/* Copyright (C) 2009-2024 Free Software Foundation, Inc.

   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/>.  */

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include JIT_READER_H  /* Please see jit-reader.exp for an explanation.  */
#include "jit-reader-host.h"

GDB_DECLARE_GPL_COMPATIBLE_READER;

enum register_mapping
{
  AMD64_RA = 16,
  AMD64_RBP = 6,
  AMD64_RSP = 7,
};

struct reader_state
{
  struct {
    uintptr_t begin;
    uintptr_t end;
  } func_stack_mangle;
};

static enum gdb_status
read_debug_info (struct gdb_reader_funcs *self,
		 struct gdb_symbol_callbacks *cbs,
                 void *memory, long memory_sz)
{
  struct jithost_abi *symfile = memory;
  struct gdb_object *object = cbs->object_open (cbs);
  struct gdb_symtab *symtab = cbs->symtab_open (cbs, object, "");

  struct reader_state *state = (struct reader_state *) self->priv_data;

  /* Record the stack mangle function's range, for the unwinder.  */
  state->func_stack_mangle.begin
    = (uintptr_t) symfile->function_stack_mangle.begin;
  state->func_stack_mangle.end
    = (uintptr_t) symfile->function_stack_mangle.end;

  cbs->block_open (cbs, symtab, NULL,
		   (GDB_CORE_ADDR) symfile->function_stack_mangle.begin,
		   (GDB_CORE_ADDR) symfile->function_stack_mangle.end,
		   "jit_function_stack_mangle");

  /* Add some line table information.  This ensures that GDB can handle
     accepting this information, and can scan the table.  However, this
     information is constructed such that none of the tests actually hit any
     of these line entries.  */
  struct gdb_line_mapping mangle_lines[] =
    {
      { 1, (GDB_CORE_ADDR) symfile->function_stack_mangle.begin + 0 },
      { 0, (GDB_CORE_ADDR) symfile->function_stack_mangle.begin + 1 },
    };
  int mangle_nlines = sizeof (mangle_lines) / sizeof (mangle_lines[0]);
  cbs->line_mapping_add (cbs, symtab, mangle_nlines, mangle_lines);

  cbs->block_open (cbs, symtab, NULL,
		   (GDB_CORE_ADDR) symfile->function_add.begin,
		   (GDB_CORE_ADDR) symfile->function_add.end,
		   "jit_function_add");

  cbs->symtab_close (cbs, symtab);
  cbs->object_close (cbs, object);
  return GDB_SUCCESS;
}

static void
free_reg_value (struct gdb_reg_value *value)
{
  free (value);
}

static void
write_register (struct gdb_unwind_callbacks *callbacks, int dw_reg,
                uintptr_t value)
{
  const int size = sizeof (uintptr_t);
  struct gdb_reg_value *reg_val =
    malloc (sizeof (struct gdb_reg_value) + size - 1);
  reg_val->defined = 1;
  reg_val->free = free_reg_value;

  memcpy (reg_val->value, &value, size);
  callbacks->reg_set (callbacks, dw_reg, reg_val);
}

static int
read_register (struct gdb_unwind_callbacks *callbacks, int dw_reg,
	       uintptr_t *value)
{
  const int size = sizeof (uintptr_t);
  struct gdb_reg_value *reg_val = callbacks->reg_get (callbacks, dw_reg);
  if (reg_val->size != size || !reg_val->defined)
    {
      reg_val->free (reg_val);
      return 0;
    }
  memcpy (value, reg_val->value, size);
  reg_val->free (reg_val);
  return 1;
}

/* Read the stack pointer into *VALUE.  IP is the address the inferior
   is currently stopped at.  Takes care of demangling the stack
   pointer if necessary.  */

static int
read_sp (struct gdb_reader_funcs *self, struct gdb_unwind_callbacks *cbs,
	 uintptr_t ip, uintptr_t *value)
{
  struct reader_state *state = (struct reader_state *) self->priv_data;
  uintptr_t sp;

  if (!read_register (cbs, AMD64_RSP, &sp))
    return GDB_FAIL;

  /* If stopped at the instruction after the "xor $-1, %rsp", demangle
     the stack pointer back.  */
  if (ip == state->func_stack_mangle.begin + 5)
    sp ^= (uintptr_t) -1;

  *value = sp;
  return GDB_SUCCESS;
}

static enum gdb_status
unwind_frame (struct gdb_reader_funcs *self, struct gdb_unwind_callbacks *cbs)
{
  const int word_size = sizeof (uintptr_t);
  uintptr_t prev_sp, this_sp;
  uintptr_t prev_ip, this_ip;
  uintptr_t prev_bp, this_bp;
  struct reader_state *state = (struct reader_state *) self->priv_data;

  if (!read_register (cbs, AMD64_RA, &this_ip))
    return GDB_FAIL;

  if (this_ip >= state->func_stack_mangle.end
      || this_ip < state->func_stack_mangle.begin)
    return GDB_FAIL;

  /* Unwind RBP in order to make the unwinder that tries to unwind
     from the just-unwound frame happy.  */
  if (!read_register (cbs, AMD64_RBP, &this_bp))
    return GDB_FAIL;
  /* RBP is unmodified.  */
  prev_bp = this_bp;

  /* Fetch the demangled stack pointer.  */
  if (!read_sp (self, cbs, this_ip, &this_sp))
    return GDB_FAIL;

  /* The return address is saved on the stack.  */
  if (cbs->target_read (this_sp, &prev_ip, word_size) == GDB_FAIL)
    return GDB_FAIL;
  prev_sp = this_sp + word_size;

  write_register (cbs, AMD64_RA, prev_ip);
  write_register (cbs, AMD64_RSP, prev_sp);
  write_register (cbs, AMD64_RBP, prev_bp);
  return GDB_SUCCESS;
}

static struct gdb_frame_id
get_frame_id (struct gdb_reader_funcs *self, struct gdb_unwind_callbacks *cbs)
{
  struct reader_state *state = (struct reader_state *) self->priv_data;
  struct gdb_frame_id frame_id;
  uintptr_t ip;
  uintptr_t sp;

  read_register (cbs, AMD64_RA, &ip);
  read_sp (self, cbs, ip, &sp);

  frame_id.code_address = (GDB_CORE_ADDR) state->func_stack_mangle.begin;
  frame_id.stack_address = (GDB_CORE_ADDR) sp;

  return frame_id;
}

static void
destroy_reader (struct gdb_reader_funcs *self)
{
  free (self->priv_data);
  free (self);
}

struct gdb_reader_funcs *
gdb_init_reader (void)
{
  struct reader_state *state = calloc (1, sizeof (struct reader_state));
  struct gdb_reader_funcs *reader_funcs =
    malloc (sizeof (struct gdb_reader_funcs));

  reader_funcs->reader_version = GDB_READER_INTERFACE_VERSION;
  reader_funcs->priv_data = state;
  reader_funcs->read = read_debug_info;
  reader_funcs->unwind = unwind_frame;
  reader_funcs->get_frame_id = get_frame_id;
  reader_funcs->destroy = destroy_reader;

  return reader_funcs;
}
