2023-03-15 23:02:09 +00:00
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---
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title: "region.h"
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summary: "virtual memory space layout"
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---
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The first 4 digits of an address can be ignored, they are also ignored by the MMU,
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but for clarity / readability reasons they are `FFFF` in the kernel space.
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See _General Concepts / Memory Layout_(todo: add reference) and _General Concepts / Process Memory Isolation_(todo: add reference) for more details.
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| Name | Start | Description |
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|----------------------------------|--------------------|---------------------------------------------------|
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| `MEM_REGION_PROCESS` | 0x0000000000000000 | This is the start of the process space |
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| `MEM_REGION_PROCESS_EXEC` | 0x0000010000000000 | Every processes' executable will be mapped here |
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| `MEM_REGION_PROCESS_THREAD_BASE` | 0x0000010100000000 | The start of the _Thread Data_ regions |
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| `MEM_REGION_KERNEL` | 0xFFFF800000000000 | This is the start of the kernel space |
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| `MEM_REGION_KERNEL_STACK_DUMMY` | 0xFFFFF00000000000 | This area is used when preparing a threads' stack |
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| `MEM_REGION_KERNEL_HEAP` | 0xFFFFF80000000000 | The kernels' heap begins here |
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| `MEM_REGION_KERNEL_THREAD_BASE` | 0xFFFFFF0000000000 | The kernel processes' _Thread Data_ regions |
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| `MEM_REGION_KERNELEXEC` | 0xFFFFFFFF80000000 | The kernel executable is mapped here |
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2023-03-16 10:04:14 +00:00
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# `MEM_REGION_THREAD_OFFSET` - macro
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2023-03-15 23:02:09 +00:00
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This time the threads id specifies its offset in its processes' _Thread Data_ region.
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2023-03-16 10:04:14 +00:00
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# `KERNEL_START_ADDRESS` - macro
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2023-03-15 23:02:09 +00:00
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Returns the address of [_kernel_start](https://nerdcult.net/projects/noxos/docs/codebase/mm/region.h/#_kernel_start---global-variable).
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2023-03-16 10:04:14 +00:00
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# `KERNEL_END_ADDRESS` - macro
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2023-03-15 23:02:09 +00:00
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Returns the address of [_kernel_end](https://nerdcult.net/projects/noxos/docs/codebase/mm/region.h/#_kernel_end---global-variable).
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2023-03-16 10:04:14 +00:00
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# `_kernel_start` - global variable
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2023-03-15 23:02:09 +00:00
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This symbol is inserted by the linker at the beginning of the kernel.
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To access its value use [KERNEL_START_ADDRESS](https://nerdcult.net/projects/noxos/docs/codebase/mm/region.h/#kernel_start_address---macro).
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2023-03-16 10:04:14 +00:00
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# `_kernel_end` - global variable
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2023-03-15 23:02:09 +00:00
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This symbol is inserted by the linker at the end of the kernel.
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To access its value use [KERNEL_END_ADDRESS](https://nerdcult.net/projects/noxos/docs/codebase/mm/region.h/#kernel_end_address---macro).
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