUMP,
 					      vdso32_pages);

 		if (ret)
 			goto up_fail;
 	}

 	current->mm->context.vdso = (void *)addr;
 	current_thread_info()->sysenter_return =
 		VDSO32_SYMBOL(addr, SYSENTER_RETURN);

   up_fail:
 	up_write(&mm->mmap_sem);

 	return ret;
 }

 #ifdef CONFIG_X86_64

 __initcall(sysenter_setup);

 #ifdef CONFIG_SYSCTL
 /* Register vsyscall32 into the ABI table */
 #include <linux/sysctl.h>

 static ctl_table abi_table2[] = {
 	{
 		.procname	= "vsyscall32",
 		.data		= &sysctl_vsyscall32,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
 	{}
 };

 static ctl_table abi_root_table2[] = {
 	{
 		.ctl_name = CTL_ABI,
 		.procname = "abi",
 		.mode = 0555,
 		.child = abi_table2
 	},
 	{}
 };

 static __init int ia32_binfmt_init(void)
 {
 	register_sysctl_table(abi_root_table2);
 	return 0;
 }
 __initcall(ia32_binfmt_init);
 #endif

 #else  /* CONFIG_X86_32 */

 const char *arch_vma_name(struct vm_area_struct *vma)
 {
 	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 		return "[vdso]";
 	return NULL;
 }

 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 {
 	struct mm_struct *mm = tsk->mm;

 	/* Check to see if this task was created in compat vdso mode */
 	if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
 		return &gate_vma;
 	return NULL;
 }

 int in_gate_area(struct task_struct *task, unsigned long addr)
 {
 	const struct vm_area_struct *vma = get_gate_vma(task);

 	return vma && addr >= vma->vm_start && addr < vma->vm_end;
 }

 int in_gate_area_no_task(unsigned long addr)
 {
 	return 0;
 }

 #endif	/* CONFIG_X86_64 */
	/*
	* (C) Copyright 2002 Linus Torvalds
	* Portions based on the vdso-randomization code from exec-shield:
	* Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
	*
	* This file contains the needed initializations to support sysenter.
	*/

	#include <linux/init.h>
	#include <linux/smp.h>
	#include <linux/thread_info.h>
	#include <linux/sched.h>
	#include <linux/gfp.h>
	#include <linux/string.h>
	#include <linux/elf.h>
	#include <linux/mm.h>
	#include <linux/err.h>
	#include <linux/module.h>

	#include <asm/cpufeature.h>
	#include <asm/msr.h>
	#include <asm/pgtable.h>
	#include <asm/unistd.h>
	#include <asm/elf.h>
	#include <asm/tlbflush.h>
	#include <asm/vdso.h>
	#include <asm/proto.h>

	enum {
	VDSO_DISABLED = 0,
	VDSO_ENABLED = 1,
	VDSO_COMPAT = 2,
	};

	#ifdef CONFIG_COMPAT_VDSO
	#define VDSO_DEFAULT VDSO_COMPAT
	#else
	#define VDSO_DEFAULT VDSO_ENABLED
	#endif

	#ifdef CONFIG_X86_64
	#define vdso_enabled sysctl_vsyscall32
	#define arch_setup_additional_pages syscall32_setup_pages
	#endif

	/*
	* This is the difference between the prelinked addresses in the vDSO images
	* and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
	* in the user address space.
	*/
	#define VDSO_ADDR_ADJUST (VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)

	/*
	* Should the kernel map a VDSO page into processes and pass its
	* address down to glibc upon exec()?
	*/
	unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;

	static int __init vdso_setup(char *s)
	{
	vdso_enabled = simple_strtoul(s, NULL, 0);

	return 1;
	}

	/*
	* For consistency, the argument vdso32=[012] affects the 32-bit vDSO
	* behavior on both 64-bit and 32-bit kernels.
	* On 32-bit kernels, vdso=[012] means the same thing.
	*/
	__setup("vdso32=", vdso_setup);

	#ifdef CONFIG_X86_32
	__setup_param("vdso=", vdso32_setup, vdso_setup, 0);

	EXPORT_SYMBOL_GPL(vdso_enabled);
	#endif

	static __init void reloc_symtab(Elf32_Ehdr *ehdr,
	unsigned offset, unsigned size)
	{
	Elf32_Sym sym = (void )ehdr + offset;
	unsigned nsym = size / sizeof(*sym);
	unsigned i;

	for(i = 0; i < nsym; i++, sym++) {
	if (sym->st_shndx == SHN_UNDEF \|\|
	sym->st_shndx == SHN_ABS)
	continue; /* skip */

	if (sym->st_shndx > SHN_LORESERVE) {
	printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
	sym->st_shndx);
	continue;
	}

