[edk2-devel] [PATCH v3 05/35] OvmfPkg/OvmfXen: Creating an ELF header
Anthony PERARD
anthony.perard at citrix.com
Thu Jul 4 14:42:03 UTC 2019
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 at citrix.com>
---
Notes:
v3:
- added license to generate_elf_header.c
which is renamed to OvmfPkg/OvmfXenElfHeaderGenerator.c
- added an ELF NOTE into the header
OvmfPkg/OvmfXen.fdf | 101 +++++++++++++++++++-
OvmfPkg/OvmfXenElfHeaderGenerator.c | 140 ++++++++++++++++++++++++++++
2 files changed, 238 insertions(+), 3 deletions(-)
create mode 100644 OvmfPkg/OvmfXenElfHeaderGenerator.c
diff --git a/OvmfPkg/OvmfXen.fdf b/OvmfPkg/OvmfXen.fdf
index 2ceff7baa2..43c268f6cb 100644
--- a/OvmfPkg/OvmfXen.fdf
+++ b/OvmfPkg/OvmfXen.fdf
@@ -15,8 +15,8 @@ [Defines]
!include OvmfPkg.fdf.inc
#
-# Build the variable store and the firmware code as one unified flash device
-# image.
+# This will allow the flash device image to be recognize as an ELF, with first
+# an ELF headers, then the firmware code.
#
[FD.OVMF]
BaseAddress = $(FW_BASE_ADDRESS)
@@ -25,7 +25,102 @@ [FD.OVMF]
BlockSize = $(BLOCK_SIZE)
NumBlocks = $(FW_BLOCKS)
-!include VarStore.fdf.inc
+!if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
+0x00000000|0x0000e000
+!endif
+!if $(FD_SIZE_IN_KB) == 4096
+0x00000000|0x00040000
+!endif
+DATA = {
+ #
+ # This hex array have been generated by OvmfPkg/OvmfXenElfHeaderGenerator.c
+ # and copied manually.
+ #
+ # ELF file header
+ 0x7f, 0x45, 0x4c, 0x46, # e_ident[0..3]: Magic number
+ 0x01, # File class: 32-bit objects
+ 0x01, # Data encoding: 2's complement, little endian
+ 0x01, # File version
+ 0x03, # OS ABI identification: Object uses GNU ELF extensions
+ 0x00, # ABI version
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, # e_ident[EI_PAD...]
+ 0x02, 0x00, # e_type = Executable file
+ 0x03, 0x00, # e_machine = Intel 80386
+ 0x01, 0x00, 0x00, 0x00, # e_version
+ 0xd0, 0xff, 0x2f, 0x00, # e_entry: Entry point virtual address
+ 0x34, 0x00, 0x00, 0x00, # e_phoff: Program header table file offset
+ 0x00, 0x00, 0x00, 0x00, # e_shoff: Section header table file offset
+ 0x00, 0x00, 0x00, 0x00, # e_flags: Processor-specific flags
+ 0x34, 0x00, # e_ehsize: ELF header size
+ 0x20, 0x00, # e_phentsize: Program header table entry size
+ 0x02, 0x00, # e_phnum: Program header table entry count
+ 0x00, 0x00, # e_shentsize: Section header table entry size
+ 0x00, 0x00, # e_shnum: Section header table entry count
+ 0x00, 0x00, # e_shstrndx
+
+ # ELF Program segment headers
+ # - Load segment
+ 0x01, 0x00, 0x00, 0x00, # p_type = Loadable program segment
+ 0x00, 0x00, 0x00, 0x00, # p_offset
+ 0x00, 0x00, 0x10, 0x00, # p_vaddr: Segment virtual address
+ 0x00, 0x00, 0x10, 0x00, # p_paddr: Segment physical address
+ 0x00, 0x00, 0x20, 0x00, # p_filesz: Segment size in file
+ 0x00, 0x00, 0x20, 0x00, # p_memsz: Segment size in memory
+ 0x07, 0x00, 0x00, 0x00, # p_flags = Segment is executable | writable | readable
+ 0x00, 0x00, 0x00, 0x00, # p_align
+ # - ELFNOTE segment
+ 0x04, 0x00, 0x00, 0x00, # p_type = PT_NOTE
+ 0x74, 0x00, 0x00, 0x00, # p_offset = point to XEN_ELFNOTE_PHYS32_ENTRY below
+ 0x74, 0x00, 0x10, 0x00,
+ 0x74, 0x00, 0x10, 0x00,
+ 0x14, 0x00, 0x00, 0x00,
+ 0x14, 0x00, 0x00, 0x00,
+ 0x04, 0x00, 0x00, 0x00, # p_flags = Segment is readable
+ 0x00, 0x00, 0x00, 0x00,
+
+ # XEN_ELFNOTE_PHYS32_ENTRY
+ 0x04, 0x00, 0x00, 0x00, # name size
+ 0x04, 0x00, 0x00, 0x00, # desc size
+ 0x12, 0x00, 0x00, 0x00, # type = XEN_ELFNOTE_PHYS32_ENTRY
+ 0x58, 0x65, 0x6e, 0x00, # name = "Xen"
+ 0xd0, 0xff, 0x2f, 0x00, # desc: PVH entry point
+ 0x00
+}
+
+!if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
+0x0000e000|0x00001000
+!endif
+!if $(FD_SIZE_IN_KB) == 4096
+0x00040000|0x00001000
+!endif
+#NV_EVENT_LOG
+
+!if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
+0x0000f000|0x00001000
+!endif
+!if $(FD_SIZE_IN_KB) == 4096
+0x00041000|0x00001000
+!endif
+#NV_FTW_WORKING
+DATA = {
+ # EFI_FAULT_TOLERANT_WORKING_BLOCK_HEADER->Signature = gEdkiiWorkingBlockSignatureGuid =
+ # { 0x9e58292b, 0x7c68, 0x497d, { 0xa0, 0xce, 0x65, 0x0, 0xfd, 0x9f, 0x1b, 0x95 }}
+ 0x2b, 0x29, 0x58, 0x9e, 0x68, 0x7c, 0x7d, 0x49,
+ 0xa0, 0xce, 0x65, 0x0, 0xfd, 0x9f, 0x1b, 0x95,
+ # Crc:UINT32 #WorkingBlockValid:1, WorkingBlockInvalid:1, Reserved
+ 0x2c, 0xaf, 0x2c, 0x64, 0xFE, 0xFF, 0xFF, 0xFF,
+ # WriteQueueSize: UINT64
+ 0xE0, 0x0F, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+}
+
+!if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
+0x00010000|0x00010000
+!endif
+!if $(FD_SIZE_IN_KB) == 4096
+0x00042000|0x00042000
+!endif
+#NV_FTW_SPARE
+
$(VARS_SIZE)|$(FVMAIN_SIZE)
FV = FVMAIN_COMPACT
diff --git a/OvmfPkg/OvmfXenElfHeaderGenerator.c b/OvmfPkg/OvmfXenElfHeaderGenerator.c
new file mode 100644
index 0000000000..6cbad8fbf7
--- /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;
+}
--
Anthony PERARD
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