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Studying ‘mmap()/munmap()’

Studying ‘mmap()/munmap()’. How we can use our ‘toolbox’ of kernel modules to examine the effects of ‘mmap()/munmap()’. Experiment #1. Remember our ‘vma.c’ module? It creates a ‘/proc’ file It shows a task’s virtual memory areas NOTE: It works only for the ‘current’ task

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Studying ‘mmap()/munmap()’

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  1. Studying ‘mmap()/munmap()’ How we can use our ‘toolbox’ of kernel modules to examine the effects of ‘mmap()/munmap()’

  2. Experiment #1 • Remember our ‘vma.c’ module? • It creates a ‘/proc’ file • It shows a task’s virtual memory areas • NOTE: It works only for the ‘current’ task • We do BEFORE and AFTER comparisons

  3. Details of our Plan #1 • Install the ‘vma.c’ module • Install ‘mysis.c’ device-driver • Write an application: ‘mmstudy1.cpp’ • Open the files ‘/dev/mysis’ and ‘/proc/vma’ • Read and display contents of ‘/proc/vma’ • Call ‘mmap()’ to map the video frame-buffer • Read and display contents of ‘/proc/vma’ • Call ‘munmap()’ to unmap the frame-buffer • Read and display contents of ‘/proc/vma’

  4. Experiment #2 • We want to examine a task’s page-tables • We need to use our ‘ram.c’ device-driver • We also need a new ‘/proc’ file: ‘cr3.c’ • CR3 = physical address of page-directory • Page-Directory = page-table addresses • We again do BEFORE and AFTER looks

  5. Details of our Plan #2 • Install modules ‘cr3.c’ and ‘ram.c’ • Write an application: ‘mmstudy2.cpp’ • Open: /proc/cr3, ‘/dev/ram’ and ‘/dev/vram’ • Read page-directory and page-table(s) • Call ‘mmap()’ to map the video frame-buffer • Read page-directory and page-table(s) • Call ‘munmap()’ to unmap the frame-buffer • Read page-directory and page-table(s) • Compare tables (to see if anything changed)

  6. What to turn in today? • Turn in a printout of your source-code: • for ‘mmstudy1.cpp’ and for ‘mmstudy2.cpp’ • Turn in a printout of your program output: • from ‘mmstudy1’ and from ‘mmstudy2’ • You may ask for assistance • from Instructor, from TA, from classmembers

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