gdb/dwarf2-frame.h

   1 /* Frame unwinder for frames with DWARF Call Frame Information.
   2
   3    Copyright (C) 2003-2020 Free Software Foundation, Inc.
   4
   5    Contributed by Mark Kettenis.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #ifndef DWARF2_FRAME_H
  23 #define DWARF2_FRAME_H 1
  24
  25 struct gdbarch;
  26 struct objfile;
  27 struct frame_info;
  28 struct dwarf2_per_cu_data;
  29 struct agent_expr;
  30 struct axs_value;
  31
  32 /* Register rule.  */
  33
  34 enum dwarf2_frame_reg_rule
  35 {
  36   /* Make certain that 0 maps onto the correct enum value; the
  37      corresponding structure is being initialized using memset zero.
  38      This indicates that CFI didn't provide any information at all
  39      about a register, leaving how to obtain its value totally
  40      unspecified.  */
  41   DWARF2_FRAME_REG_UNSPECIFIED = 0,
  42
  43   /* The term "undefined" comes from the DWARF2 CFI spec which this
  44      code is modeling; it indicates that the register's value is
  45      "undefined".  GCC uses the less formal term "unsaved".  Its
  46      definition is a combination of REG_UNDEFINED and REG_UNSPECIFIED.
  47      The failure to differentiate the two helps explain a few problems
  48      with the CFI generated by GCC.  */
  49   DWARF2_FRAME_REG_UNDEFINED,
  50   DWARF2_FRAME_REG_SAVED_OFFSET,
  51   DWARF2_FRAME_REG_SAVED_REG,
  52   DWARF2_FRAME_REG_SAVED_EXP,
  53   DWARF2_FRAME_REG_SAME_VALUE,
  54
  55   /* These are defined in Dwarf3.  */
  56   DWARF2_FRAME_REG_SAVED_VAL_OFFSET,
  57   DWARF2_FRAME_REG_SAVED_VAL_EXP,
  58
  59   /* These aren't defined by the DWARF2 CFI specification, but are
  60      used internally by GDB.  */
  61   DWARF2_FRAME_REG_FN,          /* Call a registered function.  */
  62   DWARF2_FRAME_REG_RA,          /* Return Address.  */
  63   DWARF2_FRAME_REG_RA_OFFSET,   /* Return Address with offset.  */
  64   DWARF2_FRAME_REG_CFA,         /* Call Frame Address.  */
  65   DWARF2_FRAME_REG_CFA_OFFSET   /* Call Frame Address with offset.  */
  66 };
  67
  68 /* Register state.  */
  69
  70 struct dwarf2_frame_state_reg
  71 {
  72   /* Each register save state can be described in terms of a CFA slot,
  73      another register, or a location expression.  */
  74   union {
  75     LONGEST offset;
  76     ULONGEST reg;
  77     struct
  78     {
  79       const gdb_byte *start;
  80       ULONGEST len;
  81     } exp;
  82     struct value *(*fn) (struct frame_info *this_frame, void **this_cache,
  83                          int regnum);
  84   } loc;
  85   enum dwarf2_frame_reg_rule how;
  86 };
  87
  88 enum cfa_how_kind
  89 {
  90   CFA_UNSET,
  91   CFA_REG_OFFSET,
  92   CFA_EXP
  93 };
  94
  95 struct dwarf2_frame_state_reg_info
  96 {
  97   dwarf2_frame_state_reg_info () = default;
  98   ~dwarf2_frame_state_reg_info ()
  99   {
 100     delete prev;
 101   }
 102
 103   /* Copy constructor.  */
 104   dwarf2_frame_state_reg_info (const dwarf2_frame_state_reg_info &src)
 105     : reg (src.reg), cfa_offset (src.cfa_offset),
 106       cfa_reg (src.cfa_reg), cfa_how (src.cfa_how), cfa_exp (src.cfa_exp),
 107       prev (src.prev)
 108   {
 109   }
 110
 111   /* Assignment operator for both move-assignment and copy-assignment.  */
 112   dwarf2_frame_state_reg_info&
 113   operator= (dwarf2_frame_state_reg_info rhs)
 114   {
 115     swap (*this, rhs);
 116     return *this;
 117   }
 118
 119   /* Move constructor.  */
 120   dwarf2_frame_state_reg_info (dwarf2_frame_state_reg_info &&rhs) noexcept
 121     : reg (std::move (rhs.reg)), cfa_offset (rhs.cfa_offset),
 122       cfa_reg (rhs.cfa_reg), cfa_how (rhs.cfa_how), cfa_exp (rhs.cfa_exp),
 123       prev (rhs.prev)
 124   {
 125     rhs.prev = nullptr;
 126   }
 127
 128   /* If necessary, enlarge the register set to hold NUM_REGS_REQUESTED
 129      registers.  */
 130   void alloc_regs (int num_regs_requested)
 131   {
 132     gdb_assert (num_regs_requested > 0);
 133
 134     if (num_regs_requested <= reg.size ())
 135       return;
 136
 137     reg.resize (num_regs_requested);
 138   }
 139
 140   std::vector<struct dwarf2_frame_state_reg> reg;
 141
 142   LONGEST cfa_offset = 0;
 143   ULONGEST cfa_reg = 0;
 144   enum cfa_how_kind cfa_how = CFA_UNSET;
 145   const gdb_byte *cfa_exp = NULL;
 146
 147   /* Used to implement DW_CFA_remember_state.  */
 148   struct dwarf2_frame_state_reg_info *prev = NULL;
 149
 150 private:
 151   friend void swap (dwarf2_frame_state_reg_info& lhs,
 152                     dwarf2_frame_state_reg_info& rhs)
 153   {
 154     using std::swap;
 155
 156     swap (lhs.reg, rhs.reg);
 157     swap (lhs.cfa_offset, rhs.cfa_offset);
 158     swap (lhs.cfa_reg, rhs.cfa_reg);
 159     swap (lhs.cfa_how, rhs.cfa_how);
 160     swap (lhs.cfa_exp, rhs.cfa_exp);
 161     swap (lhs.prev, rhs.prev);
 162   }
 163 };
 164
 165 struct dwarf2_cie;
 166
 167 /* Structure describing a frame state.  */
 168
 169 struct dwarf2_frame_state
 170 {
 171   dwarf2_frame_state (CORE_ADDR pc, struct dwarf2_cie *cie);
 172
 173   /* Each register save state can be described in terms of a CFA slot,
 174      another register, or a location expression.  */
 175   struct dwarf2_frame_state_reg_info regs {};
 176
 177   /* The PC described by the current frame state.  */
 178   CORE_ADDR pc;
 179
 180   /* Initial register set from the CIE.
