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Length: 2061 (0x80d)
Types: TextFile
Notes: UNIX file
Names: »vspy.2v«
└─⟦26887b7e0⟧ Bits:30009717 Comet 32 harddisk image
└─⟦28c352965⟧ »/a« UNIX Filesystem
└─⟦this⟧ »usr/man/man2/vspy.2v«
.ig @(#)vspy.2v 2.1 7/1/84 @(#)Copyright (C) 1983 by National Semiconductor Corp. .. .TH VSPY 2V .SH NAME vspy \- set up mapping to physical memory .SH SYNOPSIS .nf .B vspy(virtaddr, physaddr, flag) .B char *virtaddr; .B char *physaddr; .fi .SH DESCRIPTION .I Vspy changes the mmu mapping for the current process to allow references directly to physical memory. This capability allows user mode programs to communicate directly with the various peripherals of the system. .PP .I Virtaddr is the address in the process which is to be used to access the physical memory. .I Physaddr is the physical memory address to be accessed, or -1 to remove existing access to physical memory. .I Flag is 0 if only read access is desired, or 1 if both read and write access is desired. .PP Since the lowest mapping granularity for G\s-2ENIX\s0 is one page (1024 bytes), the low order ten bits of the given addresses are ignored, so that the whole virtual page specified by .I virtaddr will map to the whole physical memory page specified by .I physaddr. Thus to reference a particular offset into the physical memory page, you must access the same offset into the virtual memory page. .PP The .I virtaddr specified does not have to lie within the data, text, or stack segment of the process, so that memory does not have to be allocated using .IR sbrk (2) before calling .I vspy. If the page specified by .I virtaddr already exists, that page is deleted. .IR Fork (2) will duplicate the physical mapping for the new process. A successful .IR exec (2) or .IR exit (2) removes all existing physical mapping. Only the super-user is allowed to map physical memory arbitrarily. However, certain physical memory addresses corresponding to "safe" devices may be mapped by anyone. .SH "SEE ALSO" vlock(2V) .SH DIAGNOSTICS Zero is returned if the call was successful. -1 is returned if any of the arguments are illegal or if the user is not privileged. .SH BUGS I/O cannot be done to pages mapped to physical memory. Arguments to system calls cannot lie in such pages either.