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Homework #3
To be done individually. Due April 19th
Implement Strstr in x86 assembly.
To find out the semantics of Strstr, on any UNIX system, type "man strstr".
Try and follow x86 calling conventions.
Here is a set of files that you can use to test your code, as well as a template to write it in. Instructions on how to test your code are included in the file: HW3.tar.bz2
To extract the file, put it in a directory on attu and run "tar -xjvf HW3.tar.bz2" and it will put the files in a HW3 directory.
About x86:
Familiarize yourself with x86
The following is a table of the more common/basic instructions. NOTE: the table gives the CORRECT operand ordering. FOLLOW IT!
| Opcode |
Description |
| Copying values |
mov src, dest |
Copies a value from a register, immediate value or memory address to a register or memory address. |
cmove %src, %dest |
Copies from register %src to register %dest if the last comparison operation had the corresponding result (cmove: equality, cmovne: inequality, cmovg: greater, cmovl: less, cmovge: greater or equal, cmovle: less or equal). |
cmovne %src, %dest |
cmovg %src, %dest |
cmovl %src, %dest |
cmovge %src, %dest |
cmovle %src, %dest |
| Stack management |
enter $x, $0 |
Sets up a procedure’s stack frame by first pushing the current value of %rbp on to the stack, storing the current value of %esp in %ebp, and finally decreasing %esp to make room for x quadword-sized local variables. |
leave |
Removes local variables from the stack frame by restoring the old values of %rsp and %rbp. |
push src |
Decreases %rsp and places src at the new memory location pointed to by %rsp. Here, src can be a register, immediate value or memory address. |
pop dest |
Copies the value stored at the location pointed to by %rsp to dest and increases %rsp. Here, dest can be a register or memory location. |
| Control flow |
jmp target |
Jump unconditionally to target, which is specified as a memory location (for example, a label). |
je target |
Jump to target if the last comparison had the corresponding result (je: equality; jne: inequality). |
jne target |
| Arithmetic and logic |
add src, dest |
Add src to dest. |
sub src, dest |
Subtract src from dest. |
imul src, dest |
Multiply dest by src. |
idiv src, dest |
Divide dest by src. |
shr src, dest |
Shift dest to the left or right by src bits. |
shl src, dest |
ror src, dest |
Rotate dest to the left or right by src bits. |
cmp src, dest |
Set flags corresponding to whether dest is less than, equal to, or greater than src |
If the instruction that you're looking for is not in the table, you may visit this site for a more complete list of instructions.
NOTE: the instructions on this site have the WRONG operand ordering! FLIP THEM if you use them!!!
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