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3.4. INTERFACE & CLASSES CHAPTER 3. VM, PROTECTION AND PAGING 138 } 139 else 140 { 141 page_table_entry ∗pte_base = 142 ( page_table_entry ∗) get3GBAdressOfPPN ( 143 page_directory [ pde_lpn ] . pde4k . page_table_base_address 144 ) ; 145 for ( uint32 pte_lpn =0; pte_lpn < PAGE_TABLE_ENTRIES; ++pte_lpn ) 146 { 147 i f ( pte_base [ pte_lpn ] . present ) 148 { 149 pte_base [ pte_lpn ] . present = 0; 150 PageManager : : instance ()−> freePage ( pte_base [ pte_lpn ] . page_base_address ) ; 151 } 152 } 153 page_directory [ pde_lpn ] . pde4k . present =0; 154 PageManager : : instance ()−> freePage ( page_directory [ pde_lpn ] . pde4k . page_table_base_address ) ; 155 } 156 } 157 } 158 PageManager : : instance ()−> freePage ( physical_page_directory_page ) ; 159 } 160 161 bool ArchMemory : : checkAddressValid ( uint32 physical_page_directory_page , uint32 laddress_to_check ) 162 { 163 page_directory_entry ∗page_directory = 164 ( page_directory_entry ∗) get3GBAdressOfPPN ( physical_page_directory_page ) ; 165 uint32 linear_page = laddress_to_check / PAGE_SIZE; 166 uint32 pde_lpn = linear_page / PAGE_TABLE_ENTRIES; 167 uint32 pte_lpn = linear_page % PAGE_TABLE_ENTRIES; 168 i f ( page_directory [ pde_lpn ] . pde4k . present ) 169 { 170 i f ( page_directory [ pde_lpn ] . pde4m. use_4_m_pages ) 171 return true ; 172 173 page_table_entry ∗pte_base = 174 ( page_table_entry ∗) get3GBAdressOfPPN ( 175 page_directory [ pde_lpn ] . pde4k . page_table_base_address 176 ) ; 177 i f ( pte_base [ pte_lpn ] . present ) 178 return true ; 179 else 180 return false ; 181 } 182 else 183 return false ; 184 } 185 186 uint32 ArchMemory : : getPhysicalPageOfVirtualPageInKernelMapping ( uint32 linear_page , 187 188 { 189 page_directory_entry ∗page_directory = 190 ( page_directory_entry ∗) &kernel_page_directory_start ; 191 uint32 pde_lpn = linear_page / PAGE_TABLE_ENTRIES; 192 uint32 pte_lpn = linear_page % PAGE_TABLE_ENTRIES; 193 i f ( page_directory [ pde_lpn ] . pde4k . present ) //the present b i t i s the same f o r 4k and 4m 194 { 195 i f ( page_directory [ pde_lpn ] . pde4m. use_4_m_pages ) 196 { 197 ∗physical_page = page_directory [ pde_lpn ] . pde4m. page_base_address ; 198 return (PAGE_SIZE∗1024U) ; 199 } 38 of 151
CHAPTER 3. VM, PROTECTION AND PAGING 3.4. INTERFACE & CLASSES 200 else 201 { 202 page_table_entry ∗pte_base = 203 ( page_table_entry ∗) get3GBAdressOfPPN ( 204 page_directory [ pde_lpn ] . pde4k . page_table_base_address 205 ) ; 206 i f ( pte_base [ pte_lpn ] . present ) 207 { 208 ∗physical_page = pte_base [ pte_lpn ] . page_base_address ; 209 return PAGE_SIZE; 210 } 211 else 212 return 0; 213 } 214 } 215 else 216 return 0; 217 } 3.4.2 PageManager The class PageManager is a singleton class. Sweb uses PageManager to maintain what physical pages are free or used. The PageManager assumes all pages to be 4KiB in size. PageManager historically is created even before the KernelMemory- Manager and loaded at the linear address &kernel_end_address. For each physical memory page the manager uses 8 bit of kernel memory. With a memory footprint of sizeof(P ageManager)+number physicalpages ∗sizeof(uint8) and the Sweb limit of maximum 1 GiB physical memory, PageManager can consume a maximum of 12 + 256 = 268Byte. Currently Sweb knows four page usage types: PAGE_RESERVED, PAGE_KERNEL, PAGE_USERSPACE, PAGE_FREE. Pages marked reserved can never be free’d, they are memory areas used by the hardware or modules loaded by grub. The 4 remaining bits are free for future use. Interface Method static pointer createPageManager(pointer next_usable_address); static PageManager *instance(); uint32 getTotalNumPages() const; Description creates the singleton instance of PageManger. This method in turn calls the PageManager ctor using placement new. returns a pointer to singleton instance of Page- Manager. Example: PageManager::instance()- >method(); returns the number of 4KiB Pages available to Sweb. That is the size of the first usable memory region as reported by grub or a maximum of 1GiB, divided by the size of one page (4KiB) 39 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 37: CHAPTER 3. VM, PROTECTION AND PAGIN
Page 55 and 56: Chapter 4 Kernelspace Memory Manage
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Page 61 and 62: Chapter 5 Threads and Processes 5.1
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CHAPTER 7.5. SERIAL 7. CHARACTER PO
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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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