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         raw_spin_lock_irqsave(&patch_lock, *flags);
  44
  45         return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
  46 }
  47
  48 static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
  49 {
  50         clear_fixmap(fixmap);
  51
  52         raw_spin_unlock_irqrestore(&patch_lock, *flags);
  53 }
  54
  55 void __kprobes __patch_text_multiple(void *addr, u32 *insn, unsigned int len)
  56 {
  57         unsigned long start = (unsigned long)addr;
  58         unsigned long end = (unsigned long)addr + len;
  59         unsigned long flags;
  60         u32 *p, *fixmap;
  61         int mapped;
  62
  63         /* Make sure we don't have any aliases in cache */
  64         flush_kernel_dcache_range_asm(start, end);
  65         flush_kernel_icache_range_asm(start, end);
  66         flush_tlb_kernel_range(start, end);
  67
  68         p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags, &mapped);
  69
  70         while (len >= 4) {
  71                 *p++ = *insn++;
  72                 addr += sizeof(u32);
  73                 len -= sizeof(u32);
  74                 if (len && offset_in_page(addr) == 0) {
  75                         /*
  76                          * We're crossing a page boundary, so
  77                          * need to remap
  78                          */
  79                         flush_kernel_dcache_range_asm((unsigned long)fixmap,
  80                                                       (unsigned long)p);
  81                         flush_tlb_kernel_range((unsigned long)fixmap,
  82                                                (unsigned long)p);
  83                         if (mapped)
  84                                 patch_unmap(FIX_TEXT_POKE0, &flags);
  85                         p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags,
  86                                                 &mapped);
  87                 }
  88         }
  89
  90         flush_kernel_dcache_range_asm((unsigned long)fixmap, (unsigned long)p);
  91         flush_tlb_kernel_range((unsigned long)fixmap, (unsigned long)p);
  92         if (mapped)
  93                 patch_unmap(FIX_TEXT_POKE0, &flags);
  94 }
  95
  96 void __kprobes __patch_text(void *addr, u32 insn)
  97 {
  98         __patch_text_multiple(addr, &insn, sizeof(insn));
  99 }
 100
 101 static int __kprobes patch_text_stop_machine(void *data)
 102 {
 103         struct patch *patch = data;
 104
 105         __patch_text_multiple(patch->addr, patch->insn, patch->len);
 106         return 0;
 107 }
 108
 109 void __kprobes patch_text(void *addr, unsigned int insn)
 110 {
 111         struct patch patch = {
 112                 .addr = addr,
 113                 .insn = &insn,
 114                 .len = sizeof(insn),
 115         };
 116
 117         stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
 118 }
 119
 120 void __kprobes patch_text_multiple(void *addr, u32 *insn, unsigned int len)
 121 {
 122
 123         struct patch patch = {
 124                 .addr = addr,
 125                 .insn = insn,
 126                 .len = len
 127         };
 128
 129         stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
 130 }