arch/arm/kernel/patch.c

   1 #include <linux/kernel.h>
   2 #include <linux/spinlock.h>
   3 #include <linux/kprobes.h>
   4 #include <linux/mm.h>
   5 #include <linux/stop_machine.h>
   6
   7 #include <asm/cacheflush.h>
   8 #include <asm/fixmap.h>
   9 #include <asm/smp_plat.h>
  10 #include <asm/opcodes.h>
  11 #include <asm/patch.h>
  12
  13 struct patch {
  14         void *addr;
  15         unsigned int insn;
  16 };
  17
  18 static DEFINE_SPINLOCK(patch_lock);
  19
  20 static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
  21         __acquires(&patch_lock)
  22 {
  23         unsigned int uintaddr = (uintptr_t) addr;
  24         bool module = !core_kernel_text(uintaddr);
  25         struct page *page;
  26
  27         if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
  28                 page = vmalloc_to_page(addr);
  29         else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
  30                 page = virt_to_page(addr);
  31         else
  32                 return addr;
  33
  34         if (flags)
  35                 spin_lock_irqsave(&patch_lock, *flags);
  36         else
  37                 __acquire(&patch_lock);
  38
  39         set_fixmap(fixmap, page_to_phys(page));
  40
  41         return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
  42 }
  43
  44 static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
  45         __releases(&patch_lock)
  46 {
  47         clear_fixmap(fixmap);
  48
  49         if (flags)
  50                 spin_unlock_irqrestore(&patch_lock, *flags);
  51         else
  52                 __release(&patch_lock);
  53 }
  54
  55 void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
  56 {
  57         bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
  58         unsigned int uintaddr = (uintptr_t) addr;
  59         bool twopage = false;
  60         unsigned long flags;
  61         void *waddr = addr;
  62         int size;
  63
  64         if (remap)
  65                 waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
  66         else
  67                 __acquire(&patch_lock);
  68
  69         if (thumb2 && __opcode_is_thumb16(insn)) {
  70                 *(u16 *)waddr = __opcode_to_mem_thumb16(insn);
  71                 size = sizeof(u16);
  72         } else if (thumb2 && (uintaddr & 2)) {
  73                 u16 first = __opcode_thumb32_first(insn);
  74                 u16 second = __opcode_thumb32_second(insn);
  75                 u16 *addrh0 = waddr;
  76                 u16 *addrh1 = waddr + 2;
  77
  78                 twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2;
  79                 if (twopage && remap)
  80                         addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL);
  81
  82                 *addrh0 = __opcode_to_mem_thumb16(first);
  83                 *addrh1 = __opcode_to_mem_thumb16(second);
  84
  85                 if (twopage && addrh1 != addr + 2) {
  86                         flush_kernel_vmap_range(addrh1, 2);
  87                         patch_unmap(FIX_TEXT_POKE1, NULL);
  88                 }
  89
  90                 size = sizeof(u32);
  91         } else {
  92                 if (thumb2)
  93                         insn = __opcode_to_mem_thumb32(insn);
  94                 else
  95                         insn = __opcode_to_mem_arm(insn);
  96
  97                 *(u32 *)waddr = insn;
  98                 size = sizeof(u32);
  99         }
 100
 101         if (waddr != addr) {
 102                 flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
 103                 patch_unmap(FIX_TEXT_POKE0, &flags);
 104         } else
 105                 __release(&patch_lock);
 106
 107         flush_icache_range((uintptr_t)(addr),
 108                            (uintptr_t)(addr) + size);
 109 }
 110
 111 static int __kprobes patch_text_stop_machine(void *data)
 112 {
 113         struct patch *patch = data;
 114
 115         __patch_text(patch->addr, patch->insn);
 116
 117         return 0;
 118 }
 119
 120 void __kprobes patch_text(void *addr, unsigned int insn)
 121 {
 122         struct patch patch = {
 123                 .addr = addr,
 124                 .insn = insn,
 125         };
 126
 127         stop_machine(patch_text_stop_machine, &patch, NULL);
 128 }