/* Copyright (C) 2005 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_UMEM_VMM_H_
 #define _SOS_UMEM_VMM_H_
 
 /**
  * @file umem_vmm.h
  *
  * Management of the address space of a process in SOS. The so-called
  * "address space" of a process consists in the description of the
  * virtual addresses that are valid in the user space of a process (in
  * SOS: addresses 1G-4G). The kernel-space of a process is managed by
  * the "kmem" subsystem, and is kept identical accross all the
  * processes in the system.
  *
  * The umem_vmm subsystem handles the following features:
  *  - demand-mapping of resourcs (files: mmap): mapping in physical RAM
  *    will be delayed as much as possible, until the process really
  *    need to access the mapped addresses
  *  - mprotect/mremap support
  *  - private and shared mappings
  *  - Copy-On-Write (COW) of the private mappings upon fork() to favour
  *    shared physical memory as much as possible
  *  - "heap" management (brk/sbrk)
  *
  * Swap is NOT supported (yet), which means that the following is NOT
  * supported:
  *  - locked/reserved I/O pages (everything is locked in RAM)
  *  - "safe" demand-mapping of anonymous pages, ie conservative VMM
  *    allocation (alloc of anonymous pages on the swap)
  * Other unsupported features:
  *  - dynamically-resizable regions (Linux's GROWUP/GROWDOWN vma): the
  *    user stack is expected to have a suitable virtual size from the
  *    beginning, or sos_umem_vmm_resize() must be used explicitely to
  *    resize it
  *  - no provision of "stack size" accounting, since there are
  *    multiple stacks (ie user threads) in a process: which stack to
  *    consider ???
  *
  * The address space is divided into "virtual regions" (aka "VR") that
  * describe a single mapping, aka a segment of contiguous pages in
  * user-space virtual memory. Each such virtual region "maps" a
  * "resource" and is characterised by:
  *   - its base address and length in user-space
  *   - the allowed accesses, aka "protection" (read-only or read/write)
  *   - the resource it maps in virtual memory
  *
  * A so-called resource is typically:
  *   - a file
  *   - a device
  *   - an area initially full of zeros (the VR mapping this are called
  *     "anonymous mappings")
  *
  * The implementation is very close to that of Linux and Kos. This is
  * a "simple" implementation, not the most elegant one, such as those
  * based on "shadow objects" hierarchies as found in BSD 4.4 and Mach,
  * or that of Solaris (based on the "anon" lists). Actually, this
  * implementation does not use "shadow-objects"/anon list when a COW
  * page of a shared mapping is made anonymous. This won't hurt the
  * implementation of the basic demand-mapping mechanism; on the
  * contrary, it will make things simpler. But this will largely impact
  * the implementation of the swap-in/swap-out strategies, as these
  * would require a non trivial intrication of low-level and higher
  * level algorithms.
  */
 
 
 /**
  * Definition of an "address space" in Kos. This is an opaque
  * structure defined in umem_vmm.c. Its main role is to list virtual
  * regions. It mainly consists in:
  *  - a reference to the process owning it
  *  - maximum allowed protection (ie can it be mapped read-only or
  *    read/write ?)
  *  - the list of VRs mapping resources
  *  - a mm_context that reflects the configuration of the MMU
  *  - the location of the heap for this process
  *  - statistics
  */
 struct sos_umem_vmm_as;
 
 
 /**
  * Definition of a "virtual region". Linux would call them "vma"
  * (Virtual Memory Area), and Solaris: "segments". It mainly consists
  * in:
  *  - the start/end addresses of the mapping
  *  - a pointer to the resource that it maps
  *  - the type of mapping (shared/private)
  *  - the actual protection flags (@see SOS_VM_MAP_PROT_* flags in
  *    hwcore/paging.h)
  *  - a set of callbacks (@see sos_umem_vmm_vr_ops below) automatically
  *    called by the umem_vmm subsystem each time the VR is modified
  */
 struct sos_umem_vmm_vr;
 
