src/patches/suse-2.6.27.31/patches.arch/s390-11-01-kernel_ds_pgtable_walk.patch

   1 From: Gerald Schaefer <geraldsc@de.ibm.com>
   2 Subject: kernel: don't use pagetable walk for KERNEL_DS
   3 References: bnc#484767,LTC#52176
   4
   5 Symptom:     Access to KERNEL_DS via usercopy functions is very slow on
   6              pre z9 hardware.
   7 Problem:     The usercopy functions do a pagetable walk even if KERNEL_DS
   8              is set on pre z9 hardware. This was a workaroud for a common
   9              code bug in SLES 11.
  10 Solution:    Don't use pagetable walk for KERNEL_DS as the common code bug
  11              has been fixed in SLES 11 GMC.
  12
  13 Acked-by: John Jolly <jjolly@suse.de>
  14 ---
  15  arch/s390/lib/uaccess_pt.c |   32 +++++++++++++++++++++++++-------
  16  1 file changed, 25 insertions(+), 7 deletions(-)
  17
  18 Index: linux-sles11/arch/s390/lib/uaccess_pt.c
  19 ===================================================================
  20 --- linux-sles11.orig/arch/s390/lib/uaccess_pt.c
  21 +++ linux-sles11/arch/s390/lib/uaccess_pt.c
  22 @@ -43,9 +43,8 @@ static int __handle_fault(struct mm_stru
  23         int ret = -EFAULT;
  24         int fault;
  25
  26 -       if (in_atomic() || segment_eq(get_fs(), KERNEL_DS))
  27 +       if (in_atomic())
  28                 return ret;
  29 -
  30         down_read(&mm->mmap_sem);
  31         vma = find_vma(mm, address);
  32         if (unlikely(!vma))
  33 @@ -110,8 +109,6 @@ static size_t __user_copy_pt(unsigned lo
  34         pte_t *pte;
  35         void *from, *to;
  36
  37 -       if (segment_eq(get_fs(), KERNEL_DS))
  38 -               mm = &init_mm;
  39         done = 0;
  40  retry:
  41         spin_lock(&mm->page_table_lock);
  42 @@ -185,6 +182,10 @@ size_t copy_from_user_pt(size_t n, const
  43  {
  44         size_t rc;
  45
  46 +       if (segment_eq(get_fs(), KERNEL_DS)) {
  47 +               memcpy(to, (void __kernel __force *) from, n);
  48 +               return 0;
  49 +       }
  50         rc = __user_copy_pt((unsigned long) from, to, n, 0);
  51         if (unlikely(rc))
  52                 memset(to + n - rc, 0, rc);
  53 @@ -193,6 +194,10 @@ size_t copy_from_user_pt(size_t n, const
  54
  55  size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
  56  {
  57 +       if (segment_eq(get_fs(), KERNEL_DS)) {
  58 +               memcpy((void __kernel __force *) to, from, n);
  59 +               return 0;
  60 +       }
  61         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
  62  }
  63
  64 @@ -200,6 +205,10 @@ static size_t clear_user_pt(size_t n, vo
  65  {
  66         long done, size, ret;
  67
  68 +       if (segment_eq(get_fs(), KERNEL_DS)) {
  69 +               memset((void __kernel __force *) to, 0, n);
  70 +               return 0;
  71 +       }
  72         done = 0;
  73         do {
  74                 if (n - done > PAGE_SIZE)
  75 @@ -225,7 +234,7 @@ static size_t strnlen_user_pt(size_t cou
  76         size_t len_str;
  77
  78         if (segment_eq(get_fs(), KERNEL_DS))
  79 -               mm = &init_mm;
  80 +               return strnlen((const char __kernel __force *) src, count) + 1;
  81         done = 0;
  82  retry:
  83         spin_lock(&mm->page_table_lock);
  84 @@ -267,6 +276,13 @@ static size_t strncpy_from_user_pt(size_
  85                 return -EFAULT;
  86         if (n > count)
  87                 n = count;
  88 +       if (segment_eq(get_fs(), KERNEL_DS)) {
  89 +               memcpy(dst, (const char __kernel __force *) src, n);
  90 +               if (dst[n-1] == '\0')
  91 +                       return n-1;
  92 +               else
  93 +                       return n;
  94 +       }
  95         if (__user_copy_pt((unsigned long) src, dst, n, 0))
  96                 return -EFAULT;
  97         if (dst[n-1] == '\0')
  98 @@ -286,8 +302,10 @@ static size_t copy_in_user_pt(size_t n,
  99         pte_t *pte_from, *pte_to;
 100         int write_user;
 101
 102 -       if (segment_eq(get_fs(), KERNEL_DS))
 103 -               mm = &init_mm;
 104 +       if (segment_eq(get_fs(), KERNEL_DS)) {
 105 +               memcpy((void __force *) to, (void __force *) from, n);
 106 +               return 0;
 107 +       }
 108         done = 0;
 109  retry:
 110         spin_lock(&mm->page_table_lock);