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3.4. INTERFACE & CLASSES CHAPTER 3. VM, PROTECTION AND PAGING 3.4 Interface & Classes 3.4.1 ArchMemory The class ArchMemory does not get instantiated. Instead it is a collection of architecture dependent static methods related to Memory and Pages. Therefore these methods will be refereed to as functions. An alternative would have been to use namespaces, but this approach was taken. ArchMemory contains architecture dependent code and needs to be implemented separately for each platform. This document focuses on the x86 architecture. Interface Function static void initNewPageDirectory(uint32 physical_page_to_use); static void mapPage(uint32 physical_page_directory_page, uint32 linear_page, uint32 physical_page, uint32 user_access, uint32 page_size=PAGE_SIZE); static void unmapPage(uint32 physical_page_directory_page, uint32 linear_page); static void freePageDirectory(uint32 physical_page_directory_page); Description creates a new Page-Directory for an user process by copying the original kernel-only page directory. The parameter physical_page_to_use specifies where the new PDE should be. maps a linear page to a physical page (pde and pte need to be set up first). physical_page_directory_page specifies the physical page where the Page-Directory-Entry to work on can be found. With user_access the User/- Supervisor Flag can be set. page_size is optional and defaults to 4KiB pages, but you need to set it to 1024*4096 if you want to map a 4MiB page. removes the mapping of a linear_page by marking its PTE Entry as non valid The parameter physical_page_directory_page specifies the real memory page where the PDE to work on can be found. virtual_page identifies the mapping that will be invalidated. recursively removes a Page-Directory-Entry, the Page-Tables it points to and marks all mapped pages as free in the PageManger. physical_page_directory_page are the 20 most significant bits of the physical address on which the Page-Directory can be found. 34 of 151
CHAPTER 3. VM, PROTECTION AND PAGING 3.4. INTERFACE & CLASSES static pointer get3GBAdressOfPPN(uint32 ppn, uint32 page_size=PAGE_SIZE); static bool checkAddressValid(uint32 physical_page_directory_page, uint32 laddress_to_check); static uint32 getPhysicalPageOfVirtualPageInKernelMapping(uint32 linear_page, uint32 *physical_page); Because mapping is present everywhere, in sweb there is the 1:1 mapping which allows us to directly access the given page. Takes a physical page number and returns a linear address than can be used to directly access the given page. Basically, an offset of 3GiB is added and the page number is multiplied by page_size. This is a very important method, it is the only way to manipulate page directories or page tables. The parameter page_size is optional and defaults to 4KiB pages. Needs to be set to 1024*4096 when using a 4MiB page number. Checks if a given linear address is valid and therefore mapped to physical memory. physical_page_directory_page is the physical page where the Page-Directory-Entry which’s mappings are to be checked, can be found. The function returns true if a mapping of laddress_to_check exists in physical_page_directory_page and false if the given linear address is unmapped and accessing it would result in a page fault. Takes a linear_page number and searches through the Page-Directory for the physical_page number it refers to. The result can be found in the variable that *physical_page pointed to. To access that physical page directly, get3GBAddressOfPPN(..) should be used. Returns 0 if the linear page does not map to any physical page or the page size in bytes on success. (4096 for 4KiB pages or 4096*1024 for 4MiB pages) Table 3.5: ArchMemory Interface Implementation 1 #include "ArchMemory.h" 2 #include " kprintf .h" 3 #include " assert .h" 4 5 extern "C" uint32 kernel_page_directory_start ; 6 7 void ArchMemory : : initNewPageDirectory ( uint32 physical_page_to_use ) 8 { 9 page_directory_entry ∗new_page_directory = 10 ( page_directory_entry ∗) get3GBAdressOfPPN ( physical_page_to_use ) ; 11 ArchCommon: :memcpy( 12 ( pointer ) new_page_directory , 13 ( pointer ) &kernel_page_directory_start , 35 of 151
Page 1 and 2: The holy bible of SWEB SWEB-Crew Se
Page 3 and 4: Contents 1 Install 13 1.1 some note
Page 5 and 6: CONTENTS CONTENTS 6 System Calls 71
Page 7 and 8: CONTENTS CONTENTS 11.6.9Running Xen
Page 9 and 10: List of Figures 3.1 Protected Mode
Page 11 and 12: List of Tables 3.1 Segment Descript
Page 13 and 14: Chapter 1 Install Basic guidelines
Page 15 and 16: CHAPTER 1. INSTALL 1.2. RUNNING SWE
Page 17 and 18: CHAPTER 1. INSTALL 1.3. DEVELOPERS
Page 19 and 20: Chapter 2 GDB 2.1 General The GNU P
Page 21 and 22: CHAPTER 2. GDB 2.5. USING DDD The d
Page 23 and 24: CHAPTER 2. GDB 2.5. USING DDD To ge
Page 25 and 26: Chapter 3 VM, Protection and Paging
Page 27 and 28: CHAPTER 3. VM, PROTECTION AND PAGIN
Page 33: CHAPTER 3. VM, PROTECTION AND PAGIN
Page 55 and 56: Chapter 4 Kernelspace Memory Manage
Page 57 and 58: CHAPTER 4. KERNELSPACE MEMORY MANAG
Page 59 and 60: CHAPTER 4. KERNELSPACE MEMORY MANAG
Page 61 and 62: Chapter 5 Threads and Processes 5.1
Page 63 and 64: CHAPTER 5. THREADS AND PROCESSES 5.
Page 65 and 66: CHAPTER 5. THREADS AND PROCESSES5.4
Page 71 and 72: Chapter 6 System Calls 6.1 Base Inf
Page 73 and 74: CHAPTER 6. SYSTEM 6.2. CALLS SYSTEM
Page 75 and 76: CHAPTER 6. SYSTEM CALLS 6.3. SYSTEM
Page 81 and 82: Chapter 7 Character Devices 7.1 Int
Page 83 and 84: CHAPTER 7. CHARACTER DEVICES 7.3. C
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CHAPTER 7. CHARACTER DEVICES 7.4. K
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CHAPTER 7.5. SERIAL 7. CHARACTER PO
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CHAPTER 7. CHARACTER DEVICES 7.7. T
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CHAPTER 7. CHARACTER DEVICES 7.7. T
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CHAPTER 7. CHARACTER DEVICES 7.8. C
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Chapter 8 Block Devices 8.1 Introdu
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CHAPTER 8. BLOCK DEVICES 8.2. IMPLE
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Chapter 9 VFS, FS 9.1 Introduction
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CHAPTER 9. VFS, FS 9.3. VFS DATA ST
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CHAPTER 9. VFS, FS 9.4. RAMFS - MEM
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Chapter 10 Locking 10.1 Introductio
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CHAPTER 10. LOCKING 10.2. LOCKS 10.
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CHAPTER 10. LOCKING 10.4. CRITICAL
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Chapter 11 Xen 11.1 Introduction Th
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CHAPTER 11. XEN 11.3. XEN Xen diffe
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CHAPTER 11. XEN 11.4. SWEB- XEN 11.
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CHAPTER 11. XEN 11.4. SWEB- XEN 21
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CHAPTER 11. XEN 11.4. SWEB- XEN Fig
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CHAPTER 11. XEN 11.4. SWEB- XEN 11.
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CHAPTER 11. XEN 11.4. SWEB- XEN Fig
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CHAPTER 11. XEN 11.6. APPENDIX: INS
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Chapter 12 Hacking Sweb This chapte
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Bibliography [1] Wikipedia:Binary_p
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