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  * 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 DECLARE_GLOBAL_DATA_PTR;
  41
  42 struct exception_table_entry
  43 {
  44         unsigned long insn, fixup;
  45 };
  46
  47 extern const struct exception_table_entry __start___ex_table[];
  48 extern const struct exception_table_entry __stop___ex_table[];
  49
  50 static inline unsigned long
  51 search_one_table(const struct exception_table_entry *first,
  52                  const struct exception_table_entry *last,
  53                  unsigned long value)
  54 {
  55         long diff;
  56         while (first <= last) {
  57                 diff = first->insn - value;
  58                 if (diff == 0)
  59                         return first->fixup;
  60                 first++;
  61         }
  62
  63         return 0;
  64 }
  65
  66 int     ex_tab_message = 1;
  67
  68 unsigned long
  69 search_exception_table(unsigned long addr)
  70 {
  71         unsigned long ret;
  72
  73         /* There is only the kernel to search.  */
  74         ret = search_one_table(__start___ex_table, __stop___ex_table-1, addr);
  75         /* if the serial port does not hang in exception, printf can be used */
  76 #if !defined(CONFIG_SYS_SERIAL_HANG_IN_EXCEPTION)
  77         if (ex_tab_message)
  78                 debug("Bus Fault @ 0x%08lx, fixup 0x%08lx\n", addr, ret);
  79 #endif
  80         if (ret) return ret;
  81
  82         return 0;
  83 }