Constant SYS_MMAP 

pub const SYS_MMAP: usize = 100;

Map a memory region into the process address space.

• addr: desired virtual address (0 = kernel chooses)
• len: length in bytes (rounded up to page boundary)
• prot: protection flags (PROT_READ | PROT_WRITE | PROT_EXEC)
• flags: mapping flags (MAP_SHARED, MAP_PRIVATE, MAP_ANONYMOUS, etc.)
• fd: file descriptor for file-backed mappings (-1 for anonymous)
• offset: offset into the file (must be page-aligned)

Returns the mapped virtual address on success, or a negative errno.