15 213 The course that gives CMU its Zip Machine Level Programming III Procedures Sept 11 2008 IA32 x86 64 stack discipline Register saving conventions Creating pointers to local variables class06 ppt Argument passing in registers Minimizing stack usage Using stack pointer as only reference 15 213 F 08 IA32 Stack Region of memory managed with stack discipline Grows toward lower addresses Stack Bottom Increasing Addresses Register esp indicates lowest stack address address of top element Stack Pointer esp Stack Grows Down Stack Top 2 15 213 F 08 IA32 Stack Pushing Pushing pushl Src Fetch operand at Src Decrement esp by 4 Write operand at address given by esp Stack Bottom Increasing Addresses Stack Pointer esp Stack Grows Down 4 Stack Top 3 15 213 F 08 IA32 Stack Popping Popping popl Dest Read operand at address given by esp Increment esp by 4 Write to Dest Stack Bottom Increasing Addresses Stack Pointer esp Stack Grows Down 4 Stack Top 4 15 213 F 08 Procedure Control Flow Use stack to support procedure call and return Procedure call call label Push return address on stack Jump to label Return address value Address of instruction beyond call Example from disassembly 804854e e8 3d 06 00 00 call 8048b90 main 8048553 50 pushl eax Return address 0x8048553 Procedure return 5 ret Pop address from stack Jump to address 15 213 F 08 Procedure Call Example 804854e 8048553 e8 3d 06 00 00 50 call 0x110 0x110 0x10c 0x10c 0x108 123 0x108 call pushl 8048b90 main eax 8048b90 123 0x104 0x8048553 esp 0x108 esp eip 0x804854e 0x108 0x104 eip 0x8048b90 0x804854e eip is program counter 6 15 213 F 08 Procedure Return Example 8048591 c3 ret ret 0x110 0x110 0x10c 0x10c 0x108 123 0x108 0x104 0x8048553 esp 0x104 eip 0x8048591 123 0x8048553 esp 0x104 0x108 eip 0x8048553 0x8048591 eip is program counter 7 15 213 F 08 Stack Based Languages Languages that Support Recursion e g C Pascal Java Code must be Reentrant Multiple simultaneous instantiations of single procedure Need some place to store state of each instantiation Arguments Local variables Return pointer Stack Discipline State for given procedure needed for limited time From when called to when return Callee returns before caller does Stack Allocated in Frames 8 state for single procedure instantiation 15 213 F 08 Call Chain Example Code Structure yoo who 9 Call Chain yoo who amI amI Procedure amI recursive who amI amI amI amI amI amI 15 213 F 08 Stack Frames Contents Local variables Return information Temporary space yoo who Management amI Space allocated when enter procedure Set up code Deallocated when return Finish code Pointers Stack Stack pointer esp indicates stack Pointer top Frame pointer ebp indicates start of esp current frame 10 Frame Pointer ebp proc Stack Top 15 213 F 08 Stack Operation yoo who 11 Call Chain yoo Frame Pointer ebp Stack Pointer esp yoo 15 213 F 08 Stack Operation who amI amI 12 Call Chain yoo who Frame Pointer ebp Stack Pointer esp yoo who 15 213 F 08 Stack Operation amI amI 13 Call Chain yoo yoo who amI Frame Pointer ebp Stack Pointer esp who amI 15 213 F 08 Stack Operation amI amI Call Chain yoo yoo who who amI amI Frame Pointer ebp Stack Pointer esp 14 amI amI 15 213 F 08 Stack Operation amI amI Call Chain yoo yoo who who amI amI amI amI Frame Pointer ebp Stack Pointer esp 15 amI amI 15 213 F 08 Stack Operation amI amI Call Chain yoo yoo who who amI amI amI 16 Frame Pointer ebp Stack Pointer esp amI amI 15 213 F 08 Stack Operation amI amI Call Chain yoo yoo who amI amI Frame Pointer ebp Stack Pointer esp who amI amI 17 15 213 F 08 Stack Operation who amI amI Call Chain yoo who amI Frame Pointer ebp Stack Pointer esp yoo who amI amI 18 15 213 F 08 Stack Operation amI Call Chain yoo yoo Frame Pointer ebp who amI amI amI Stack Pointer esp who amI amI 19 15 213 F 08 Stack Operation who amI amI Call Chain yoo who amI amI Frame Pointer ebp Stack Pointer esp yoo who amI amI 20 15 213 F 08 Stack Operation yoo who Call Chain Frame Pointer ebp Stack Pointer esp yoo yoo who amI amI amI amI 21 15 213 F 08 IA32 Linux Stack Frame Current Stack Frame Top to Bottom Parameters for function about to call Caller Frame Argument build Local variables If can t keep in registers Saved register context Old frame pointer Arguments Frame Pointer ebp Saved Registers Local Variables Caller Stack Frame Return address Pushed by call instruction 22 Arguments for this call Return Addr Old ebp Stack Pointer esp Argument Build 15 213 F 08 Revisiting swap Calling swap from call swap int zip1 15213 int zip2 91125 void call swap swap zip1 zip2 void swap int xp int yp int t0 xp int t1 yp xp t1 yp t0 23 call swap pushl zip2 pushl zip1 call swap Global Var Global Var Resulting Stack zip2 zip1 Rtn adr esp 15 213 F 08 Revisiting swap void swap int xp int yp int t0 xp int t1 yp xp t1 yp t0 swap pushl ebp movl esp ebp pushl ebx movl movl movl movl movl movl Set Up 12 ebp ecx 8 ebp edx ecx eax edx ebx eax edx ebx ecx movl 4 ebp ebx movl ebp esp popl ebp ret 24 Body Finish 15 213 F 08 swap Setup 1 Entering Stack ebp Resulting Stack zip2 yp zip1 xp Rtn adr esp ebp Rtn adr Old ebp esp swap pushl ebp movl esp ebp pushl ebx 25 15 213 F 08 swap Setup 2 Entering Stack ebp Resulting Stack zip2 yp zip1 xp Rtn adr esp Rtn adr Old ebp ebp esp swap pushl ebp movl esp ebp pushl ebx 26 15 213 F 08 swap Setup 3 Entering Stack ebp Resulting Stack zip2 yp zip1 xp Rtn adr esp Rtn adr Old ebp ebp Old ebx esp swap pushl ebp movl esp ebp pushl ebx 27 15 213 F 08 Effect of swap Setup Entering Stack Resulting Stack ebp Offset relative to ebp zip2 12 yp zip1 8 xp 4 Rtn adr Rtn adr esp movl 12 ebp ecx get yp movl 8 ebp edx get xp 28 0 Old ebp ebp Old ebx esp Body 15 213 F 08 swap Finish 1 swap s Stack Offset 29 Offset 12 yp 12 yp 8 xp 8 xp 4 Rtn adr 4 Rtn adr 0 Old ebp ebp 0 Old ebp ebp 4 Old ebx esp 4 Old ebx esp Observation Saved restored register ebx movl 4 ebp ebx movl ebp esp popl ebp ret 15 213 F 08 swap Finish 2 swap s Stack Offset swap s Stack Offset 12 yp 12 yp 8 xp xp 4 Rtn adr 8 4 Rtn adr 0 Old ebp ebp 4 Old ebx esp 0 Old ebp ebp esp movl 4 ebp ebx movl ebp esp popl ebp ret 30 15 213 F 08 swap Finish 3 swap s Stack …
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