src/patches/suse-2.6.27.25/patches.xen/xen3-x86-mark_rodata_rw.patch

   1 From: Nick Piggin <npiggin@novell.com>
   2 Subject: Add mark_rodata_rw() to un-protect read-only kernel code pages
   3 References: bnc#439348
   4
   5 CONFIG_RODATA presents a problem for antivirus vendors who do not have a
   6 clean user-space interface for getting virus scanning triggered, and
   7 currently resort to patching the kernel code instead (presumably the
   8 ystem call table). With CONFIG_RODATA enabled, the kernel rejects such
   9 write accesses.
  10
  11 Add a new mark_rodata_rw() function to un-protect the read-only kernel code
  12 pages for now, and export mark_rodata_ro() and mark_rodata_rw() to modules.
  13
  14 This is not meant as a permanent workaround, and will be removed again in the
  15 next release!
  16
  17 Acked-by: Andres Gruenbacher <agruen@suse.de>
  18
  19 Automatically created from "patches.suse/x86-mark_rodata_rw.patch" by xen-port-patches.py
  20
  21 --- sle11-2009-03-16.orig/arch/x86/mm/init_32-xen.c     2009-03-16 16:38:33.000000000 +0100
  22 +++ sle11-2009-03-16/arch/x86/mm/init_32-xen.c  2009-03-16 16:39:50.000000000 +0100
  23 @@ -1125,6 +1125,28 @@ void mark_rodata_ro(void)
  24         set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
  25  #endif
  26  }
  27 +EXPORT_SYMBOL(mark_rodata_ro);
  28 +
  29 +void mark_rodata_rw(void)
  30 +{
  31 +       unsigned long start = PFN_ALIGN(_text);
  32 +       unsigned long size = PFN_ALIGN(_etext) - start;
  33 +
  34 +#ifndef CONFIG_DYNAMIC_FTRACE
  35 +       /* Dynamic tracing modifies the kernel text section */
  36 +       set_pages_rw_force(virt_to_page(start), size >> PAGE_SHIFT);
  37 +       printk(KERN_INFO "Write enabling the kernel text: %luk\n",
  38 +               size >> 10);
  39 +
  40 +#endif /* CONFIG_DYNAMIC_FTRACE */
  41 +
  42 +       start += size;
  43 +       size = (unsigned long)__end_rodata - start;
  44 +       set_pages_rw_force(virt_to_page(start), size >> PAGE_SHIFT);
  45 +       printk(KERN_INFO "Write enabling the kernel read-only data: %luk\n",
  46 +               size >> 10);
  47 +}
  48 +EXPORT_SYMBOL(mark_rodata_rw);
  49  #endif
  50
  51  void free_init_pages(char *what, unsigned long begin, unsigned long end)
  52 --- sle11-2009-03-16.orig/arch/x86/mm/init_64-xen.c     2009-03-16 16:39:48.000000000 +0100
  53 +++ sle11-2009-03-16/arch/x86/mm/init_64-xen.c  2009-03-16 16:39:50.000000000 +0100
  54 @@ -1202,7 +1202,24 @@ void mark_rodata_ro(void)
  55         set_memory_ro(start, (end-start) >> PAGE_SHIFT);
  56  #endif
  57  }
  58 +EXPORT_SYMBOL(mark_rodata_ro);
  59
  60 +void mark_rodata_rw(void)
  61 +{
  62 +       unsigned long start = PFN_ALIGN(_stext), end = PFN_ALIGN(__end_rodata);
  63 +#ifdef CONFIG_DYNAMIC_FTRACE
  64 +       unsigned long rodata_start =
  65 +               ((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK;
  66 +
  67 +       /* Dynamic tracing modifies the kernel text section */
  68 +       start = rodata_start;
  69 +#endif
  70 +
  71 +       printk(KERN_INFO "Write enabling the kernel read-only data: %luk\n",
  72 +              (end - start) >> 10);
  73 +       set_memory_rw_force(start, (end - start) >> PAGE_SHIFT);
  74 +}
  75 +EXPORT_SYMBOL(mark_rodata_rw);
  76  #endif
  77
  78  #ifdef CONFIG_BLK_DEV_INITRD
  79 --- sle11-2009-03-16.orig/arch/x86/mm/pageattr-xen.c    2009-03-16 16:38:38.000000000 +0100
  80 +++ sle11-2009-03-16/arch/x86/mm/pageattr-xen.c 2009-03-16 16:39:50.000000000 +0100
  81 @@ -190,6 +190,8 @@ static void cpa_flush_range(unsigned lon
  82         }
  83  }
  84
  85 +static int static_protections_allow_rodata __read_mostly;
  86 +
  87  /*
  88   * Certain areas of memory on x86 require very specific protection flags,
  89   * for example the BIOS area or kernel text. Callers don't always get this
  90 @@ -223,8 +225,10 @@ static inline pgprot_t static_protection
  91          * catches all aliases.
  92          */
  93         if (within(pfn, __pa((unsigned long)__start_rodata) >> PAGE_SHIFT,
  94 -                  __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
  95 -               pgprot_val(forbidden) |= _PAGE_RW;
  96 +                  __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) {
  97 +               if (!static_protections_allow_rodata)
  98 +                       pgprot_val(forbidden) |= _PAGE_RW;
  99 +       }
 100
 101         prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
 102
 103 @@ -1014,6 +1018,21 @@ int set_memory_rw(unsigned long addr, in
 104         return change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
 105  }
 106
 107 +/* hack: bypass kernel rodata section static_protections check. */
 108 +int set_memory_rw_force(unsigned long addr, int numpages)
 109 +{
 110 +       static DEFINE_MUTEX(lock);
 111 +       int ret;
 112 +
 113 +       mutex_lock(&lock);
 114 +       static_protections_allow_rodata = 1;
 115 +       ret = change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
 116 +       static_protections_allow_rodata = 0;
 117 +       mutex_unlock(&lock);
 118 +
 119 +       return ret;
 120 +}
 121 +
 122  int set_memory_np(unsigned long addr, int numpages)
 123  {
 124         return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_PRESENT));
 125 @@ -1071,6 +1090,13 @@ int set_pages_rw(struct page *page, int
 126         return set_memory_rw(addr, numpages);
 127  }
 128
 129 +int set_pages_rw_force(struct page *page, int numpages)
 130 +{
 131 +       unsigned long addr = (unsigned long)page_address(page);
 132 +
 133 +       return set_memory_rw_force(addr, numpages);
 134 +}
 135 +
 136  #ifdef CONFIG_DEBUG_PAGEALLOC
 137
 138  static int __set_pages_p(struct page *page, int numpages)