gdb/addrmap.h

   1 /* addrmap.h --- interface to address map data structure.
   2
   3    Copyright (C) 2007-2024 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 #ifndef ADDRMAP_H
  21 #define ADDRMAP_H
  22
  23 #include "splay-tree.h"
  24 #include "gdbsupport/function-view.h"
  25
  26 /* An address map is essentially a table mapping CORE_ADDRs onto GDB
  27    data structures, like blocks, symtabs, partial symtabs, and so on.
  28    An address map uses memory proportional to the number of
  29    transitions in the map, where a CORE_ADDR N is mapped to one
  30    object, and N+1 is mapped to a different object.
  31
  32    Address maps come in two flavors: fixed, and mutable.  Mutable
  33    address maps consume more memory, but can be changed and extended.
  34    A fixed address map, once constructed (from a mutable address map),
  35    can't be edited.  */
  36
  37 /* The type of a function used to iterate over the map.
  38    OBJ is NULL for unmapped regions.  */
  39 using addrmap_foreach_fn
  40   = gdb::function_view<int (CORE_ADDR start_addr, void *obj)>;
  41 using addrmap_foreach_const_fn
  42   = gdb::function_view<int (CORE_ADDR start_addr, const void *obj)>;
  43
  44 /* The base class for addrmaps.  */
  45 struct addrmap
  46 {
  47   virtual ~addrmap () = default;
  48
  49   /* Return the object associated with ADDR in MAP.  */
  50   const void *find (CORE_ADDR addr) const
  51   { return this->do_find (addr); }
  52
  53   void *find (CORE_ADDR addr)
  54   { return this->do_find (addr); }
  55
  56   /* Relocate all the addresses in MAP by OFFSET.  (This can be applied
  57      to either mutable or immutable maps.)  */
  58   virtual void relocate (CORE_ADDR offset) = 0;
  59
  60   /* Call FN for every address in MAP, following an in-order traversal.
  61      If FN ever returns a non-zero value, the iteration ceases
  62      immediately, and the value is returned.  Otherwise, this function
  63      returns 0.  */
  64   int foreach (addrmap_foreach_const_fn fn) const
  65   { return this->do_foreach (fn); }
  66
  67   int foreach (addrmap_foreach_fn fn)
  68   { return this->do_foreach (fn); }
  69
  70
  71 private:
  72   /* Worker for find, implemented by sub-classes.  */
  73   virtual void *do_find (CORE_ADDR addr) const = 0;
  74
  75   /* Worker for foreach, implemented by sub-classes.  */
  76   virtual int do_foreach (addrmap_foreach_fn fn) const = 0;
  77 };
  78
  79 struct addrmap_mutable;
  80
  81 /* Fixed address maps.  */
  82 struct addrmap_fixed : public addrmap,
  83                        public allocate_on_obstack
  84 {
  85 public:
  86
  87   addrmap_fixed (struct obstack *obstack, addrmap_mutable *mut);
  88   DISABLE_COPY_AND_ASSIGN (addrmap_fixed);
  89
  90   void relocate (CORE_ADDR offset) override;
  91
  92 private:
  93   void *do_find (CORE_ADDR addr) const override;
  94   int do_foreach (addrmap_foreach_fn fn) const override;
  95
  96   /* A transition: a point in an address map where the value changes.
  97      The map maps ADDR to VALUE, but if ADDR > 0, it maps ADDR-1 to
  98      something else.  */
  99   struct addrmap_transition
 100   {
 101     CORE_ADDR addr;
 102     void *value;
 103   };
 104
 105   /* The number of transitions in TRANSITIONS.  */
 106   size_t num_transitions;
 107
 108   /* An array of transitions, sorted by address.  For every point in
 109      the map where either ADDR == 0 or ADDR is mapped to one value and
 110      ADDR - 1 is mapped to something different, we have an entry here
 111      containing ADDR and VALUE.  (Note that this means we always have
 112      an entry for address 0).  */
 113   struct addrmap_transition *transitions;
 114 };
 115
 116 /* Mutable address maps.  */
 117
 118 struct addrmap_mutable : public addrmap
 119 {
 120 public:
 121
 122   addrmap_mutable ();
 123   ~addrmap_mutable ();
 124   DISABLE_COPY_AND_ASSIGN (addrmap_mutable);
 125
 126   /* In the mutable address map MAP, associate the addresses from START
 127      to END_INCLUSIVE that are currently associated with NULL with OBJ
 128      instead.  Addresses mapped to an object other than NULL are left
 129      unchanged.
