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 /* 32bit VDSOs mapped into user space. */
  18 asm(".section \".init.data\",\"aw\"\n"
  19     "syscall32_syscall:\n"
  20     ".incbin \"arch/x86_64/ia32/vsyscall-syscall.so\"\n"
  21     "syscall32_syscall_end:\n"
  22     "syscall32_sysenter:\n"
  23     ".incbin \"arch/x86_64/ia32/vsyscall-sysenter.so\"\n"
  24     "syscall32_sysenter_end:\n"
  25     ".previous");
  26
  27 extern unsigned char syscall32_syscall[], syscall32_syscall_end[];
  28 extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];
  29 extern int sysctl_vsyscall32;
  30
  31 char *syscall32_page;
  32 static int use_sysenter = -1;
  33
  34 static struct page *
  35 syscall32_nopage(struct vm_area_struct *vma, unsigned long adr, int *type)
  36 {
  37         struct page *p = virt_to_page(adr - vma->vm_start + syscall32_page);
  38         get_page(p);
  39         return p;
  40 }
  41
  42 /* Prevent VMA merging */
  43 static void syscall32_vma_close(struct vm_area_struct *vma)
  44 {
  45 }
  46
  47 static struct vm_operations_struct syscall32_vm_ops = {
  48         .close = syscall32_vma_close,
  49         .nopage = syscall32_nopage,
  50 };
  51
  52 struct linux_binprm;
  53
  54 /* Setup a VMA at program startup for the vsyscall page */
  55 int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
  56 {
  57         int npages = (VSYSCALL32_END - VSYSCALL32_BASE) >> PAGE_SHIFT;
  58         struct vm_area_struct *vma;
  59         struct mm_struct *mm = current->mm;
  60
  61         vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
  62         if (!vma)
  63                 return -ENOMEM;
  64         if (security_vm_enough_memory(npages)) {
  65                 kmem_cache_free(vm_area_cachep, vma);
  66                 return -ENOMEM;
  67         }
  68
  69         memset(vma, 0, sizeof(struct vm_area_struct));
  70         /* Could randomize here */
  71         vma->vm_start = VSYSCALL32_BASE;
  72         vma->vm_end = VSYSCALL32_END;
  73         /* MAYWRITE to allow gdb to COW and set breakpoints */
  74         vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYEXEC|VM_MAYWRITE;
  75         vma->vm_flags |= mm->def_flags;
  76         vma->vm_page_prot = protection_map[vma->vm_flags & 7];
  77         vma->vm_ops = &syscall32_vm_ops;
  78         vma->vm_mm = mm;
  79
  80         down_write(&mm->mmap_sem);
  81         insert_vm_struct(mm, vma);
  82         mm->total_vm += npages;
  83         up_write(&mm->mmap_sem);
  84         return 0;
  85 }
  86
  87 static int __init init_syscall32(void)
  88 {
  89         syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);
  90         if (!syscall32_page)
  91                 panic("Cannot allocate syscall32 page");
  92         if (use_sysenter > 0) {
  93                 memcpy(syscall32_page, syscall32_sysenter,
  94                        syscall32_sysenter_end - syscall32_sysenter);
  95         } else {
  96                 memcpy(syscall32_page, syscall32_syscall,
  97                        syscall32_syscall_end - syscall32_syscall);
  98         }
  99         return 0;
 100 }
 101
 102 __initcall(init_syscall32);
 103
 104 /* May not be __init: called during resume */
 105 void syscall32_cpu_init(void)
 106 {
 107         if (use_sysenter < 0)
 108                 use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
 109
 110         /* Load these always in case some future AMD CPU supports
 111            SYSENTER from compat mode too. */
 112         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 113         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 114         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 115
 116         wrmsrl(MSR_CSTAR, ia32_cstar_target);
 117 }