 
 /** VR flag: region can be shared between a process and its
     children */
 #define SOS_VR_MAP_SHARED (1 << 0)
 
 
 #include <sos/types.h>
 #include <sos/process.h>
 
 
 /**
  * The callbacks applicable on a virtual region. Automatically called
  * by the umem_vmm subsystem.
  *
  * Calling sequences:
  * - duplicate_as() (aka fork()):
  *    vr->ops->ref()
  *    add vr to lists
  * - delete_as() (aka exit()):
  *    vr->ops->unmap()
  *    remove vr from lists
  *    vr->ops->unref()
  * - mmap():
  *    -> left + new + right VRs can fusion:
  *        remove right_vr from list
  *        right_vr->ops->unref()
  *    -> left + new VRs can fusion:
  *        nothing
  *    -> new + right VRs can fusion:
  *        nothing
  *    -> isolated:
  *        add new_vr to lists
  *        new_vr->map()
  *        new_vr->ops->ref()
  * - munmap():
  *    -> VR totally unmapped:
  *        vr->ops->unmap()
  *        remove vr from lists
  *        vr->ops->unref()
  *    -> VR unmapped in the middle (split into 2):
  *        add (new) right VR into the lists
  *        vr->unmap(middle_unmapped_area)
  *        right_vr->ops->ref()
  *    -> VR unmapped on its left:
  *        vr->ops->unmap(left_unmapped_area)
  *    -> VR unmapped on its right:
  *        vr->ops->unmap(right_unmapped_area)
  * - chprot():
  *    -> VR totally chprot:
  *        nothing
  *    -> VR chprot in the middle (split into 3):
  *        add (new) middle+right VRs into the lists
  *        middle_vr->ops->ref()
  *        right_vr->ops->ref()
  *    -> VR chprot on its left (split into 2):
  *        add (new) right VR into the lists
  *        right_vr->ops->ref()
  *    -> VR chprot on its right (split into 2):
  *        add (new) right VR into the lists
  *        right_vr->ops->ref()
  * - resize():
  *    -> if moving the VR: map/unmap
  *    -> otherwise: nothing
  */
 struct sos_umem_vmm_vr_ops
 {
   /**
    * Called after the virtual region has been inserted
    * inside its address space.
    * @note Optional
    */
   void (*ref)(struct sos_umem_vmm_vr * vr);
 
   /**
    * Called when the virtual region is removed from its
    * address space
    * @note Optional
    */
   void (*unref)(struct sos_umem_vmm_vr * vr);
 
   /**
    * Called when part or all a VR is unmapped
    * @note Optional
    */
   void (*unmap)(struct sos_umem_vmm_vr * vr,
                 sos_uaddr_t uaddr, sos_size_t size);
 
   /**
    * Called by the page fault handler to map data at the given virtual
    * address. In the Linux kernel, this callback is named "nopage".
    *
    * @note MANDATORY
    */
   sos_ret_t (*page_in)(struct sos_umem_vmm_vr * vr,
                        sos_uaddr_t uaddr,
                        sos_bool_t write_access);
 };
 
 
 /**
  * The definition of a mapped resource. Typically, a mapped resource
  * is a file or a device: in both cases, only part of the resource is
  * mapped by each VR, this part is given by the offset_in_resource
  * field of the VR, and the size field of the VR.
  */
 struct sos_umem_vmm_mapped_resource
 {
   /** Represent the maximum authrized SOS_VR_PROT_* for the VRs mapping
       it */
   sos_ui32_t  allowed_access_rights;
 
   /** Some flags associated with the resource. Currently only
       SOS_MAPPED_RESOURCE_ANONYMOUS is supported */
   sos_ui32_t  flags;
 
   /** List of VRs mapping this resource */
   struct sos_umem_vmm_vr * list_vr;
 
   /**
    * MANDATORY Callback function called when a new VR is created,
    * which maps the resource. This callback is allowed to change the
    * following fields of the VR:
    *   - sos_umem_vmm_set_ops_of_vr()
    */
   sos_ret_t (*mmap)(struct sos_umem_vmm_vr *);
 
