lib_ppc/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  * See file CREDITS for list of people who contributed to this
   8  * project.
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License as
  12  * published by the Free Software Foundation; either version 2 of
  13  * the License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  23  * MA 02111-1307 USA
  24  */
  25 #include <common.h>
  26
  27 /*
  28  * The exception table consists of pairs of addresses: the first is the
  29  * address of an instruction that is allowed to fault, and the second is
  30  * the address at which the program should continue.  No registers are
  31  * modified, so it is entirely up to the continuation code to figure out
  32  * what to do.
  33  *
  34  * All the routines below use bits of fixup code that are out of line
  35  * with the main instruction path.  This means when everything is well,
  36  * we don't even have to jump over them.  Further, they do not intrude
  37  * on our cache or tlb entries.
  38  */
  39
  40 struct exception_table_entry
  41 {
  42         unsigned long insn, fixup;
  43 };
  44
  45 extern const struct exception_table_entry __start___ex_table[];
  46 extern const struct exception_table_entry __stop___ex_table[];
  47
  48 static inline unsigned long
  49 search_one_table(const struct exception_table_entry *first,
  50                  const struct exception_table_entry *last,
  51                  unsigned long value)
  52 {
  53         while (first <= last) {
  54                 const struct exception_table_entry *mid;
  55                 long diff;
  56
  57                 mid = (last - first) / 2 + first;
  58                 diff = mid->insn - value;
  59                 if (diff == 0)
  60                         return mid->fixup;
  61                 else if (diff < 0)
  62                         first = mid+1;
  63                 else
  64                         last = mid-1;
  65         }
  66         return 0;
  67 }
  68
  69 int     ex_tab_message = 1;
  70
  71 unsigned long
  72 search_exception_table(unsigned long addr)
  73 {
  74         unsigned long ret;
  75
  76         /* There is only the kernel to search.  */
  77         ret = search_one_table(__start___ex_table, __stop___ex_table-1, addr);
  78         if (ex_tab_message)
  79                 printf("Bus Fault @ 0x%08lx, fixup 0x%08lx\n", addr, ret);
  80         if (ret) return ret;
  81
  82         return 0;
  83 }