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/mman.h>
20 #include <linux/module.h>
21 #include <linux/vs_base.h>
22 #include <linux/vs_memory.h>
24 #include <asm/cpufeature.h>
26 #include <asm/pgtable.h>
27 #include <asm/unistd.h>
30 #include <xen/interface/callback.h>
34 * Should the kernel map a VDSO page into processes and pass its
35 * address down to glibc upon exec()?
37 unsigned int __read_mostly vdso_enabled = 1;
39 EXPORT_SYMBOL_GPL(vdso_enabled);
41 static int __init vdso_setup(char *s)
43 vdso_enabled = simple_strtoul(s, NULL, 0);
48 __setup("vdso=", vdso_setup);
50 extern asmlinkage void sysenter_entry(void);
52 void enable_sep_cpu(void)
54 #ifndef CONFIG_X86_NO_TSS
56 struct tss_struct *tss = &per_cpu(init_tss, cpu);
58 if (!boot_cpu_has(X86_FEATURE_SEP)) {
63 tss->ss1 = __KERNEL_CS;
64 tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
65 wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
66 wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
67 wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
73 * These symbols are defined by vsyscall.o to mark the bounds
74 * of the ELF DSO images included therein.
76 extern const char vsyscall_int80_start, vsyscall_int80_end;
77 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
78 static void *syscall_page;
80 int __init sysenter_setup(void)
82 syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
85 if (boot_cpu_has(X86_FEATURE_SEP)) {
86 struct callback_register sysenter = {
87 .type = CALLBACKTYPE_sysenter,
88 .address = { __KERNEL_CS, (unsigned long)sysenter_entry },
91 if (HYPERVISOR_callback_op(CALLBACKOP_register, &sysenter) < 0)
92 clear_bit(X86_FEATURE_SEP, boot_cpu_data.x86_capability);
96 #ifdef CONFIG_COMPAT_VDSO
97 __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY);
98 printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
101 * In the non-compat case the ELF coredumping code needs the fixmap:
104 __set_fixmap(FIX_VDSO, virt_to_machine(syscall_page), PAGE_KERNEL_RO);
106 __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_KERNEL_RO);
110 if (!boot_cpu_has(X86_FEATURE_SEP)) {
112 &vsyscall_int80_start,
113 &vsyscall_int80_end - &vsyscall_int80_start);
118 &vsyscall_sysenter_start,
119 &vsyscall_sysenter_end - &vsyscall_sysenter_start);
124 static struct page *syscall_nopage(struct vm_area_struct *vma,
125 unsigned long adr, int *type)
127 struct page *p = virt_to_page(adr - vma->vm_start + syscall_page);
132 /* Prevent VMA merging */
133 static void syscall_vma_close(struct vm_area_struct *vma)
137 static struct vm_operations_struct syscall_vm_ops = {
138 .close = syscall_vma_close,
139 .nopage = syscall_nopage,
142 /* Defined in vsyscall-sysenter.S */
143 extern void SYSENTER_RETURN;
145 /* Setup a VMA at program startup for the vsyscall page */
146 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack,
147 unsigned long start_code, unsigned long interp_map_address)
149 struct vm_area_struct *vma;
150 struct mm_struct *mm = current->mm;
154 down_write(&mm->mmap_sem);
155 addr = get_unmapped_area_prot(NULL, 0, PAGE_SIZE, 0, 0, 1);
156 if (IS_ERR_VALUE(addr)) {
161 vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL);
167 vma->vm_start = addr;
168 vma->vm_end = addr + PAGE_SIZE;
169 /* MAYWRITE to allow gdb to COW and set breakpoints */
170 vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
171 vma->vm_flags |= mm->def_flags;
172 vma->vm_page_prot = protection_map[vma->vm_flags & 7];
173 vma->vm_ops = &syscall_vm_ops;
176 ret = insert_vm_struct(mm, vma);
178 kmem_cache_free(vm_area_cachep, vma);
182 current->mm->context.vdso = (void *)addr;
183 current_thread_info()->sysenter_return =
184 (void *)VDSO_SYM(&SYSENTER_RETURN);
187 up_write(&mm->mmap_sem);
191 const char *arch_vma_name(struct vm_area_struct *vma)
193 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
198 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
203 int in_gate_area(struct task_struct *task, unsigned long addr)
208 int in_gate_area_no_task(unsigned long addr)