update 3.md and 4.md

notes/3.md

@@ -52,7 +52,7 @@ void sumstore(long x, long y, long *dest) {
 ```
 
 ```sh {cmd hide}
-while ![ -r 3_1.o ]; do sleep .1; done; objdump -d 3_1.o
+while ! [ -r 3_1.o ]; do sleep .1; done; objdump -d 3_1.o
 ```
 
 ### Integer Registers
@@ -267,7 +267,7 @@ long absdiff(long x, long y) {
 ```
 
 ```sh { cmd hide }
-while ![ -r 3_3.o ]; do sleep .1; done; objdump -d 3_3.o -Msuffix
+while ! [ -r 3_3.o ]; do sleep .1; done; objdump -d 3_3.o -Msuffix
 ```
 
 **expressing with `goto`**
@@ -300,7 +300,7 @@ long absdiff(long x, long y) {
 ```
 
 ```sh {cmd hide}
-while ![ -r 3_5.o ]; do sleep .1; done; objdump -d 3_5.o -Msuffix
+while ! [ -r 3_5.o ]; do sleep .1; done; objdump -d 3_5.o -Msuffix
 ```
 
 However, there are several *bad cases* for conditional move.
@@ -357,7 +357,7 @@ loop:
 </table>
 
 ```sh {cmd hide}
-while ![ -r 3_6.o ]; do sleep .1; done; objdump -d 3_6.o -Msuffix
+while ! [ -r 3_6.o ]; do sleep .1; done; objdump -d 3_6.o -Msuffix
 ```
 
 **general do-while translation**
@@ -426,7 +426,7 @@ long pcount_while(unsigned long x) {
 ```
 ```sh {cmd hide}
 echo "jmp-to-middle translation"
-while ![ -r 3_7.o ]; do sleep .1; done; objdump -d 3_7.o -Msuffix
+while ! [ -r 3_7.o ]; do sleep .1; done; objdump -d 3_7.o -Msuffix
 ```
 
 **general while translation#2**
@@ -478,7 +478,7 @@ long pcount_while(unsigned long x) {
 ```
 ```sh {cmd hide}
 echo "while to do-while conversion"
-while ![ -r 3_8.o ]; do sleep .1; done; objdump -d 3_8.o -Msuffix
+while ! [ -r 3_8.o ]; do sleep .1; done; objdump -d 3_8.o -Msuffix
 ```
 
 #### for loop form
@@ -560,13 +560,13 @@ long pcount_for(unsigned long x) {
 <td>
 
 ```sh {cmd hide}
-while ![ -r 3_9.o ]; do sleep .1; done; objdump -d 3_9.o -Msuffix
+while ! [ -r 3_9.o ]; do sleep .1; done; objdump -d 3_9.o -Msuffix
 ```
 </td>
 <td>
 
 ```sh {cmd hide}
-while ![ -r 3_10.o ]; do sleep .1; done; objdump -d 3_10.o -Msuffix
+while ! [ -r 3_10.o ]; do sleep .1; done; objdump -d 3_10.o -Msuffix
 ```
 </td>
 </tr>
@@ -614,7 +614,7 @@ long switch_eg (long x, long y, long z) {
 <td>
 
 ```sh {cmd hide}
-while ![ -r 3_11.s ]; do sleep .1; done; cat 3_11.s
+while ! [ -r 3_11.s ]; do sleep .1; done; cat 3_11.s
 ```
 </td>
 </tr>
@@ -667,7 +667,7 @@ void multstore(long x, long y, long *dest) {
 ```
 
 ```sh {cmd hide}
-while ![ -r 3_12.o ]; do sleep .1; done; objdump -d 3_12.o -Msuffix
+while ! [ -r 3_12.o ]; do sleep .1; done; objdump -d 3_12.o -Msuffix
 ```
 
 Procedure call `call label`
@@ -687,7 +687,7 @@ Procedure return: `ret`
 for example with above example
 
 ```sh {cmd hide}
-while ![ -r 3_12.o ]; do sleep .1; done; objdump -d 3_12.o -Msuffix
+while ! [ -r 3_12.o ]; do sleep .1; done; objdump -d 3_12.o -Msuffix
 ```
 
 * with above `mult2` variable `t` is already stored in `%rax`
@@ -718,6 +718,38 @@ Deallocated when return, "finish" code and includes pop by `ret`.
 
 #### x86-64/Linux Stack Frame
 
+![stack frame image](/assets/3_1stackframe.png)
+
+* Arguments
+* Local variables
+* Old `rbp`
+
+### Register Saving Conventions
+
+When calling function, the temporary value of registers could be removed by called function, it could be trouble. So there are **conventions** to save the registers value.
+
+When procedure `yoo` calls `who`: `yoo` is `caller`, `who` is `callee`
+* Caller saves temporary values in its frame before the call.
+* Callee saves saves temporary values in its frame before using and restores them before returning to caller.
+
+
+#### x86-64 Linux Register Usage
+
+`%rbx`, `%r12`, `%r13`, `%r14`, `%r15`
+* Callee-saved
+* Callee must save & restore
+
+`%rbp`
+* Callee-saved
+* Callee must save & restore
+* May be used as frame pointer by callee
+* Can mix & match
+
+`%rsp`
+* Special form of callee-saved
+* Restored to original value upon exit from procedure
+
+#### EX 
 
 * for compile w/o *stack canary*, add option `-fno-stack-protector`
 ```c {cmd=gcc args=[-Og -x c -fno-stack-protector -c $input_file -o 3_13.o]}
@@ -735,5 +767,27 @@ long call_incr() {
 ```
 
 ```sh {cmd hide}
-while ![ -r 3_13.o ]; do sleep .1; done; objdump -d 3_13.o -Msuffix
-```
+while ! [ -r 3_13.o ]; do sleep .1; done; objdump -d 3_13.o -Msuffix
+```
+
+### Recursive Function
+
+```c {cmd=gcc args=[-O1 -x c -fno-stack-protector -c $input_file -o 3_14.o]}
+long pcount_r(unsigned long x) {
+  if (x == 0) {
+    return 0;
+  } else {
+    return (x & 1) + pcount_r(x >> 1);
+  }
+}
+```
+
+```sh {cmd hide}
+while ! [ -r 3_14.o ]; do sleep .1; done; objdump -d 3_14.o -Msuffix
+```
+
+Recursion is not a special function.
+* Stack frames mean that each function call has private storage.
+* Register saving conventions prevent one function call from corrupting another's data. *unless the explictly corrupting like buffer overflow*
+* Stack discipline follows call/return pattern LIFO
+