Task 3: hello

1. Return Process PID – Modify sys_hello to return the calling process's PID instead of returning a fixed 0.

2. Repeating Message – Update the syscall hello(void) to hello(int n), where the kernel prints the message n times.

3. Print Execution Core – Modify the kernel handler to print which CPU core (hart ID) is currently executing the call.

4. User-Provided Name – Create a syscall hello_user(char *name) that fetches a string from user space to print "Hello [name]".

5. Global Call Counter – Add a global counter in kernel/sysproc.c that tracks and returns the total times hello was called.

6. PID Filtering – Modify the kernel handler to print "Hello from Kernel!" only if the caller has PID 1 or 2.

7. Rate Limiting – Change the syscall to return -1 (failure) if it is called more than 3 times by the same process.

8. Kernel Arithmetic – Implement a version where hello(int a, int b) prints the sum of the two integers in the kernel log.

9. Syscall Number Logging – Modify kernel/syscall.c to log the syscall number specifically whenever SYS_hello is invoked.

10. Conditional Success Output – Update the user program hello.c to print "Syscall Successful" only if the return value is exactly 0.