memlayout.h

// Memory layout

#define EXTMEM  0x100000            // Start of extended memory (1MB)
#define PHYSTOP 0xE000000           // Top physical memory (224MB)
#define DEVSPACE 0xFE000000         // Other devices are at high addresses

// Key addresses for address space layout (see kmap in vm.c for layout)
#define KERNBASE 0x80000000         // First kernel virtual address...
                                    // physical addrs 0..EXTMEM are mapped here,
                                    // followed by...
#define KERNLINK (KERNBASE+EXTMEM)  // Address where kernel is linked

// + note from vm.c:
// The kernel allocates physical memory for its heap and for user memory
// between V2P(end)   (i.e. end of kernel's data segment, some dist above EXTMEM)
// and the end of physical memory (PHYSTOP)
// (in kernel code these pages are directly addressable from end..P2V(PHYSTOP)).

// These macros only work for kernel v.addresses, not user v.addresses
#define V2P(a) (((uint) (a)) - KERNBASE)
#define P2V(a) ((void *)(((char *) (a)) + KERNBASE))

#define V2P_WO(x) ((x) - KERNBASE)    // same as V2P, but without casts
#define P2V_WO(x) ((x) + KERNBASE)    // same as P2V, but without casts