MirBSD manpage: i386_get_ldt(2), i386_set_ldt(2)

I386_GET_LDT(2)         BSD Programmer's Manual (i386)         I386_GET_LDT(2)


     i386_get_ldt, i386_set_ldt - manage i386 per-process Local Descriptor
     Table entries


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

     i386_get_ldt(int start_sel, union descriptor *descs, int num_sels);

     i386_set_ldt(int start_sel, union descriptor *descs, int num_sels);


     i386_get_ldt() will return the list of i386 descriptors that the process
     has in its LDT. i386_set_ldt() will set a list of i386 descriptors for
     the current process in its LDT. Both routines accept a starting selector
     number start_sel, an array of memory that will contain the descriptors to
     be set or returned descs, and the number of entries to set or return

     The argument descs can be either segment_descriptor or gate_descriptor,
     as defined in <i386/segments.h>. These structures are defined by the ar-
     chitecture as disjoint bit-fields, so care must be taken in constructing

     Before this API can be used the functionality has to be enabled using the
     machdep.userldt sysctl(8) variable.

     Note: Code using the i386_get_ldt() and i386_set_ldt() functions must be
     compiled using -li386.


     Upon successful completion, i386_get_ldt() returns the number of descrip-
     tors currently in the LDT. i386_set_ldt() returns the first selector set.
     Otherwise, a value of -1 is returned and the global variable errno is set
     to indicate the error.


     i386_get_ldt() and i386_set_ldt() will fail if:

     [EINVAL]  An inappropriate parameter was used for start_sel or num_sels.

     [EACCES]  The caller attempted to use a descriptor that would circumvent
               protection or cause a failure.


     Intel, i386 Microprocessor Programmer's Reference Manual.


     You can really hose your process using this.

MirBSD #10-current            September 20, 1993                             1

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