arch/x86_64/ia32/syscall32.c

   1 /* Copyright 2002,2003 Andi Kleen, SuSE Labs */
   2
   3 /* vsyscall handling for 32bit processes. Map a stub page into it
   4    on demand because 32bit cannot reach the kernel's fixmaps */
   5
   6 #include <linux/mm.h>
   7 #include <linux/string.h>
   8 #include <linux/kernel.h>
   9 #include <linux/gfp.h>
  10 #include <linux/init.h>
  11 #include <linux/stringify.h>
  12 #include <linux/security.h>
  13 #include <asm/proto.h>
  14 #include <asm/tlbflush.h>
  15 #include <asm/ia32_unistd.h>
  16
  17 extern unsigned char syscall32_syscall[], syscall32_syscall_end[];
  18 extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];
  19 extern int sysctl_vsyscall32;
  20
  21 char *syscall32_page;
  22 static int use_sysenter = -1;
  23
  24 static struct page *
  25 syscall32_nopage(struct vm_area_struct *vma, unsigned long adr, int *type)
  26 {
  27         struct page *p = virt_to_page(adr - vma->vm_start + syscall32_page);
  28         get_page(p);
  29         return p;
  30 }
  31
  32 /* Prevent VMA merging */
  33 static void syscall32_vma_close(struct vm_area_struct *vma)
  34 {
  35 }
  36
  37 static struct vm_operations_struct syscall32_vm_ops = {
  38         .close = syscall32_vma_close,
  39         .nopage = syscall32_nopage,
  40 };
  41
  42 struct linux_binprm;
  43
  44 /* Setup a VMA at program startup for the vsyscall page */
  45 int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
  46 {
  47         int npages = (VSYSCALL32_END - VSYSCALL32_BASE) >> PAGE_SHIFT;
  48         struct vm_area_struct *vma;
  49         struct mm_struct *mm = current->mm;
  50         int ret;
  51
  52         vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
  53         if (!vma)
  54                 return -ENOMEM;
  55
  56         memset(vma, 0, sizeof(struct vm_area_struct));
  57         /* Could randomize here */
  58         vma->vm_start = VSYSCALL32_BASE;
  59         vma->vm_end = VSYSCALL32_END;
  60         /* MAYWRITE to allow gdb to COW and set breakpoints */
  61         vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
  62         vma->vm_flags |= mm->def_flags;
  63         vma->vm_page_prot = protection_map[vma->vm_flags & 7];
  64         vma->vm_ops = &syscall32_vm_ops;
  65         vma->vm_mm = mm;
  66
  67         down_write(&mm->mmap_sem);
  68         if ((ret = insert_vm_struct(mm, vma))) {
  69                 up_write(&mm->mmap_sem);
  70                 kmem_cache_free(vm_area_cachep, vma);
  71                 return ret;
  72         }
  73         mm->total_vm += npages;
  74         up_write(&mm->mmap_sem);
  75         return 0;
  76 }
  77
  78 static int __init init_syscall32(void)
  79 {
  80         syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);
  81         if (!syscall32_page)
  82                 panic("Cannot allocate syscall32 page");
  83         if (use_sysenter > 0) {
  84                 memcpy(syscall32_page, syscall32_sysenter,
  85                        syscall32_sysenter_end - syscall32_sysenter);
  86         } else {
  87                 memcpy(syscall32_page, syscall32_syscall,
  88                        syscall32_syscall_end - syscall32_syscall);
  89         }
  90         return 0;
  91 }
  92
  93 __initcall(init_syscall32);
  94
  95 /* May not be __init: called during resume */
  96 void syscall32_cpu_init(void)
  97 {
  98         if (use_sysenter < 0)
  99                 use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
 100
 101         /* Load these always in case some future AMD CPU supports
 102            SYSENTER from compat mode too. */
 103         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 104         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 105         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 106
 107         wrmsrl(MSR_CSTAR, ia32_cstar_target);
 108 }