	switch(ELF_ST_TYPE(sym->st_info)) {
	case STT_OBJECT:
	case STT_FUNC:
	case STT_SECTION:
	case STT_FILE:
	sym->st_value += VDSO_ADDR_ADJUST;
	}
	}
	}

	static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
	{
	Elf32_Dyn dyn = (void )ehdr + offset;

	for(; dyn->d_tag != DT_NULL; dyn++)
	switch(dyn->d_tag) {
	case DT_PLTGOT:
	case DT_HASH:
	case DT_STRTAB:
	case DT_SYMTAB:
	case DT_RELA:
	case DT_INIT:
	case DT_FINI:
	case DT_REL:
	case DT_DEBUG:
	case DT_JMPREL:
	case DT_VERSYM:
	case DT_VERDEF:
	case DT_VERNEED:
	case DT_ADDRRNGLO ... DT_ADDRRNGHI:
	/* definitely pointers needing relocation */
	dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
	break;

	case DT_ENCODING ... OLD_DT_LOOS-1:
	case DT_LOOS ... DT_HIOS-1:
	/* Tags above DT_ENCODING are pointers if
	they're even */
	if (dyn->d_tag >= DT_ENCODING &&
	(dyn->d_tag & 1) == 0)
	dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
	break;

	case DT_VERDEFNUM:
	case DT_VERNEEDNUM:
	case DT_FLAGS_1:
	case DT_RELACOUNT:
	case DT_RELCOUNT:
	case DT_VALRNGLO ... DT_VALRNGHI:
	/* definitely not pointers */
	break;

	case OLD_DT_LOOS ... DT_LOOS-1:
	case DT_HIOS ... DT_VALRNGLO-1:
	default:
	if (dyn->d_tag > DT_ENCODING)
	printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
	dyn->d_tag);
	break;
	}
	}

	static __init void relocate_vdso(Elf32_Ehdr *ehdr)
	{
	Elf32_Phdr *phdr;
	Elf32_Shdr *shdr;
	int i;

	BUG_ON(memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0 \|\|
	!elf_check_arch_ia32(ehdr) \|\|
	ehdr->e_type != ET_DYN);

	ehdr->e_entry += VDSO_ADDR_ADJUST;

	/* rebase phdrs */
	phdr = (void *)ehdr + ehdr->e_phoff;
	for (i = 0; i < ehdr->e_phnum; i++) {
	phdr[i].p_vaddr += VDSO_ADDR_ADJUST;

	/* relocate dynamic stuff */
	if (phdr[i].p_type == PT_DYNAMIC)
	reloc_dyn(ehdr, phdr[i].p_offset);
	}

	/* rebase sections */
	shdr = (void *)ehdr + ehdr->e_shoff;
	for(i = 0; i < ehdr->e_shnum; i++) {
	if (!(shdr[i].sh_flags & SHF_ALLOC))
	continue;

	shdr[i].sh_addr += VDSO_ADDR_ADJUST;

	if (shdr[i].sh_type == SHT_SYMTAB \|\|
	shdr[i].sh_type == SHT_DYNSYM)
	reloc_symtab(ehdr, shdr[i].sh_offset,
	shdr[i].sh_size);
	}
	}

	/*
	* These symbols are defined by vdso32.S to mark the bounds
	* of the ELF DSO images included therein.
	*/
	extern const char vdso32_default_start, vdso32_default_end;
	extern const char vdso32_sysenter_start, vdso32_sysenter_end;
	static struct page *vdso32_pages[1];

	#ifdef CONFIG_X86_64

	static int use_sysenter __read_mostly = -1;

	#define vdso32_sysenter() (use_sysenter > 0)

	/* May not be __init: called during resume */
	void syscall32_cpu_init(void)
	{
	if (use_sysenter < 0) {
	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
	use_sysenter = 1;
	if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR)
	use_sysenter = 1;
	}

	/* Load these always in case some future AMD CPU supports
	SYSENTER from compat mode too. */
	checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
	checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
	checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);

	wrmsrl(MSR_CSTAR, ia32_cstar_target);
	}

	#define compat_uses_vma 1

	static inline void map_compat_vdso(int map)
	{
	}

	#else /* CONFIG_X86_32 */

	#define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SEP))

	void enable_sep_cpu(void)
	{
	int cpu = get_cpu();
	struct tss_struct *tss = &per_cpu(init_tss, cpu);

	if (!boot_cpu_has(X86_FEATURE_SEP)) {
	put_cpu();
	return;
	}

	tss->x86_tss.ss1 = __KERNEL_CS;
	tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
	wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
	wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
	wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
	put_cpu();
	}

	static struct vm_area_struct gate_vma;

	static int __init gate_vma_init(void)
	{
	gate_vma.vm_mm = NULL;
	gate_vma.vm_start = FIXADDR_USER_START;
	gate_vma.vm_end = FIXADDR_USER_END;
	gate_vma.vm_flags = VM_READ \| VM_MAYREAD \| VM_EXEC \| VM_MAYEXEC;
	gate_vma.vm_page_prot = __P101;
	/*
	* Make sure the vDSO gets into every core dump.
	* Dumping its contents makes post-mortem fully interpretable later
	* without matching up the same kernel and hardware config to see
	* what PC values meant.
	*/
	gate_vma.vm_flags \|= VM_ALWAYSDUMP;
	return 0;
	}

