arch/parisc/kernel/patch.c

   1 // SPDX-License-Identifier: GPL-2.0
   2  /*
   3   * functions to patch RO kernel text during runtime
   4   *
   5   * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
   6   */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/spinlock.h>
  10 #include <linux/kprobes.h>
  11 #include <linux/mm.h>
  12 #include <linux/stop_machine.h>
  13
  14 #include <asm/cacheflush.h>
  15 #include <asm/fixmap.h>
  16 #include <asm/patch.h>
  17
  18 struct patch {
  19         void *addr;
  20         u32 *insn;
  21         unsigned int len;
  22 };
  23
  24 static DEFINE_RAW_SPINLOCK(patch_lock);
  25
  26 static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags,
  27                                  int *need_unmap)
  28 {
  29         unsigned long uintaddr = (uintptr_t) addr;
  30         bool module = !core_kernel_text(uintaddr);
  31         struct page *page;
  32
  33         *need_unmap = 0;
  34         if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
  35                 page = vmalloc_to_page(addr);
  36         else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
  37                 page = virt_to_page(addr);
  38         else
  39                 return addr;
  40
  41         *need_unmap = 1;
  42         set_fixmap(fixmap, page_to_phys(page));
  43         if (flags)
  44                 raw_spin_lock_irqsave(&patch_lock, *flags);
  45         else
  46                 __acquire(&patch_lock);
  47
  48         return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
  49 }
  50
  51 static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
  52 {
  53         clear_fixmap(fixmap);
  54
  55         if (flags)
  56                 raw_spin_unlock_irqrestore(&patch_lock, *flags);
  57         else
  58                 __release(&patch_lock);
  59 }
  60
  61 void __kprobes __patch_text_multiple(void *addr, u32 *insn, unsigned int len)
  62 {
  63         unsigned long start = (unsigned long)addr;
  64         unsigned long end = (unsigned long)addr + len;
  65         unsigned long flags;
  66         u32 *p, *fixmap;
  67         int mapped;
  68
  69         /* Make sure we don't have any aliases in cache */
  70         flush_kernel_vmap_range(addr, len);
  71         flush_icache_range(start, end);
  72
  73         p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags, &mapped);
  74
  75         while (len >= 4) {
  76                 *p++ = *insn++;
  77                 addr += sizeof(u32);
  78                 len -= sizeof(u32);
  79                 if (len && offset_in_page(addr) == 0) {
  80                         /*
  81                          * We're crossing a page boundary, so
  82                          * need to remap
  83                          */
  84                         flush_kernel_vmap_range((void *)fixmap,
  85                                                 (p-fixmap) * sizeof(*p));
  86                         if (mapped)
  87                                 patch_unmap(FIX_TEXT_POKE0, &flags);
  88                         p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags,
  89                                                 &mapped);
  90                 }
  91         }
  92
  93         flush_kernel_vmap_range((void *)fixmap, (p-fixmap) * sizeof(*p));
  94         if (mapped)
  95                 patch_unmap(FIX_TEXT_POKE0, &flags);
  96         flush_icache_range(start, end);
  97 }
  98
  99 void __kprobes __patch_text(void *addr, u32 insn)
 100 {
 101         __patch_text_multiple(addr, &insn, sizeof(insn));
 102 }
 103
 104 static int __kprobes patch_text_stop_machine(void *data)
 105 {
 106         struct patch *patch = data;
 107
 108         __patch_text_multiple(patch->addr, patch->insn, patch->len);
 109         return 0;
 110 }
 111
 112 void __kprobes patch_text(void *addr, unsigned int insn)
 113 {
 114         struct patch patch = {
 115                 .addr = addr,
 116                 .insn = &insn,
 117                 .len = sizeof(insn),
 118         };
 119
 120         stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
 121 }
 122
 123 void __kprobes patch_text_multiple(void *addr, u32 *insn, unsigned int len)
 124 {
 125
 126         struct patch patch = {
 127                 .addr = addr,
 128                 .insn = insn,
 129                 .len = len
 130         };
 131
 132         stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
 133 }