loader: Allow ELF loader to auto-detect the ELF arch

If the caller didn't specify an architecture for the ELF machine
the load_elf() function will auto detect it based on the ELF file.
Signed-off-by: NAlistair Francis <alistair.francis@xilinx.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: f2d70b47fcad31445f947f8817a0e146d80a046b.1474331683.git.alistair.francis@xilinx.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

include/hw/elf_ops.h

@@ -280,6 +280,11 @@ static int glue(load_elf, SZ)(const char *name, int fd,
         glue(bswap_ehdr, SZ)(&ehdr);
     }
 
+    if (elf_machine <= EM_NONE) {
+        /* The caller didn't specify an ARCH, we can figure it out */
+        elf_machine = ehdr.e_machine;
+    }
+
     switch (elf_machine) {
         case EM_PPC64:
             if (ehdr.e_machine != EM_PPC64) {

include/hw/loader.h

@@ -68,6 +68,8 @@ const char *load_elf_strerror(int error);
  * load will fail if the target ELF does not match. Some architectures
  * have some architecture-specific behaviours that come into effect when
  * their particular values for @elf_machine are set.
+ * If @elf_machine is EM_NONE then the machine type will be read from the
+ * ELF header and no checks will be carried out against the machine type.
  */
 
 int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),