[kvm-unit-tests RFC 01/16] x86 UEFI: Copy code from GNU-EFI

[Zixuan Wang <zixuanwang@google.com>]

To build x86 test cases with UEFI, we need to borrow a linker script
from GNU-EFI. This commit only copies the source code, without any
modification. The linker script will be used by KVM-Unit-Tests in the
following commits in this patch series.

The following source code is copied from GNU-EFI:
   1. x86/efi/elf_x86_64_efi.lds

We will put EFI-specific files under a new dir `x86/efi` because:
   1. EFI-related code is easy to find
   2. EFI-related code is separated from the original code in `x86/`
   3. EFI-related code can still reuse the Makefile and test case code
      in its parent dir `x86/`

GNU-EFI repo and version:
   GIT URL: https://git.code.sf.net/p/gnu-efi/code
   Commit ID: 4fe83e102674
   Website: https://sourceforge.net/p/gnu-efi/code/ci/4fe83e/tree/

Signed-off-by: Zixuan Wang <zixuanwang@google.com>
---
 x86/efi/README.md          | 25 +++++++++++++
 x86/efi/elf_x86_64_efi.lds | 77 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)
 create mode 100644 x86/efi/README.md
 create mode 100644 x86/efi/elf_x86_64_efi.lds

diff --git a/x86/efi/README.md b/x86/efi/README.md
new file mode 100644
index 0000000..4deba6e
--- /dev/null
+++ b/x86/efi/README.md
@@ -0,0 +1,25 @@
+# EFI Startup Code and Linker Script
+
+This dir contains a linker script copied from
+[GNU-EFI](https://sourceforge.net/projects/gnu-efi/):
+   - elf_x86_64_efi.lds: linker script to build an EFI application
+
+The following pre-compiled object files ship with GNU-EFI library, and are used
+to build KVM-Unit-Tests with GNU-EFI:
+   - crt0-efi-x86_64.o: startup code of an EFI application
+   - libgnuefi.a: position independent x86_64 ELF shared object relocator
+
+EFI application binaries should be relocatable as UEFI loads binaries to dynamic
+runtime addresses. To build such relocatable binaries, GNU-EFI utilizes the
+above-mentioned files in its build process:
+
+   1. build an ELF shared object and link it using linker script
+      `elf_x86_64_efi.lds` to organize the sections in a way UEFI recognizes
+   2. link the shared object with self-relocator `libgnuefi.a` that applies
+      dynamic relocations that may be present in the shared object
+   3. link the entry point code `crt0-efi-x86_64.o` that invokes self-relocator
+      and then jumps to EFI application's `efi_main()` function
+   4. convert the shared object to an EFI binary
+
+More details can be found in `GNU-EFI/README.gnuefi`, section "Building
+Relocatable Binaries".
diff --git a/x86/efi/elf_x86_64_efi.lds b/x86/efi/elf_x86_64_efi.lds
new file mode 100644
index 0000000..5eae376
--- /dev/null
+++ b/x86/efi/elf_x86_64_efi.lds
@@ -0,0 +1,77 @@
+/* Copied from GNU-EFI/gnuefi/elf_x86_64_efi.lds, licensed under GNU GPL */
+/* Same as elf_x86_64_fbsd_efi.lds, except for OUTPUT_FORMAT below - KEEP IN SYNC */
+OUTPUT_FORMAT("elf64-x86-64", "elf64-x86-64", "elf64-x86-64")
+OUTPUT_ARCH(i386:x86-64)
+ENTRY(_start)
+SECTIONS
+{
+  . = 0;
+  ImageBase = .;
+  /* .hash and/or .gnu.hash MUST come first! */
+  .hash : { *(.hash) }
+  .gnu.hash : { *(.gnu.hash) }
+  . = ALIGN(4096);
+  .eh_frame : 
+  { 
+    *(.eh_frame)
+  }
+  . = ALIGN(4096);
+  .text :
+  {
+   _text = .;
+   *(.text)
+   *(.text.*)
+   *(.gnu.linkonce.t.*)
+   . = ALIGN(16);
+  }
+  _etext = .;
+  _text_size = . - _text;
+  . = ALIGN(4096);
+  .reloc :
+  {
+   *(.reloc)
+  }
+  . = ALIGN(4096);
+  .data :
+  {
+   _data = .;
+   *(.rodata*)
+   *(.got.plt)
+   *(.got)
+   *(.data*)
+   *(.sdata)
+   /* the EFI loader doesn't seem to like a .bss section, so we stick
+      it all into .data: */
+   *(.sbss)
+   *(.scommon)
+   *(.dynbss)
+   *(.bss)
+   *(COMMON)
+   *(.rel.local)
+  }
+  .note.gnu.build-id : { *(.note.gnu.build-id) }
+
+  _edata = .;
+  _data_size = . - _etext;
+  . = ALIGN(4096);
+  .dynamic  : { *(.dynamic) }
+  . = ALIGN(4096);
+  .rela :
+  {
+    *(.rela.data*)
+    *(.rela.got)
+    *(.rela.stab)
+  }
+  . = ALIGN(4096);
+  .dynsym   : { *(.dynsym) }
+  . = ALIGN(4096);
+  .dynstr   : { *(.dynstr) }
+  . = ALIGN(4096);
+  .ignored.reloc :
+  {
+    *(.rela.reloc)
+    *(.eh_frame)
+    *(.note.GNU-stack)
+  }
+  .comment 0 : { *(.comment) }
+}
-- 
2.33.0.rc1.237.g0d66db33f3-goog