OvmfPkg/OvmfXenElfHeaderGenerator.c

   1 /** @file
   2   This program generates a hex array to be manually coppied into
   3   OvmfXen.fdf.
   4
   5   The purpose is for the flash device image to be recognize as an ELF.
   6
   7   Copyright (c) 2019, Citrix Systems, Inc.
   8
   9   SPDX-License-Identifier: BSD-2-Clause-Patent
  10 **/
  11
  12 #include "elf.h"
  13 #include "stdio.h"
  14 #include "stddef.h"
  15
  16 void
  17 print_hdr (
  18   void    *s,
  19   size_t  size
  20   )
  21 {
  22   char  *c = s;
  23
  24   while (size--) {
  25     printf ("0x%02hhx, ", *(c++));
  26   }
  27 }
  28
  29 /* Format for the XEN_ELFNOTE_PHYS32_ENTRY program segment */
  30 #define XEN_ELFNOTE_PHYS32_ENTRY  18
  31 typedef struct {
  32   uint32_t    name_size;
  33   uint32_t    desc_size;
  34   uint32_t    type;
  35   char        name[4];
  36   uint32_t    desc;
  37 } xen_elfnote_phys32_entry;
  38
  39 int
  40 main (
  41   void
  42   )
  43 {
  44   /* FW_SIZE */
  45   size_t  ovmf_blob_size = 0x00200000;
  46   /* Load OVMF at 1MB when running as PVH guest */
  47   uint32_t  ovmf_base_address = 0x00100000;
  48   /* Xen PVH entry point */
  49   uint32_t  ovmfxen_pvh_entry_point = ovmf_base_address + ovmf_blob_size - 0x30;
  50   size_t    offset_into_file        = 0;
  51
  52   /* ELF file header */
  53   Elf32_Ehdr  hdr = {
  54     .e_ident     = ELFMAG,
  55     .e_type      = ET_EXEC,
  56     .e_machine   = EM_386,
  57     .e_version   = EV_CURRENT,
  58     .e_entry     = ovmfxen_pvh_entry_point,
  59     .e_flags     = R_386_NONE,
  60     .e_ehsize    = sizeof (hdr),
  61     .e_phentsize = sizeof (Elf32_Phdr),
  62   };
  63
  64   offset_into_file += sizeof (hdr);
  65
  66   hdr.e_ident[EI_CLASS]   = ELFCLASS32;
  67   hdr.e_ident[EI_DATA]    = ELFDATA2LSB;
  68   hdr.e_ident[EI_VERSION] = EV_CURRENT;
  69   hdr.e_ident[EI_OSABI]   = ELFOSABI_LINUX;
  70   /* Placing program headers just after hdr */
  71   hdr.e_phoff = sizeof (hdr);
  72
  73   /* program header */
  74   Elf32_Phdr  phdr_load = {
  75     .p_type   = PT_LOAD,
  76     .p_offset = 0, /* load everything */
  77     .p_paddr  = ovmf_base_address,
  78     .p_filesz = ovmf_blob_size,
  79     .p_memsz  = ovmf_blob_size,
  80     .p_flags  = PF_X | PF_W | PF_R,
  81     .p_align  = 0,
  82   };
  83
  84   phdr_load.p_vaddr = phdr_load.p_paddr;
  85   hdr.e_phnum      += 1;
  86   offset_into_file += sizeof (phdr_load);
  87
  88   /* Xen ELF Note. */
  89
  90   xen_elfnote_phys32_entry  xen_elf_note = {
  91     .type      = XEN_ELFNOTE_PHYS32_ENTRY,
  92     .name      = "Xen",
  93     .desc      = ovmfxen_pvh_entry_point,
  94     .name_size =
  95       offsetof (xen_elfnote_phys32_entry, desc) -
  96       offsetof (xen_elfnote_phys32_entry, name),
  97     .desc_size =
  98       sizeof (xen_elfnote_phys32_entry) -
  99       offsetof (xen_elfnote_phys32_entry, desc),
 100   };
 101   Elf32_Phdr                phdr_note = {
 102     .p_type   = PT_NOTE,
 103     .p_filesz = sizeof (xen_elf_note),
 104     .p_memsz  = sizeof (xen_elf_note),
 105     .p_flags  = PF_R,
 106     .p_align  = 0,
 107   };
 108
 109   hdr.e_phnum       += 1;
 110   offset_into_file  += sizeof (phdr_note);
 111   phdr_note.p_offset = offset_into_file;
 112   phdr_note.p_paddr  = ovmf_base_address + phdr_note.p_offset;
 113   phdr_note.p_vaddr  = phdr_note.p_paddr;
 114
 115   /*
 116    * print elf header
 117    */
 118
 119   size_t  i;
 120   size_t  hdr_size  = sizeof (hdr);
 121   size_t  entry_off = offsetof (typeof(hdr), e_entry);
 122
 123   printf ("# ELF file header\n");
 124   print_hdr (&hdr, entry_off);
 125   printf ("\n");
 126   print_hdr (&hdr.e_entry, sizeof (hdr.e_entry));
 127   printf (" # hdr.e_entry\n");
 128   print_hdr (&hdr.e_entry + 1, hdr_size - entry_off - sizeof (hdr.e_entry));
 129
 130   printf ("\n\n# ELF Program segment headers\n");
 131   printf ("# - Load segment\n");
 132   for (i = 0; i < sizeof (phdr_load); i += 4) {
 133     print_hdr (((char *)&phdr_load) + i, 4);
 134     printf ("\n");
 135   }
 136
 137   printf ("# - ELFNOTE segment\n");
 138   for (i = 0; i < sizeof (phdr_note); i += 4) {
 139     print_hdr (((char *)&phdr_note) + i, 4);
 140     printf ("\n");
 141   }
 142
 143   printf ("\n# XEN_ELFNOTE_PHYS32_ENTRY\n");
 144   for (i = 0; i < sizeof (xen_elf_note); i += 4) {
 145     print_hdr (((char *)&xen_elf_note) + i, 4);
 146     printf ("\n");
 147   }
 148
 149   return 0;
 150 }