 130
 131      As the name suggests, END_INCLUSIVE is also mapped to OBJ.  This
 132      convention is unusual, but it allows callers to accurately specify
 133      ranges that abut the top of the address space, and ranges that
 134      cover the entire address space.
 135
 136      This operation seems a bit complicated for a primitive: if it's
 137      needed, why not just have a simpler primitive operation that sets a
 138      range to a value, wiping out whatever was there before, and then
 139      let the caller construct more complicated operations from that,
 140      along with some others for traversal?
 141
 142      It turns out this is the mutation operation we want to use all the
 143      time, at least for now.  Our immediate use for address maps is to
 144      represent lexical blocks whose address ranges are not contiguous.
 145      We walk the tree of lexical blocks present in the debug info, and
 146      only create 'struct block' objects after we've traversed all a
 147      block's children.  If a lexical block declares no local variables
 148      (and isn't the lexical block for a function's body), we omit it
 149      from GDB's data structures entirely.
 150
 151      However, this means that we don't decide to create a block (and
 152      thus record it in the address map) until after we've traversed its
 153      children.  If we do decide to create the block, we do so at a time
 154      when all its children have already been recorded in the map.  So
 155      this operation --- change only those addresses left unset --- is
 156      actually the operation we want to use every time.
 157
 158      It seems simpler to let the code which operates on the
 159      representation directly deal with the hair of implementing these
 160      semantics than to provide an interface which allows it to be
 161      implemented efficiently, but doesn't reveal too much of the
 162      representation.  */
 163   void set_empty (CORE_ADDR start, CORE_ADDR end_inclusive,
 164                   void *obj);
 165   void relocate (CORE_ADDR offset) override;
 166
 167 private:
 168   void *do_find (CORE_ADDR addr) const override;
 169   int do_foreach (addrmap_foreach_fn fn) const override;
 170
 171   /* A splay tree, with a node for each transition; there is a
 172      transition at address T if T-1 and T map to different objects.
 173
 174      Any addresses below the first node map to NULL.  (Unlike
 175      fixed maps, we have no entry at (CORE_ADDR) 0; it doesn't
 176      simplify enough.)
 177
 178      The last region is assumed to end at CORE_ADDR_MAX.
 179
 180      Since we can't know whether CORE_ADDR is larger or smaller than
 181      splay_tree_key (unsigned long) --- I think both are possible,
 182      given all combinations of 32- and 64-bit hosts and targets ---
 183      our keys are pointers to CORE_ADDR values.  Since the splay tree
 184      library doesn't pass any closure pointer to the key free
 185      function, we can't keep a freelist for keys.  Since mutable
 186      addrmaps are only used temporarily right now, we just leak keys
 187      from deleted nodes; they'll be freed when the obstack is freed.  */
 188   splay_tree tree;
 189
 190   /* Various helper methods.  */
 191   splay_tree_key allocate_key (CORE_ADDR addr);
 192   void force_transition (CORE_ADDR addr);
 193   splay_tree_node splay_tree_lookup (CORE_ADDR addr) const;
 194   splay_tree_node splay_tree_predecessor (CORE_ADDR addr) const;
 195   splay_tree_node splay_tree_successor (CORE_ADDR addr);
 196   void splay_tree_remove (CORE_ADDR addr);
 197   void splay_tree_insert (CORE_ADDR key, void *value);
 198 };
 199
 200
 201 /* Dump the addrmap to OUTFILE.  If PAYLOAD is non-NULL, only dump any
 202    components that map to PAYLOAD.  (If PAYLOAD is NULL, the entire
 203    map is dumped.)  */
 204 void addrmap_dump (struct addrmap *map, struct ui_file *outfile,
 205                    void *payload);
 206
 207 #endif /* ADDRMAP_H */