grub2/debian/patches/elf_bi_endian.patch

From 4a42ac8d567ce0a74687f2da6afb9e88f6d4099d Mon Sep 17 00:00:00 2001
From: Tomohiro B Berry <tbberry@us.ibm.com>
Date: Tue, 14 Jan 2014 17:43:25 +0000
Subject: Add bi-endian support to ELF parser

This patch adds bi-endian support for both 32-bit and 64-bit elf files.

It compares the native endianness to the endianness of the elf file, and
swaps the header bytes if necessary.  This will allow, for example,
32-bit Big Endian grub to load a 64-bit Little Endian kernel.

Origin: other, https://lists.gnu.org/archive/html/grub-devel/2014-01/msg00039.html

Patch-Name: elf_bi_endian.patch
---
 grub-core/kern/elf.c   | 55 ++++++++++++++++++++++++++++++++++++++++++++++++--
 grub-core/kern/elfXX.c | 43 +++++++++++++++++++++++++++++++++++++++
 include/grub/elf.h     |  7 +++++++
 3 files changed, 103 insertions(+), 2 deletions(-)

diff --git a/grub-core/kern/elf.c b/grub-core/kern/elf.c
index 5f99c43..9a3cc71 100644
--- a/grub-core/kern/elf.c
+++ b/grub-core/kern/elf.c
@@ -28,20 +28,45 @@
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
+void grub_elf32_byteswap_header (grub_elf_t elf);
+void grub_elf64_byteswap_header (grub_elf_t elf);
+grub_err_t grub_elf32_check_version (grub_elf_t elf);
+grub_err_t grub_elf64_check_version (grub_elf_t elf);
+
 /* Check if EHDR is a valid ELF header.  */
 static grub_err_t
 grub_elf_check_header (grub_elf_t elf)
 {
+  /* e_ident is the same for both 64-bit and 32-bit so just load into a 32-bit struct for now */
   Elf32_Ehdr *e = &elf->ehdr.ehdr32;
 
+  /* check if it is an ELF image at all */
   if (e->e_ident[EI_MAG0] != ELFMAG0
       || e->e_ident[EI_MAG1] != ELFMAG1
       || e->e_ident[EI_MAG2] != ELFMAG2
       || e->e_ident[EI_MAG3] != ELFMAG3
-      || e->e_ident[EI_VERSION] != EV_CURRENT
-      || e->e_version != EV_CURRENT)
+      || e->e_ident[EI_VERSION] != EV_CURRENT)
     return grub_error (GRUB_ERR_BAD_OS, N_("invalid arch-independent ELF magic"));
 
+  switch (e->e_ident[EI_CLASS])
+    {
+      case ELFCLASS32:
+        if (e->e_ident[EI_DATA] != ELFDATA_NATIVE)
+          grub_elf32_byteswap_header (elf);
+        if (grub_elf32_check_version (elf) != GRUB_ERR_NONE)
+          return grub_errno;
+        break;
+      case ELFCLASS64:
+        if (e->e_ident[EI_DATA] != ELFDATA_NATIVE)
+          grub_elf64_byteswap_header (elf);
+        if (grub_elf64_check_version (elf) != GRUB_ERR_NONE)
+          return grub_errno;
+        break;
+      default:
+        return grub_error (GRUB_ERR_BAD_OS, N_("unrecognized ELF class"));
+        break;
+    }
+
   return GRUB_ERR_NONE;
 }
 
@@ -127,7 +152,16 @@ grub_elf_open (const char *name)
 #define grub_elf_is_elfXX grub_elf_is_elf32
 #define grub_elfXX_load_phdrs grub_elf32_load_phdrs
 #define ElfXX_Phdr Elf32_Phdr
+#define ElfXX_Ehdr Elf32_Ehdr
 #define grub_uintXX_t grub_uint32_t
+/* for phdr/ehdr byte swaps */
+#define byte_swap_halfXX grub_swap_bytes16
+#define byte_swap_wordXX grub_swap_bytes32
+#define byte_swap_addrXX grub_swap_bytes32
+#define byte_swap_offXX grub_swap_bytes32
+#define byte_swap_XwordXX byte_swap_wordXX /* the 64-bit phdr uses Xwords and the 32-bit uses words */
+#define grub_elfXX_byteswap_header grub_elf32_byteswap_header
+#define grub_elfXX_check_version grub_elf32_check_version
 
 #include "elfXX.c"
 
