2 * linux/arch/i386/kernel/sysenter.c
4 * (C) Copyright 2002 Linus Torvalds
5 * Portions based on the vdso-randomization code from exec-shield:
6 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
8 * This file contains the needed initializations to support sysenter.
11 #include <linux/init.h>
12 #include <linux/smp.h>
13 #include <linux/thread_info.h>
14 #include <linux/sched.h>
15 #include <linux/gfp.h>
16 #include <linux/string.h>
17 #include <linux/elf.h>
19 #include <linux/module.h>
20 #include <linux/vs_memory.h>
22 #include <asm/cpufeature.h>
24 #include <asm/pgtable.h>
25 #include <asm/unistd.h>
28 #include <xen/interface/callback.h>
32 * Should the kernel map a VDSO page into processes and pass its
33 * address down to glibc upon exec()?
35 unsigned int __read_mostly vdso_enabled = 1;
37 EXPORT_SYMBOL_GPL(vdso_enabled);
39 static int __init vdso_setup(char *s)
41 vdso_enabled = simple_strtoul(s, NULL, 0);
46 __setup("vdso=", vdso_setup);
48 extern asmlinkage void sysenter_entry(void);
50 void enable_sep_cpu(void)
52 #ifndef CONFIG_X86_NO_TSS
54 struct tss_struct *tss = &per_cpu(init_tss, cpu);
56 if (!boot_cpu_has(X86_FEATURE_SEP)) {
61 tss->ss1 = __KERNEL_CS;
62 tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
63 wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
64 wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
65 wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
71 * These symbols are defined by vsyscall.o to mark the bounds
72 * of the ELF DSO images included therein.
74 extern const char vsyscall_int80_start, vsyscall_int80_end;
75 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
76 static void *syscall_page;
78 int __init sysenter_setup(void)
80 syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
83 if (boot_cpu_has(X86_FEATURE_SEP)) {
84 struct callback_register sysenter = {
85 .type = CALLBACKTYPE_sysenter,
86 .address = { __KERNEL_CS, (unsigned long)sysenter_entry },
89 if (HYPERVISOR_callback_op(CALLBACKOP_register, &sysenter) < 0)
90 clear_bit(X86_FEATURE_SEP, boot_cpu_data.x86_capability);
94 #ifdef CONFIG_COMPAT_VDSO
95 __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY);
96 printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
99 * In the non-compat case the ELF coredumping code needs the fixmap:
102 __set_fixmap(FIX_VDSO, virt_to_machine(syscall_page), PAGE_KERNEL_RO);
104 __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_KERNEL_RO);
108 if (!boot_cpu_has(X86_FEATURE_SEP)) {
110 &vsyscall_int80_start,
111 &vsyscall_int80_end - &vsyscall_int80_start);
116 &vsyscall_sysenter_start,
117 &vsyscall_sysenter_end - &vsyscall_sysenter_start);
122 static struct page *syscall_nopage(struct vm_area_struct *vma,
123 unsigned long adr, int *type)
125 struct page *p = virt_to_page(adr - vma->vm_start + syscall_page);
130 /* Prevent VMA merging */
131 static void syscall_vma_close(struct vm_area_struct *vma)
135 static struct vm_operations_struct syscall_vm_ops = {
136 .close = syscall_vma_close,
137 .nopage = syscall_nopage,
140 /* Defined in vsyscall-sysenter.S */
141 extern void SYSENTER_RETURN;
143 /* Setup a VMA at program startup for the vsyscall page */
144 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack,
145 unsigned long start_code, unsigned long interp_map_address)
147 struct vm_area_struct *vma;
148 struct mm_struct *mm = current->mm;
152 down_write(&mm->mmap_sem);
153 addr = get_unmapped_area_prot(NULL, 0, PAGE_SIZE, 0, 0, 1);
154 if (IS_ERR_VALUE(addr)) {
159 vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL);
165 vma->vm_start = addr;
166 vma->vm_end = addr + PAGE_SIZE;
167 /* MAYWRITE to allow gdb to COW and set breakpoints */
168 vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
169 vma->vm_flags |= mm->def_flags;
170 vma->vm_page_prot = protection_map[vma->vm_flags & 7];
171 vma->vm_ops = &syscall_vm_ops;
174 ret = insert_vm_struct(mm, vma);
176 kmem_cache_free(vm_area_cachep, vma);
180 current->mm->context.vdso = (void *)addr;
181 current_thread_info()->sysenter_return =
182 (void *)VDSO_SYM(&SYSENTER_RETURN);
185 up_write(&mm->mmap_sem);
189 const char *arch_vma_name(struct vm_area_struct *vma)
191 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
196 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
201 int in_gate_area(struct task_struct *task, unsigned long addr)
206 int in_gate_area_no_task(unsigned long addr)