libgcc/unwind-dw2-fde.h

   1 /* Subroutines needed for unwinding stack frames for exception handling.  */
   2 /* Copyright (C) 1997-2019 Free Software Foundation, Inc.
   3    Contributed by Jason Merrill <jason@cygnus.com>.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 Under Section 7 of GPL version 3, you are granted additional
  18 permissions described in the GCC Runtime Library Exception, version
  19 3.1, as published by the Free Software Foundation.
  20
  21 You should have received a copy of the GNU General Public License and
  22 a copy of the GCC Runtime Library Exception along with this program;
  23 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 <http://www.gnu.org/licenses/>.  */
  25
  26 #ifndef GCC_UNWIND_DW2_FDE_H
  27 #define GCC_UNWIND_DW2_FDE_H
  28
  29 #ifndef HIDE_EXPORTS
  30 #pragma GCC visibility push(default)
  31 #endif
  32
  33 struct fde_vector
  34 {
  35   const void *orig_data;
  36   size_t count;
  37   const struct dwarf_fde *array[];
  38 };
  39
  40 struct object
  41 {
  42   void *pc_begin;
  43   void *tbase;
  44   void *dbase;
  45   union {
  46     const struct dwarf_fde *single;
  47     struct dwarf_fde **array;
  48     struct fde_vector *sort;
  49   } u;
  50
  51   union {
  52     struct {
  53       unsigned long sorted : 1;
  54       unsigned long from_array : 1;
  55       unsigned long mixed_encoding : 1;
  56       unsigned long encoding : 8;
  57       /* ??? Wish there was an easy way to detect a 64-bit host here;
  58          we've got 32 bits left to play with...  */
  59       unsigned long count : 21;
  60     } b;
  61     size_t i;
  62   } s;
  63
  64 #ifdef DWARF2_OBJECT_END_PTR_EXTENSION
  65   char *fde_end;
  66 #endif
  67
  68   struct object *next;
  69 };
  70
  71 /* This is the original definition of struct object.  While the struct
  72    itself was opaque to users, they did know how large it was, and
  73    allocate one statically in crtbegin for each DSO.  Keep this around
  74    so that we're aware of the static size limitations for the new struct.  */
  75 struct old_object
  76 {
  77   void *pc_begin;
  78   void *pc_end;
  79   struct dwarf_fde *fde_begin;
  80   struct dwarf_fde **fde_array;
  81   size_t count;
  82   struct old_object *next;
  83 };
  84
  85 struct dwarf_eh_bases
  86 {
  87   void *tbase;
  88   void *dbase;
  89   void *func;
  90 };
  91
  92
  93 extern void __register_frame_info_bases (const void *, struct object *,
  94                                          void *, void *);
  95 extern void __register_frame_info (const void *, struct object *);
  96 extern void __register_frame (void *);
  97 extern void __register_frame_info_table_bases (void *, struct object *,
  98                                                void *, void *);
  99 extern void __register_frame_info_table (void *, struct object *);
 100 extern void __register_frame_table (void *);
 101 extern void *__deregister_frame_info (const void *);
 102 extern void *__deregister_frame_info_bases (const void *);
 103 extern void __deregister_frame (void *);
 104
 105 \f
 106 typedef          int  sword __attribute__ ((mode (SI)));
 107 typedef unsigned int  uword __attribute__ ((mode (SI)));
 108 typedef unsigned int  uaddr __attribute__ ((mode (pointer)));
 109 typedef          int  saddr __attribute__ ((mode (pointer)));
 110 typedef unsigned char ubyte;
 111
 112 /* Terminology:
 113    CIE - Common Information Element
 114    FDE - Frame Descriptor Element
 115
 116    There is one per function, and it describes where the function code
 117    is located, and what the register lifetimes and stack layout are
 118    within the function.
 119
 120    The data structures are defined in the DWARF specification, although
 121    not in a very readable way (see LITERATURE).
 122
 123    Every time an exception is thrown, the code needs to locate the FDE
 124    for the current function, and starts to look for exception regions
 125    from that FDE. This works in a two-level search:
 126    a) in a linear search, find the shared image (i.e. DLL) containing
 127       the PC
 128    b) using the FDE table for that shared object, locate the FDE using
 129       binary search (which requires the sorting).  */
 130
 131 /* The first few fields of a CIE.  The CIE_id field is 0 for a CIE,
 132    to distinguish it from a valid FDE.  FDEs are aligned to an addressing
 133    unit boundary, but the fields within are unaligned.  */
 134 struct dwarf_cie
 135 {
 136   uword length;
 137   sword CIE_id;
 138   ubyte version;
 139   unsigned char augmentation[];
 140 } __attribute__ ((packed, aligned (__alignof__ (void *))));
 141
 142 /* The first few fields of an FDE.  */
 143 struct dwarf_fde
 144 {
 145   uword length;
 146   sword CIE_delta;
 147   unsigned char pc_begin[];
 148 } __attribute__ ((packed, aligned (__alignof__ (void *))));
 149
 150 typedef struct dwarf_fde fde;
 151
 152 /* Locate the CIE for a given FDE.  */
 153
 154 static inline const struct dwarf_cie *
 155 get_cie (const struct dwarf_fde *f)
 156 {
 157   return (const void *)&f->CIE_delta - f->CIE_delta;
 158 }
 159
 160 static inline const fde *
 161 next_fde (const fde *f)
 162 {
 163   return (const fde *) ((const char *) f + f->length + sizeof (f->length));
 164 }
 165
 166 extern const fde * _Unwind_Find_FDE (void *, struct dwarf_eh_bases *);
 167
 168 static inline int
 169 last_fde (struct object *obj __attribute__ ((__unused__)), const fde *f)
 170 {
 171 #ifdef DWARF2_OBJECT_END_PTR_EXTENSION
 172   return f == (const fde *) obj->fde_end || f->length == 0;
 173 #else
 174   return f->length == 0;
 175 #endif
 176 }
 177
 178 #ifndef HIDE_EXPORTS
 179 #pragma GCC visibility pop
 180 #endif
 181
 182 #endif /* unwind-dw2-fde.h */