	#define compat_uses_vma 0

	static void map_compat_vdso(int map)
	{
	static int vdso_mapped;

	if (map == vdso_mapped)
	return;

	vdso_mapped = map;

	__set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
	map ? PAGE_READONLY_EXEC : PAGE_NONE);

	/* flush stray tlbs */
	flush_tlb_all();
	}

	#endif /* CONFIG_X86_64 */

	int __init sysenter_setup(void)
	{
	void syscall_page = (void )get_zeroed_page(GFP_ATOMIC);
	const void *vsyscall;
	size_t vsyscall_len;

	vdso32_pages[0] = virt_to_page(syscall_page);

	#ifdef CONFIG_X86_32
	gate_vma_init();
	#endif

	if (!vdso32_sysenter()) {
	vsyscall = &vdso32_default_start;
	vsyscall_len = &vdso32_default_end - &vdso32_default_start;
	} else {
	vsyscall = &vdso32_sysenter_start;
	vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
	}

	memcpy(syscall_page, vsyscall, vsyscall_len);
	relocate_vdso(syscall_page);

	return 0;
	}

	/* Setup a VMA at program startup for the vsyscall page */
	int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
	{
	struct mm_struct *mm = current->mm;
	unsigned long addr;
	int ret = 0;
	bool compat;

	if (vdso_enabled == VDSO_DISABLED)
	return 0;

	down_write(&mm->mmap_sem);

	/* Test compat mode once here, in case someone
	changes it via sysctl */
	compat = (vdso_enabled == VDSO_COMPAT);

	map_compat_vdso(compat);

	if (compat)
	addr = VDSO_HIGH_BASE;
	else {
	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
	if (IS_ERR_VALUE(addr)) {
	ret = addr;
	goto up_fail;
	}
	}

	if (compat_uses_vma \|\| !compat) {
	/*
	* MAYWRITE to allow gdb to COW and set breakpoints
	*
	* Make sure the vDSO gets into every core dump.
	* Dumping its contents makes post-mortem fully
	* interpretable later without matching up the same
	* kernel and hardware config to see what PC values
	* meant.
	*/
	ret = install_special_mapping(mm, addr, PAGE_SIZE,
	VM_READ\|VM_EXEC\|
	VM_MAYREAD\|VM_MAYWRITE\|VM_MAYEXEC\|
	VM_ALWAYSDUMP,
	vdso32_pages);

	if (ret)
	goto up_fail;
	}

	current->mm->context.vdso = (void *)addr;
	current_thread_info()->sysenter_return =
	VDSO32_SYMBOL(addr, SYSENTER_RETURN);

	up_fail:
	up_write(&mm->mmap_sem);

	return ret;
	}

	#ifdef CONFIG_X86_64

	__initcall(sysenter_setup);

	#ifdef CONFIG_SYSCTL
	/* Register vsyscall32 into the ABI table */
	#include <linux/sysctl.h>

	static ctl_table abi_table2[] = {
	{
	.procname = "vsyscall32",
	.data = &sysctl_vsyscall32,
	.maxlen = sizeof(int),
	.mode = 0644,
	.proc_handler = proc_dointvec
	},
	{}
	};

	static ctl_table abi_root_table2[] = {
	{
	.ctl_name = CTL_ABI,
	.procname = "abi",
	.mode = 0555,
	.child = abi_table2
	},
	{}
	};

	static __init int ia32_binfmt_init(void)
	{
	register_sysctl_table(abi_root_table2);
	return 0;
	}
	__initcall(ia32_binfmt_init);
	#endif

	#else /* CONFIG_X86_32 */

	const char arch_vma_name(struct vm_area_struct vma)
	{
	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
	return "[vdso]";
	return NULL;
	}

	struct vm_area_struct get_gate_vma(struct task_struct tsk)
	{
	struct mm_struct *mm = tsk->mm;

	/* Check to see if this task was created in compat vdso mode */
	if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
	return &gate_vma;
	return NULL;
	}

	int in_gate_area(struct task_struct *task, unsigned long addr)
	{
	const struct vm_area_struct *vma = get_gate_vma(task);

	return vma && addr >= vma->vm_start && addr < vma->vm_end;
	}

	int in_gate_area_no_task(unsigned long addr)
	{
	return 0;
	}

	#endif /* CONFIG_X86_64 */