path: root/gdb/dwarf2-frame.h

/* Frame unwinder for frames with DWARF Call Frame Information.

   Copyright (C) 2003-2018 Free Software Foundation, Inc.

   Contributed by Mark Kettenis.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef DWARF2_FRAME_H
#define DWARF2_FRAME_H 1

struct gdbarch;
struct objfile;
struct frame_info;
struct dwarf2_per_cu_data;
struct agent_expr;
struct axs_value;

/* Register rule.  */

enum dwarf2_frame_reg_rule
{
  /* Make certain that 0 maps onto the correct enum value; the
     corresponding structure is being initialized using memset zero.
     This indicates that CFI didn't provide any information at all
     about a register, leaving how to obtain its value totally
     unspecified.  */
  DWARF2_FRAME_REG_UNSPECIFIED = 0,

  /* The term "undefined" comes from the DWARF2 CFI spec which this
     code is moddeling; it indicates that the register's value is
     "undefined".  GCC uses the less formal term "unsaved".  Its
     definition is a combination of REG_UNDEFINED and REG_UNSPECIFIED.
     The failure to differentiate the two helps explain a few problems
     with the CFI generated by GCC.  */
  DWARF2_FRAME_REG_UNDEFINED,
  DWARF2_FRAME_REG_SAVED_OFFSET,
  DWARF2_FRAME_REG_SAVED_REG,
  DWARF2_FRAME_REG_SAVED_EXP,
  DWARF2_FRAME_REG_SAME_VALUE,

  /* These are defined in Dwarf3.  */
  DWARF2_FRAME_REG_SAVED_VAL_OFFSET,
  DWARF2_FRAME_REG_SAVED_VAL_EXP,

  /* These aren't defined by the DWARF2 CFI specification, but are
     used internally by GDB.  */
  DWARF2_FRAME_REG_FN,		/* Call a registered function.  */
  DWARF2_FRAME_REG_RA,		/* Return Address.  */
  DWARF2_FRAME_REG_RA_OFFSET,	/* Return Address with offset.  */
  DWARF2_FRAME_REG_CFA,		/* Call Frame Address.  */
  DWARF2_FRAME_REG_CFA_OFFSET	/* Call Frame Address with offset.  */
};

/* Register state.  */

struct dwarf2_frame_state_reg
{
  /* Each register save state can be described in terms of a CFA slot,
     another register, or a location expression.  */
  union {
    LONGEST offset;
    ULONGEST reg;
    struct
    {
      const gdb_byte *start;
      ULONGEST len;
    } exp;
    struct value *(*fn) (struct frame_info *this_frame, void **this_cache,
			 int regnum);
  } loc;
  enum dwarf2_frame_reg_rule how;
};

enum cfa_how_kind
{
  CFA_UNSET,
  CFA_REG_OFFSET,
  CFA_EXP
};

struct dwarf2_frame_state_reg_info
{
  dwarf2_frame_state_reg_info () = default;
  ~dwarf2_frame_state_reg_info ()
  {
    delete prev;
    xfree (reg);
  }

  /* Copy constructor.  */
  dwarf2_frame_state_reg_info (const dwarf2_frame_state_reg_info &src)
    : num_regs (src.num_regs), cfa_offset (src.cfa_offset),
      cfa_reg (src.cfa_reg), cfa_how (src.cfa_how), cfa_exp (src.cfa_exp),
      prev (src.prev)
  {
    size_t size = src.num_regs * sizeof (struct dwarf2_frame_state_reg);

    reg = (struct dwarf2_frame_state_reg *) xmalloc (size);
    memcpy (reg, src.reg, size);
  }

  /* Assignment operator for both move-assignment and copy-assignment.  */
  dwarf2_frame_state_reg_info&
  operator= (dwarf2_frame_state_reg_info rhs)
  {
    swap (*this, rhs);
    return *this;
  }

  /* Move constructor.  */
  dwarf2_frame_state_reg_info (dwarf2_frame_state_reg_info &&rhs) noexcept
    : reg (rhs.reg), num_regs (rhs.num_regs), cfa_offset (rhs.cfa_offset),
      cfa_reg (rhs.cfa_reg), cfa_how (rhs.cfa_how), cfa_exp (rhs.cfa_exp),
      prev (rhs.prev)
  {
    rhs.prev = nullptr;
    rhs.reg = nullptr;
  }

/* Assert that the register set RS is large enough to store gdbarch_num_regs
   columns.  If necessary, enlarge the register set.  */
  void alloc_regs (int num_regs_requested)
  {
    if (num_regs_requested <= num_regs)
      return;

    size_t size = sizeof (struct dwarf2_frame_state_reg);

    reg = (struct dwarf2_frame_state_reg *)
      xrealloc (reg, num_regs_requested * size);

