sysdeps/generic/unwind-dw2-fde.h

   1 /* Subroutines needed for unwinding stack frames for exception handling.  */
   2 /* Copyright (C) 1997-2024 Free Software Foundation, Inc.
   3
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20
  21 struct fde_vector
  22 {
  23   void *orig_data;
  24   size_t count;
  25   struct dwarf_fde *array __flexarr;
  26 };
  27
  28 #ifdef _LIBC
  29 #include <gccframe.h>
  30 #else
  31 struct object
  32 {
  33   void *pc_begin;
  34   void *tbase;
  35   void *dbase;
  36   union {
  37     struct dwarf_fde *single;
  38     struct dwarf_fde **array;
  39     struct fde_vector *sort;
  40   } u;
  41
  42   union {
  43     struct {
  44       unsigned long sorted : 1;
  45       unsigned long from_array : 1;
  46       unsigned long mixed_encoding : 1;
  47       unsigned long encoding : 8;
  48       /* ??? Wish there was an easy way to detect a 64-bit host here;
  49          we've got 32 bits left to play with...  */
  50       unsigned long count : 21;
  51     } b;
  52     size_t i;
  53   } s;
  54
  55 #ifdef DWARF2_OBJECT_END_PTR_EXTENSION
  56   char *fde_end;
  57 #endif
  58
  59   struct object *next;
  60 };
  61 #endif
  62
  63 /* This is the original definition of struct object.  While the struct
  64    itself was opaque to users, they did know how large it was, and
  65    allocate one statically in crtbegin for each DSO.  Keep this around
  66    so that we're aware of the static size limitations for the new struct.  */
  67 struct old_object
  68 {
  69   void *pc_begin;
  70   void *pc_end;
  71   struct dwarf_fde *fde_begin;
  72   struct dwarf_fde **fde_array;
  73   size_t count;
  74   struct old_object *next;
  75 };
  76
  77 struct dwarf_eh_bases
  78 {
  79   void *tbase;
  80   void *dbase;
  81   void *func;
  82 };
  83
  84
  85 extern void __register_frame_info_bases (void *, struct object *,
  86                                          void *, void *);
  87 extern void __register_frame_info (void *, struct object *);
  88 extern void __register_frame (void *);
  89 extern void __register_frame_info_table_bases (void *, struct object *,
  90                                                void *, void *);
  91 extern void __register_frame_info_table (void *, struct object *);
  92 extern void __register_frame_table (void *);
  93 extern void *__deregister_frame_info (void *);
  94 extern void *__deregister_frame_info_bases (void *);
  95 extern void __deregister_frame (void *);
  96
  97 \f
  98 typedef          int  sword __attribute__ ((mode (SI)));
  99 typedef unsigned int  uword __attribute__ ((mode (SI)));
 100 typedef unsigned int  uaddr __attribute__ ((mode (pointer)));
 101 typedef          int  saddr __attribute__ ((mode (pointer)));
 102 typedef unsigned char ubyte;
 103
 104 /* Terminology:
 105    CIE - Common Information Element
 106    FDE - Frame Descriptor Element
 107
 108    There is one per function, and it describes where the function code
 109    is located, and what the register lifetimes and stack layout are
 110    within the function.
 111
 112    The data structures are defined in the DWARF specification, although
 113    not in a very readable way (see LITERATURE).
 114
 115    Every time an exception is thrown, the code needs to locate the FDE
 116    for the current function, and starts to look for exception regions
 117    from that FDE. This works in a two-level search:
 118    a) in a linear search, find the shared image (i.e. DLL) containing
 119       the PC
 120    b) using the FDE table for that shared object, locate the FDE using
 121       binary search (which requires the sorting).  */
 122
 123 /* The first few fields of a CIE.  The CIE_id field is 0 for a CIE,
 124    to distinguish it from a valid FDE.  FDEs are aligned to an addressing
 125    unit boundary, but the fields within are unaligned.  */
 126 struct dwarf_cie
 127 {
 128   uword length;
 129   sword CIE_id;
 130   ubyte version;
 131   unsigned char augmentation __flexarr;
 132 } __attribute__ ((packed, aligned (__alignof__ (void *))));
 133
 134 /* The first few fields of an FDE.  */
 135 struct dwarf_fde
 136 {
 137   uword length;
 138   sword CIE_delta;
 139   unsigned char pc_begin __flexarr;
 140 } __attribute__ ((packed, aligned (__alignof__ (void *))));
 141
 142 typedef struct dwarf_fde fde;
 143
 144 /* Locate the CIE for a given FDE.  */
 145
 146 static inline struct dwarf_cie *
 147 get_cie (struct dwarf_fde *f)
 148 {
 149   return (void *)&f->CIE_delta - f->CIE_delta;
 150 }
 151
 152 static inline fde *
 153 next_fde (fde *f)
 154 {
 155   return (fde *) ((char *) f + f->length + sizeof (f->length));
 156 }
 157
 158 extern fde * _Unwind_Find_FDE (void *, struct dwarf_eh_bases *);
 159
 160 static inline int
 161 last_fde (struct object *obj __attribute__ ((__unused__)), fde *f)
 162 {
 163 #ifdef DWARF2_OBJECT_END_PTR_EXTENSION
 164   return (char *)f == obj->fde_end || f->length == 0;
 165 #else
 166   return f->length == 0;
 167 #endif
 168 }