From: Chris Zankel <chris@zankel.net>
Date: Wed, 29 Jan 2014 06:09:51 +0000 (-0800)
Subject: xtensa: fix fast_syscall_spill_registers
X-Git-Tag: v3.14-rc5~25^2~1
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=c0e50d41126e4786d9cf1105bdf783e55c99f915;p=karo-tx-linux.git

xtensa: fix fast_syscall_spill_registers

The original implementation could clobber registers under certain conditions.

The Xtensa processor architecture uses windowed registers and the original
implementation was using a4 as a temporary register, which under certain
conditions could be register a0 of the oldest window frame, and didn't always
restore the content correctly.

By moving the _spill_registers routine inside the fast system call, it frees
up one more register (the return address is not required anymore) for the
spill routine.

Signed-off-by: Chris Zankel <chris@zankel.net>
---

diff --git a/arch/xtensa/kernel/vectors.S b/arch/xtensa/kernel/vectors.S
index cb8fd44caabc..f9e1ec346e35 100644
--- a/arch/xtensa/kernel/vectors.S
+++ b/arch/xtensa/kernel/vectors.S
@@ -235,7 +235,7 @@ ENTRY(_DoubleExceptionVector)
 
 	/* Check for overflow/underflow exception, jump if overflow. */
 
-	_bbci.l	a0, 6, _DoubleExceptionVector_WindowOverflow
+	bbci.l	a0, 6, _DoubleExceptionVector_WindowOverflow
 
 	/*
 	 * Restart window underflow exception.
diff --git a/arch/xtensa/kernel/xtensa_ksyms.c b/arch/xtensa/kernel/xtensa_ksyms.c
index 74a60c7e085e..80b33ed51f31 100644
--- a/arch/xtensa/kernel/xtensa_ksyms.c
+++ b/arch/xtensa/kernel/xtensa_ksyms.c
@@ -122,9 +122,7 @@ EXPORT_SYMBOL(insw);
 EXPORT_SYMBOL(insl);
 
 extern long common_exception_return;
-extern long _spill_registers;
 EXPORT_SYMBOL(common_exception_return);
-EXPORT_SYMBOL(_spill_registers);
 
 #ifdef CONFIG_FUNCTION_TRACER
 EXPORT_SYMBOL(_mcount);