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mmap(0,...) placement optionsmmap(0,...) placement optionsPosted May 6, 2003 14:48 UTC (Tue) by jreiser (subscriber, #11027)Parent article: "Exec Shield" for Linux A related idea is giving the user more control over mmap(0,...) in general. Make TASK_UNMAPPED_BASE an inherited part of process state, and control it with setrlimit()/getrlimit(). With .task_unmapped_base set to 1MB, then in Ingo's "cat" example even the locale pages would reside in ASCII Armor. The cost is 4 bytes of process state, plus a few lines in setrlimit/getrlimit. Kasper Dupont has developed patches to support this. See here. Also, the builders of applications can arrange for "ASCII Armor" placement of mmap(0,...) even in systems without kernel patches. See my project tub. Further, if the kernel provided a binary structure interface to /proc/self/maps then it would be much easier and more reliable for users to do these things by themselves. Win32 has an interface VirtualQuery() which provides for introspective examination of the address space mappings.
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