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, const addrmap_mutable *mut);
  89   DISABLE_COPY_AND_ASSIGN (addrmap_fixed);
  90
  91   /* It's fine to use the default move operators, because this addrmap
  92      does not own the storage for the elements.  */
  93   addrmap_fixed (addrmap_fixed &&other) = default;
  94   addrmap_fixed &operator= (addrmap_fixed &&) = default;
  95
  96   void relocate (CORE_ADDR offset) override;
  97
  98 private:
  99   void *do_find (CORE_ADDR addr) const override;
 100   int do_foreach (addrmap_foreach_fn fn) const override;
 101
 102   /* A transition: a point in an address map where the value changes.
 103      The map maps ADDR to VALUE, but if ADDR > 0, it maps ADDR-1 to
 104      something else.  */
 105   struct addrmap_transition
 106   {
 107     CORE_ADDR addr;
 108     void *value;
 109   };
 110
 111   /* The number of transitions in TRANSITIONS.  */
 112   size_t num_transitions;
 113
 114   /* An array of transitions, sorted by address.  For every point in
 115      the map where either ADDR == 0 or ADDR is mapped to one value and
 116      ADDR - 1 is mapped to something different, we have an entry here
 117      containing ADDR and VALUE.  (Note that this means we always have
 118      an entry for address 0).  */
 119   struct addrmap_transition *transitions;
 120 };
 121
 122 /* Mutable address maps.  */
 123
 124 struct addrmap_mutable final : public addrmap
 125 {
 126 public:
 127
 128   addrmap_mutable ();
 129   ~addrmap_mutable ();
 130   DISABLE_COPY_AND_ASSIGN (addrmap_mutable);
 131
 132   addrmap_mutable (addrmap_mutable &&other)
 133     : tree (other.tree)
 134   {
 135     other.tree = nullptr;
 136   }
 137
 138   addrmap_mutable &operator= (addrmap_mutable &&other)
 139   {
 140     std::swap (tree, other.tree);
 141     return *this;
 142   }
 143
 144   /* In the mutable address map MAP, associate the addresses from START
 145      to END_INCLUSIVE that are currently associated with NULL with OBJ
 146      instead.  Addresses mapped to an object other than NULL are left
 147      unchanged.
 148
 149      As the name suggests, END_INCLUSIVE is also mapped to OBJ.  This
 150      convention is unusual, but it allows callers to accurately specify
 151      ranges that abut the top of the address space, and ranges that
 152      cover the entire address space.
 153
 154      This operation seems a bit complicated for a primitive: if it's
 155      needed, why not just have a simpler primitive operation that sets a
 156      range to a value, wiping out whatever was there before, and then
 157      let the caller construct more complicated operations from that,
 158      along with some others for traversal?
 159
 160      It turns out this is the mutation operation we want to use all the
 161      time, at least for now.  Our immediate use for address maps is to
 162      represent lexical blocks whose address ranges are not contiguous.
 163      We walk the tree of lexical blocks present in the debug info, and
 164      only create 'struct block' objects after we've traversed all a
 165      block's children.  If a lexical block declares no local variables
 166      (and isn't the lexical block for a function's body), we omit it
 167      from GDB's data structures entirely.
 168
 169      However, this means that we don't decide to create a block (and
 170      thus record it in the address map) until after we've traversed its
 171      children.  If we do decide to create the block, we do so at a time
 172      when all its children have already been recorded in the map.  So
 173      this operation --- change only those addresses left unset --- is
 174      actually the operation we want to use every time.
 175
 176      It seems simpler to let the code which operates on the
 177      representation directly deal with the hair of implementing these
 178      semantics than to provide an interface which allows it to be
 179      implemented efficiently, but doesn't reveal too much of the
 180      representation.  */
 181   void set_empty (CORE_ADDR start, CORE_ADDR end_inclusive,
 182                   void *obj);
 183   void relocate (CORE_ADDR offset) override;
 184
 185 private:
 186   void *do_find (CORE_ADDR addr) const override;
 187   int do_foreach (addrmap_foreach_fn fn) const override;
 188
 189   /* A splay tree, with a node for each transition; there is a
 190      transition at address T if T-1 and T map to different objects.
 191
 192      Any addresses below the first node map to NULL.  (Unlike
 193      fixed maps, we have no entry at (CORE_ADDR) 0; it doesn't
 194      simplify enough.)
 195
 196      The last region is assumed to end at CORE_ADDR_MAX.
 197
 198      Since we can't know whether CORE_ADDR is larger or smaller than
 199      splay_tree_key (unsigned long) --- I think both are possible,
 200      given all combinations of 32- and 64-bit hosts and targets ---
 201      our keys are pointers to CORE_ADDR values.  Since the splay tree
 202      library doesn't pass any closure pointer to the key free
 203      function, we can't keep a freelist for keys.  Since mutable
 204      addrmaps are only used temporarily right now, we just leak keys
 205      from deleted nodes; they'll be freed when the obstack is freed.  */
 206   splay_tree tree;
 207
 208   /* Various helper methods.  */
 209   splay_tree_key allocate_key (CORE_ADDR addr);
 210   void force_transition (CORE_ADDR addr);
 211   splay_tree_node splay_tree_lookup (CORE_ADDR addr) const;
 212   splay_tree_node splay_tree_predecessor (CORE_ADDR addr) const;
 213   splay_tree_node splay_tree_successor (CORE_ADDR addr);
 214   void splay_tree_remove (CORE_ADDR addr);
 215   void splay_tree_insert (CORE_ADDR key, void *value);
 216 };
 217
 218
 219 /* Dump the addrmap to OUTFILE.  If PAYLOAD is non-NULL, only dump any
 220    components that map to PAYLOAD.  (If PAYLOAD is NULL, the entire
 221    map is dumped.)  */
 222 void addrmap_dump (struct addrmap *map, struct ui_file *outfile,
 223                    void *payload);
 224
 225 #endif /* ADDRMAP_H */