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