gdb/arch/i386-linux-tdesc.c

/* Target description related code for GNU/Linux i386.

   Copyright (C) 2024-2025 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "arch/x86-linux-tdesc.h"
#include "arch/i386-linux-tdesc.h"
#include "arch/i386.h"
#include "arch/x86-linux-tdesc-features.h"

/* See arch/i386-linux-tdesc.h.  */

const target_desc *
i386_linux_read_description (uint64_t xstate_bv)
{
  /* Cache of previously seen i386 target descriptions, indexed by the
     xstate_bv value that created the target description.  This
     needs to be static within this function to ensure it is initialised
     before first use.  */
  static std::unordered_map<uint64_t, const target_desc_up> i386_tdesc_cache;

  /* Only some bits are checked when creating a tdesc, but the
     XSTATE_BV value contains other feature bits that are not relevant
     for tdesc creation.  When indexing into the I386_TDESC_CACHE
     we need to use a consistent XSTATE_BV value otherwise we might fail
     to find an existing tdesc which has the same set of relevant bits
     set.  */
  xstate_bv &= x86_linux_i386_xstate_bv_feature_mask ();

  const auto it = i386_tdesc_cache.find (xstate_bv);
  if (it != i386_tdesc_cache.end ())
    return it->second.get ();

  /* Create the previously unseen target description.  */
  target_desc_up tdesc
    (i386_create_target_description (xstate_bv, true, false));
  x86_linux_post_init_tdesc (tdesc.get (), false);

  /* Add to the cache, and return a pointer borrowed from the
     target_desc_up.  This is safe as the cache (and the pointers contained
     within it) are not deleted until GDB exits.  */
  target_desc *ptr = tdesc.get ();
  i386_tdesc_cache.emplace (xstate_bv, std::move (tdesc));
  return ptr;
}