Проект OpenNet: MAN i386_set_ldt (2) Системные вызовы (FreeBSD и Linux)

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i386_set_ldt (2)

>> i386_set_ldt (2) ( FreeBSD man: Системные вызовы )

BSD mandoc

NAME



i386_get_ldt

 
i386_set_ldt

 - manage i386 per-process Local Descriptor Table entries

LIBRARY

Lb libc

SYNOPSIS

#include <machine/segments.h>
#include <machine/sysarch.h>
int i386_get_ldt (int start_sel union descriptor *descs int num_sels);
int i386_set_ldt (int start_sel union descriptor *descs int num_sels);

DESCRIPTION

The i386_get_ldt ();
system call returns a list of the i386 descriptors in the current process' LDT. The i386_set_ldt ();
system call sets a list of i386 descriptors in the current process' LDT. For both routines, Fa start_sel specifies the index of the selector in the LDT at which to begin and Fa descs points to an array of Fa num_sels descriptors to be set or returned.

Each entry in the Fa descs array can be either a segment_descriptor or gate_descriptor and are defined in In i386/segments.h . These structures are defined by the architecture as disjoint bit-fields, so care must be taken in constructing them.

If Fa start_sel is LDT_AUTO_ALLOC Fa num_sels is 1 and the descriptor pointed to by Fa descs is legal, then i386_set_ldt ();
will allocate a descriptor and return its selector number.

If Fa num_descs is 1, Fa start_sels is valid, and Fa descs is NULL, then i386_set_ldt ();
will free that descriptor (making it available to be reallocated again later).

If Fa num_descs is 0, Fa start_sels is 0 and Fa descs is NULL then, as a special case, i386_set_ldt ();
will free all descriptors.

RETURN VALUES

Upon successful completion, i386_get_ldt ();
returns the number of descriptors currently in the LDT. The i386_set_ldt ();
system call returns the first selector set on success. If the kernel allocated a descriptor in the LDT, the allocated index is returned. Otherwise, a value of -1 is returned and the global variable errno is set to indicate the error.

ERRORS

The i386_get_ldt ();
and i386_set_ldt ();
system calls will fail if:

Bq Er EINVAL: An inappropriate value was used for Fa start_sel or Fa num_sels .
Bq Er EACCES: The caller attempted to use a descriptor that would circumvent protection or cause a failure.