1 files changed, 122 insertions, 4 deletions

diff --git a/arch/i386/kernel/sysenter.c b/arch/i386/kernel/sysenter.c
index 0bada1870bdf..713ba39d32c6 100644
--- a/arch/i386/kernel/sysenter.c
+++ b/arch/i386/kernel/sysenter.c
@@ -2,6 +2,8 @@
  * linux/arch/i386/kernel/sysenter.c
  *
  * (C) Copyright 2002 Linus Torvalds
+ * Portions based on the vdso-randomization code from exec-shield:
+ * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
  *
  * This file contains the needed initializations to support sysenter.
  */
@@ -13,12 +15,31 @@
 #include <linux/gfp.h>
 #include <linux/string.h>
 #include <linux/elf.h>
+#include <linux/mm.h>
+#include <linux/module.h>
 
 #include <asm/cpufeature.h>
 #include <asm/msr.h>
 #include <asm/pgtable.h>
 #include <asm/unistd.h>
 
+/*
+ * Should the kernel map a VDSO page into processes and pass its
+ * address down to glibc upon exec()?
+ */
+unsigned int __read_mostly vdso_enabled = 1;
+
+EXPORT_SYMBOL_GPL(vdso_enabled);
+
+static int __init vdso_setup(char *s)
+{
+        vdso_enabled = simple_strtoul(s, NULL, 0);
+
+        return 1;
+}
+
+__setup("vdso=", vdso_setup);
+
 extern asmlinkage void sysenter_entry(void);
 
 void enable_sep_cpu(void)
@@ -45,23 +66,120 @@ void enable_sep_cpu(void)
  */
 extern const char vsyscall_int80_start, vsyscall_int80_end;
 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
+static void *syscall_page;
 
 int __init sysenter_setup(void)
 {
-        void *page = (void *)get_zeroed_page(GFP_ATOMIC);
+        syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 
-        __set_fixmap(FIX_VSYSCALL, __pa(page), PAGE_READONLY_EXEC);
+#ifdef CONFIG_COMPAT_VDSO
+        __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY);
+        printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
+#else
+        /*
+         * In the non-compat case the ELF coredumping code needs the fixmap:
+         */
+        __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_KERNEL_RO);
+#endif
 
         if (!boot_cpu_has(X86_FEATURE_SEP)) {
-                memcpy(page,
+                memcpy(syscall_page,
                        &vsyscall_int80_start,
                        &vsyscall_int80_end - &vsyscall_int80_start);
                 return 0;
         }
 
-        memcpy(page,
+        memcpy(syscall_page,
                &vsyscall_sysenter_start,
                &vsyscall_sysenter_end - &vsyscall_sysenter_start);
 
         return 0;
 }
+
+static struct page *syscall_nopage(struct vm_area_struct *vma,
+                                unsigned long adr, int *type)
+{
+        struct page *p = virt_to_page(adr - vma->vm_start + syscall_page);
+        get_page(p);
+        return p;
+}
+
+/* Prevent VMA merging */
+static void syscall_vma_close(struct vm_area_struct *vma)
+{
+}
+
+static struct vm_operations_struct syscall_vm_ops = {
+        .close = syscall_vma_close,
+        .nopage = syscall_nopage,
+};
+
+/* Defined in vsyscall-sysenter.S */
+extern void SYSENTER_RETURN;
+
+/* Setup a VMA at program startup for the vsyscall page */
+int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
+{
+        struct vm_area_struct *vma;
+        struct mm_struct *mm = current->mm;
+        unsigned long addr;
+        int ret;
+
+        down_write(&mm->mmap_sem);
+        addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
+        if (IS_ERR_VALUE(addr)) {
+                ret = addr;
+                goto up_fail;
+        }
+
+        vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL);
+        if (!vma) {
+                ret = -ENOMEM;
+                goto up_fail;
+        }
+
+        vma->vm_start = addr;
+        vma->vm_end = addr + PAGE_SIZE;
+        /* 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 = &syscall_vm_ops;
+        vma->vm_mm = mm;
+
+        ret = insert_vm_struct(mm, vma);
+        if (unlikely(ret)) {
+                kmem_cache_free(vm_area_cachep, vma);
+                goto up_fail;
+        }
+
+        current->mm->context.vdso = (void *)addr;
+        current_thread_info()->sysenter_return =
+                                    (void *)VDSO_SYM(&SYSENTER_RETURN);
+        mm->total_vm++;
+up_fail:
+        up_write(&mm->mmap_sem);
+        return ret;
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+        if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
+                return "[vdso]";
+        return NULL;
+}
+
+struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
+{
+        return NULL;
+}
+
+int in_gate_area(struct task_struct *task, unsigned long addr)
+{
+        return 0;
+}
+
+int in_gate_area_no_task(unsigned long addr)
+{
+        return 0;
+}