intercept_template.s - add more debug information

Add some dwarf information on the whereabouts of some
register values saved on the stack. The faked return address
points a debugger to a backtrace_placeholder routine, where the
return address (in debug builds) is found on the top of the
stack, and with this patch the values of some other registers
are also found on the stack by a debugger. These registers are
pushed on the stack by an instance generated from the assembly
template, so the offsets in the placeholder routines (which are
never actually executed) must match the offsets resulting from
the push instructions in the actually executed code.

Author: GBuella

src/intercept_template.s

@@ -248,7 +248,25 @@
 
 backtrace_placeholder:
 	.cfi_startproc
+	/*
+	 * Call Frame Information. The stack size is 0x580,
+	 * and the cfi_offset entries mark the place of a each
+	 * register's previous value in the call frame.
+	 */
 	.cfi_def_cfa_offset 0x580
+	.cfi_offset 6, -136    /* rbp */
+	.cfi_offset 15, -152   /* r15 */
+	.cfi_offset 14, -160   /* r14 */
+	.cfi_offset 13, -168   /* r13 */
+	.cfi_offset 12, -176   /* r12 */
+	.cfi_offset 10, -184   /* r10 */
+	.cfi_offset 9, -192    /* r9  */
+	.cfi_offset 8, -200    /* r8  */
+	.cfi_offset 2, -208    /* rcx */
+	.cfi_offset 4, -216    /* rdx */
+	/* rsi at -224 */
+	/* rdi at -232 */
+	.cfi_offset 3, -240    /* rbx */
 	nop
 	nop
 	nop
@@ -260,6 +278,19 @@ backtrace_placeholder:
 backtrace_placeholder_2:
 	.cfi_startproc
 	.cfi_def_cfa_offset 0x588
+	.cfi_offset 6, -136    /* rbp */
+	.cfi_offset 15, -152   /* r15 */
+	.cfi_offset 14, -160   /* r14 */
+	.cfi_offset 13, -168   /* r13 */
+	.cfi_offset 12, -176   /* r12 */
+	.cfi_offset 10, -184   /* r10 */
+	.cfi_offset 9, -192    /* r9  */
+	.cfi_offset 8, -200    /* r8  */
+	.cfi_offset 2, -208    /* rcx */
+	.cfi_offset 4, -216    /* rdx */
+	/* rsi at -224 */
+	/* rdi at -232 */
+	.cfi_offset 3, -240    /* rbx */
 	nop
 	nop
 	nop