Revert "powerpc/64s: Remove support for ELFv1 little endian userspace"

This reverts commit 606787fe.

ELFv1 with LE has never been a thing, and people who try to make ELFv1 LE
binaries are maniacs who need to be stopped, but unfortunately there are
ELFv1 LE binaries out there in the wild.

One such binary is the ppc64el (as Debian calls it) helper for
arch-test[0], a tool for detecting architectures that can be executed on a
given machine by means of attempting to execute helper binaries compiled
for each architecture and seeing which binaries succeed and fail. The
helpers are small snippets of assembly, and the ppc64el assembly doesn't
include the right directives to generate an ELFv2 binary.

This results in arch-test incorrectly determining that a ppc64el kernel
can't execute a ppc64el userspace, which in turn means that a number of
developer tools such as debootstrap will break (assuming arch-test is
installed).

[0] https://github.com/kilobyte/arch-testSigned-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230719071821.320594-1-ajd@linux.ibm.com

arch/powerpc/include/asm/elf.h

@@ -12,14 +12,8 @@
 
 /*
  * This is used to ensure we don't load something for the wrong architecture.
- * 64le only supports ELFv2 64-bit binaries (64be supports v1 and v2).
  */
-#if defined(CONFIG_PPC64) && defined(CONFIG_CPU_LITTLE_ENDIAN)
-#define elf_check_arch(x) (((x)->e_machine == ELF_ARCH) && \
-			   (((x)->e_flags & 0x3) == 0x2))
-#else
 #define elf_check_arch(x) ((x)->e_machine == ELF_ARCH)
-#endif
 #define compat_elf_check_arch(x)	((x)->e_machine == EM_PPC)
 
 #define CORE_DUMP_USE_REGSET

arch/powerpc/include/asm/thread_info.h

@@ -183,13 +183,9 @@ static inline bool test_thread_local_flags(unsigned int flags)
 #define clear_tsk_compat_task(tsk) do { } while (0)
 #endif
 
-#ifdef CONFIG_PPC64
-#ifdef CONFIG_CPU_BIG_ENDIAN
+#if defined(CONFIG_PPC64)
 #define is_elf2_task() (test_thread_flag(TIF_ELF2ABI))
 #else
-#define is_elf2_task() (1)
-#endif
-#else
 #define is_elf2_task() (0)
 #endif