arch/parisc/kernel/alternative.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *    Alternative live-patching for parisc.
   4  *    Copyright (C) 2018 Helge Deller <deller@gmx.de>
   5  *
   6  */
   7
   8 #include <asm/processor.h>
   9 #include <asm/sections.h>
  10 #include <asm/alternative.h>
  11
  12 #include <linux/module.h>
  13
  14 static int no_alternatives;
  15 static int __init setup_no_alternatives(char *str)
  16 {
  17         no_alternatives = 1;
  18         return 1;
  19 }
  20 __setup("no-alternatives", setup_no_alternatives);
  21
  22 void __init_or_module apply_alternatives(struct alt_instr *start,
  23                  struct alt_instr *end, const char *module_name)
  24 {
  25         struct alt_instr *entry;
  26         int index = 0, applied = 0;
  27         int num_cpus = num_online_cpus();
  28         u32 cond_check;
  29
  30         cond_check = ALT_COND_ALWAYS |
  31                 ((num_cpus == 1) ? ALT_COND_NO_SMP : 0) |
  32                 ((cache_info.dc_size == 0) ? ALT_COND_NO_DCACHE : 0) |
  33                 ((cache_info.ic_size == 0) ? ALT_COND_NO_ICACHE : 0) |
  34                 (running_on_qemu ? ALT_COND_RUN_ON_QEMU : 0) |
  35                 ((split_tlb == 0) ? ALT_COND_NO_SPLIT_TLB : 0) |
  36                 /*
  37                  * If the PDC_MODEL capabilities has Non-coherent IO-PDIR bit
  38                  * set (bit #61, big endian), we have to flush and sync every
  39                  * time IO-PDIR is changed in Ike/Astro.
  40                  */
  41                 (((boot_cpu_data.cpu_type > pcxw_) &&
  42                   ((boot_cpu_data.pdc.capabilities & PDC_MODEL_IOPDIR_FDC) == 0))
  43                         ? ALT_COND_NO_IOC_FDC : 0);
  44
  45         for (entry = start; entry < end; entry++, index++) {
  46
  47                 u32 *from, cond, replacement;
  48                 s32 len;
  49
  50                 from = (u32 *)((ulong)&entry->orig_offset + entry->orig_offset);
  51                 len = entry->len;
  52                 cond = entry->cond;
  53                 replacement = entry->replacement;
  54
  55                 WARN_ON(!cond);
  56
  57                 if ((cond & ALT_COND_ALWAYS) == 0 && no_alternatives)
  58                         continue;
  59
  60                 pr_debug("Check %d: Cond 0x%x, Replace %02d instructions @ 0x%px with 0x%08x\n",
  61                         index, cond, len, from, replacement);
  62
  63                 /* Bounce out if none of the conditions are true. */
  64                 if ((cond & cond_check) == 0)
  65                         continue;
  66
  67                 /* Want to replace pdtlb by a pdtlb,l instruction? */
  68                 if (replacement == INSN_PxTLB) {
  69                         replacement = *from;
  70                         if (boot_cpu_data.cpu_type >= pcxu) /* >= pa2.0 ? */
  71                                 replacement |= (1 << 10); /* set el bit */
  72                 }
  73
  74                 /*
  75                  * Replace instruction with NOPs?
  76                  * For long distance insert a branch instruction instead.
  77                  */
  78                 if (replacement == INSN_NOP && len > 1)
  79                         replacement = 0xe8000002 + (len-2)*8; /* "b,n .+8" */
  80
  81                 pr_debug("ALTERNATIVE %3d: Cond %2x, Replace %2d instructions to 0x%08x @ 0x%px (%pS)\n",
  82                         index, cond, len, replacement, from, from);
  83
  84                 if (len < 0) {
  85                         /* Replace multiple instruction by new code */
  86                         u32 *source;
  87                         len = -len;
  88                         source = (u32 *)((ulong)&entry->replacement + entry->replacement);
  89                         memcpy(from, source, 4 * len);
  90                 } else {
  91                         /* Replace by one instruction */
  92                         *from = replacement;
  93                 }
  94                 applied++;
  95         }
  96
  97         pr_info("%s%salternatives: applied %d out of %d patches\n",
  98                 module_name ? : "", module_name ? " " : "",
  99                 applied, index);
 100 }
 101
 102
 103 void __init apply_alternatives_all(void)
 104 {
 105         set_kernel_text_rw(1);
 106
 107         apply_alternatives((struct alt_instr *) &__alt_instructions,
 108                 (struct alt_instr *) &__alt_instructions_end, NULL);
 109
 110         set_kernel_text_rw(0);
 111 }