FENIX_kernel/include/memlayout.h

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2020-12-02 03:00:41 +00:00
/*
* <memlayout.h> - Memory layout for Fenix
* Largely based off memlayout.h from Xv6.
*/
#ifndef _MEMLAYOUT
#define _MEMLAYOUT
/*
* For future reference on how memory works.
* Extended memory starts at 0x100000 (1 MB).
* It runs from there to some space below the
* end of the actual physical memory. Here,
* that space is defined at 0xE000000 (~224 MB).
* 32-bit devices fill in from the end of
* physical memory down, starting here at like
* 256 MB and filling down to the top of
* our available memory.
*/
/* TODO: Maybe we want more than 256 MB available? */
/*
Counterpoint: This system isn't designed to use
a lot of RAM, and it designed to be like a system
of yore. 256 MB may be too much.
-Kat
*/
#define EXTMEM 0x100000 /* Extended memory start */
#define PHYSTOP 0xE000000 /* Top of physical memory */
#define DEVSPACE 0xFE000000 /* 32-bit devices */
/* Important address space layout stuff */
#define KERNBASE 0x80000000 /* First kernel virtual address */
#define KERNLINK (KERNBASE+EXTMEM) /* Kernel link address */
/* Translations between physical and virtual memory */
#define V2P(a) (((uint) (a)) - KERNBASE)
#define P2V(a) ((void *)(((char *) (a)) + KERNBASE))
/* The above without casts (NC -> No Cast) */
#define V2P_NC(a) ((a) - KERNBASE)
#define P2V_NC(a) ((a) + KERNBASE)
#endif