x86 - Reading performance registers from the kernel

I want to read certain performance counters. I know that there are tools like perf, that can do it for me in the user space itself, I want the code to be inside the Linux kernel.

I want to write a mechanism to monitor performance counters on Intel(R) Core(TM) i7-3770 CPU. On top of using I am using Ubuntu kernel 4.19.2. I have gotten the following method from easyperf

Here's part of my code to read instructions.

  struct perf_event_attr *attr
  memset (&pe, 0, sizeof (struct perf_event_attr));
  pe.type = PERF_TYPE_HARDWARE;
  pe.size = sizeof (struct perf_event_attr);
  pe.config = PERF_COUNT_HW_INSTRUCTIONS;
  pe.disabled = 0;
  pe.exclude_kernel = 0;
  pe.exclude_user = 0;
  pe.exclude_hv = 0;
  pe.exclude_idle = 0;


  fd = syscall(__NR_perf_event_open, hw, pid, cpu, grp, flags);

  uint64_t perf_read(int fd) {
    uint64_t val;
    int rc;
    rc = read(fd, &val, sizeof(val));
    assert(rc == sizeof(val));
    return val;
  }

I want to put the same lines in the kernel code (in the context switch function) and check the values being read.

My end goal is to figure out a way to read performance counters for a process, every time it switches to another, from the kernel(4.19.2) itself.

To achieve this I check out the code for the system call number __NR_perf_event_open. It can be found here
To make to usable I copied the code inside as a separate function, named it perf_event_open() in the same file and exported.

Now the problem is whenever I call perf_event_open() in the same way as above, the descriptor returned is -2. Checking with the error codes, I figured out that the error was ENOENT. In the perf_event_open() man page, the cause of this error is defined as wrong type field.

Since file descriptors are associated to the process that's opened them, how can one use them from the kernel? Is there an alternative way to configure the pmu to start counting without involving file descriptors?