    /* Initialize newly allocated registers.  */
    memset (reg + num_regs, 0, (num_regs_requested - num_regs) * size);
    num_regs = num_regs_requested;
  }

  struct dwarf2_frame_state_reg *reg = NULL;
  int num_regs = 0;

  LONGEST cfa_offset = 0;
  ULONGEST cfa_reg = 0;
  enum cfa_how_kind cfa_how = CFA_UNSET;
  const gdb_byte *cfa_exp = NULL;

  /* Used to implement DW_CFA_remember_state.  */
  struct dwarf2_frame_state_reg_info *prev = NULL;

private:
  friend void swap (dwarf2_frame_state_reg_info& lhs,
		    dwarf2_frame_state_reg_info& rhs)
  {
    using std::swap;

    swap (lhs.reg, rhs.reg);
    swap (lhs.num_regs, rhs.num_regs);
    swap (lhs.cfa_offset, rhs.cfa_offset);
    swap (lhs.cfa_reg, rhs.cfa_reg);
    swap (lhs.cfa_how, rhs.cfa_how);
    swap (lhs.cfa_exp, rhs.cfa_exp);
    swap (lhs.prev, rhs.prev);
  }
};

struct dwarf2_cie;

/* Structure describing a frame state.  */

struct dwarf2_frame_state
{
  dwarf2_frame_state (CORE_ADDR pc, struct dwarf2_cie *cie);

  /* Each register save state can be described in terms of a CFA slot,
     another register, or a location expression.  */
  struct dwarf2_frame_state_reg_info regs {};

  /* The PC described by the current frame state.  */
  CORE_ADDR pc;

  /* Initial register set from the CIE.
     Used to implement DW_CFA_restore.  */
  struct dwarf2_frame_state_reg_info initial {};

  /* The information we care about from the CIE.  */
  const LONGEST data_align;
  const ULONGEST code_align;
  const ULONGEST retaddr_column;

  /* Flags for known producer quirks.  */

  /* The ARM compilers, in DWARF2 mode, assume that DW_CFA_def_cfa
     and DW_CFA_def_cfa_offset takes a factored offset.  */
  bool armcc_cfa_offsets_sf = false;

  /* The ARM compilers, in DWARF2 or DWARF3 mode, may assume that
     the CFA is defined as REG - OFFSET rather than REG + OFFSET.  */
  bool armcc_cfa_offsets_reversed = false;
};

/* Set the architecture-specific register state initialization
   function for GDBARCH to INIT_REG.  */

extern void dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
				       void (*init_reg) (struct gdbarch *, int,
					     struct dwarf2_frame_state_reg *,
					     struct frame_info *));

/* Set the architecture-specific signal trampoline recognition
   function for GDBARCH to SIGNAL_FRAME_P.  */

extern void
  dwarf2_frame_set_signal_frame_p (struct gdbarch *gdbarch,
				   int (*signal_frame_p) (struct gdbarch *,
							  struct frame_info *));

/* Set the architecture-specific adjustment of .eh_frame and .debug_frame
   register numbers.  */

extern void
  dwarf2_frame_set_adjust_regnum (struct gdbarch *gdbarch,
				  int (*adjust_regnum) (struct gdbarch *,
							int, int));

/* Append the DWARF-2 frame unwinders to GDBARCH's list.  */

void dwarf2_append_unwinders (struct gdbarch *gdbarch);

/* Return the frame base methods for the function that contains PC, or
   NULL if it can't be handled by the DWARF CFI frame unwinder.  */

extern const struct frame_base *
  dwarf2_frame_base_sniffer (struct frame_info *this_frame);

/* Compute the DWARF CFA for a frame.  */

CORE_ADDR dwarf2_frame_cfa (struct frame_info *this_frame);

/* Find the CFA information for PC.

   Return 1 if a register is used for the CFA, or 0 if another
   expression is used.  Throw an exception on error.

   GDBARCH is the architecture to use.
   DATA is the per-CU data.

   REGNUM_OUT is an out parameter that is set to the register number.
   OFFSET_OUT is the offset to use from this register.
   These are only filled in when 1 is returned.

   TEXT_OFFSET_OUT, CFA_START_OUT, and CFA_END_OUT describe the CFA
   in other cases.  These are only used when 0 is returned.  */

extern int dwarf2_fetch_cfa_info (struct gdbarch *gdbarch, CORE_ADDR pc,
				  struct dwarf2_per_cu_data *data,
				  int *regnum_out, LONGEST *offset_out,
				  CORE_ADDR *text_offset_out,
				  const gdb_byte **cfa_start_out,
				  const gdb_byte **cfa_end_out);

#endif /* dwarf2-frame.h */