gdb/arch/i386-linux-tdesc.c

   1 /* Target description related code for GNU/Linux i386.
   2
   3    Copyright (C) 2024 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "arch/x86-linux-tdesc.h"
  21 #include "arch/i386-linux-tdesc.h"
  22 #include "arch/i386.h"
  23 #include "arch/x86-linux-tdesc-features.h"
  24
  25 /* See arch/i386-linux-tdesc.h.  */
  26
  27 const target_desc *
  28 i386_linux_read_description (uint64_t xcr0)
  29 {
  30   /* Cache of previously seen i386 target descriptions, indexed by the xcr0
  31      value that created the target description.  This needs to be static
  32      within this function to ensure it is initialised before first use.  */
  33   static std::unordered_map<uint64_t, const target_desc_up> i386_tdesc_cache;
  34
  35   /* Only some bits are checked when creating a tdesc, but the XCR0 value
  36      contains other feature bits that are not relevant for tdesc creation.
  37      When indexing into the I386_TDESC_CACHE we need to use a consistent
  38      xcr0 value otherwise we might fail to find an existing tdesc which has
  39      the same set of relevant bits set.  */
  40   xcr0 &= x86_linux_i386_xcr0_feature_mask ();
  41
  42   const auto it = i386_tdesc_cache.find (xcr0);
  43   if (it != i386_tdesc_cache.end ())
  44     return it->second.get ();
  45
  46   /* Create the previously unseen target description.  */
  47   target_desc_up tdesc (i386_create_target_description (xcr0, true, false));
  48   x86_linux_post_init_tdesc (tdesc.get (), false);
  49
  50   /* Add to the cache, and return a pointer borrowed from the
  51      target_desc_up.  This is safe as the cache (and the pointers contained
  52      within it) are not deleted until GDB exits.  */
  53   target_desc *ptr = tdesc.get ();
  54   i386_tdesc_cache.emplace (xcr0, std::move (tdesc));
  55   return ptr;
  56 }