x15/kern/init.h

/*
 * Copyright (c) 2010-2017 Richard Braun.
 *
 * 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/>.
 *
 *
 * Init sections and operations.
 */

#ifndef KERN_INIT_H
#define KERN_INIT_H

/*
 * These sections should contain code and data which can be discarded once
 * kernel initialization is done.
 */
#define INIT_SECTION        .init.text
#define INIT_DATA_SECTION   .init.data

/*
 * This section must only contain init operation structures, and must be
 * located inside the .init section.
 */
#define INIT_OPS_SECTION    .init.ops

/*
 * Alignment is important to make sure initialization operations are
 * stored as a C array in the reserved init op section.
 */
#define INIT_OP_ALIGN 64

#ifndef __ASSEMBLER__

#include <errno.h>
#include <stdalign.h>
#include <stdbool.h>
#include <stddef.h>

#include <kern/macros.h>
#include <kern/slist_types.h>

#define __init       __section (QUOTE (INIT_SECTION))
#define __initdata   __section (QUOTE (INIT_DATA_SECTION))

// Boundaries of the .init section.
extern char _init;
extern char _init_end;

// Type for initialization operation functions.
typedef int (*init_op_fn_t) (void);

#define __initop __section(QUOTE(INIT_OPS_SECTION))

#define INIT_OP_STATE_UNLINKED      0
#define INIT_OP_STATE_PENDING       1
#define INIT_OP_STATE_COMPLETE      2

struct init_op
{
  alignas (INIT_OP_ALIGN) struct slist_node list_node;
  struct slist_node stack_node;
  const char *name;
  init_op_fn_t fn;
  struct init_op_dep *deps;
  int error;
  unsigned char state;
  unsigned char nr_deps;
  unsigned char nr_parents;
};

struct init_op_dep
{
  struct init_op *op;
  bool required;
};

#define INIT_OP_DEPS(fn)   CONCAT (fn, _init_op_deps)
#define INIT_OP(fn)        CONCAT (fn, _init_op)

// Forge an init operation declaration.
#define INIT_OP_DECLARE(fn)   extern struct init_op INIT_OP (fn)

/*
 * Foge an entry suitable as an init operation dependency.
 *
 * If a dependency isn't required, it's still used to determine run
 * order, but its result is ignored, and the operation depending on it
 * behaves as if that dependency succeeded.
 */
#define INIT_OP_DEP(fn, required)   { &INIT_OP (fn), required }

/*
 * Init operation definition macro.
 *
 * This macro is used to define a structure named after the given function.
 * Init operations are placed in a specific section which doesn't contain
 * any other object type, making it a system-wide array of init operations.
 * There is no need to actively register init operations; this module finds
 * them all from their section. Dependencies are given as a variable-length
 * argument list of entries built with the INIT_OP_DEP() macro.
 */
#define INIT_OP_DEFINE(_fn, ...)   \
  static struct init_op_dep INIT_OP_DEPS(_fn)[] __initdata =   \
    {   \
      __VA_ARGS__   \
    };   \
   \
  struct init_op INIT_OP(_fn) __initop __used =   \
    {   \
      .name = QUOTE (_fn),   \
      .fn = _fn,   \
      .deps = INIT_OP_DEPS (_fn),   \
      .error = EAGAIN,   \
      .state = INIT_OP_STATE_UNLINKED,   \
      .nr_deps = ARRAY_SIZE (INIT_OP_DEPS (_fn)),   \
      .nr_parents = 0,   \
    }

/*
 * Initialize the init module.
 *
 * Scan the section containing init operations, resolve all dependencies,
 * and run operations in an appropriate order.
 */
void init_setup (void);

#endif   // __ASSEMBLER__

#endif