Add support for loading little endian ELF binaries.

We byte swap the entire header in place in elf_check_file.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>

4 files changed, 102 insertions, 6 deletions

diff --git a/include/libelf.h b/include/libelf.h
index 9446fcf..495d697 100644
--- a/include/libelf.h
+++ b/include/libelf.h
@@ -26,6 +26,10 @@
 #define ET_DYN		3	/* Shared object file */
 #define ET_CORE		4	/* Core file */
 
+/* ELF object endian */
+#define ELFDATA2LSB	1	/* 2's complement, little endian */
+#define ELFDATA2MSB	2	/* 2's complement, big endian */
+
 /* Generic ELF header */
 struct ehdr {
 	uint32_t ei_ident;
@@ -72,6 +76,9 @@ int elf_load_file_to_addr(void *file_addr, void *addr, unsigned long *entry,
                           int (*pre_load)(void*, long),
                           void (*post_load)(void*, long));
 
+void elf_byteswap_header32(void *file_addr);
+void elf_byteswap_header64(void *file_addr);
+
 unsigned int elf_load_segments32(void *file_addr, signed long offset,
                                  int (*pre_load)(void*, long),
                                  void (*post_load)(void*, long));
diff --git a/lib/libelf/elf.c b/lib/libelf/elf.c
index 33d9211..1340103 100644
--- a/lib/libelf/elf.c
+++ b/lib/libelf/elf.c
@@ -33,19 +33,28 @@ static int
 elf_check_file(unsigned long *file_addr)
 {
 	struct ehdr *ehdr = (struct ehdr *) file_addr;
+	uint8_t native_endian;
+
 	/* check if it is an ELF image at all */
 	if (cpu_to_be32(ehdr->ei_ident) != 0x7f454c46)
 		return -1;
 
-	/* endian check */
 #ifdef __BIG_ENDIAN__
-	if (ehdr->ei_data != 2)
-		/* not a big endian image */
+	native_endian = ELFDATA2MSB;
 #else
-	if (ehdr->ei_data == 2)
-		/* not a little endian image */
+	native_endian = ELFDATA2LSB;
 #endif
-		return -2;
+
+	if (native_endian != ehdr->ei_data) {
+		switch (ehdr->ei_class) {
+		case 1:
+			elf_byteswap_header32(file_addr);
+			break;
+		case 2:
+			elf_byteswap_header64(file_addr);
+			break;
+		}
+	}
 
 	/* check if it is an ELF executable ... and also
 	 * allow DYN files, since this is specified by ePAPR */
diff --git a/lib/libelf/elf32.c b/lib/libelf/elf32.c
index 840df5d..3f5f374 100644
--- a/lib/libelf/elf32.c
+++ b/lib/libelf/elf32.c
@@ -16,6 +16,7 @@
  
 #include <string.h>
 #include <libelf.h>
+#include <byteorder.h>
 
 struct ehdr32 {
 	uint32_t ei_ident;
@@ -142,3 +143,42 @@ elf_get_base_addr32(void *file_addr)
 
 	return 0;
 }
+
+void
+elf_byteswap_header32(void *file_addr)
+{
+	struct ehdr32 *ehdr = (struct ehdr32 *) file_addr;
+	struct phdr32 *phdr;
+	int i;
+
+	bswap_16p(&ehdr->e_type);
+	bswap_16p(&ehdr->e_machine);
+	bswap_32p(&ehdr->e_version);
+	bswap_32p(&ehdr->e_entry);
+	bswap_32p(&ehdr->e_phoff);
+	bswap_32p(&ehdr->e_shoff);
+	bswap_32p(&ehdr->e_flags);
+	bswap_16p(&ehdr->e_ehsize);
+	bswap_16p(&ehdr->e_phentsize);
+	bswap_16p(&ehdr->e_phnum);
+	bswap_16p(&ehdr->e_shentsize);
+	bswap_16p(&ehdr->e_shnum);
+	bswap_16p(&ehdr->e_shstrndx);
+
+	phdr = get_phdr32(file_addr);
+
+	/* loop e_phnum times */
+	for (i = 0; i <= ehdr->e_phnum; i++) {
+		bswap_32p(&phdr->p_type);
+		bswap_32p(&phdr->p_offset);
+		bswap_32p(&phdr->p_vaddr);
+		bswap_32p(&phdr->p_paddr);
+		bswap_32p(&phdr->p_filesz);
+		bswap_32p(&phdr->p_memsz);
+		bswap_32p(&phdr->p_flags);
+		bswap_32p(&phdr->p_align);
+
+		/* step to next header */
+		phdr = (struct phdr32 *)(((uint8_t *)phdr) + ehdr->e_phentsize);
+	}
+}
diff --git a/lib/libelf/elf64.c b/lib/libelf/elf64.c
index 78b7697..faddbfb 100644
--- a/lib/libelf/elf64.c
+++ b/lib/libelf/elf64.c
@@ -19,6 +19,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <libelf.h>
+#include <byteorder.h>
 
 struct ehdr64
 {
@@ -422,3 +423,42 @@ elf_relocate64(void *file_addr, signed long offset)
 		}
 	}
 }
+
+void
+elf_byteswap_header64(void *file_addr)
+{
+	struct ehdr64 *ehdr = (struct ehdr64 *) file_addr;
+	struct phdr64 *phdr;
+	int i;
+
+	bswap_16p(&ehdr->e_type);
+	bswap_16p(&ehdr->e_machine);
+	bswap_32p(&ehdr->e_version);
+	bswap_64p(&ehdr->e_entry);
+	bswap_64p(&ehdr->e_phoff);
+	bswap_64p(&ehdr->e_shoff);
+	bswap_32p(&ehdr->e_flags);
+	bswap_16p(&ehdr->e_ehsize);
+	bswap_16p(&ehdr->e_phentsize);
+	bswap_16p(&ehdr->e_phnum);
+	bswap_16p(&ehdr->e_shentsize);
+	bswap_16p(&ehdr->e_shnum);
+	bswap_16p(&ehdr->e_shstrndx);
+
+	phdr = get_phdr64(file_addr);
+
+	/* loop e_phnum times */
+	for (i = 0; i <= ehdr->e_phnum; i++) {
+		bswap_32p(&phdr->p_type);
+		bswap_32p(&phdr->p_flags);
+		bswap_64p(&phdr->p_offset);
+		bswap_64p(&phdr->p_vaddr);
+		bswap_64p(&phdr->p_paddr);
+		bswap_64p(&phdr->p_filesz);
+		bswap_64p(&phdr->p_memsz);
+		bswap_64p(&phdr->p_align);
+
+		/* step to next header */
+		phdr = (struct phdr64 *)(((uint8_t *)phdr) + ehdr->e_phentsize);
+	}
+}