Merge pull request #28 from tin-z/trace_tips_2

adding trace instructions example

src/trace-instructions.md

@@ -0,0 +1,35 @@
+# 从起始地址（$start_pc）跟踪指令至结束地址（$end_pc），并将输出保存在 'gdb.txt' 文件中
+
+```
+# set tracing points
+set $start_pc=<trace-from-address>
+set $end_pc=<trace-to-address>
+
+# disable pagination
+set pagination off
+
+# log output to gdb.txt file instead of standard output
+set logging on
+set logging redirect on
+
+# Warning: 'set logging on', an alias for the command 'set logging enabled', is deprecated. Use 'set logging enabled on'.
+
+# run until $start_pc address hit
+tbreak *$start_pc
+run
+
+# for each breakpoint hit print the instruction
+display/i $pc
+while $while_true
+  si
+  if $pc == $end_pc
+    printf "Breakpoint reached\n"
+    set $while_true=0
+  end
+end
+```
+
+
+## 贡献者
+
+tin-z