   /**
    * Custom data that the user is free to define: the umem_vmm
    * subsystem won't ever look at it or change it
    */
   void *custom_data;
 };
 
 
 /** Inidicate that this resource is not backed by any physical
     storage. This means that the "offset_in_resource" field of the
     VRs will be computed by sos_umem_vmm_map() */
 #define SOS_MAPPED_RESOURCE_ANONYMOUS (1 << 0)
 
 
 /**
  * Physical address of THE page (full of 0s) used for anonymous
  * mappings. Anybody can map it provided it is ALWAYS in read-only
  * mode
  */
 extern sos_paddr_t sos_zero_page;
 
 
 /**
  * Setup the umem_vmm subsystem.
  */
 sos_ret_t sos_umem_vmm_subsystem_setup();
 
 
 /**
  * Create a new, empty, address space
  *
  * @param owner The process that will own the new address space
  *
  * @note no need to call
  * sos_thread_prepare_user_space_access()/sos_thread_end_user_space_access()
  */
 struct sos_umem_vmm_as *
 sos_umem_vmm_create_empty_as(struct sos_process *owner);
 
 
 /**
  * Create a new address space, copy of the current thread's address
  * space. All the translations belonging to private mappings are
  * marked 'read-only' to activate the "copy-on-write" semantics.
  *
  * @param owner The process that will hold the new address space
  *
  * @note automatically calls
  * sos_thread_prepare_user_space_access()/sos_thread_end_user_space_access()
  */
 struct sos_umem_vmm_as *
 sos_umem_vmm_duplicate_current_thread_as(struct sos_process *owner);
 
 
 /**
  * Called at process deletion time, to remove all mappings present in
  * the address space. This function not only delete all the VR data
  * structures, it also calls the unmap()/unref() callbacks of these
  * VRs. However, the physical pages mapped inside the address space
  * won't be unmapped at this stage: they will be unmapped all in one
  * go when the undelying mm_context will become unused.
  *
  * @note no need to call
  * sos_thread_prepare_user_space_access()/sos_thread_end_user_space_access()
  */
 sos_ret_t
 sos_umem_vmm_delete_as(struct sos_umem_vmm_as * as);
 
 
 /*
  * Accessor functions for the address space
  */
 
 /** Retrieve the pointer (NOT a new reference !) to the process owning
     the given address space. */
 struct sos_process *
 sos_umem_vmm_get_process(struct sos_umem_vmm_as * as);
 
 /** Retrieve the pointer (NOT a new reference !) to the MMU
     configuration for the given address space */
 struct sos_mm_context *
 sos_umem_vmm_get_mm_context(struct sos_umem_vmm_as * as);
 
 /** Retrieve a pointer to the VR that covers the given virtual address
     in the given address space */
 struct sos_umem_vmm_vr *
 sos_umem_vmm_get_vr_at_address(struct sos_umem_vmm_as * as,
                                sos_uaddr_t uaddr);
 
 
 /*
  * Accessor functions for the virtual regions
  */
 
 /** Retrieve the address space owning the given VR */
 struct sos_umem_vmm_as *
 sos_umem_vmm_get_as_of_vr(struct sos_umem_vmm_vr * vr);
 
 /** Retrieve the set of callbacks of the given VR */
 struct sos_umem_vmm_vr_ops *
 sos_umem_vmm_get_ops_of_vr(struct sos_umem_vmm_vr * vr);
 
 /** Retrieve the current protection of the given VR */
 sos_ui32_t sos_umem_vmm_get_prot_of_vr(struct sos_umem_vmm_vr * vr);
 
 /** Retrieve the flags of the given VR. One will especially be
     interested in the SOS_VR_MAP_SHARED bit */
 sos_ui32_t sos_umem_vmm_get_flags_of_vr(struct sos_umem_vmm_vr * vr);
 
