mach-o/loader.h Kernel.framework

The 32-bit mach header appears at the very beginning of the object file for 32-bit architectures.

The 64-bit mach header appears at the very beginning of object files for 64-bit architectures.

The segment load command indicates that a part of this file is to be mapped into the task's address space. The size of this segment in memory, vmsize, maybe equal to or larger than the amount to map from this file, filesize. The file is mapped starting at fileoff to the beginning of the segment in memory, vmaddr. The rest of the memory of the segment, if any, is allocated zero fill on demand. The segment's maximum virtual memory protection and initial virtual memory protection are specified by the maxprot and initprot fields. If the segment has sections then the section structures directly follow the segment command and their size is reflected in cmdsize.

The 64-bit segment load command indicates that a part of this file is to be mapped into a 64-bit task's address space. If the 64-bit segment has sections then section_64 structures directly follow the 64-bit segment command and their size is reflected in cmdsize.