Where could I find the definition of __vm_deallocate() called by __munmap()?

[ur bridge]

Hello,
I’m reading the malloc.c code, and find that when __munmap() is called to free a mmapped chunk, the control flow will fall into sysdeps/mach/munmap.c, where __vm_deallocate() will be called. However, I cannot find its definition. Where could it be?

(Actually, I expected that syscall munmap() would be called in Linux kernel. But there is no such a declaration in sysdeps/unix/sysv/linux/.)

Thanks