 /** Retrieve the resource mapped by the VR */
 struct sos_umem_vmm_mapped_resource *
 sos_umem_vmm_get_mapped_resource_of_vr(struct sos_umem_vmm_vr * vr);
 
 /** Retrieve the start user address for the given mapping */
 sos_uaddr_t sos_umem_vmm_get_start_of_vr(struct sos_umem_vmm_vr * vr);
 
 /** Retrieve the size (in user space) of the given mapping */
 sos_size_t sos_umem_vmm_get_size_of_vr(struct sos_umem_vmm_vr * vr);
 
 /** Retrieve the offset in the resource of the mapping */
 sos_luoffset_t
 sos_umem_vmm_get_offset_in_resource(struct sos_umem_vmm_vr * vr);
 
 
 /*
  * Restricted accessor functions. May only be called from inside the
  * map() callback of a VR
  */
 
 /**
  * Function that is not called directly by the umem_subsystem: It MUST
  * always be called by the mmap() callback of the resource being
  * mapped (@see sos_umem_vmm_mapped_resource::mmap()). The mmap()
  * method is called at VR creation time, automatically by
  * sos_umem_vmm_map().
  *
  * @note The VR MUST NOT already have a set of operations (fatal error)
  */
 sos_ret_t sos_umem_vmm_set_ops_of_vr(struct sos_umem_vmm_vr * vr,
                                      struct sos_umem_vmm_vr_ops * ops);
 
 
 /*
  * mmap API
  */
 
 
 /** sos_umem_vmm_map() flag: the address given as parameter to
     sos_umem_vmm_map() is not only a hint, it is where the VR is
     expected to be mapped */
 #define SOS_VR_MAP_FIXED  (1 << 31)
 
 
 /**
  * Add a new VR in the given address space, that maps the given
  * resource. Its semantics follows that of the UNIX mmap() call
  * (including SOS_VR_MAP_FIXED). Real mapping in physical memory will
  * be delayed as much as possible (demand paging) and the physical
  * pages will be shared among processes as much as possible (COW).
  *
  * @param *uaddr must be page-aligned, and can be NULL. It stores the
  * address of the mapping, when successful
  *
  * @param size The size of the mapping in user space
  *
  * @param access_rights The allowed accesses to the mapped resource
  * (@see SOS_VM_MAP_PROT_* flags in hwcore/paging.h)
  *
  * @param flags mainly: is it shared mapping (SOS_VR_MAP_SHARED) or not ?
  *
  * @param resource MUST be NON NULL, and its mmap() method must also
  * be NON NULL
  *
  * @param offset_in_resource where inside the resource does the
  * mapping start
  *
  * @return SOS_OK on success (address of the mapping stored in uaddr)
  *
  * @note no need to call
  * sos_thread_prepare_user_space_access()/sos_thread_end_user_space_access()
  */
 sos_ret_t
 sos_umem_vmm_map(struct sos_umem_vmm_as * as,
                  sos_uaddr_t *uaddr, sos_size_t size,
                  sos_ui32_t access_rights,
                  sos_ui32_t flags,
                  struct sos_umem_vmm_mapped_resource * resource,
                  sos_luoffset_t offset_in_resource);
 
 
 /**
  * Unmap the given address interval. This might imply the partial or
  * complete unmapping of 0, 1 or more VRs. Same semantics as unix
  * munmap()
  *
  * @note automatically calls
  * sos_thread_prepare_user_space_access()/sos_thread_end_user_space_access()
  */
 sos_ret_t
 sos_umem_vmm_unmap(struct sos_umem_vmm_as * as,
                    sos_uaddr_t uaddr, sos_size_t size);
 
