arch/arm64/kernel/patching.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/kernel.h>
   3 #include <linux/mm.h>
   4 #include <linux/smp.h>
   5 #include <linux/spinlock.h>
   6 #include <linux/stop_machine.h>
   7 #include <linux/uaccess.h>
   8
   9 #include <asm/cacheflush.h>
  10 #include <asm/fixmap.h>
  11 #include <asm/insn.h>
  12 #include <asm/kprobes.h>
  13 #include <asm/patching.h>
  14 #include <asm/sections.h>
  15
  16 static DEFINE_RAW_SPINLOCK(patch_lock);
  17
  18 static bool is_exit_text(unsigned long addr)
  19 {
  20         /* discarded with init text/data */
  21         return system_state < SYSTEM_RUNNING &&
  22                 addr >= (unsigned long)__exittext_begin &&
  23                 addr < (unsigned long)__exittext_end;
  24 }
  25
  26 static bool is_image_text(unsigned long addr)
  27 {
  28         return core_kernel_text(addr) || is_exit_text(addr);
  29 }
  30
  31 static void __kprobes *patch_map(void *addr, int fixmap)
  32 {
  33         unsigned long uintaddr = (uintptr_t) addr;
  34         bool image = is_image_text(uintaddr);
  35         struct page *page;
  36
  37         if (image)
  38                 page = phys_to_page(__pa_symbol(addr));
  39         else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
  40                 page = vmalloc_to_page(addr);
  41         else
  42                 return addr;
  43
  44         BUG_ON(!page);
  45         return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
  46                         (uintaddr & ~PAGE_MASK));
  47 }
  48
  49 static void __kprobes patch_unmap(int fixmap)
  50 {
  51         clear_fixmap(fixmap);
  52 }
  53 /*
  54  * In ARMv8-A, A64 instructions have a fixed length of 32 bits and are always
  55  * little-endian.
  56  */
  57 int __kprobes aarch64_insn_read(void *addr, u32 *insnp)
  58 {
  59         int ret;
  60         __le32 val;
  61
  62         ret = copy_from_kernel_nofault(&val, addr, AARCH64_INSN_SIZE);
  63         if (!ret)
  64                 *insnp = le32_to_cpu(val);
  65
  66         return ret;
  67 }
  68
  69 static int __kprobes __aarch64_insn_write(void *addr, __le32 insn)
  70 {
  71         void *waddr = addr;
  72         unsigned long flags = 0;
  73         int ret;
  74
  75         raw_spin_lock_irqsave(&patch_lock, flags);
  76         waddr = patch_map(addr, FIX_TEXT_POKE0);
  77
  78         ret = copy_to_kernel_nofault(waddr, &insn, AARCH64_INSN_SIZE);
  79
  80         patch_unmap(FIX_TEXT_POKE0);
  81         raw_spin_unlock_irqrestore(&patch_lock, flags);
  82
  83         return ret;
  84 }
  85
  86 int __kprobes aarch64_insn_write(void *addr, u32 insn)
  87 {
  88         return __aarch64_insn_write(addr, cpu_to_le32(insn));
  89 }
  90
  91 int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
  92 {
  93         u32 *tp = addr;
  94         int ret;
  95
  96         /* A64 instructions must be word aligned */
  97         if ((uintptr_t)tp & 0x3)
  98                 return -EINVAL;
  99
 100         ret = aarch64_insn_write(tp, insn);
 101         if (ret == 0)
 102                 caches_clean_inval_pou((uintptr_t)tp,
 103                                      (uintptr_t)tp + AARCH64_INSN_SIZE);
 104
 105         return ret;
 106 }
 107
 108 struct aarch64_insn_patch {
 109         void            **text_addrs;
 110         u32             *new_insns;
 111         int             insn_cnt;
 112         atomic_t        cpu_count;
 113 };
 114
 115 static int __kprobes aarch64_insn_patch_text_cb(void *arg)
 116 {
 117         int i, ret = 0;
 118         struct aarch64_insn_patch *pp = arg;
 119
 120         /* The first CPU becomes master */
 121         if (atomic_inc_return(&pp->cpu_count) == 1) {
 122                 for (i = 0; ret == 0 && i < pp->insn_cnt; i++)
 123                         ret = aarch64_insn_patch_text_nosync(pp->text_addrs[i],
 124                                                              pp->new_insns[i]);
 125                 /* Notify other processors with an additional increment. */
 126                 atomic_inc(&pp->cpu_count);
 127         } else {
 128                 while (atomic_read(&pp->cpu_count) <= num_online_cpus())
 129                         cpu_relax();
 130                 isb();
 131         }
 132
 133         return ret;
 134 }
 135
 136 int __kprobes aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt)
 137 {
 138         struct aarch64_insn_patch patch = {
 139                 .text_addrs = addrs,
 140                 .new_insns = insns,
 141                 .insn_cnt = cnt,
 142                 .cpu_count = ATOMIC_INIT(0),
 143         };
 144
 145         if (cnt <= 0)
 146                 return -EINVAL;
 147
 148         return stop_machine_cpuslocked(aarch64_insn_patch_text_cb, &patch,
 149                                        cpu_online_mask);
 150 }