Xv6 adds a system call that takes system calls into account

EDIT:

Got it

here is what i did:

in syscall.c:

extern int numSysCalls;

in sysproc.c:

int numSysCalls = -1;

Okay, so I'm working on introducing a simple system call that returns the number of system call attempts. Seems easy, but I get an error that I don't understand ...

Basically, here's what I did: in syscall.c there is a syscall () function that checks if it is syscall or not. I basically declared a variable and increment it every time this function is called.

Var declaration in syscall.c:

18: int16_t numSysCalls = -1; //global

Syscall () function:

115:  void syscall(void){
116:     numSysCalls++; 
...

The error I get is:

kernel/syscall.c:116: error: ‘numSysCalls’ undeclared (first use in this function)
kernel/syscall.c:116: error: (Each undeclared identifier is reported only once
kernel/syscall.c:116: error: for each function it appears in.)

Then in sysproc.c I have the same extern int and just return int when I call my numCalls function, as follows:

External variable in sysproc.c:

extern int numSysCalls;

Method used:

int sys_numSys(void){
if (numSysCalls == -1) return numSysCalls;
else return numSysCalls + 1;
}

: numSysCalls syscall ( ) - .

numSys -1, .