/* Copyright 2002,2003 Andi Kleen, SuSE Labs *//* vsyscall handling for 32bit processes. Map a stub page into it    on demand because 32bit cannot reach the kernel's fixmaps */#include <linux/mm.h>#include <linux/string.h>#include <linux/kernel.h>#include <linux/gfp.h>#include <linux/init.h>#include <linux/stringify.h>#include <linux/security.h>#include <asm/proto.h>#include <asm/tlbflush.h>#include <asm/ia32_unistd.h>extern unsigned char syscall32_syscall[], syscall32_syscall_end[];extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];extern int sysctl_vsyscall32;char *syscall32_page; static int use_sysenter = -1;static struct page *syscall32_nopage(struct vm_area_struct *vma, unsigned long adr, int *type){	struct page *p = virt_to_page(adr - vma->vm_start + syscall32_page);	get_page(p);	return p;}/* Prevent VMA merging */static void syscall32_vma_close(struct vm_area_struct *vma){}static struct vm_operations_struct syscall32_vm_ops = {	.close = syscall32_vma_close,	.nopage = syscall32_nopage,};struct linux_binprm;/* Setup a VMA at program startup for the vsyscall page */int syscall32_setup_pages(struct linux_binprm *bprm, int exstack){	int npages = (VSYSCALL32_END - VSYSCALL32_BASE) >> PAGE_SHIFT;	struct vm_area_struct *vma;	struct mm_struct *mm = current->mm;	int ret;	vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);	if (!vma)		return -ENOMEM;	memset(vma, 0, sizeof(struct vm_area_struct));	/* Could randomize here */	vma->vm_start = VSYSCALL32_BASE;	vma->vm_end = VSYSCALL32_END;	/* MAYWRITE to allow gdb to COW and set breakpoints */	vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;	vma->vm_flags |= mm->def_flags;	vma->vm_page_prot = protection_map[vma->vm_flags & 7];	vma->vm_ops = &syscall32_vm_ops;	vma->vm_mm = mm;	down_write(&mm->mmap_sem);	if ((ret = insert_vm_struct(mm, vma))) {		up_write(&mm->mmap_sem);		kmem_cache_free(vm_area_cachep, vma);		return ret;	}	mm->total_vm += npages;	up_write(&mm->mmap_sem);	return 0;}static int __init init_syscall32(void){ 	syscall32_page = (void *)get_zeroed_page(GFP_KERNEL); 	if (!syscall32_page) 		panic("Cannot allocate syscall32 page");  	if (use_sysenter > 0) { 		memcpy(syscall32_page, syscall32_sysenter, 		       syscall32_sysenter_end - syscall32_sysenter); 	} else {  		memcpy(syscall32_page, syscall32_syscall,  		       syscall32_syscall_end - syscall32_syscall);  	}		return 0;} 	__initcall(init_syscall32); /* May not be __init: called during resume */void syscall32_cpu_init(void){	if (use_sysenter < 0) 		use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);	/* 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);}