Description
Problem 1: 10 points.
It is \believed” that a program can have only one entry point. Your tasks is test out this hypothesis. You need to write a program in standalone assembly language program that has two functions { a start function (not main) where the execution begins, and a second function, lets call it checkGreater. The program should begin execution from the start function. The start func-tion should call the checkGreater along with two arguments x and y such that the function checks is x >y. If yes, then the function should print a string “1”, else it should print a string “0” using the write(). You could call the write() system call using assembly language code snippet. For your convenience you could use the following reference:
https://jameshfisher.com/2018/03/10/linux-assembly-hello-world/ Your task is to explore if it is possible to write a regular C program, having
a main() that should be able to call the checkGreater function, like you would normally do in other scenarios where a C program calls a assembly function.
Like previous cases, you need to compile (not link) the programs separately and thereafter link them together in a single binary.
What to submit:
The source codes of the assembly and the C programs. Make le to compile the programs and link them.
Description of the programs and if and why they work together, i.e. if main() can call checkGreater or not, along with an explaination for the same.
Problem 2: 5 points.
Try to compile the following code snippet (no need to link).
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add ( f l o a t a , f l o a t b )
f
r e t u r n ( f l o a t ) ( round ( a)+round ( b ) ) ;
g
Would the compilation of this code snippet result in errors or warnings if any ? Accurately describe your answers and the reason as to why you observe what you observe.
What to submit:
Command (with appropriate arguments) that were used to compile the snippet.
A writeup showing all the compilation errors and warnings that you may have encountered and their possible explanations.
Problem 3: 5 points.
The following code snippet is being provided to you:
v o i d main ( )
f
c h a r x [ 6 4 ] ;
.
.
g
You need to complete the above code snippet to rstly store eight 64-bit integers using a pointer to type long int. Repeat the same exercise to store sixteen 32-bit integers using a pointer to type int.
What to submit:
The modi ed program for the two di erent scenarios listed above, i.e. one where eight 64-bit integers, and the other where sixteen 32-bit integers are respectively saved in the array.
A writeup describing the rationale behind your code.
Problem 4: 10 points.
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Write a function called ’long add’ in x86 (32-bit) assembly, which takes four integers and returns their sum. Then, write a C program that calls this assembly function.
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Is there any change needed in ’long add’ function if we want to run the assembly function in x86-64 (64-bit)? If change is needed, modify the function and name it ’extended add’. Justify why such change is needed or is not needed.
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What to submit:
The source codes of the assembly and the C programs (with the names ‘P4 1.asm’, optionally ‘P4 2.asm’ and ‘P4.c’.
Make le to compile the programs.
A text le named ‘A4.txt’ with the justi cation as to why a change is needed or not needed.
Problem 5: 4 points.
Suppose you have an x86-64 processor in an embedded system with only 320KB of RAM. Then, would you ever use the long mode (64-bit mode) or would you prefer to use real mode (16-bit mode) for running your program. Please justify your answer.
What to submit
A text le named ‘A5.txt’ with the justi cation.
Problem 6: 6 points.
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Write a program to store a string containing your name in main memory.
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Would your program change if you want to store this string on the disk? If so, write the program. If not, justify why the program does not change.
What to submit:
The C program in a le named ‘P6 1.c’ for the rst part of the question. For the second part of the question, name the le as either ‘P6 2.c’ and ‘A6 2.txt’ depending on whether you submit a C program or give a justi-
cation.
Note: All your les and submissions must be enclosed in a zip le whose le name should be same as your roll number.
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