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Segment selectors
Segments

## Detailed Description

The kernel maintains a table to translate selector values to segment base paragraphs.

A Paragraph is a 16byte quantity. This table and translation is necessary because IBM PC uses 16bit selectors in instructions but segments may reside anywhere in the linear addressing space. For example, if a segment with selector 5 resides at 0x400000, we need to have selector translation 5 -> 0x400000. For 16bit programs the selector translation table is usually empty, selector values are equal to segment base paragraphs.

## Functions
idaman bool ida_export | getn_selector (int n, sel_t *sel, ea_t *base)
| Get description of selector (0..get_selector_qty()-1)
idaman int ida_export | get_selector_qty (void)
| Get number of defined selectors.
idaman sel_t ida_export | setup_selector (ea_t segbase)
| Allocate a selector for a segment if necessary. More...
idaman sel_t ida_export | allocate_selector (ea_t segbase)
| Allocate a selector for a segment unconditionally. More...
idaman sel_t ida_export | find_free_selector (void)
| Find first unused selector. More...
idaman int ida_export | set_selector (sel_t selector, ea_t paragraph)
| Set mapping of selector to a paragraph. More...
idaman void ida_export | del_selector (sel_t selector)
| Delete mapping of a selector. More...
idaman ea_t ida_export | ask_selector (sel_t selector)
| Get mapping of a selector. More...
idaman ea_t ida_export | sel2ea (sel_t selector)
| Get mapping of a selector as a linear address. More...
idaman sel_t ida_export | find_selector (ea_t base)
| Find a selector that has mapping to the specified paragraph. More...
idaman int ida_export | enumerate_selectors (int(idaapi *func)(sel_t sel, ea_t para))
| Enumerate all selectors from the translation table. More...
idaman ea_t ida_export | enumerate_segments_with_selector (sel_t selector, ea_t(idaapi *func)(segment_t *s, void *ud), void *ud)
| Enumerate all segments with the specified selector. More...
idaman segment_t *ida_export | get_segm_by_sel (sel_t selector)
| Get pointer to segment structure. More...

## Function Documentation

idaman sel_t ida_export setup_selector | ( | ea_t | segbase | ) |

Allocate a selector for a segment if necessary.

You must call this function before calling add_segm_ex(). add_segm() calls this function itself, so you don't need to allocate a selector. This function will allocate a selector if 'segbase' requires more than 16 bits and the current processor is IBM PC. Otherwise it will return the segbase value.

Parameters

  segbase | a new segment base paragraph

Returns
  the allocated selector number

idaman sel_t ida_export allocate_selector | ( | ea_t | segbase | ) |

Allocate a selector for a segment unconditionally.

You must call this function before calling add_segm_ex(). add_segm() calls this function itself, so you don't need to allocate a selector. This function will allocate a new free selector and setup its mapping using find_free_selector() and set_selector() functions.

Parameters

  segbase | a new segment base paragraph

Returns
  the allocated selector number

idaman sel_t ida_export find_free_selector | ( | void |  | ) |

Find first unused selector.

Returns
  a number >= 1

idaman int ida_export set_selector | ( | sel_t | selector,
|  | ea_t | paragraph
| ) |  |

Set mapping of selector to a paragraph.

You should call this function _before_ creating a segment which uses the selector, otherwise the creation of the segment will fail.

Parameters

  selector | number of selector to map if selector == BADSEL, then return 0 (fail) if the selector has had a mapping, old mapping is destroyed if the selector number is equal to paragraph value, then the mapping is destroyed because we don't need to keep trivial mappings.
  paragraph | paragraph to map selector

Return values

  1 | ok
  0 | failure (bad selector or too many mappings)

idaman void ida_export del_selector | ( | sel_t | selector | ) |

Delete mapping of a selector.

Be wary of deleting selectors that are being used in the program, this can make a mess in the segments.

Parameters

  selector | number of selector to remove from the translation table

idaman ea_t ida_export ask_selector | ( | sel_t | selector | ) |

Get mapping of a selector.

Parameters

  selector | number of selector to translate

Returns
  paragraph the specified selector is mapped to. if there is no mapping, returns 'selector'.

idaman ea_t ida_export sel2ea | ( | sel_t | selector | ) |

Get mapping of a selector as a linear address.

Parameters

  selector | number of selector to translate to linear address

Returns
  linear address the specified selector is mapped to. if there is no mapping, returns toEA(selector,0);

idaman sel_t ida_export find_selector | ( | ea_t | base | ) |

Find a selector that has mapping to the specified paragraph.

Parameters

  base | paragraph to search in the translation table

Returns
  selector value or base

idaman int ida_export enumerate_selectors | ( | int(idaapi *)(sel_t sel, ea_t para) | func | ) |

Enumerate all selectors from the translation table.

This function calls 'func' for each selector in the translation table. If 'func' returns non-zero code, enumeration is stopped and this code is returned.

Parameters

  func | callback function sel: selector number para: selector mapping

Returns
  0 or code returned by 'func'.

idaman ea_t ida_export enumerate_segments_with_selector | ( | sel_t | selector,
|  | ea_t(idaapi *)(segment_t *s, void *ud) | func,
|  | void * | ud
| ) |  |

Enumerate all segments with the specified selector.

This function will call the callback function 'func' for each segment that has the specified selector. Enumeration starts from the last segment and stops at the first segment (reverse order). If the callback function 'func' returns a value != BADADDR, the enumeration is stopped and this value is returned to the caller.

Parameters

  selector | segments that have this selector are enumerated
  func | callback function s: pointer to segment structure ud: user data
  ud | pointer to user data. this pointer will be passed to the callback function

Returns
  BADADDR or the value returned by the callback function 'func'

idaman segment_t* ida_export get_segm_by_sel | ( | sel_t | selector | ) |

Get pointer to segment structure.

This function finds a segment by its selector. If there are several segments with the same selectors, the last one will be returned.

Parameters

  selector | a segment with the specified selector will be returned

Returns
  pointer to segment or NULL