/* 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>#include <asm/vsyscall32.h>extern unsigned char syscall32_syscall[], syscall32_syscall_end[];extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];extern int sysctl_vsyscall32;static struct page *syscall32_pages[1];static int use_sysenter = -1;struct linux_binprm;/* Setup a VMA at program startup for the vsyscall page */int syscall32_setup_pages(struct linux_binprm *bprm, int exstack){	struct mm_struct *mm = current->mm;	int ret;	down_write(&mm->mmap_sem);	/*	 * 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.	 */	/* Could randomize here */	ret = install_special_mapping(mm, VSYSCALL32_BASE, PAGE_SIZE,				      VM_READ|VM_EXEC|				      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|				      VM_ALWAYSDUMP,				      syscall32_pages);	up_write(&mm->mmap_sem);	return ret;}static int __init init_syscall32(void){ 	char *syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);	if (!syscall32_page) 		panic("Cannot allocate syscall32 page"); 	syscall32_pages[0] = virt_to_page(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);}