arch/s390/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * vdso setup for s390
   4  *
   5  *  Copyright IBM Corp. 2008
   6  *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
   7  */
   8
   9 #include <linux/binfmts.h>
  10 #include <linux/compat.h>
  11 #include <linux/elf.h>
  12 #include <linux/errno.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/mm.h>
  16 #include <linux/slab.h>
  17 #include <linux/smp.h>
  18 #include <vdso/datapage.h>
  19 #include <asm/vdso.h>
  20
  21 extern char vdso64_start[], vdso64_end[];
  22 static unsigned int vdso_pages;
  23 static struct page **vdso_pagelist;
  24
  25 static union {
  26         struct vdso_data        data[CS_BASES];
  27         u8                      page[PAGE_SIZE];
  28 } vdso_data_store __page_aligned_data;
  29
  30 struct vdso_data *vdso_data = vdso_data_store.data;
  31
  32 unsigned int __read_mostly vdso_enabled = 1;
  33
  34 static int __init vdso_setup(char *str)
  35 {
  36         bool enabled;
  37
  38         if (!kstrtobool(str, &enabled))
  39                 vdso_enabled = enabled;
  40         return 1;
  41 }
  42 __setup("vdso=", vdso_setup);
  43
  44 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
  45                       struct vm_area_struct *vma, struct vm_fault *vmf)
  46 {
  47         if (vmf->pgoff >= vdso_pages)
  48                 return VM_FAULT_SIGBUS;
  49
  50         vmf->page = vdso_pagelist[vmf->pgoff];
  51         get_page(vmf->page);
  52         return 0;
  53 }
  54
  55 static int vdso_mremap(const struct vm_special_mapping *sm,
  56                        struct vm_area_struct *vma)
  57 {
  58         current->mm->context.vdso_base = vma->vm_start;
  59         return 0;
  60 }
  61
  62 static const struct vm_special_mapping vdso_mapping = {
  63         .name = "[vdso]",
  64         .fault = vdso_fault,
  65         .mremap = vdso_mremap,
  66 };
  67
  68 int vdso_getcpu_init(void)
  69 {
  70         set_tod_programmable_field(smp_processor_id());
  71         return 0;
  72 }
  73 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */
  74
  75 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  76 {
  77         struct mm_struct *mm = current->mm;
  78         struct vm_area_struct *vma;
  79         unsigned long vdso_base;
  80         int rc;
  81
  82         if (!vdso_enabled || is_compat_task())
  83                 return 0;
  84         if (mmap_write_lock_killable(mm))
  85                 return -EINTR;
  86         vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
  87         rc = vdso_base;
  88         if (IS_ERR_VALUE(vdso_base))
  89                 goto out;
  90         /*
  91          * our vma flags don't have VM_WRITE so by default, the process
  92          * isn't allowed to write those pages.
  93          * gdb can break that with ptrace interface, and thus trigger COW
  94          * on those pages but it's then your responsibility to never do that
  95          * on the "data" page of the vDSO or you'll stop getting kernel
  96          * updates and your nice userland gettimeofday will be totally dead.
  97          * It's fine to use that for setting breakpoints in the vDSO code
  98          * pages though.
  99          */
 100         vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
 101                                        VM_READ|VM_EXEC|
 102                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 103                                        &vdso_mapping);
 104         rc = PTR_ERR(vma);
 105         if (IS_ERR(vma))
 106                 goto out;
 107         current->mm->context.vdso_base = vdso_base;
 108         rc = 0;
 109 out:
 110         mmap_write_unlock(mm);
 111         return rc;
 112 }
 113
 114 static int __init vdso_init(void)
 115 {
 116         int i;
 117
 118         vdso_pages = ((vdso64_end - vdso64_start) >> PAGE_SHIFT) + 1;
 119         /* Make sure pages are in the correct state */
 120         vdso_pagelist = kcalloc(vdso_pages + 1, sizeof(struct page *),
 121                                 GFP_KERNEL);
 122         if (!vdso_pagelist) {
 123                 vdso_enabled = 0;
 124                 return -ENOMEM;
 125         }
 126         for (i = 0; i < vdso_pages - 1; i++) {
 127                 struct page *pg = virt_to_page(vdso64_start + i * PAGE_SIZE);
 128                 get_page(pg);
 129                 vdso_pagelist[i] = pg;
 130         }
 131         vdso_pagelist[vdso_pages - 1] = virt_to_page(vdso_data);
 132         vdso_pagelist[vdso_pages] = NULL;
 133         get_page(virt_to_page(vdso_data));
 134         return 0;
 135 }
 136 arch_initcall(vdso_init);