x86_kernel_memory.h
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/*
* Copyright (C) 2014 René Kijewski <rene.kijewski@fu-berlin.de>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* Layout of the kernel memory. The symbols are set in the linker.ld.
*
* @ingroup x86
* @{
* @file
* @author René Kijewski <rene.kijewski@fu-berlin.de>
*/
#ifndef KERNEL_MEMORY_H__
#define KERNEL_MEMORY_H__
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief First byte inside the elf segments.
*
* Expected to be the start of the high memory, i.e. 1MB.
*/
extern char _kernel_memory_start;
/**
* @brief Start of first byte of code inside the .text segment.
*
* This symbol does not have to be aligned.
*/
extern char _section_text_start;
/**
* @brief First byte after the code.
*
* This symbol does not have to be aligned.
*/
extern char _section_text_end;
/**
* @brief First byte inside the .rodata segment.
*
* This symbol is expected to be aligned.
*/
extern char _section_rodata_start;
/**
* @brief First byte after the .rodata segment.
*
* This symbol does not have to be aligned.
*/
extern char _section_rodata_end;
/**
* @brief First byte inside the .data segment.
*
* This symbol is expected to be aligned.
*/
extern char _section_data_start;
/**
* @brief First byte after the .data segment.
*
* This symbol does not have to be aligned, since it shares the same previleges as the .bss segment.
*/
extern char _section_data_end;
/**
* @brief Start of the .bss segment.
*
* Probably unaligned.
* The .bss segment must follow the .data segment with no other segment inbetween.
* It's likely that `&_section_data_end == &_section_bss_start`.
*/
extern char _section_bss_start;
/**
* @brief First byte after the .bss segment.
*
* This symbol should not to be aligned, because RAM cycles would be wasted to clear unused bytes otherwise.
*/
extern char _section_bss_end;
/**
* @brief First byte after the last of the common elf segments.
*
* This symbol is expected to be aligned.
* The "common elf segments" are .text, .rodata, .data and .bss.
* All the (physical) memory beyond this point will be overwritten at the pleasure of the kernel.
*/
extern char _kernel_memory_end;
/**
* @brief First byte that may be mapped as the heap
*
* This symbol is expected to be aligned.
* Must be bigger than _kernel_memory_end.
* There should be a space between _kernel_memory_end and _heap_start, but it does not have to.
*/
extern char _heap_start;
#ifdef __cplusplus
}
#endif
#endif
/** @} */