hppa: start.S: rework references to fix PIE TEXTRELs [BZ #18421]

The startup code was not using PIC friendly references leading to TEXTRELs
in every PIE ELF.

ChangeLog

@@ -1,3 +1,11 @@
+2015-08-18  Alan Modra  <amodra@gmail.com>
+
+	[BZ #18421]
+	* sysdeps/hppa/start.S [SHARED]: Use .section .data.rel.ro and define
+	.Lp__global.
+	(_start): Load %dp via .Lp__global.
+	[!SHARED]: Use .section .rodata.
+
 2015-08-18  Mike Frysinger  <vapier@gentoo.org>
 
 	* sysdeps/unix/sysv/linux/hppa/bits/timerfd.h: New file.

sysdeps/hppa/start.S

@@ -42,7 +42,11 @@
 	/* Have the linker create plabel words so we get PLABEL32
 	   relocs and not 21/14.  The use of 21/14 relocs is only
 	   supported in the latest dynamic linker.  */
-	.section	.rodata
+#ifdef SHARED
+	.section	.data.rel.ro,"aw",@progbits
+#else
+	.section	.rodata,"a",@progbits
+#endif
 	.align 4
 .Lpmain:
 	.word P%main
@@ -52,6 +56,10 @@
 	.word P%__libc_csu_fini
 .Lp__libc_csu_init:
 	.word P%__libc_csu_init
+#ifdef SHARED
+.Lp__global:
+	.word $global$
+#endif
 
 	.text
 	.align 4
@@ -122,10 +130,14 @@ _start:
 	/* void *stack_end (7th argument) */
 	stw	%sp, -60(%sp)
 
+#ifdef SHARED
+	addil	LT'.Lp__global, %r19
+	ldw	RT'.Lp__global(%r1), %dp
+#else
 	/* load global */
 	ldil	L%$global$, %dp
 	ldo	R%$global$(%dp), %dp
-
+#endif
 	bl	__libc_start_main,%r2
 	nop
 	/* die horribly if it returned (it shouldn't) */