xtensa: provide custom CALLER_ADDR* implementations

Definition of CALLER_ADDR* through __builtin_return_address makes
compiler insert calls to __xtensa_libgcc_window_spill, which in turn
makes fast_syscall_spill_registers syscall that clobbers registers when
called from the kernel mode, leading to invalid opcode exceptions on
return to userspace.

Provide definition for CALLER_ADDR0 as MAKE_PC_FROM_RA(a0, a1) and in
case CONFIG_FRAME_POINTER is enabled extract CALLER_ADDR{1-3} from
stack.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

diff --git a/arch/xtensa/include/asm/ftrace.h b/arch/xtensa/include/asm/ftrace.h
index 40a8c178f10d9e85a2873c83247c3f2fe553f408..36dc7a6843978253a0373eda900e9afedfbb4922 100644 (file)
--- a/arch/xtensa/include/asm/ftrace.h
+++ b/arch/xtensa/include/asm/ftrace.h
@@ -1 +1,33 @@
-/* empty */
+/*
+ * arch/xtensa/include/asm/ftrace.h
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2013 Tensilica Inc.
+ */
+#ifndef _XTENSA_FTRACE_H
+#define _XTENSA_FTRACE_H
+
+#include <asm/processor.h>
+
+#define HAVE_ARCH_CALLER_ADDR
+#define CALLER_ADDR0 ({ unsigned long a0, a1; \
+               __asm__ __volatile__ ( \
+                       "mov %0, a0\n" \
+                       "mov %1, a1\n" \
+                       : "=r"(a0), "=r"(a1) : : ); \
+               MAKE_PC_FROM_RA(a0, a1); })
+#ifdef CONFIG_FRAME_POINTER
+extern unsigned long return_address(unsigned level);
+#define CALLER_ADDR1 return_address(1)
+#define CALLER_ADDR2 return_address(2)
+#define CALLER_ADDR3 return_address(3)
+#else
+#define CALLER_ADDR1 (0)
+#define CALLER_ADDR2 (0)
+#define CALLER_ADDR3 (0)
+#endif
+
+#endif /* _XTENSA_FTRACE_H */

diff --git a/arch/xtensa/kernel/stacktrace.c b/arch/xtensa/kernel/stacktrace.c
index e3aff95751833d29a1fa39990fc778d5bde1e262..7d2c317bd98b30eb2a82e2770d0ff236de66fe03 100644 (file)
--- a/arch/xtensa/kernel/stacktrace.c
+++ b/arch/xtensa/kernel/stacktrace.c
@@ -85,3 +85,36 @@ void save_stack_trace(struct stack_trace *trace)
 EXPORT_SYMBOL_GPL(save_stack_trace);
 
 #endif
+
+#ifdef CONFIG_FRAME_POINTER
+
+struct return_addr_data {
+       unsigned long addr;
+       unsigned skip;
+};
+
+static int return_address_cb(struct stackframe *frame, void *data)
+{
+       struct return_addr_data *r = data;
+
+       if (r->skip) {
+               --r->skip;
+               return 0;
+       }
+       if (!kernel_text_address(frame->pc))
+               return 0;
+       r->addr = frame->pc;
+       return 1;
+}
+
+unsigned long return_address(unsigned level)
+{
+       struct return_addr_data r = {
+               .skip = level + 1,
+       };
+       walk_stackframe(stack_pointer(NULL), return_address_cb, &r);
+       return r.addr;
+}
+EXPORT_SYMBOL(return_address);
+
+#endif