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i386_get_ldt (2)
  • >> i386_get_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.

     

    SEE ALSO

    i386 Microprocessor Programmer's Reference Manual, Intel  

    WARNING

    You can really hose your process using this.


     

    Index

    NAME
    LIBRARY
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    ERRORS
    SEE ALSO
    WARNING


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