This default ldt segment descriptor is stored in the gdt 這個默認ldt段描述符存儲在gdt中。
By default it contains a null segment descriptor 默認情況下,其中會包含一個空的段描述符。
Linux uses following segments descriptors Linux使用以下段描述符:
The corresponding segment descriptor stored in the gdt has following values 存儲在gdt中的對應段描述符的值如下:
Each segment descriptor is eight bytes long and represents a single segment in memory 每個段描述符長8個字節(jié),表示內(nèi)存中的一個段。
A 13 - bit index that identifies the corresponding segment descriptor entry contained in the gdt or ldt 一個13位的索引,用來標識gdt或ldt中包含的對應段描述符條目
This enables linux to use a limited number of segment descriptors , therefore all descriptors can be kept in the gdt 這使linux所用的段描述符數(shù)量受限,從而可將所有描述符都保存在gdt之中。
In addition to these segment descriptors , the gdt contains two more segment descriptors for each process created - the tss and ldt segments 除了這些段描述符之外, gdt還包含了另外兩個用于每個創(chuàng)建的進程的段描述符tss和ldt段。
Each time a segment selector is loaded on to segment registers , the corresponding segment descriptor is loaded from memory into a matching non - programmable cpu register 每次將段選擇器加載到段寄存器中時,對應的段描述符都會從內(nèi)存加載到相匹配的不可編程cpu寄存器中。
Since a segment descriptor is eight bytes long , its relative address inside the gdt or ldt is obtained by multiplying the most significant 13 bits of segment selector by 8 由于一個段描述符的大小是8個字節(jié),因此它在gdt或ldt中的相對地址可以這樣計算:段選擇器的高13位乘以8 。