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 frame_info;
  27 struct dwarf2_per_cu_data;
  28 struct agent_expr;
  29 struct axs_value;
  30
  31 /* Register rule.  */
  32
  33 enum dwarf2_frame_reg_rule
  34 {
  35   /* Make certain that 0 maps onto the correct enum value; the
  36      corresponding structure is being initialized using memset zero.
  37      This indicates that CFI didn't provide any information at all
  38      about a register, leaving how to obtain its value totally
  39      unspecified.  */
  40   DWARF2_FRAME_REG_UNSPECIFIED = 0,
  41
  42   /* The term "undefined" comes from the DWARF2 CFI spec which this
  43      code is modeling; it indicates that the register's value is
  44      "undefined".  GCC uses the less formal term "unsaved".  Its
  45      definition is a combination of REG_UNDEFINED and REG_UNSPECIFIED.
  46      The failure to differentiate the two helps explain a few problems
  47      with the CFI generated by GCC.  */
  48   DWARF2_FRAME_REG_UNDEFINED,
  49   DWARF2_FRAME_REG_SAVED_OFFSET,
  50   DWARF2_FRAME_REG_SAVED_REG,
  51   DWARF2_FRAME_REG_SAVED_EXP,
  52   DWARF2_FRAME_REG_SAME_VALUE,
  53
  54   /* These are defined in Dwarf3.  */
  55   DWARF2_FRAME_REG_SAVED_VAL_OFFSET,
  56   DWARF2_FRAME_REG_SAVED_VAL_EXP,
  57
  58   /* These aren't defined by the DWARF2 CFI specification, but are
  59      used internally by GDB.  */
  60   DWARF2_FRAME_REG_FN,          /* Call a registered function.  */
  61   DWARF2_FRAME_REG_RA,          /* Return Address.  */
  62   DWARF2_FRAME_REG_RA_OFFSET,   /* Return Address with offset.  */
  63   DWARF2_FRAME_REG_CFA,         /* Call Frame Address.  */
  64   DWARF2_FRAME_REG_CFA_OFFSET   /* Call Frame Address with offset.  */
  65 };
  66
  67 /* Register state.  */
  68
  69 struct dwarf2_frame_state_reg
  70 {
  71   /* Each register save state can be described in terms of a CFA slot,
  72      another register, or a location expression.  */
  73   union {
  74     LONGEST offset;
  75     ULONGEST reg;
  76     struct
  77     {
  78       const gdb_byte *start;
  79       ULONGEST len;
  80     } exp;
  81     struct value *(*fn) (struct frame_info *this_frame, void **this_cache,
  82                          int regnum);
  83   } loc;
  84   enum dwarf2_frame_reg_rule how;
  85 };
  86
  87 enum cfa_how_kind
  88 {
  89   CFA_UNSET,
  90   CFA_REG_OFFSET,
  91   CFA_EXP
  92 };
  93
  94 struct dwarf2_frame_state_reg_info
  95 {
  96   dwarf2_frame_state_reg_info () = default;
  97   ~dwarf2_frame_state_reg_info ()
  98   {
  99     delete prev;
 100   }
 101
 102   /* Copy constructor.  */
 103   dwarf2_frame_state_reg_info (const dwarf2_frame_state_reg_info &src)
 104     : reg (src.reg), cfa_offset (src.cfa_offset),
 105       cfa_reg (src.cfa_reg), cfa_how (src.cfa_how), cfa_exp (src.cfa_exp),
 106       prev (src.prev)
 107   {
 108   }
 109
 110   /* Assignment operator for both move-assignment and copy-assignment.  */
 111   dwarf2_frame_state_reg_info&
 112   operator= (dwarf2_frame_state_reg_info rhs)
 113   {
 114     swap (*this, rhs);
 115     return *this;
 116   }
 117
 118   /* Move constructor.  */
 119   dwarf2_frame_state_reg_info (dwarf2_frame_state_reg_info &&rhs) noexcept
 120     : reg (std::move (rhs.reg)), cfa_offset (rhs.cfa_offset),
 121       cfa_reg (rhs.cfa_reg), cfa_how (rhs.cfa_how), cfa_exp (rhs.cfa_exp),
 122       prev (rhs.prev)
 123   {
 124     rhs.prev = nullptr;
 125   }
 126
 127   /* If necessary, enlarge the register set to hold NUM_REGS_REQUESTED
 128      registers.  */
 129   void alloc_regs (int num_regs_requested)
 130   {
 131     gdb_assert (num_regs_requested > 0);
 132
 133     if (num_regs_requested <= reg.size ())
 134       return;
 135
 136     reg.resize (num_regs_requested);
 137   }
 138
 139   std::vector<struct dwarf2_frame_state_reg> reg;
 140
 141   LONGEST cfa_offset = 0;
 142   ULONGEST cfa_reg = 0;
 143   enum cfa_how_kind cfa_how = CFA_UNSET;
 144   const gdb_byte *cfa_exp = NULL;
 145
 146   /* Used to implement DW_CFA_remember_state.  */
 147   struct dwarf2_frame_state_reg_info *prev = NULL;
 148
 149 private:
 150   friend void swap (dwarf2_frame_state_reg_info& lhs,
 151                     dwarf2_frame_state_reg_info& rhs)
 152   {
 153     using std::swap;
 154
 155     swap (lhs.reg, rhs.reg);
 156     swap (lhs.cfa_offset, rhs.cfa_offset);
 157     swap (lhs.cfa_reg, rhs.cfa_reg);
 158     swap (lhs.cfa_how, rhs.cfa_how);
 159     swap (lhs.cfa_exp, rhs.cfa_exp);
 160     swap (lhs.prev, rhs.prev);
 161   }
 162 };
 163
 164 struct dwarf2_cie;
 165
 166 /* Structure describing a frame state.  */
 167
 168 struct dwarf2_frame_state
 169 {
 170   dwarf2_frame_state (CORE_ADDR pc, struct dwarf2_cie *cie);
 171
 172   /* Each register save state can be described in terms of a CFA slot,
 173      another register, or a location expression.  */
 174   struct dwarf2_frame_state_reg_info regs {};
 175
 176   /* The PC described by the current frame state.  */
 177   CORE_ADDR pc;
 178
 179   /* Initial register set from the CIE.
