cachestat

query the page cache statistics of a file

sys_cachestat(unsigned int fd, struct cachestat_range *cstat_range, struct cachestat *cstat, unsigned int flags)

register	value
`v0`	561, the syscall number
`a0`	unsigned int fd
`a1`	struct cachestat_range *cstat_range
`a2`	struct cachestat *cstat
`a3`	unsigned int flags
`v0`	the return value

Then run callsys to enter the kernel.

Same syscall on other architectures