i386_get_ldt, i386_set_ldt - manage i386 per-process Local Descriptor
i386 Architecture Library (libi386, -li386)
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
and are defined in <i386/segments.h> .
These structures are defined by the architecure as disjoint bit-fields,
so care must be taken in constructing them.
Upon successful completion, i386_get_ldt() returns the number of descriptors
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.
[EACESS] The caller attempted to use a descriptor that would circumvent
protection or cause a failure.
i386 Microprocessor Programmer's Reference Manual, Intel
You can really hose your process using this.
BSD September 20, 1993 BSD
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