懂 GNU 链接器的进来帮一下忙

Buddy_Zhang1

在分析一个链接脚本的时候，有个地方看不懂，请大神赐教

__ksymtab       0 : { *(SORT(___ksymtab+*)) }

该指令中 “0” 的作用是什么？

nswcfd

1. 3.6.1 Output Section Description
   
2. --------------------------------
   
3. 
   
4. The full description of an output section looks like this:
   
5.      SECTION [ADDRESS] [(TYPE)] :
   
6.        [AT(LMA)]
   
7.        [ALIGN(SECTION_ALIGN)]
   
8.        [SUBALIGN(SUBSECTION_ALIGN)]
   
9.        [CONSTRAINT]
   
10.        {
    
11.          OUTPUT-SECTION-COMMAND
    
12.          OUTPUT-SECTION-COMMAND
    
13.          ...
    
14.        } [>REGION] [AT>LMA_REGION] [:PHDR :PHDR ...] [=FILLEXP]
    
15. 
    
16.    Most output sections do not use most of the optional section
    
17. attributes.
    
18. 
    
19.    The whitespace around SECTION is required, so that the section name
    
20. is unambiguous.  The colon and the curly braces are also required.  The
    
21. line breaks and other white space are optional.
    
22. 
    
23.    Each OUTPUT-SECTION-COMMAND may be one of the following:
    
24. 
    
25.    * a symbol assignment (*note Assignments::)
    
26. 
    
27.    * an input section description (*note Input Section::)
    
28. 
    
29.    * data values to include directly (*note Output Section Data::)
    
30. 
    
31.    * a special output section keyword (*note Output Section Keywords::)

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看起来像是ADDRESS

1. 3.6.3 Output Section Address
   
2. ----------------------------
   
3. 
   
4. The ADDRESS is an expression for the VMA (the virtual memory address)
   
5. of the output section.  If you do not provide ADDRESS, the linker will
   
6. set it based on REGION if present, or otherwise based on the current
   
7. value of the location counter.
   
8. 
   
9.    If you provide ADDRESS, the address of the output section will be
   
10. set to precisely that.  If you provide neither ADDRESS nor REGION, then
    
11. the address of the output section will be set to the current value of
    
12. the location counter aligned to the alignment requirements of the
    
13. output section.  The alignment requirement of the output section is the
    
14. strictest alignment of any input section contained within the output
    
15. section.
    

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