how to read all parameters from a function - ebpf

Question

So I have these macros

#define PT_REGS_PARM1(x) ((x)->di)
#define PT_REGS_PARM2(x) ((x)->si)
#define PT_REGS_PARM3(x) ((x)->dx)
#define PT_REGS_PARM4(x) ((x)->cx)
#define PT_REGS_PARM5(x) ((x)->r8)
#define PT_REGS_RET(x) ((x)->sp)
#define PT_REGS_FP(x) ((x)->bp)
#define PT_REGS_RC(x) ((x)->ax)
#define PT_REGS_SP(x) ((x)->sp)
#define PT_REGS_IP(x) ((x)->ip)

But the above does not say how to get specific parameter from function say `__sys_write

consider sys_write as

 long sys_write(unsigned int fd, const char __user *buf,
              size_t count);

so I need buffer, I have been trying different macros but not really sure which one giving me what?

So can anyone please clearify it

If will also read buffer if I am reading buffer then count needed too so my ebpf program get loaded and not give out of bounds access error. can anyone tell