arch/x86/include/asm/orc_lookup.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
   4  */
   5 #ifndef _ORC_LOOKUP_H
   6 #define _ORC_LOOKUP_H
   7
   8 /*
   9  * This is a lookup table for speeding up access to the .orc_unwind table.
  10  * Given an input address offset, the corresponding lookup table entry
  11  * specifies a subset of the .orc_unwind table to search.
  12  *
  13  * Each block represents the end of the previous range and the start of the
  14  * next range.  An extra block is added to give the last range an end.
  15  *
  16  * The block size should be a power of 2 to avoid a costly 'div' instruction.
  17  *
  18  * A block size of 256 was chosen because it roughly doubles unwinder
  19  * performance while only adding ~5% to the ORC data footprint.
  20  */
  21 #define LOOKUP_BLOCK_ORDER      8
  22 #define LOOKUP_BLOCK_SIZE       (1 << LOOKUP_BLOCK_ORDER)
  23
  24 #ifndef LINKER_SCRIPT
  25
  26 extern unsigned int orc_lookup[];
  27 extern unsigned int orc_lookup_end[];
  28
  29 #define LOOKUP_START_IP         (unsigned long)_stext
  30 #define LOOKUP_STOP_IP          (unsigned long)_etext
  31
  32 #endif /* LINKER_SCRIPT */
  33
  34 #endif /* _ORC_LOOKUP_H */