docs: documented ELF parser
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@ -256,7 +256,9 @@ This is not a really a placeholder, but you can use this to mask the % sign,
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so it will be interpreted as just a `%` instead of a placeholder.
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##
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## Executables
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NoxOS uses the **ELF** executable format, which is the linux/unix standard.
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Further information can be found in the `Syscalls` and `drivers/elf/elf.h` documentation.
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---
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@ -284,6 +286,144 @@ More information can be found on the limine project's [GitHub](https://github.co
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## drivers
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### elf/elf.h
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#### `elf_executable_T` - struct
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This struct holds the parsed data of an ELF executable.
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| Name | Type | Description |
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|--------------|--------------|----------------------------------------------------------------------------------------------------------------------------------|
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| header | elf_header_T | The header of the elf file |
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| num_symbols | uint64_t | The size of _symbols_ |
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| symbols | symbol_T* | An array containing all symbols of the elf file |
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| string_table | void* | A copy of the elf files `.strtab` section, all strings are referenced here to have them available even if the elf file is closed |
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#### `elf_executable_temp_T` - struct
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This struct is used while generating an `elf_executable_T`.
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It holds parse-time information about the elf file.
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| Name | Type | Description |
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|-----------------------------|-------------------|------------------------------------------------|
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| executable | elf_executable_T* | A pointer to the final `elf_executable_T` |
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| symbol_table | elf_section_T* | A pointer to `.symtab` in _buffer_ |
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| section_header_string_table | elf_section_T* | A pointer to `.shstrtab` in _buffer_ |
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| buffer | uint8_t* | The buffer where the executable is loaded from |
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#### `elf_executable_create(buffer)` - function (elf_executable_T*)
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Generates an `elf_executable_T` from an elf file loaded to **_buffer_** and returns a pointer to it.
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#### `elf_executable_destruct(executable)` - function (void)
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Frees all memory allocated for **_executable_**.
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### elf/header.h
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The enums in this header describe the possible values that a field of the elf header can have.
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#### `elf_target_architecture_E` - enum
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Field in header: **identity[4]**
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#### `elf_endianness_E` - enum
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Field in header: **identity[5]**
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#### `elf_sysabi_E` - enum
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Field in header: **identity[7]**
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#### `elf_object_type_E` - enum
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Field in header: **type**
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#### `elf_instruction_set_E` - enum
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Field in header: **isa**
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#### `elf_header_T` - struct
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| Name | Type | Description |
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|----------------------------|-------------|-------------------------------------------------------------------|
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| identity | uint8_t[16] | Information like the used endian and the SysABI is stored in here |
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| type | uint16_t | The type of the elf file -> `elf_object_type_E` |
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| isa | uint16_t | The used instruction set -> `elf_instruction_set_E` |
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| version | uint32_t | ELF version |
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| address_entry_point | uint64_t | The start point for program execution |
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| offset_program_header | uint64_t | The position of the program header array in the file |
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| offset_section_header | uint64_t | The position of the section header array in the file |
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| flags | uint32_t | Architecture dependent, can be ignored |
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| len_header | uint16_t | The size of this header |
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| len_program_header_entry | uint16_t | The size of one program header |
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| num_program_header_entries | uint16_t | The amount of program headers |
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| len_section_header_entry | uint16_t | The size of one section header |
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| num_section_header_entries | uint16_t | The amount of section headers |
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| string_section_index | uint16_t | The section header index of the `.shstrtab` section |
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#### `g_elf_target_architecture_strings` - global variable
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An array of strings matching `elf_target_architecture_E`.
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#### `g_elf_endianness_strings` - global variable
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An array of strings matching `elf_endianess_E`.
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#### `g_elf_sysabi_strings` - global variable
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An array of strings matching `elf_sysabi_E`.
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#### `g_elf_object_type_strings` - global variable
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An array of strings matching `elf_object_type_E`.
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#### `g_elf_instruction_set_strings` - global variable
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An array of strings matching `elf_instruction_set_E`.
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### elf/section.h
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#### `elf_section_type_E` - enum
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- **Null** - These sections can be ignored
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- **Program Data** - These link to segments, if I remember right
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- **Symbol Table** - Here are all the executables' symbols stored
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- **String Table** - Here are all strings stored
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- **RelocationA** - Contains relocation information
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- **Hash** - Symbol Table hash table
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- **Dynamic Link** - This provides information for the dynamic linker
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- **Note** - notes that were created by the compiler / toolchain
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- **Nobits** - Nulled data like `.bss`
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#### `elf_section_T` - struct
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| Name | Type | Description |
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|-----------------|----------|-------------------------------------------------------------------|
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| name_offset | uint32_t | The offset of the sections name in `.shstrtab` |
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| type | uint32_t | The type of the section -> `elf_section_type_E` |
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| flags | uint64_t | Sections attribute flags |
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| virtual_address | uint64_t | The address where the section should be mapped to (if it's not 0) |
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| offset | uint64_t | The sections offset in the file |
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| length | uint64_t | The size of the section |
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| link | uint32_t | Type specific link to another section |
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| info | uint32_t | Type specific information |
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| alignment | uint64_t | If the section is aligned, this value specifies the alignment |
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| entry_size | uint64_t | The size of the sections entries |
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#### `g_elf_section_type_strings` - global variable
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An array of strings matching `elf_section_type_E`.
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### elf/symbol.h
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#### `ELF_SYMBOL_TYPE(info)` - macro
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Extracts the `elf_symbol_type_E` from the symbols info value.
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#### `elf_symbol_type_E` - enum
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- **None** - Unspecified type
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- **Object** - Data objects like variables, arrays, etc.
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- **Func** - Function
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- **Section** - Associated section
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- **File** - The path to the source file associated with the object
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- **Common** - Uninitialized common blocks
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- **TLS** - Thread Local Storage
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#### `elf_symbol_T` - struct
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| Name | Type | Description |
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|-----------------------|-------------------------------------------------------------------|-------------|
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| name_offset | The offset of the symbols name in `.strtab` | |
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| info | Information about the symbol (type, bind) | |
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| other | Information about the symbol (visibility) | |
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| related_section_index | The index of the symbols related section | |
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| value | Value, in most cases this is an address | |
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| length | The size of the symbol (e.g. num bytes if the symbol is an array) | |
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### fs/ramfs.h
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**Warning:** This is a filesystem specific driver, by this it should only be accessed by the vfs.
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