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School of Computer Science & Engineering
University of New South Wales
 Advanced Operating Systems 
 COMP9242 2002/S2 

Message header format

Data structure l4/types.h:l4_msghdr_t

w2

w0

receive fpage: describes how to map any incoming fpages

w1

message size dope: specifies the total buffer space available
words: size of buffer in words (total for fpages and in-line data)
strings: number of string dopes

w2

message send dope: buffer space used on sending i.e., buffer size used (words) and string dopes used (strings) must be less than or equal specifications of message size dope

Note: specified buffer/message size is in addition to registers

.