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• #91 tocsa senior tag Darth Vader #89

  2004-02-25 15:38:27 #91

  Összes hozzászólása itt Válaszok az összes hozzászólására itt Válaszok erre a hozzászólásra

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  válasz Darth Vader #89 üzenetére

  Megnéztem az Understanding The Linux Kernel idevágó részeit.
  Mint kideritettem OReilly könyv, orosz site-ról sikerült letölteni pdf-ben. :)
  
  A Linux kernel beli szegmentálás:
  ''The 2.2 version of Linux uses segmentation only when required by the Intel 80x86
  architecture. In particular, all processes use the same logical addresses, so the total number of segments to be defined is quite limited and it is possible to store all Segment Descriptors in the Global Descriptor Table (GDT).''
  ...
  ''For each process, therefore, the GDT contains two different Segment Descriptors: one for the TSS segment and one for the LDT segment.''
  
  Lapozás
  ''Furthermore, instead of the three types of access rights (Read, Write, Execute) associated with segments, only two types of access rights (Read, Write) are associated with pages. If the Read/Write flag of a Page Directory or Page Table entry is equal to 0, the corresponding Page Table or page can only be read; otherwise it can be read and written.''
  
  ''pte_exec( )
  Returns the value of the User/Supervisor flag (indicating whether the page is
  accessible in User Mode). Notice that pages on the Intel processor cannot be protected against code execution.''
  
  
  PAE:
  
  ''The other main change is related to physical memory addressing. Recent Intel 80x86
  microprocessors include a feature called Physical Address Extension (PAE), which adds four extra bits to the standard 32-bit physical address. Linux 2.4 takes advantage of PAE and supports up to 64 GB of RAM. However, a linear address is still composed by 32 bits, so that only 4 GB of RAM can be ''permanently mapped'' and accessed at any time.''
  

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