add gdb note

Author: tmp-coder

MIT6.828-fa18/README.md

@@ -2,4 +2,5 @@
 this is some note about learning MIT 6.828 fa18
 
 - [lab1 note](./note/lab1-note.md)
-- [hw1-boot-xv6](./note/hw1-boot-xv6.md)
+- [hw1-boot-xv6](./note/hw1-boot-xv6.md)
+- [lec3-gdb-note.md](./note/lec3-gdb-note.md)

MIT6.828-fa18/lec/gdb_slides.pdf

@@ -0,0 +1,17 @@
+
+这是课件3,关于GDB内容的整理,一些常用指令: ```c,si,n,b```就不说了
+
+- finish runs code until the current function returns.
+- advance \<location> runs code until the instruction pointer gets to the specied location.
+- Modify breakpoints using delete, disable, enable.
+- break \<location> if \<condition> sets a breakpoint at the specied location, but only breaks if the condition is satised. 
+- cond <number> <condition> adds a condition on an existing breakpoint.
+- watch \<expression> will stop execution whenever the expression's value changes.
+- watch -l \<address> will stop execution whenever the contents of the specied memory address change.
+- info frame prints the current stack frame.
+- list <location> prints the source code of the function at the specied location.
+- backtrace might be useful as you work on lab 1!
+
+更多内容可见 help
+or [gdb_slides.pdf](../lec/gdb_slides.pdf)
+