/* Support for an sbrk-like function that uses mmap. */

/* Copyright (c) 2010-2020. The SimGrid Team.
 * All rights reserved.                                                     */

/* This program is free software; you can redistribute it and/or modify it
 * under the terms of the license (GNU LGPL) which comes with this package. */

/* Copyright 1992, 2000 Free Software Foundation, Inc.

   Contributed by Fred Fish at Cygnus Support.   fnf@cygnus.com */

#include "src/internal_config.h"
#if HAVE_UNISTD_H
#include <unistd.h>             /* Prototypes for lseek */
#endif
#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <errno.h>

#include "mmprivate.h"

#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS MAP_ANON
#endif

#define PAGE_ALIGN(addr) (void*) (((long)(addr) + xbt_pagesize - 1) &   \
                                  ~((long)xbt_pagesize - 1))

/* Return MAP_PRIVATE if MDP represents /dev/zero.  Otherwise, return
   MAP_SHARED.  */
#define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
                                    ? MAP_PRIVATE                       \
                                    : MAP_SHARED)

/* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
#define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
                               ? MAP_ANONYMOUS                      \
                               : 0)

/* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
#define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
                             ? -1                                 \
                             : (MDP) -> fd)

/* Return 0if MDP uses anonymous mapping. Otherwise, return off */
#define MAP_ANON_OR_OFFSET(MDP, off) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
                             ? 0                                           \
                             : off)

/** @brief Add memory to this heap
 *
 *  Get core for the memory region specified by MDP, using SIZE as the
 *  amount to either add to or subtract from the existing region.  Works
 *  like sbrk(), but using mmap().
 *
 *  It never returns NULL. Instead, it dies verbosely on errors.
 *
 *  @param mdp  The heap
 *  @param size Bytes to allocate for this heap (or <0 to free memory from this heap)
 */
void *mmorecore(struct mdesc *mdp, ssize_t size)
{
  void* result;                 // please keep it uninitialized to track issues
  off_t foffset;                /* File offset at which new mapping will start */
  size_t mapbytes;              /* Number of bytes to map */
  void* moveto;                 /* Address where we wish to move "break value" to */
  void* mapto;                  /* Address we actually mapped to */
  char buf = 0;                 /* Single byte to write to extend mapped file */

  if (size == 0) {
    /* Just return the current "break" value. */
    return mdp->breakval;
  }

  if (size < 0) {
    /* We are deallocating memory.  If the amount requested would cause us to try to deallocate back past the base of
     * the mmap'd region then die verbosely.  Otherwise, deallocate the memory and return the old break value. */
    if (((char*)mdp->breakval) + size >= (char*)mdp->base) {
      result        = (void*)mdp->breakval;
      mdp->breakval = (char*)mdp->breakval + size;
      moveto = PAGE_ALIGN(mdp->breakval);
      munmap(moveto, (size_t)(((char*)mdp->top) - ((char*)moveto)) - 1);
      mdp->top = moveto;
    } else {
      fprintf(stderr,"Internal error: mmap was asked to deallocate more memory than it previously allocated. Bailling out now!\n");
      abort();
    }
  } else {
    /* We are allocating memory. Make sure we have an open file descriptor if not working with anonymous memory. */
    if (!(mdp->flags & MMALLOC_ANONYMOUS) && mdp->fd < 0) {
      fprintf(stderr,"Internal error: mmap file descriptor <0 (%d), without MMALLOC_ANONYMOUS being in the flags.\n",mdp->fd);
      abort();
    } else if ((char*)mdp->breakval + size > (char*)mdp->top) {
      /* The request would move us past the end of the currently mapped memory, so map in enough more memory to satisfy
         the request.  This means we also have to grow the mapped-to file by an appropriate amount, since mmap cannot
         be used to extend a file. */
      moveto   = PAGE_ALIGN((char*)mdp->breakval + size);
      mapbytes = (char*)moveto - (char*)mdp->top;
      foffset  = (char*)mdp->top - (char*)mdp->base;

      if (mdp->fd > 0) {
        if (lseek(mdp->fd, foffset + mapbytes - 1, SEEK_SET) == -1) {
          fprintf(stderr, "Internal error: lseek into mmap'ed fd failed! error: %s", strerror(errno));
          abort();
        }
        if (write(mdp->fd, &buf, 1) == -1) {
          fprintf(stderr,"Internal error: write to mmap'ed fd failed! error: %s", strerror(errno));
          abort();
        }
      }

      /* Let's call mmap. Note that it is possible that mdp->top is 0. In this case mmap will choose the address for us.
         This call might very well overwrite an already existing memory mapping (leading to weird bugs).
       */
      mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
                   MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
                   MAP_FIXED, MAP_ANON_OR_FD(mdp), MAP_ANON_OR_OFFSET(mdp, foffset));

      if (mapto == MAP_FAILED) {
        char buff[1024];
        fprintf(stderr,"Internal error: mmap returned MAP_FAILED! error: %s\n",strerror(errno));
        snprintf(buff,1024,"cat /proc/%d/maps",getpid());
        int status = system(buff);
        if (status == -1 || !(WIFEXITED(status) && WEXITSTATUS(status) == 0))
          fprintf(stderr, "Something went wrong when trying to %s\n", buff);
        sleep(1);
        abort();
      }

      if (mdp->top == 0)
        mdp->base = mdp->breakval = mapto;

      mdp->top      = PAGE_ALIGN((char*)mdp->breakval + size);
      result = (void *) mdp->breakval;
      mdp->breakval = (char*)mdp->breakval + size;
    } else {
      /* Memory is already mapped, we only need to increase the breakval: */
      result = (void *) mdp->breakval;
      mdp->breakval = (char*)mdp->breakval + size;
    }
  }
  return (result);
}

void* __mmalloc_remap_core(const s_xbt_mheap_t* mdp)
{
  /* FIXME:  Quick hack, needs error checking and other attention. */

  return mmap(mdp->base, (char*) mdp->top - (char*) mdp->base,
              PROT_READ | PROT_WRITE | PROT_EXEC,
              MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED, mdp->fd, 0);
}

