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+/* Copyright (C) 2004  David Decotigny
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+   
+   This program 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 General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+   USA. 
+*/
+#ifndef _SOS_PAGING_H_
+#define _SOS_PAGING_H_
+
+/**
+ * @file paging.h
+ *
+ * MMU management routines (arch-dependent). Setup the MMU without
+ * identity-mapping physical<->virtual addresses over the whole
+ * physical address space: a single, restricted and known, area is
+ * identity-mapped, the remaining kernel/user space is not. To access
+ * and manage the MMU translation tables (PD/PT on x86), we rely on a
+ * particular configuration, called "mirroring", where the top-level
+ * translation table (PD on x86) maps itself at a known and fixed (virtual)
+ * address. The only assumption for this to be possible is that the
+ * structure of the translation table entries are compatible at the
+ * different levels of vadddr->paddr translation process (PDE and PTE
+ * on x86 are Ok). Credits go to Christophe Avoinne for that.
+ */
+
+#include <sos/types.h>
+#include <sos/errno.h>
+
+
+/**
+ * Basic SOS virtual memory organization
+ */
+/** Frontier between kernel and user space virtual addresses */
+#define SOS_PAGING_BASE_USER_ADDRESS (0x40000000) /* 1GB */
+#define SOS_PAGING_TOP_USER_ADDRESS (0xFFFFFFFF) /* 4GB */
+
+/** Length of the space reserved for the mirroring in the kernel
+    virtual space */
+#define SOS_PAGING_MIRROR_SIZE  (1 << 22)  /* 1 PD = 1024 Page Tables = 4MB */
+
+/** Virtual address where the mirroring takes place */
+#define SOS_PAGING_MIRROR_VADDR \
+   (SOS_PAGING_BASE_USER_ADDRESS - SOS_PAGING_MIRROR_SIZE)
+
+
+/**
+ * sos_paging_map flags
+ */
+/** Usual virtual memory access rights */
+#define SOS_VM_MAP_PROT_NONE  0
+#define SOS_VM_MAP_PROT_READ  (1<<0)
+#define SOS_VM_MAP_PROT_WRITE (1<<1)
+/* EXEC not supported */
+
+/** Mapping a page may involve an physical page allocation (for a new
+    PT), hence may potentially block */
+#define SOS_VM_MAP_ATOMIC     (1<<31)
+
+
+/**
+ * Setup initial page directory structure where the kernel is
+ * identically-mapped, and the mirroring. This routine also
+ * identity-maps the BIOS and video areas, to allow some debugging
+ * text to be printed to the console. Finally, this routine installs
+ * the whole configuration into the MMU.
+ */
+sos_ret_t sos_paging_subsystem_setup(sos_paddr_t identity_mapping_base,
+				     sos_paddr_t identity_mapping_top);
+
+/**
+ * Map the given physical page at the given virtual address in the
+ * current address space.
+ *
+ * @note *IMPORTANT*: The physical page ppage_paddr *MUST* have been
+ * referenced by the caller through either a call to
+ * sos_physmem_ref_physpage_new() or sos_physmem_ref_physpage_at(). It
+ * would work if this were untrue, but this would be INCORRECT (it is
+ * expected that one is owning the page before mapping it, or
+ * otherwise the page could have been stolen by an interrupt or
+ * another thread).
+ *
+ * @param ppage_paddr  The address of a physical page (page-aligned)
+ * @param vpage_vaddr  The address of the virtual page (page-aligned)
+ * @param is_user_page TRUE when the page is available from user space
+ * @param flags        A mask made of SOS_VM_* bits
+ *
+ * @note Unless the SOS_VM_MAP_ATOMIC bit is set in the flags, the
+ * function may potentially block, because a physical page may be
+ * allocated for a new PT.
+ */
+sos_ret_t sos_paging_map(sos_paddr_t ppage_paddr,
+			 sos_vaddr_t vpage_vaddr,
+			 sos_bool_t is_user_page,
+			 sos_ui32_t flags);
+
+/**
+ * Undo the mapping from vaddr to the underlying physical page (if any)
+ * @param vpage_vaddr  The address of the virtual page (page-aligned)
+ */
+sos_ret_t sos_paging_unmap(sos_vaddr_t vpage_vaddr);
+
+/**
+ * Return the page protection flags (SOS_VM_MAP_PROT_*) associated
+ * with the address, or SOS_VM_MAP_PROT_NONE when page is not mapped
+ */
+int sos_paging_get_prot(sos_vaddr_t vaddr);
+
+/**
+ * Return the physical address of the given virtual address. Since page
+ * at physical addr 0 is not mapped, the NULL result means "page not
+ * mapped".
+ */
+sos_paddr_t sos_paging_get_paddr(sos_vaddr_t vaddr);
+
+/**
+ * Tell whether the address is physically mapped
+ */
+#define sos_paging_check_present(vaddr) \
+  (sos_paging_get_paddr(vaddr) != NULL)
+
+#endif /* _SOS_PAGING_H_ */