 
 /**
  * Change the access rights of the given address interval. This might
  * concern 0, 1 or more VRs, and result in the splitting in 1 or 2 VRs
  * if they are partially concerned by the change in protection.. Same
  * semantics as unix mprotect()
  *
  * @param new_access_rights @see SOS_VM_MAP_PROT_* flags in hwcore/paging.h
  *
  * @note MAKE SURE YOU CALL
  * sos_thread_prepare_user_space_access()/sos_thread_end_user_space_access()
  */
 sos_ret_t
 sos_umem_vmm_chprot(struct sos_umem_vmm_as * as,
                     sos_uaddr_t uaddr, sos_size_t size,
                     sos_ui32_t new_access_rights);
 
 
 
 /**
  * Flag for sos_umem_vmm_resize() to indicate that the VR being
  * resized can be moved elsewhere if there is not enough room to
  * resize it in-place
  */
 #define SOS_VR_REMAP_MAYMOVE (1 << 30)
 
 /**
  * Lookup the region covering the old_uaddr/old_size interval, and
  * resize it to match the *new_uaddr/new_size requirements. This is a
  * variant of Unix's mremap() that allow to resize the VR by its
  * low-addresses (mremap only allows to resize a VR by its
  * top-address).
  *
  * @param old_uaddr Low address of the interval covered by the VR to resize
  *
  * @param old_size Size of the interval covered by the VR to resize
  *
  * @param new_uaddr MUST BE page-aligned ! Initially: the new start
  * address of the VR, allowing to change the low-address. Once the
  * function returns: the actual start address of the VR (which might
  * be different, due to SOS_VR_REMAP_MAYMOVE flag, when set)
  *
  * @param new_size The size requested for the VR. Might be
  * smaller/larger than the original VR size
  *
  * @param flags Essentially: 0 or SOS_VR_REMAP_MAYMOVE
  *
  * @note MAKE SURE YOU CALL
  * sos_thread_prepare_user_space_access()/sos_thread_end_user_space_access()
  */
 sos_ret_t
 sos_umem_vmm_resize(struct sos_umem_vmm_as * as,
                     sos_uaddr_t old_uaddr, sos_size_t old_size,
                     sos_uaddr_t /* in/out */*new_uaddr, sos_size_t new_size,
                     sos_ui32_t flags);
 
 
 /*
  * Heap management API (ie libc's malloc support)
  */
 
 /**
  * Change the top address of the heap.
  *
  * @param new_top_uaddr When NULL don't change anything. Otherwise:
  * change the top address of the heap
  *
  * @return The top address of the heap after having been updated (if
  * ever)
  */
 sos_uaddr_t
 sos_umem_vmm_brk(struct sos_umem_vmm_as * as,
                  sos_uaddr_t new_top_uaddr);
 
 
 /*
  * Reserved functions
  */
 
 /**
  * Called by the main page fault handler when a physical page is not
  * mapped for the given address of the current address space. This
  * function is called only if:
  *  - The access (read / write) is allowed on this VR
  *  - no physical page is mapped yet
  * This function first calls the sos_paging_try_resolve_COW() to
  * resolve the COW if a COW access pattern is detected, and, if
  * unsuccessful, the sos_umem_vmm_vr_ops::page_in() method of the VR.
  *
  * @param uaddr The address that was accessed, causing the fault.
  *
  * @param write_access Was it write access ?
  *
  * @param user_access Was it a user access ? Or a kernel access (by
  * uaccess.h functions) ?
  *
  * @return SOS_OK when the fault could be solved, ie a page could be
  * mapped for the given address. -SOS_EFAULT otherwise, meaning the
  * faulting thread should be terminated or signalled (SIGSEGV)
  *
  * @note: The current mm_context MUST be that of the current thread
  * (which caused the exception) !
  */
 sos_ret_t sos_umem_vmm_try_resolve_page_fault(sos_uaddr_t uaddr,
                                               sos_bool_t write_access,
                                               sos_bool_t user_access);
 
 
 
 /**
  * Initialize the initial heap once the program code/data is mapped
  * Called by the ELF32 program loader.
  */
 sos_ret_t
 sos_umem_vmm_init_heap(struct sos_umem_vmm_as * as,
                        sos_uaddr_t heap_start);
 
 #endif /* _SOS_UMEM_VMM_H_ */