ARM: lib: add call_with_stack function for safely changing stack

[pandora-kernel.git] / arch / arm / lib / call_with_stack.S

diff --git a/arch/arm/lib/call_with_stack.S b/arch/arm/lib/call_with_stack.S
new file mode 100644 (file)
index 0000000..916c80f
--- /dev/null
+++ b/arch/arm/lib/call_with_stack.S
@@ -0,0 +1,44 @@
+/*
+ * arch/arm/lib/call_with_stack.S
+ *
+ * Copyright (C) 2011 ARM Ltd.
+ * Written by Will Deacon <will.deacon@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * void call_with_stack(void (*fn)(void *), void *arg, void *sp)
+ *
+ * Change the stack to that pointed at by sp, then invoke fn(arg) with
+ * the new stack.
+ */
+ENTRY(call_with_stack)
+       str     sp, [r2, #-4]!
+       str     lr, [r2, #-4]!
+
+       mov     sp, r2
+       mov     r2, r0
+       mov     r0, r1
+
+       adr     lr, BSYM(1f)
+       mov     pc, r2
+
+1:     ldr     lr, [sp]
+       ldr     sp, [sp, #4]
+       mov     pc, lr
+ENDPROC(call_with_stack)