arch/arm/kernel/patch.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/kernel.h>
   3 #include <linux/spinlock.h>
   4 #include <linux/kprobes.h>
   5 #include <linux/mm.h>
   6 #include <linux/stop_machine.h>
   7
   8 #include <asm/cacheflush.h>
   9 #include <asm/fixmap.h>
  10 #include <asm/smp_plat.h>
  11 #include <asm/opcodes.h>
  12 #include <asm/patch.h>
  13
  14 struct patch {
  15         void *addr;
  16         unsigned int insn;
  17 };
  18
  19 static DEFINE_SPINLOCK(patch_lock);
  20
  21 static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
  22         __acquires(&patch_lock)
  23 {
  24         unsigned int uintaddr = (uintptr_t) addr;
  25         bool module = !core_kernel_text(uintaddr);
  26         struct page *page;
  27
  28         if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
  29                 page = vmalloc_to_page(addr);
  30         else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
  31                 page = virt_to_page(addr);
  32         else
  33                 return addr;
  34
  35         if (flags)
  36                 spin_lock_irqsave(&patch_lock, *flags);
  37         else
  38                 __acquire(&patch_lock);
  39
  40         set_fixmap(fixmap, page_to_phys(page));
  41
  42         return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
  43 }
  44
  45 static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
  46         __releases(&patch_lock)
  47 {
  48         clear_fixmap(fixmap);
  49
  50         if (flags)
  51                 spin_unlock_irqrestore(&patch_lock, *flags);
  52         else
  53                 __release(&patch_lock);
  54 }
  55
  56 void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
  57 {
  58         bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
  59         unsigned int uintaddr = (uintptr_t) addr;
  60         bool twopage = false;
  61         unsigned long flags;
  62         void *waddr = addr;
  63         int size;
  64
  65         if (remap)
  66                 waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
  67         else
  68                 __acquire(&patch_lock);
  69
  70         if (thumb2 && __opcode_is_thumb16(insn)) {
  71                 *(u16 *)waddr = __opcode_to_mem_thumb16(insn);
  72                 size = sizeof(u16);
  73         } else if (thumb2 && (uintaddr & 2)) {
  74                 u16 first = __opcode_thumb32_first(insn);
  75                 u16 second = __opcode_thumb32_second(insn);
  76                 u16 *addrh0 = waddr;
  77                 u16 *addrh1 = waddr + 2;
  78
  79                 twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2;
  80                 if (twopage && remap)
  81                         addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL);
  82
  83                 *addrh0 = __opcode_to_mem_thumb16(first);
  84                 *addrh1 = __opcode_to_mem_thumb16(second);
  85
  86                 if (twopage && addrh1 != addr + 2) {
  87                         flush_kernel_vmap_range(addrh1, 2);
  88                         patch_unmap(FIX_TEXT_POKE1, NULL);
  89                 }
  90
  91                 size = sizeof(u32);
  92         } else {
  93                 if (thumb2)
  94                         insn = __opcode_to_mem_thumb32(insn);
  95                 else
  96                         insn = __opcode_to_mem_arm(insn);
  97
  98                 *(u32 *)waddr = insn;
  99                 size = sizeof(u32);
 100         }
 101
 102         if (waddr != addr) {
 103                 flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
 104                 patch_unmap(FIX_TEXT_POKE0, &flags);
 105         } else
 106                 __release(&patch_lock);
 107
 108         flush_icache_range((uintptr_t)(addr),
 109                            (uintptr_t)(addr) + size);
 110 }
 111
 112 static int __kprobes patch_text_stop_machine(void *data)
 113 {
 114         struct patch *patch = data;
 115
 116         __patch_text(patch->addr, patch->insn);
 117
 118         return 0;
 119 }
 120
 121 void __kprobes patch_text(void *addr, unsigned int insn)
 122 {
 123         struct patch patch = {
 124                 .addr = addr,
 125                 .insn = insn,
 126         };
 127
 128         stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
 129 }