arch/powerpc/lib/extable.c

   1 /*
   2  * Copyright (C) 1999  Magnus Damm <kieraypc01.p.y.kie.era.ericsson.se>
   3  *
   4  * (C) Copyright 2000
   5  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   6  *
   7  * SPDX-License-Identifier:     GPL-2.0+
   8  */
   9 #include <common.h>
  10
  11 /*
  12  * The exception table consists of pairs of addresses: the first is the
  13  * address of an instruction that is allowed to fault, and the second is
  14  * the address at which the program should continue.  No registers are
  15  * modified, so it is entirely up to the continuation code to figure out
  16  * what to do.
  17  *
  18  * All the routines below use bits of fixup code that are out of line
  19  * with the main instruction path.  This means when everything is well,
  20  * we don't even have to jump over them.  Further, they do not intrude
  21  * on our cache or tlb entries.
  22  */
  23
  24 DECLARE_GLOBAL_DATA_PTR;
  25
  26 struct exception_table_entry
  27 {
  28         unsigned long insn, fixup;
  29 };
  30
  31 extern const struct exception_table_entry __start___ex_table[];
  32 extern const struct exception_table_entry __stop___ex_table[];
  33
  34 static inline unsigned long
  35 search_one_table(const struct exception_table_entry *first,
  36                  const struct exception_table_entry *last,
  37                  unsigned long value)
  38 {
  39         long diff;
  40         while (first <= last) {
  41                 diff = first->insn - value;
  42                 if (diff == 0)
  43                         return first->fixup;
  44                 first++;
  45         }
  46
  47         return 0;
  48 }
  49
  50 unsigned long
  51 search_exception_table(unsigned long addr)
  52 {
  53         unsigned long ret;
  54
  55         /* There is only the kernel to search.  */
  56         ret = search_one_table(__start___ex_table, __stop___ex_table-1, addr);
  57         /* if the serial port does not hang in exception, printf can be used */
  58 #if !defined(CONFIG_SYS_SERIAL_HANG_IN_EXCEPTION)
  59         debug("Bus Fault @ 0x%08lx, fixup 0x%08lx\n", addr, ret);
  60 #endif
  61         if (ret) return ret;
  62
  63         return 0;
  64 }