Merge pull request #763 from douglas-raillard-arm/dr/add_debug_frame_info

Add CFI debug frame information for ASM functions

include/common/asm_macros_common.S

@@ -33,12 +33,30 @@
 	/*
 	 * This macro is used to create a function label and place the
 	 * code into a separate text section based on the function name
-	 * to enable elimination of unused code during linking
+	 * to enable elimination of unused code during linking. It also adds
+	 * basic debug information to enable call stack printing most of the
+	 * time.
 	 */
 	.macro func _name
+	/*
+	 * Add Call Frame Information entry in the .debug_frame section for
+	 * debugger consumption. This enables callstack printing in debuggers.
+	 * This does not use any space in the final loaded binary, only in the
+	 * ELF file.
+	 * Note that a function manipulating the CFA pointer location (i.e. the
+	 * x29 frame pointer on AArch64) should declare it using the
+	 * appropriate .cfi* directives, or be prepared to have a degraded
+	 * debugging experience.
+	 */
+	.cfi_sections .debug_frame
 	.section .text.\_name, "ax"
 	.type \_name, %function
 	.func \_name
+	/*
+	 * .cfi_startproc and .cfi_endproc are needed to output entries in
+	 * .debug_frame
+	 */
+	.cfi_startproc
 	\_name:
 	.endm
 
@@ -47,6 +65,7 @@
 	 */
 	.macro endfunc _name
 	.endfunc
+	.cfi_endproc
 	.size \_name, . - \_name
 	.endm