powerpc/vdso: remove deprecated VDS64_HAS_DESCRIPTORS references

The original 2005 patch that introduced the powerpc vdso, pre-git
("ppc64: Implement a vDSO and use it for signal trampoline") notes that:

  ... symbols exposed by the vDSO aren't "normal" function symbols, apps
  can't be expected to link against them directly, the vDSO's are both
  seen as if they were linked at 0 and the symbols just contain offsets
  to the various functions.  This is done on purpose to avoid a
  relocation step (ppc64 functions normally have descriptors with abs
  addresses in them).  When glibc uses those functions, it's expected to
  use it's own trampolines that know how to reach them.

Despite that explanation, there remains dead #ifdef
VDS64_HAS_DESCRIPTORS code-blocks that provide alternate function
definitions that setup function descriptors.

Since VDS64_HAS_DESCRIPTORS has been unused for all these years, we
might as well finally remove it from the codebase.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200224211848.26087-1-joe.lawrence@redhat.com

arch/powerpc/include/asm/vdso.h

@@ -13,9 +13,6 @@
 
 #define VDSO_VERSION_STRING	LINUX_2.6.15
 
-/* Define if 64 bits VDSO has procedure descriptors */
-#undef VDS64_HAS_DESCRIPTORS
-
 #ifndef __ASSEMBLY__
 
 /* Offsets relative to thread->vdso_base */
@@ -28,25 +25,6 @@ int vdso_getcpu_init(void);
 #else /* __ASSEMBLY__ */
 
 #ifdef __VDSO64__
-#ifdef VDS64_HAS_DESCRIPTORS
-#define V_FUNCTION_BEGIN(name)		\
-	.globl name;			\
-        .section ".opd","a";		\
-        .align 3;			\
-	name:				\
-	.quad .name,.TOC.@tocbase,0;	\
-	.previous;			\
-	.globl .name;			\
-	.type .name,@function; 		\
-	.name:				\
-
-#define V_FUNCTION_END(name)		\
-	.size .name,.-.name;
-
-#define V_LOCAL_FUNC(name) (.name)
-
-#else /* VDS64_HAS_DESCRIPTORS */
-
 #define V_FUNCTION_BEGIN(name)		\
 	.globl name;			\
 	name:				\
@@ -55,8 +33,6 @@ int vdso_getcpu_init(void);
 	.size name,.-name;
 
 #define V_LOCAL_FUNC(name) (name)
-
-#endif /* VDS64_HAS_DESCRIPTORS */
 #endif /* __VDSO64__ */
 
 #ifdef __VDSO32__

arch/powerpc/kernel/vdso.c

@@ -391,12 +391,7 @@ static unsigned long __init find_function64(struct lib64_elfinfo *lib,
 		       symname);
 		return 0;
 	}
-#ifdef VDS64_HAS_DESCRIPTORS
-	return *((u64 *)(vdso64_kbase + sym->st_value - VDSO64_LBASE)) -
-		VDSO64_LBASE;
-#else
 	return sym->st_value - VDSO64_LBASE;
-#endif
 }
 
 static int __init vdso_do_func_patch64(struct lib32_elfinfo *v32,