@@ -140,7 +174,15 @@ grub_elf_open (const char *name)
 #undef grub_elf_is_elfXX
 #undef grub_elfXX_load_phdrs
 #undef ElfXX_Phdr
+#undef ElfXX_Ehdr
 #undef grub_uintXX_t
+#undef byte_swap_halfXX
+#undef byte_swap_wordXX
+#undef byte_swap_addrXX
+#undef byte_swap_offXX
+#undef byte_swap_XwordXX
+#undef grub_elfXX_byteswap_header
+#undef grub_elfXX_check_version
 
 
 /* 64-bit */
@@ -153,6 +195,15 @@ grub_elf_open (const char *name)
 #define grub_elf_is_elfXX grub_elf_is_elf64
 #define grub_elfXX_load_phdrs grub_elf64_load_phdrs
 #define ElfXX_Phdr Elf64_Phdr
+#define ElfXX_Ehdr Elf64_Ehdr
 #define grub_uintXX_t grub_uint64_t
+/* for phdr/ehdr byte swaps */
+#define byte_swap_halfXX grub_swap_bytes16
+#define byte_swap_wordXX grub_swap_bytes32
+#define byte_swap_addrXX grub_swap_bytes64
+#define byte_swap_offXX grub_swap_bytes64
+#define byte_swap_XwordXX grub_swap_bytes64
+#define grub_elfXX_byteswap_header grub_elf64_byteswap_header
+#define grub_elfXX_check_version grub_elf64_check_version
 
 #include "elfXX.c"
diff --git a/grub-core/kern/elfXX.c b/grub-core/kern/elfXX.c
index 1d09971..639cda6 100644
--- a/grub-core/kern/elfXX.c
+++ b/grub-core/kern/elfXX.c
@@ -154,3 +154,46 @@ grub_elfXX_load (grub_elf_t elf, const char *filename,
 
   return grub_errno;
 }
+
+void
+grub_elfXX_byteswap_header (grub_elf_t elf)
+{
+  ElfXX_Ehdr *e = &(elf->ehdr.ehdrXX);
+  ElfXX_Phdr *phdr;
+
+  e->e_type = byte_swap_halfXX (e->e_type);
+  e->e_machine = byte_swap_halfXX (e->e_machine);
+  e->e_version = byte_swap_wordXX (e->e_version);
+  e->e_entry = byte_swap_addrXX (e->e_entry);
+  e->e_phoff = byte_swap_offXX (e->e_phoff);
+  e->e_shoff = byte_swap_offXX (e->e_shoff);
+  e->e_flags = byte_swap_wordXX (e->e_flags);
+  e->e_ehsize = byte_swap_halfXX (e->e_ehsize);
+  e->e_phentsize = byte_swap_halfXX (e->e_phentsize);
+  e->e_phnum = byte_swap_halfXX (e->e_phnum);
+  e->e_shentsize = byte_swap_halfXX (e->e_shentsize);
+  e->e_shnum = byte_swap_halfXX (e->e_shnum);
+  e->e_shstrndx = byte_swap_halfXX (e->e_shstrndx);
+
+  FOR_ELFXX_PHDRS (elf,phdr)
+    {
+      phdr->p_type = byte_swap_wordXX (phdr->p_type);
+      phdr->p_flags = byte_swap_wordXX (phdr->p_flags);
+      phdr->p_offset = byte_swap_offXX (phdr->p_offset);
+      phdr->p_vaddr = byte_swap_addrXX (phdr->p_vaddr);
+      phdr->p_paddr = byte_swap_addrXX (phdr->p_paddr);
+      phdr->p_filesz = byte_swap_XwordXX (phdr->p_filesz);
+      phdr->p_memsz = byte_swap_XwordXX (phdr->p_memsz);
+      phdr->p_align = byte_swap_XwordXX (phdr->p_align);
+    }
+
+}
+
+grub_err_t
+grub_elfXX_check_version (grub_elf_t elf)
+{
+  if (elf->ehdr.ehdrXX.e_version != EV_CURRENT)
+    return grub_error (GRUB_ERR_BAD_OS, N_("invalid arch-independent ELF magic"));
+
+  return GRUB_ERR_NONE;
+}
diff --git a/include/grub/elf.h b/include/grub/elf.h
index caa7963..ca6e436 100644
--- a/include/grub/elf.h
+++ b/include/grub/elf.h
@@ -56,6 +56,13 @@ typedef grub_uint16_t Elf64_Section;
 typedef Elf32_Half Elf32_Versym;
 typedef Elf64_Half Elf64_Versym;
 
+/* Define the native endianness */
+
+#ifdef GRUB_CPU_WORDS_BIGENDIAN
+#define ELFDATA_NATIVE         ELFDATA2MSB
+#else
+#define ELFDATA_NATIVE         ELFDATA2LSB
+#endif
 
 /* The ELF file header.  This appears at the start of every ELF file.  */