arch/s390/kernel/alternative.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/uaccess.h>
   4 #include <asm/nospec-branch.h>
   5 #include <asm/abs_lowcore.h>
   6 #include <asm/alternative.h>
   7 #include <asm/facility.h>
   8
   9 void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx)
  10 {
  11         u8 *instr, *replacement;
  12         struct alt_instr *a;
  13         bool replace;
  14
  15         /*
  16          * The scan order should be from start to end. A later scanned
  17          * alternative code can overwrite previously scanned alternative code.
  18          */
  19         for (a = start; a < end; a++) {
  20                 if (!(a->ctx & ctx))
  21                         continue;
  22                 switch (a->type) {
  23                 case ALT_TYPE_FACILITY:
  24                         replace = test_facility(a->data);
  25                         break;
  26                 case ALT_TYPE_SPEC:
  27                         replace = nobp_enabled();
  28                         break;
  29                 case ALT_TYPE_LOWCORE:
  30                         replace = have_relocated_lowcore();
  31                         break;
  32                 default:
  33                         replace = false;
  34                 }
  35                 if (!replace)
  36                         continue;
  37                 instr = (u8 *)&a->instr_offset + a->instr_offset;
  38                 replacement = (u8 *)&a->repl_offset + a->repl_offset;
  39                 s390_kernel_write(instr, replacement, a->instrlen);
  40         }
  41 }