Revert "ANDROID: Revert "arm: move ELF_ET_DYN_BASE to 4MB""

This reverts commit 040c05c6e4.

ASan can handle the new memory layout in Android P and later, which
means this change can be reverted in 4.14.

Bug: 67425063
Signed-off-by: Evgenii Stepanov <eugenis@google.com>
Change-Id: I128de2797bca0bc17fe991e1cb48788ecf5f25de

arch/arm/include/asm/elf.h

@@ -113,12 +113,8 @@ int dump_task_regs(struct task_struct *t, elf_gregset_t *elfregs);
 #define CORE_DUMP_USE_REGSET
 #define ELF_EXEC_PAGESIZE	4096
 
-/* This is the location that an ET_DYN program is loaded if exec'ed.  Typical
-   use of this is to invoke "./ld.so someprog" to test out a new version of
-   the loader.  We need to make sure that it is out of the way of the program
-   that it will "exec", and that there is sufficient room for the brk.  */
-
-#define ELF_ET_DYN_BASE	(TASK_SIZE / 3 * 2)
+/* This is the base location for PIE (ET_DYN with INTERP) loads. */
+#define ELF_ET_DYN_BASE		0x400000UL
 
 /* When the program starts, a1 contains a pointer to a function to be 
    registered with atexit, as per the SVR4 ABI.  A value of 0 means we