i386_vm86(2) [debian man page]

I386_VM86(2)						      BSD System Calls Manual						      I386_VM86(2)

NAME

     i386_vm86 -- control vm86-related functions

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/types.h>
     #include <machine/sysarch.h>
     #include <machine/vm86.h>

     int
     i386_vm86(int function, void *data);

DESCRIPTION

     The i386_vm86() system call is used to call various vm86 related functions.  The function argument can be one of the following values:

	   VM86_INIT	 This will initialize the kernel's vm86 parameter area for the process, and permit the process to make vm86 calls.  The
			 data argument points to the following structure:

			 struct vm86_init_args {
				 int	 debug;
				 int	 cpu_type;
				 u_char  int_map[32];
			 };

			 The debug argument is used to turn on debugging code.	The cpu_type argument controls the type of CPU being emulated, and
			 is currently unimplemented.  The int_map argument is a bitmap which determines whether vm86 interrupts should be handled
			 in vm86 mode, or reflected back to the process.  If the Nth bit is set, the interrupt will be reflected to the process,
			 otherwise it will be dispatched by the vm86 interrupt table.

	   VM86_INTCALL  This allows calls to be made to vm86 interrupt handlers by the process.  It effectively simulates an INT instruction.
			 data should point to the following structure:

			 struct vm86_intcall_args {
				 int	 intnum;
				 struct  vm86frame vmf;
			 };

			 intnum specifies the operand of INT for the simulated call.  A value of 0x10, for example, would often be used to call
			 into the VGA BIOS.  vmf is used to initialize CPU registers according to the calling convention for the interrupt han-
			 dler.

	   VM86_GET_VME  This is used to retrieve the current state of the Pentium(r) processor's VME (Virtual-8086 Mode Extensions) flag, which
			 is bit 0 of CR4.  data should be initialized to point to the following:

			 struct vm86_vme_args {
				 int	 state; 		 /* status */
			 };

			 state will contain the state of the VME flag on return.

     vm86 mode is entered by calling sigreturn(2) with the correct machine context for vm86, and with the PSL_VM bit set.  Control returns to the
     process upon delivery of a signal.

RETURN VALUES

     The i386_vm86() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
     cate the error.

ERRORS

     The i386_vm86() system call will fail if:

     [EINVAL]		The kernel does not have vm86 support, or an invalid function was specified.

     [ENOMEM]		There is not enough memory to initialize the kernel data structures.

AUTHORS

     This man page was written by Jonathan Lemon, and updated by Bruce M Simpson.

BSD
								   July 27, 1998							       BSD

Check Out this Related Man Page

MODIFY_LDT(2)						     Linux Programmer's Manual						     MODIFY_LDT(2)

NAME

       modify_ldt - get or set ldt

SYNOPSIS

       #include <sys/types.h>

       int modify_ldt(int func, void *ptr, unsigned long bytecount);

       Note: There is no glibc wrapper for this system call; see NOTES.

DESCRIPTION

       modify_ldt()  reads or writes the local descriptor table (ldt) for a process.  The ldt is a per-process memory management table used by the
       i386 processor.	For more information on this table, see an Intel 386 processor handbook.

       When func is 0, modify_ldt() reads the ldt into the memory pointed to by ptr.  The number of bytes read is the smaller of bytecount and the
       actual size of the ldt.

       When  func is 1, modify_ldt() modifies one ldt entry.  ptr points to a user_desc structure and bytecount must equal the size of this struc-
       ture.

       The user_desc structure is defined in <asm/ldt.h> as:

	   struct user_desc {
	       unsigned int  entry_number;
	       unsigned long base_addr;
	       unsigned int  limit;
	       unsigned int  seg_32bit:1;
	       unsigned int  contents:2;
	       unsigned int  read_exec_only:1;
	       unsigned int  limit_in_pages:1;
	       unsigned int  seg_not_present:1;
	       unsigned int  useable:1;
	   };

       In Linux 2.4 and earlier, this structure was named modify_ldt_ldt_s.

RETURN VALUE

       On success, modify_ldt() returns either the actual number of bytes read (for reading) or 0 (for writing).  On failure, modify_ldt() returns
       -1 and sets errno to indicate the error.

ERRORS

       EFAULT ptr points outside the address space.

       EINVAL ptr  is 0, or func is 1 and bytecount is not equal to the size of the structure modify_ldt_ldt_s, or func is 1 and the new ldt entry
	      has invalid values.

       ENOSYS func is neither 0 nor 1.

CONFORMING TO

       This call is Linux-specific and should not be used in programs intended to be portable.

NOTES

       Glibc does not provide a wrapper for this system call; call it using syscall(2).

SEE ALSO

       vm86(2)

COLOPHON

       This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2012-07-13							     MODIFY_LDT(2)

Linux and UNIX Man Pages

i386_vm86(2) [debian man page]

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