Paul Brook writes:

The attached patch adds support for compiling arm uClibc as pure Thumb code.  
This is needed because some recent ARM codes do not implement traditional ARM 
mode.  Specifically: 

* Cortex-M1 - An extremely minimal FPGA based core that only implements 
Thumb-1 (aka ARMv6-M).
* Cortex-M3 - A Thumb-2 only ARMv7-M core.

Most of uClibc already builds in Thumb mode, all that is left are a handful of 
assembly bits.

Tested on arm-uclinuxeabi.

1 files changed, 28 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/arm/bits/arm_asm.h b/libc/sysdeps/linux/arm/bits/arm_asm.h
new file mode 100644
index 000000000..1d87df6eb
--- /dev/null
+++ b/libc/sysdeps/linux/arm/bits/arm_asm.h
@@ -0,0 +1,28 @@
+/* Various definitons used the the ARM uClibc assembly code.  */
+#ifndef _ARM_ASM_H
+#define _ARM_ASM_H
+
+#ifdef __thumb2__
+.thumb
+.syntax unified
+#define IT(t, cond) i##t cond
+#else
+/* XXX: This can be removed if/when we require an assembler that supports
+   unified assembly syntax.  */
+#define IT(t, cond)
+/* Code to return from a thumb function stub.  */
+#ifdef __ARM_ARCH_4T__
+#define POP_RET pop	{r2, pc}
+#else
+#define POP_RET pop	{r2, r3}; bx	r3
+#endif
+#endif
+
+#if defined(__ARM_ARCH_6M__)
+/* Force arm mode to flush out errors on M profile cores.  */
+#undef IT
+#define THUMB1_ONLY 1
+#endif
+
+#endif /* _ARM_ASM_H */
+