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Unformatted text preview: ume a NULL start address. Figure 10.34 depicts the meaning of these arguments. 10.8. MEMORY MAPPING 521 length (bytes) length(bytes) offset (bytes)
0 0 start (or address chosen by the kernel) Disk file specified by file descriptor fd Process virtual memory Figure 10.34: Visual interpretation of mmap arguments. The prot argument contains bits that describe the access permissions of the newly mapped virtual memory area (i.e., the vm prot bits in the corresponding area struct). ¯ ¯ ¯ ¯ PROT EXEC: Pages in the area consist of instructions that may be executed by the CPU. PROT READ: Pages in the area may be read. PROT WRITE: Pages in the area may be written. PROT NONE: Pages in the area cannot be accessed. The flags argument consists of bits that describe the type of the mapped object. If the MAP ANON ﬂag bit is set and fd is NULL, then the backing store is an anonymous object and the corresponding virtual pages are demand-zero. MAP PRIVATE indicates a private copy-on-write object, and MAP SHARED indicates a shared object. For examp...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.
- Spring '10
- The American