powerpc: Align vDSO base address

The ABI specifies a 64K alignment, we need to map the vDSO accordingly
Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/vdso.c

@@ -50,6 +50,9 @@
 /* Max supported size for symbol names */
 #define MAX_SYMNAME	64
 
+/* The alignment of the vDSO */
+#define VDSO_ALIGNMENT	(1 << 16)
+
 extern char vdso32_start, vdso32_end;
 static void *vdso32_kbase = &vdso32_start;
 static unsigned int vdso32_pages;
@@ -231,15 +234,21 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	 * pick a base address for the vDSO in process space. We try to put it
 	 * at vdso_base which is the "natural" base for it, but we might fail
 	 * and end up putting it elsewhere.
+	 * Add enough to the size so that the result can be aligned.
 	 */
 	down_write(&mm->mmap_sem);
 	vdso_base = get_unmapped_area(NULL, vdso_base,
-				      vdso_pages << PAGE_SHIFT, 0, 0);
+				      (vdso_pages << PAGE_SHIFT) +
+				      ((VDSO_ALIGNMENT - 1) & PAGE_MASK),
+				      0, 0);
 	if (IS_ERR_VALUE(vdso_base)) {
 		rc = vdso_base;
 		goto fail_mmapsem;
 	}
 
+	/* Add required alignment. */
+	vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
+
 	/*
 	 * Put vDSO base into mm struct. We need to do this before calling
 	 * install_special_mapping or the perf counter mmap tracking code