perf_event_open

set up performance monitoring

sys_perf_event_open(struct perf_event_attr *attr_uptr, pid_t pid, int cpu, int group_fd, unsigned long flags)

register	value
`r20`	318, the syscall number
`r26`	struct perf_event_attr *attr_uptr
`r25`	pid_t pid
`r24`	int cpu
`r23`	int group_fd
`r22`	unsigned long flags
`r28`	the return value

Then run ble 0x100(%sr2, %r0) to enter the kernel.

Same syscall on other architectures