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