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_memory.h>
23 #include <asm/cpufeature.h>
25 #include <asm/pgtable.h>
26 #include <asm/unistd.h>
29 #include <xen/interface/callback.h>
33 * Should the kernel map a VDSO page into processes and pass its
34 * address down to glibc upon exec()?
36 #ifdef CONFIG_PARAVIRT
37 unsigned int __read_mostly vdso_enabled = 0;
39 unsigned int __read_mostly vdso_enabled = 1;
42 EXPORT_SYMBOL_GPL(vdso_enabled);
44 static int __init vdso_setup(char *s)
46 vdso_enabled = simple_strtoul(s, NULL, 0);
51 __setup("vdso=", vdso_setup);
53 extern asmlinkage void sysenter_entry(void);
55 void enable_sep_cpu(void)
57 #ifndef CONFIG_X86_NO_TSS
59 struct tss_struct *tss = &per_cpu(init_tss, cpu);
61 if (!boot_cpu_has(X86_FEATURE_SEP)) {
66 tss->ss1 = __KERNEL_CS;
67 tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
68 wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
69 wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
70 wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
76 * These symbols are defined by vsyscall.o to mark the bounds
77 * of the ELF DSO images included therein.
79 extern const char vsyscall_int80_start, vsyscall_int80_end;
80 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
81 static void *syscall_page;
83 int __init sysenter_setup(void)
85 syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
88 if (boot_cpu_has(X86_FEATURE_SEP)) {
89 struct callback_register sysenter = {
90 .type = CALLBACKTYPE_sysenter,
91 .address = { __KERNEL_CS, (unsigned long)sysenter_entry },
94 if (HYPERVISOR_callback_op(CALLBACKOP_register, &sysenter) < 0)
95 clear_bit(X86_FEATURE_SEP, boot_cpu_data.x86_capability);
99 #ifdef CONFIG_COMPAT_VDSO
100 __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY_EXEC);
101 printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
104 if (!boot_cpu_has(X86_FEATURE_SEP)) {
106 &vsyscall_int80_start,
107 &vsyscall_int80_end - &vsyscall_int80_start);
112 &vsyscall_sysenter_start,
113 &vsyscall_sysenter_end - &vsyscall_sysenter_start);
118 #ifndef CONFIG_COMPAT_VDSO
119 static struct page *syscall_nopage(struct vm_area_struct *vma,
120 unsigned long adr, int *type)
122 struct page *p = virt_to_page(adr - vma->vm_start + syscall_page);
127 /* Prevent VMA merging */
128 static void syscall_vma_close(struct vm_area_struct *vma)
132 static struct vm_operations_struct syscall_vm_ops = {
133 .close = syscall_vma_close,
134 .nopage = syscall_nopage,
137 /* Defined in vsyscall-sysenter.S */
138 extern void SYSENTER_RETURN;
140 /* Setup a VMA at program startup for the vsyscall page */
141 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack,
142 unsigned long start_code, unsigned long interp_map_address)
144 struct vm_area_struct *vma;
145 struct mm_struct *mm = current->mm;
149 down_write(&mm->mmap_sem);
150 addr = get_unmapped_area_prot(NULL, 0, PAGE_SIZE, 0, 0, 1);
151 if (IS_ERR_VALUE(addr)) {
156 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
162 vma->vm_start = addr;
163 vma->vm_end = addr + PAGE_SIZE;
164 /* MAYWRITE to allow gdb to COW and set breakpoints */
165 vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
167 * Make sure the vDSO gets into every core dump.
168 * Dumping its contents makes post-mortem fully interpretable later
169 * without matching up the same kernel and hardware config to see
170 * what PC values meant.
172 vma->vm_flags |= VM_ALWAYSDUMP;
173 vma->vm_flags |= mm->def_flags;
174 vma->vm_page_prot = protection_map[vma->vm_flags & 7];
175 vma->vm_ops = &syscall_vm_ops;
178 ret = insert_vm_struct(mm, vma);
180 kmem_cache_free(vm_area_cachep, vma);
184 current->mm->context.vdso = (void *)addr;
185 current_thread_info()->sysenter_return =
186 (void *)VDSO_SYM(&SYSENTER_RETURN);
189 up_write(&mm->mmap_sem);
193 const char *arch_vma_name(struct vm_area_struct *vma)
195 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
200 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
205 int in_gate_area(struct task_struct *task, unsigned long addr)
210 int in_gate_area_no_task(unsigned long addr)