xtensa: make sure bFLT stack is 16 byte aligned

commit 0773495b1f5f1c5e23551843f87b5ff37e7af8f7 upstream.

Xtensa ABI requires stack alignment to be at least 16. In noMMU
configuration ARCH_SLAB_MINALIGN is used to align stack. Make it at
least 16.

This fixes the following runtime error in noMMU configuration, caused by
interaction between insufficiently aligned stack and alloca function,
that results in corruption of on-stack variable in the libc function
glob:

 Caught unhandled exception in 'sh' (pid = 47, pc = 0x02d05d65)
  - should not happen
  EXCCAUSE is 15

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/xtensa/include/asm/processor.h b/arch/xtensa/include/asm/processor.h
index 83e2e4b..d3ac00f 100644 (file)
--- a/arch/xtensa/include/asm/processor.h
+++ b/arch/xtensa/include/asm/processor.h
@@ -24,7 +24,11 @@
 # error Linux requires the Xtensa Windowed Registers Option.
 #endif
 
-#define ARCH_SLAB_MINALIGN     XCHAL_DATA_WIDTH
+/* Xtensa ABI requires stack alignment to be at least 16 */
+
+#define STACK_ALIGN (XCHAL_DATA_WIDTH > 16 ? XCHAL_DATA_WIDTH : 16)
+
+#define ARCH_SLAB_MINALIGN STACK_ALIGN
 
 /*
  * User space process size: 1 GB.