 180      Used to implement DW_CFA_restore.  */
 181   struct dwarf2_frame_state_reg_info initial {};
 182
 183   /* The information we care about from the CIE.  */
 184   const LONGEST data_align;
 185   const ULONGEST code_align;
 186   const ULONGEST retaddr_column;
 187
 188   /* Flags for known producer quirks.  */
 189
 190   /* The ARM compilers, in DWARF2 mode, assume that DW_CFA_def_cfa
 191      and DW_CFA_def_cfa_offset takes a factored offset.  */
 192   bool armcc_cfa_offsets_sf = false;
 193
 194   /* The ARM compilers, in DWARF2 or DWARF3 mode, may assume that
 195      the CFA is defined as REG - OFFSET rather than REG + OFFSET.  */
 196   bool armcc_cfa_offsets_reversed = false;
 197 };
 198
 199 /* When this is true the DWARF frame unwinders can be used if they are
 200    registered with the gdbarch.  Not all architectures can or do use the
 201    DWARF unwinders.  Setting this to true on a target that does not
 202    otherwise support the DWARF unwinders has no effect.  */
 203 extern bool dwarf2_frame_unwinders_enabled_p;
 204
 205 /* Set the architecture-specific register state initialization
 206    function for GDBARCH to INIT_REG.  */
 207
 208 extern void dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
 209                                        void (*init_reg) (struct gdbarch *, int,
 210                                              struct dwarf2_frame_state_reg *,
 211                                              struct frame_info *));
 212
 213 /* Set the architecture-specific signal trampoline recognition
 214    function for GDBARCH to SIGNAL_FRAME_P.  */
 215
 216 extern void
 217   dwarf2_frame_set_signal_frame_p (struct gdbarch *gdbarch,
 218                                    int (*signal_frame_p) (struct gdbarch *,
 219                                                           struct frame_info *));
 220
 221 /* Set the architecture-specific adjustment of .eh_frame and .debug_frame
 222    register numbers.  */
 223
 224 extern void
 225   dwarf2_frame_set_adjust_regnum (struct gdbarch *gdbarch,
 226                                   int (*adjust_regnum) (struct gdbarch *,
 227                                                         int, int));
 228
 229 /* Append the DWARF-2 frame unwinders to GDBARCH's list.  */
 230
 231 void dwarf2_append_unwinders (struct gdbarch *gdbarch);
 232
 233 /* Return the frame base methods for the function that contains PC, or
 234    NULL if it can't be handled by the DWARF CFI frame unwinder.  */
 235
 236 extern const struct frame_base *
 237   dwarf2_frame_base_sniffer (struct frame_info *this_frame);
 238
 239 /* Compute the DWARF CFA for a frame.  */
 240
 241 CORE_ADDR dwarf2_frame_cfa (struct frame_info *this_frame);
 242
 243 /* Find the CFA information for PC.
 244
 245    Return 1 if a register is used for the CFA, or 0 if another
 246    expression is used.  Throw an exception on error.
 247
 248    GDBARCH is the architecture to use.
 249    DATA is the per-CU data.
 250
 251    REGNUM_OUT is an out parameter that is set to the register number.
 252    OFFSET_OUT is the offset to use from this register.
 253    These are only filled in when 1 is returned.
 254
 255    TEXT_OFFSET_OUT, CFA_START_OUT, and CFA_END_OUT describe the CFA
 256    in other cases.  These are only used when 0 is returned.  */
 257
 258 extern int dwarf2_fetch_cfa_info (struct gdbarch *gdbarch, CORE_ADDR pc,
 259                                   struct dwarf2_per_cu_data *data,
 260                                   int *regnum_out, LONGEST *offset_out,
 261                                   CORE_ADDR *text_offset_out,
 262                                   const gdb_byte **cfa_start_out,
 263                                   const gdb_byte **cfa_end_out);
 264
 265 #endif /* dwarf2-frame.h */