[PATCH roland/arm-sfi-tlsdesc] ARM: Make dl-tlsdesc.S use sfi_breg, respect ARM_ALWAYS_BX and ARM_NO_INDEX_REGISTER.

[Roland McGrath <roland@hack.frob.com>]

Verified on armv7l-linux-gnueabihf that no object code changes.

There is lots more nontrivial work involved in making dynamic linking work
for arm-nacl and I'm not tackling that yet.  But it was easy enough to hack
up dl-tlsdesc.S in isolation, so I did it early.


Thanks,
Roland


ports/ChangeLog.arm
2013-03-15  Roland McGrath  <roland@hack.frob.com>

	* sysdeps/arm/dl-tlsdesc.S: Include <arm-features.h>.
	Use sfi_breg macro throughout.
	(_dl_tlsdesc_dynamic) [!ARM_NO_INDEX_REGISTER]: Avoid two-register
	addressing mode.
	(_dl_tlsdesc_dynamic) [ARM_ALWAYS_BX]: Don't pop into pc.

	* sysdeps/arm/arm-features.h: Add comment for ARM_NO_INDEX_REGISTER.

--- a/ports/sysdeps/arm/arm-features.h
+++ b/ports/sysdeps/arm/arm-features.h
@@ -53,4 +53,7 @@
 # define ARM_BX_ALIGN_LOG2	2
 #endif
 
+/* An OS-specific arm-features.h file may define ARM_NO_INDEX_REGISTER to
+   indicate that the two-register addressing modes must never be used.  */
+
 #endif  /* arm-features.h */
--- a/ports/sysdeps/arm/dl-tlsdesc.S
+++ b/ports/sysdeps/arm/dl-tlsdesc.S
@@ -17,6 +17,7 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <sysdep.h>
+#include <arm-features.h>
 #include <tls.h>
 #include "tlsdesc.h"
 
@@ -31,7 +32,8 @@
 	.fnstart
 	.align 2
 _dl_tlsdesc_return:
-	ldr	r0, [r0]
+	sfi_breg r0, \
+	ldr	r0, [\B]
 	BX	(lr)
 	.fnend
 	cfi_endproc
@@ -90,16 +92,27 @@ _dl_tlsdesc_dynamic:
 	cfi_rel_offset (r3,4)
 	cfi_rel_offset (r4,8)
 	cfi_rel_offset (lr,12)
-	ldr	r1, [r0] /* td */
+	sfi_breg r0, \
+	ldr	r1, [\B] /* td */
 	GET_TLS (lr)
 	mov	r4, r0 /* r4 = tp */
-	ldr	r0, [r0]
-	ldr	r2, [r1, #8] /* gen_count */
-	ldr	r3, [r0]
+	sfi_breg r0, \
+	ldr	r0, [\B]
+	sfi_breg r1, \
+	ldr	r2, [\B, #8] /* gen_count */
+	sfi_breg r0, \
+	ldr	r3, [\B]
 	cmp	r2, r3
 	bhi	1f
-	ldr	r3, [r1]
+	sfi_breg r1, \
+	ldr	r3, [\B]
+#ifndef ARM_NO_INDEX_REGISTER
 	ldr	r2, [r0, r3, lsl #3]
+#else
+	add	lr, r0, r3, lsl #3
+	sfi_breg lr, \
+	ldr	r2, [\B]
+#endif
 	cmn	r2, #1
 	ittt	ne
 	ldrne	r3, [r1, #4]
@@ -110,7 +123,8 @@ _dl_tlsdesc_dynamic:
 	bl	__tls_get_addr
 	rsb	r0, r4, r0
 2:
-#if defined (__ARM_ARCH_4T__) && defined (__THUMB_INTERWORK__)
+#if ((defined (__ARM_ARCH_4T__) && defined (__THUMB_INTERWORK__)) \
+     || defined (ARM_ALWAYS_BX))
 	pop	{r2,r3,r4, lr}
 	cfi_adjust_cfa_offset (-16)
 	cfi_restore (lr)
@@ -163,7 +177,8 @@ _dl_tlsdesc_lazy_resolver:
 	pop	{r2}
 	cfi_adjust_cfa_offset (-4)
 	cfi_restore (r2)
-	ldr	r1, [r0, #4]
+	sfi_breg r0, \
+	ldr	r1, [\B, #4]
 	BX	(r1)
 	.fnend
 	cfi_endproc
@@ -202,7 +217,8 @@ _dl_tlsdesc_resolve_hold:
 	pop	{r2}
 	cfi_adjust_cfa_offset (-4)
 	cfi_restore (r2)
-	ldr     r1, [r0, #4]
+	sfi_breg r0, \
+	ldr     r1, [\B, #4]
 	BX      (r1)
 	.fnend
 	cfi_endproc