ARC: dw2 unwind: add infrastructure for adding cfi pseudo ops to asm

1. detect whether binutils supports the cfi pseudo ops
2. define conditional macros to generate the ops
3. define new ENTRY_CFI/END_CFI to annotate hand asm code.
   - Needed because we don't want to emit dwarf info in general ENTRY/END
     used by lowest level trap/exception/interrutp handlers as unwinder
     gets confused trying to unwind out of them. We want unwinder to
     instead stop when it hits onfo those routines
   - These provide minimal start/end cfi ops assuming routine doesn't
     touch stack memory/regs

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

3 files changed, 52 insertions, 1 deletions

diff --git a/arch/arc/Makefile b/arch/arc/Makefile
index a2a6a4614241..aa82d13d4213 100644
--- a/arch/arc/Makefile
+++ b/arch/arc/Makefile
@@ -65,7 +65,8 @@ endif
 
 endif
 
-cflags-$(CONFIG_ARC_DW2_UNWIND)         += -fasynchronous-unwind-tables
+cfi := $(call as-instr,.cfi_startproc\n.cfi_endproc,-DARC_DW2_UNWIND_AS_CFI)
+cflags-$(CONFIG_ARC_DW2_UNWIND)         += -fasynchronous-unwind-tables $(cfi)
 
 ifndef CONFIG_CC_OPTIMIZE_FOR_SIZE
 # Generic build system uses -O2, we want -O3
diff --git a/arch/arc/include/asm/dwarf.h b/arch/arc/include/asm/dwarf.h
new file mode 100644
index 000000000000..bb7bdbc59a44
--- /dev/null
+++ b/arch/arc/include/asm/dwarf.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2016-17 Synopsys, Inc. (www.synopsys.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.
+ */
+
+#ifndef _ASM_ARC_DWARF_H
+#define _ASM_ARC_DWARF_H
+
+#ifdef __ASSEMBLY__
+
+#ifdef ARC_DW2_UNWIND_AS_CFI
+
+#define CFI_STARTPROC   .cfi_startproc
+#define CFI_ENDPROC     .cfi_endproc
+#define CFI_DEF_CFA     .cfi_def_cfa
+#define CFI_REGISTER    .cfi_register
+#define CFI_REL_OFFSET  .cfi_rel_offset
+#define CFI_UNDEFINED   .cfi_undefined
+
+#else
+
+#define CFI_IGNORE      #
+
+#define CFI_STARTPROC   CFI_IGNORE
+#define CFI_ENDPROC     CFI_IGNORE
+#define CFI_DEF_CFA     CFI_IGNORE
+#define CFI_REGISTER    CFI_IGNORE
+#define CFI_REL_OFFSET  CFI_IGNORE
+#define CFI_UNDEFINED   CFI_IGNORE
+
+#endif  /* !ARC_DW2_UNWIND_AS_CFI */
+
+#endif  /* __ASSEMBLY__ */
+
+#endif  /* _ASM_ARC_DWARF_H */
diff --git a/arch/arc/include/asm/linkage.h b/arch/arc/include/asm/linkage.h
index 5faad17118b4..b29f1a9fd6f7 100644
--- a/arch/arc/include/asm/linkage.h
+++ b/arch/arc/include/asm/linkage.h
@@ -9,6 +9,8 @@
 #ifndef __ASM_LINKAGE_H
 #define __ASM_LINKAGE_H
 
+#include <asm/dwarf.h>
+
 #ifdef __ASSEMBLY__
 
 #define ASM_NL           `      /* use '`' to mark new line in macro */
@@ -32,6 +34,16 @@
 #endif
 .endm
 
+#define ENTRY_CFI(name)         \
+        .globl name ASM_NL      \
+        ALIGN ASM_NL            \
+        name: ASM_NL            \
+        CFI_STARTPROC ASM_NL
+
+#define END_CFI(name)           \
+        CFI_ENDPROC ASM_NL      \
+        .size name, .-name
+
 #else   /* !__ASSEMBLY__ */
 
 #ifdef CONFIG_ARC_HAS_ICCM