 181      Used to implement DW_CFA_restore.  */
 182   struct dwarf2_frame_state_reg_info initial {};
 183
 184   /* The information we care about from the CIE.  */
 185   const LONGEST data_align;
 186   const ULONGEST code_align;
 187   const ULONGEST retaddr_column;
 188
 189   /* Flags for known producer quirks.  */
 190
 191   /* The ARM compilers, in DWARF2 mode, assume that DW_CFA_def_cfa
 192      and DW_CFA_def_cfa_offset takes a factored offset.  */
 193   bool armcc_cfa_offsets_sf = false;
 194
 195   /* The ARM compilers, in DWARF2 or DWARF3 mode, may assume that
 196      the CFA is defined as REG - OFFSET rather than REG + OFFSET.  */
 197   bool armcc_cfa_offsets_reversed = false;
 198 };
 199
 200 /* When this is true the DWARF frame unwinders can be used if they are
 201    registered with the gdbarch.  Not all architectures can or do use the
 202    DWARF unwinders.  Setting this to true on a target that does not
 203    otherwise support the DWARF unwinders has no effect.  */
 204 extern bool dwarf2_frame_unwinders_enabled_p;
 205
 206 /* Set the architecture-specific register state initialization
 207    function for GDBARCH to INIT_REG.  */
 208
 209 extern void dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
 210                                        void (*init_reg) (struct gdbarch *, int,
 211                                              struct dwarf2_frame_state_reg *,
 212                                              struct frame_info *));
 213
 214 /* Set the architecture-specific signal trampoline recognition
 215    function for GDBARCH to SIGNAL_FRAME_P.  */
 216
 217 extern void
 218   dwarf2_frame_set_signal_frame_p (struct gdbarch *gdbarch,
 219                                    int (*signal_frame_p) (struct gdbarch *,
 220                                                           struct frame_info *));
 221
 222 /* Set the architecture-specific adjustment of .eh_frame and .debug_frame
 223    register numbers.  */
 224
 225 extern void
 226   dwarf2_frame_set_adjust_regnum (struct gdbarch *gdbarch,
 227                                   int (*adjust_regnum) (struct gdbarch *,
 228                                                         int, int));
 229
 230 /* Append the DWARF-2 frame unwinders to GDBARCH's list.  */
 231
 232 void dwarf2_append_unwinders (struct gdbarch *gdbarch);
 233
 234 /* Return the frame base methods for the function that contains PC, or
 235    NULL if it can't be handled by the DWARF CFI frame unwinder.  */
 236
 237 extern const struct frame_base *
 238   dwarf2_frame_base_sniffer (struct frame_info *this_frame);
 239
 240 /* Compute the DWARF CFA for a frame.  */
 241
 242 CORE_ADDR dwarf2_frame_cfa (struct frame_info *this_frame);
 243
 244 /* Find the CFA information for PC.
 245
 246    Return 1 if a register is used for the CFA, or 0 if another
 247    expression is used.  Throw an exception on error.
 248
 249    GDBARCH is the architecture to use.
 250    DATA is the per-CU data.
 251
 252    REGNUM_OUT is an out parameter that is set to the register number.
 253    OFFSET_OUT is the offset to use from this register.
 254    These are only filled in when 1 is returned.
 255
 256    TEXT_OFFSET_OUT, CFA_START_OUT, and CFA_END_OUT describe the CFA
 257    in other cases.  These are only used when 0 is returned.  */
 258
 259 extern int dwarf2_fetch_cfa_info (struct gdbarch *gdbarch, CORE_ADDR pc,
 260                                   struct dwarf2_per_cu_data *data,
 261                                   int *regnum_out, LONGEST *offset_out,
 262                                   CORE_ADDR *text_offset_out,
 263                                   const gdb_byte **cfa_start_out,
 264                                   const gdb_byte **cfa_end_out);
 265
 266 #endif /* dwarf2-frame.h */