sysdeps/generic/unwind-dw2-fde.h

   1 /* Subroutines needed for unwinding stack frames for exception handling.  */
   2 /* Copyright (C) 1997-2020 Free Software Foundation, Inc.
   3    Contributed by Jason Merrill <jason@cygnus.com>.
   4
   5    This file is part of the GNU C Library.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library 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 GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <https://www.gnu.org/licenses/>.  */
  20
  21
  22 struct fde_vector
  23 {
  24   void *orig_data;
  25   size_t count;
  26   struct dwarf_fde *array __flexarr;
  27 };
  28
  29 #ifdef _LIBC
  30 #include <gccframe.h>
  31 #else
  32 struct object
  33 {
  34   void *pc_begin;
  35   void *tbase;
  36   void *dbase;
  37   union {
  38     struct dwarf_fde *single;
  39     struct dwarf_fde **array;
  40     struct fde_vector *sort;
  41   } u;
  42
  43   union {
  44     struct {
  45       unsigned long sorted : 1;
  46       unsigned long from_array : 1;
  47       unsigned long mixed_encoding : 1;
  48       unsigned long encoding : 8;
  49       /* ??? Wish there was an easy way to detect a 64-bit host here;
  50          we've got 32 bits left to play with...  */
  51       unsigned long count : 21;
  52     } b;
  53     size_t i;
  54   } s;
  55
  56 #ifdef DWARF2_OBJECT_END_PTR_EXTENSION
  57   char *fde_end;
  58 #endif
  59
  60   struct object *next;
  61 };
  62 #endif
  63
  64 /* This is the original definition of struct object.  While the struct
  65    itself was opaque to users, they did know how large it was, and
  66    allocate one statically in crtbegin for each DSO.  Keep this around
  67    so that we're aware of the static size limitations for the new struct.  */
  68 struct old_object
  69 {
  70   void *pc_begin;
  71   void *pc_end;
  72   struct dwarf_fde *fde_begin;
  73   struct dwarf_fde **fde_array;
  74   size_t count;
  75   struct old_object *next;
  76 };
  77
  78 struct dwarf_eh_bases
  79 {
  80   void *tbase;
  81   void *dbase;
  82   void *func;
  83 };
  84
  85
  86 extern void __register_frame_info_bases (void *, struct object *,
  87                                          void *, void *);
  88 extern void __register_frame_info (void *, struct object *);
  89 extern void __register_frame (void *);
  90 extern void __register_frame_info_table_bases (void *, struct object *,
  91                                                void *, void *);
  92 extern void __register_frame_info_table (void *, struct object *);
  93 extern void __register_frame_table (void *);
  94 extern void *__deregister_frame_info (void *);
  95 extern void *__deregister_frame_info_bases (void *);
  96 extern void __deregister_frame (void *);
  97
  98 \f
  99 typedef          int  sword __attribute__ ((mode (SI)));
 100 typedef unsigned int  uword __attribute__ ((mode (SI)));
 101 typedef unsigned int  uaddr __attribute__ ((mode (pointer)));
 102 typedef          int  saddr __attribute__ ((mode (pointer)));
 103 typedef unsigned char ubyte;
 104
 105 /* Terminology:
 106    CIE - Common Information Element
 107    FDE - Frame Descriptor Element
 108
 109    There is one per function, and it describes where the function code
 110    is located, and what the register lifetimes and stack layout are
 111    within the function.
 112
 113    The data structures are defined in the DWARF specification, although
 114    not in a very readable way (see LITERATURE).
 115
 116    Every time an exception is thrown, the code needs to locate the FDE
 117    for the current function, and starts to look for exception regions
 118    from that FDE. This works in a two-level search:
 119    a) in a linear search, find the shared image (i.e. DLL) containing
 120       the PC
 121    b) using the FDE table for that shared object, locate the FDE using
 122       binary search (which requires the sorting).  */
 123
 124 /* The first few fields of a CIE.  The CIE_id field is 0 for a CIE,
 125    to distinguish it from a valid FDE.  FDEs are aligned to an addressing
 126    unit boundary, but the fields within are unaligned.  */
 127 struct dwarf_cie
 128 {
 129   uword length;
 130   sword CIE_id;
 131   ubyte version;
 132   unsigned char augmentation __flexarr;
 133 } __attribute__ ((packed, aligned (__alignof__ (void *))));
 134
 135 /* The first few fields of an FDE.  */
 136 struct dwarf_fde
 137 {
 138   uword length;
 139   sword CIE_delta;
 140   unsigned char pc_begin __flexarr;
 141 } __attribute__ ((packed, aligned (__alignof__ (void *))));
 142
 143 typedef struct dwarf_fde fde;
 144
 145 /* Locate the CIE for a given FDE.  */
 146
 147 static inline struct dwarf_cie *
 148 get_cie (struct dwarf_fde *f)
 149 {
 150   return (void *)&f->CIE_delta - f->CIE_delta;
 151 }
 152
 153 static inline fde *
 154 next_fde (fde *f)
 155 {
 156   return (fde *) ((char *) f + f->length + sizeof (f->length));
 157 }
 158
 159 extern fde * _Unwind_Find_FDE (void *, struct dwarf_eh_bases *);
 160
 161 static inline int
 162 last_fde (struct object *obj __attribute__ ((__unused__)), fde *f)
 163 {
 164 #ifdef DWARF2_OBJECT_END_PTR_EXTENSION
 165   return (char *)f == obj->fde_end || f->length == 0;
 166 #else
 167   return f->length == 0;
 168 #endif
 169 }