/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009 H. Peter Anvin - All Rights Reserved
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

/*
 * mem.c
 *
 * Obtain a memory map for a Multiboot OS
 *
 * This differs from the libcom32 memory map functions in that it doesn't
 * attempt to filter out memory regions...
 */

#include "mboot.h"
#include <com32.h>

struct e820_entry {
  uint64_t start;
  uint64_t len;
  uint32_t type;
};

#define RANGE_ALLOC_BLOCK	128

static int mboot_scan_memory(struct AddrRangeDesc **ardp, uint32_t *dosmem)
{
  com32sys_t ireg, oreg;
  struct e820_entry *e820buf = __com32.cs_bounce;
  struct AddrRangeDesc *ard;
  size_t ard_count, ard_space;

  /* Use INT 12h to get DOS memory */
  __intcall(0x12, &__com32_zero_regs, &oreg);
  *dosmem = oreg.eax.w[0] << 10;
  if (*dosmem < 32*1024 || *dosmem > 640*1024) {
    /* INT 12h reports nonsense... now what? */
    uint16_t ebda_seg = *(uint16_t *)0x40e;
    if (ebda_seg >= 0x8000 && ebda_seg < 0xa000)
      *dosmem = ebda_seg << 4;
    else
      *dosmem = 640*1024;	/* Hope for the best... */
  }

  /* Allocate initial space */
  *ardp = ard = malloc(RANGE_ALLOC_BLOCK * sizeof *ard);
  if (!ard)
    return 0;

  ard_count = 0;
  ard_space = RANGE_ALLOC_BLOCK;

  /* First try INT 15h AX=E820h */
  memset(&ireg, 0, sizeof ireg);
  ireg.eax.l    = 0xe820;
  ireg.edx.l    = 0x534d4150;
  /* ireg.ebx.l    = 0; */
  ireg.ecx.l    = sizeof(*e820buf);
  ireg.es       = SEG(e820buf);
  ireg.edi.w[0] = OFFS(e820buf);
  memset(e820buf, 0, sizeof *e820buf);

  do {
    __intcall(0x15, &ireg, &oreg);

    if ((oreg.eflags.l & EFLAGS_CF) ||
	(oreg.eax.l != 0x534d4150) ||
	(oreg.ecx.l < 20))
      break;

    if (ard_count >= ard_space) {
      ard_space += RANGE_ALLOC_BLOCK;
      *ardp = ard = realloc(ard, ard_space*sizeof *ard);
      if (!ard)
	return ard_count;
    }

    ard[ard_count].size     = 20;
    ard[ard_count].BaseAddr = e820buf->start;
    ard[ard_count].Length   = e820buf->len;
    ard[ard_count].Type     = e820buf->type;
    ard_count++;

    ireg.ebx.l = oreg.ebx.l;
  } while (oreg.ebx.l);

  if (ard_count)
    return ard_count;

  ard[0].size = 20;
  ard[0].BaseAddr = 0;
  ard[0].Length = *dosmem << 10;
  ard[0].Type = 1;

  /* Next try INT 15h AX=E801h */
  ireg.eax.w[0] = 0xe801;
  __intcall(0x15, &ireg, &oreg);

  if (!(oreg.eflags.l & EFLAGS_CF) && oreg.ecx.w[0]) {
    ard[1].size = 20;
    ard[1].BaseAddr = 1 << 20;
    ard[1].Length = oreg.ecx.w[0] << 10;
    ard[1].Type = 1;

    if (oreg.edx.w[0]) {
      ard[2].size = 20;
      ard[2].BaseAddr = 16 << 20;
      ard[2].Length = oreg.edx.w[0] << 16;
      ard[2].Type = 1;
      return 3;
    } else {
      return 2;
    }
  }

  /* Finally try INT 15h AH=88h */
  ireg.eax.w[0] = 0x8800;
  if (!(oreg.eflags.l & EFLAGS_CF) && oreg.eax.w[0]) {
    ard[1].size = 20;
    ard[1].BaseAddr = 1 << 20;
    ard[1].Length = oreg.ecx.w[0] << 10;
    ard[1].Type = 1;
    return 2;
  }

  return 1;			/* ... problematic ... */
}

void mboot_make_memmap(void)
{
  int i, nmap;
  struct AddrRangeDesc *ard;
  uint32_t lowmem, highmem;
  uint32_t highrsvd;

  /* Always report DOS memory as "lowmem", this may be overly conservative
     (e.g. if we're dropping PXE), but it should be *safe*... */

  nmap = mboot_scan_memory(&ard, &lowmem);

  highmem  = 0x100000;
  highrsvd = 0xfff00000;

 again:
  for (i = 0; i < nmap; i++) {
    uint64_t start, end;

    start = ard[i].BaseAddr;
    end = start + ard[i].Length;

    if (end < start)
      end = ~0ULL;

    if (start & 0xffffffff00000000ULL)
      continue;			/* Not interested in 64-bit memory */

    if (start < highmem)
      start = highmem;

    if (end <= start)
      continue;

    if (ard[i].Type == 1 && start == highmem) {
      highmem = end;
      goto again;
    } else if (ard[i].Type != 1 && start < highrsvd)
      highrsvd = start;
  }

  if (highmem > highrsvd)
    highmem = highrsvd;

  mbinfo.mem_lower = lowmem >> 10;
  mbinfo.mem_upper = (highmem - 0x100000) >> 10;
  mbinfo.flags |= MB_INFO_MEMORY;

  /* The spec says this address should be +4, but Grub disagrees */
  mbinfo.mmap_addr = map_data(ard, nmap*sizeof *ard, 4, false);
  if (mbinfo.mmap_addr) {
    mbinfo.mmap_length = nmap*sizeof *ard;
    mbinfo.flags |= MB_INFO_MEM_MAP;
  }
}
