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author | Anthony PERARD <anthony.perard@citrix.com> | 2019-08-13 12:30:49 +0100 |
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committer | Laszlo Ersek <lersek@redhat.com> | 2019-08-21 18:03:49 +0200 |
commit | 1e9d6b0f98b53498f8ae4104502da087493eba2c (patch) | |
tree | 56619502f67c2e73202e17050c08485e6e78c6c5 /OvmfPkg/OvmfXenElfHeaderGenerator.c | |
parent | 3b96221f77f4181524657e145b51fa423f3faebe (diff) | |
download | edk2-1e9d6b0f98b53498f8ae4104502da087493eba2c.zip edk2-1e9d6b0f98b53498f8ae4104502da087493eba2c.tar.gz edk2-1e9d6b0f98b53498f8ae4104502da087493eba2c.tar.bz2 |
OvmfPkg/OvmfXen: Creating an ELF header
This patch changes the flash device image of OvmfXen to make it look
like it's an ELF. For this, we replace the empty embedded variable store
by a binary array, which is a ELF file header.
The ELF header explain to a loader to load the binary at the address
1MB, then jump to the PVH entry point which will be created in a later
patch. The header also includes a Xen ELF note that is part of the
PVH ABI.
That patch include OvmfXenElfHeaderGenerator.c which can be use to
regenerate the ELF header, but this will be a manual step.
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20190813113119.14804-6-anthony.perard@citrix.com>
Diffstat (limited to 'OvmfPkg/OvmfXenElfHeaderGenerator.c')
-rw-r--r-- | OvmfPkg/OvmfXenElfHeaderGenerator.c | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/OvmfPkg/OvmfXenElfHeaderGenerator.c b/OvmfPkg/OvmfXenElfHeaderGenerator.c new file mode 100644 index 0000000..90f0574 --- /dev/null +++ b/OvmfPkg/OvmfXenElfHeaderGenerator.c @@ -0,0 +1,140 @@ +/** @file
+ This program generates a hex array to be manually coppied into
+ OvmfXen.fdf.
+
+ The purpose is for the flash device image to be recognize as an ELF.
+
+ Copyright (c) 2019, Citrix Systems, Inc.
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include "elf.h"
+#include "stdio.h"
+#include "stddef.h"
+
+void print_hdr(void *s, size_t size)
+{
+ char *c = s;
+
+ while (size--) {
+ printf("0x%02hhx, ", *(c++));
+ }
+}
+
+/* Format for the XEN_ELFNOTE_PHYS32_ENTRY program segment */
+#define XEN_ELFNOTE_PHYS32_ENTRY 18
+typedef struct {
+ uint32_t name_size;
+ uint32_t desc_size;
+ uint32_t type;
+ char name[4];
+ uint32_t desc;
+} xen_elfnote_phys32_entry;
+
+int main(void)
+{
+ /* FW_SIZE */
+ size_t ovmf_blob_size = 0x00200000;
+ /* Load OVMF at 1MB when running as PVH guest */
+ uint32_t ovmf_base_address = 0x00100000;
+ /* Xen PVH entry point */
+ uint32_t ovmfxen_pvh_entry_point = ovmf_base_address + ovmf_blob_size - 0x30;
+ size_t offset_into_file = 0;
+
+ /* ELF file header */
+ Elf32_Ehdr hdr = {
+ .e_ident = ELFMAG,
+ .e_type = ET_EXEC,
+ .e_machine = EM_386,
+ .e_version = EV_CURRENT,
+ .e_entry = ovmfxen_pvh_entry_point,
+ .e_flags = R_386_NONE,
+ .e_ehsize = sizeof (hdr),
+ .e_phentsize = sizeof (Elf32_Phdr),
+ };
+ offset_into_file += sizeof (hdr);
+
+ hdr.e_ident[EI_CLASS] = ELFCLASS32;
+ hdr.e_ident[EI_DATA] = ELFDATA2LSB;
+ hdr.e_ident[EI_VERSION] = EV_CURRENT;
+ hdr.e_ident[EI_OSABI] = ELFOSABI_LINUX;
+ /* Placing program headers just after hdr */
+ hdr.e_phoff = sizeof (hdr);
+
+ /* program header */
+ Elf32_Phdr phdr_load = {
+ .p_type = PT_LOAD,
+ .p_offset = 0, /* load everything */
+ .p_paddr = ovmf_base_address,
+ .p_filesz = ovmf_blob_size,
+ .p_memsz = ovmf_blob_size,
+ .p_flags = PF_X | PF_W | PF_R,
+ .p_align = 0,
+ };
+ phdr_load.p_vaddr = phdr_load.p_paddr;
+ hdr.e_phnum += 1;
+ offset_into_file += sizeof (phdr_load);
+
+ /* Xen ELF Note. */
+
+ xen_elfnote_phys32_entry xen_elf_note = {
+ .type = XEN_ELFNOTE_PHYS32_ENTRY,
+ .name = "Xen",
+ .desc = ovmfxen_pvh_entry_point,
+ .name_size =
+ offsetof (xen_elfnote_phys32_entry, desc) -
+ offsetof (xen_elfnote_phys32_entry, name),
+ .desc_size =
+ sizeof (xen_elfnote_phys32_entry) -
+ offsetof (xen_elfnote_phys32_entry, desc),
+ };
+ Elf32_Phdr phdr_note = {
+ .p_type = PT_NOTE,
+ .p_filesz = sizeof (xen_elf_note),
+ .p_memsz = sizeof (xen_elf_note),
+ .p_flags = PF_R,
+ .p_align = 0,
+ };
+ hdr.e_phnum += 1;
+ offset_into_file += sizeof (phdr_note);
+ phdr_note.p_offset = offset_into_file;
+ phdr_note.p_paddr = ovmf_base_address + phdr_note.p_offset;
+ phdr_note.p_vaddr = phdr_note.p_paddr;
+
+
+ /*
+ * print elf header
+ */
+
+ size_t i;
+ size_t hdr_size = sizeof (hdr);
+ size_t entry_off = offsetof(typeof(hdr), e_entry);
+
+ printf("# ELF file header\n");
+ print_hdr(&hdr, entry_off);
+ printf("\n");
+ print_hdr(&hdr.e_entry, sizeof (hdr.e_entry));
+ printf(" # hdr.e_entry\n");
+ print_hdr(&hdr.e_entry + 1, hdr_size - entry_off - sizeof (hdr.e_entry));
+
+ printf("\n\n# ELF Program segment headers\n");
+ printf("# - Load segment\n");
+ for (i = 0; i < sizeof (phdr_load); i += 4) {
+ print_hdr(((char*)&phdr_load) + i, 4);
+ printf("\n");
+ }
+ printf("# - ELFNOTE segment\n");
+ for (i = 0; i < sizeof (phdr_note); i += 4) {
+ print_hdr(((char*)&phdr_note) + i, 4);
+ printf("\n");
+ }
+
+ printf("\n# XEN_ELFNOTE_PHYS32_ENTRY\n");
+ for (i = 0; i < sizeof (xen_elf_note); i += 4) {
+ print_hdr(((char*)&xen_elf_note) + i, 4);
+ printf("\n");
+ }
+
+ return 0;
+}
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