arm: Introduce and use GET_TLS

Factor out the sequence needed to call kuser_get_tls, as we can't
play subtract into pc games in thumb mode.  Prepare for hard-tp,
pulling the save of LR into the macro.

6 files changed, 40 insertions, 22 deletions

diff --git a/ports/sysdeps/unix/sysv/linux/arm/aeabi_read_tp.S b/ports/sysdeps/unix/sysv/linux/arm/aeabi_read_tp.S
index c4ddbc69ff..ecdc3228a3 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/aeabi_read_tp.S
+++ b/ports/sysdeps/unix/sysv/linux/arm/aeabi_read_tp.S
@@ -41,6 +41,12 @@
 
 	.hidden __aeabi_read_tp
 ENTRY (__aeabi_read_tp)
+#ifdef __thumb2__
+	movw	r0, #0x0fe0
+	movt	r0, #0xffff
+	bx	r0
+#else
 	mov	r0, #0xffff0fff
 	sub	pc, r0, #31
+#endif
 END (__aeabi_read_tp)
diff --git a/ports/sysdeps/unix/sysv/linux/arm/clone.S b/ports/sysdeps/unix/sysv/linux/arm/clone.S
index 653bd74102..9009393f33 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/clone.S
+++ b/ports/sysdeps/unix/sysv/linux/arm/clone.S
@@ -74,9 +74,7 @@ PSEUDO_END (__clone)
 #ifdef RESET_PID
 	tst	ip, #CLONE_THREAD
 	bne	3f
-	mov	r0, #0xffff0fff
-	mov	lr, pc
-	sub	pc, r0, #31
+	GET_TLS (lr)
 	mov	r1, r0
 	tst	ip, #CLONE_VM
 	ldr	r7, =SYS_ify(getpid)
diff --git a/ports/sysdeps/unix/sysv/linux/arm/nptl/pt-vfork.S b/ports/sysdeps/unix/sysv/linux/arm/nptl/pt-vfork.S
index f79bb66f2b..ca50457070 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/nptl/pt-vfork.S
+++ b/ports/sysdeps/unix/sysv/linux/arm/nptl/pt-vfork.S
@@ -19,15 +19,7 @@
 
 /* Save the PID value.  */
 #define SAVE_PID \
-	str	lr, [sp, #-4]!;		/* Save LR.  */			\
-	cfi_adjust_cfa_offset (4);					\
-	cfi_rel_offset (lr, 0);						\
-	mov	r0, #0xffff0fff;	/* Point to the high page.  */	\
-	mov	lr, pc;			/* Save our return address.  */	\
-	sub	pc, r0, #31;		/* Jump to the TLS entry.  */	\
-	ldr	lr, [sp], #4;		/* Restore LR.  */		\
-	cfi_adjust_cfa_offset (-4);					\
-	cfi_restore (lr);						\
+	GET_TLS (r2);							\
 	NEGOFF_ADJ_BASE2 (r2, r0, PID_OFFSET); /* Save the TLS addr in r2. */ \
 	ldr	r3, NEGOFF_OFF1 (r2, PID_OFFSET); /* Load the saved PID.  */  \
 	rsb	r0, r3, #0;		/* Negate it.  */		     \
diff --git a/ports/sysdeps/unix/sysv/linux/arm/nptl/sysdep-cancel.h b/ports/sysdeps/unix/sysv/linux/arm/nptl/sysdep-cancel.h
index 9157d03270..2fc053523f 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/nptl/sysdep-cancel.h
+++ b/ports/sysdeps/unix/sysv/linux/arm/nptl/sysdep-cancel.h
@@ -216,7 +216,7 @@ extern int __local_multiple_threads attribute_hidden;
 	stmfd	sp!, {r0, lr};						\
 	cfi_adjust_cfa_offset (8);					\
 	cfi_rel_offset (lr, 4);						\
-	bl	__aeabi_read_tp;					\
+	GET_TLS (lr);							\
 	NEGOFF_ADJ_BASE (r0, MULTIPLE_THREADS_OFFSET);			\
 	ldr	ip, NEGOFF_OFF1 (r0, MULTIPLE_THREADS_OFFSET);		\
 	ldmfd	sp!, {r0, lr};						\
diff --git a/ports/sysdeps/unix/sysv/linux/arm/nptl/vfork.S b/ports/sysdeps/unix/sysv/linux/arm/nptl/vfork.S
index 1c6f3bb2bf..216fb2d2eb 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/nptl/vfork.S
+++ b/ports/sysdeps/unix/sysv/linux/arm/nptl/vfork.S
@@ -19,15 +19,7 @@
 
 /* Save the PID value.  */
 #define SAVE_PID \
-	str	lr, [sp, #-4]!;		/* Save LR.  */			\
-	cfi_adjust_cfa_offset (4);					\
-	cfi_rel_offset (lr, 0);						\
-	mov	r0, #0xffff0fff;	/* Point to the high page.  */	\
-	mov	lr, pc;			/* Save our return address.  */	\
-	sub	pc, r0, #31;		/* Jump to the TLS entry.  */	\
-	ldr	lr, [sp], #4;		/* Restore LR.  */		\
-	cfi_adjust_cfa_offset (-4);					\
-	cfi_restore (lr);						\
+	GET_TLS (r2);							\
 	NEGOFF_ADJ_BASE2 (r2, r0, PID_OFFSET); /* Save the TLS addr in r2.  */ \
 	ldr	r3, NEGOFF_OFF1 (r2, PID_OFFSET); /* Load the saved PID.  */   \
 	rsbs	r0, r3, #0;		/* Negate it.  */		      \
diff --git a/ports/sysdeps/unix/sysv/linux/arm/sysdep.h b/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
index 89208a9f19..dc2058b275 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
+++ b/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
@@ -45,6 +45,36 @@
 
 #ifdef __ASSEMBLER__
 
+/* Internal macro calling the linux kernel kuser_get_tls helper.
+   Note that in thumb mode, a constant pool break is often out of range, so
+   we always expand the constant inline.  */
+#ifdef __thumb2__
+# define GET_TLS_BODY			\
+	movw	r0, #0x0fe0;		\
+	movt	r0, #0xffff;		\
+	blx	r0
+#else
+# define GET_TLS_BODY \
+	mov	r0, #0xffff0fff;	/* Point to the high page.  */	\
+	mov	lr, pc;			/* Save our return address.  */	\
+	sub	pc, r0, #31		/* Jump to the TLS entry.  */
+#endif
+
+/* Helper to get the TLS base pointer.  Save LR in TMP, return in R0,
+   and no other registers clobbered.  TMP may be LR itself to indicate
+   that no save is necessary.  */
+#undef GET_TLS
+#define GET_TLS(TMP)			\
+  .ifnc TMP, lr;			\
+	mov	TMP, lr;		\
+	cfi_register (lr, TMP);		\
+	GET_TLS_BODY;			\
+	mov	lr, TMP;		\
+	cfi_restore (lr);		\
+  .else;				\
+	GET_TLS_BODY;			\
+  .endif
+
 /* Linux uses a negative return value to indicate syscall errors,
    unlike most Unices, which use the condition codes' carry flag.