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/****************************************************************************
* arch/arm/src/arm/up_allocpage.c
* Allocate a new page and map it to the fault address of a task.
*
* Copyright (C) 2010 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <stdbool.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/sched.h>
#ifdef CONFIG_PAGING
#include <nuttx/page.h>
#include "pg_macros.h"
#include "up_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
#if CONFIG_PAGING_NPPAGED < 256
typedef uint8_t pgndx_t;
#elif CONFIG_PAGING_NPPAGED < 65536
typedef uint16_t pgndx_t;
#else
typedef uint32_t pgndx_t;
#endif
#if PG_POOL_MAXL1NDX < 256
typedef uint8_t L1ndx_t;
#elif PG_POOL_MAXL1NDX < 65536
typedef uint16_t L1ndx_t;
#else
typedef uint32_t L1ndx_t;
#endif
/****************************************************************************
* Private Data
****************************************************************************/
/* Free pages in memory are managed by indices ranging from up to
* CONFIG_PAGING_NPAGED. Initially all pages are free so the page can be
* simply allocated in order: 0, 1, 2, ... . After all CONFIG_PAGING_NPAGED
* pages have be filled, then they are blindly freed and re-used in the
* same order 0, 1, 2, ... because we don't know any better. No smart "least
* recently used" kind of logic is supported.
*/
static pgndx_t g_pgndx;
/* After CONFIG_PAGING_NPAGED have been allocated, the pages will be re-used.
* In order to re-used the page, we will have un-map the page from its previous
* mapping. In order to that, we need to be able to map a physical address to
* to an index into the PTE where it was mapped. The following table supports
* this backward lookup - it is indexed by the page number index, and holds
* another index to the mapped virtual page.
*/
static L1ndx_t g_ptemap[CONFIG_PAGING_NPPAGED];
/* The contents of g_ptemap[] are not valid until g_pgndx has wrapped at
* least one time.
*/
static bool g_pgwrap;
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_allocpage()
*
* Description:
* This architecture-specific function will set aside page in memory and map
* the page to its correct virtual address. Architecture-specific context
* information saved within the TCB will provide the function with the
* information needed to identify the virtual miss address.
*
* This function will return the allocated physical page address in vpage.
* The size of the underlying physical page is determined by the
* configuration setting CONFIG_PAGING_PAGESIZE.
*
* NOTE 1: This function must always return a page allocation. If all
* available pages are in-use (the typical case), then this function will
* select a page in-use, un-map it, and make it available.
*
* NOTE 2: If an in-use page is un-mapped, it may be necessary to flush the
* instruction cache in some architectures.
*
* NOTE 3: Allocating and filling a page is a two step process. up_allocpage()
* allocates the page, and up_fillpage() fills it with data from some non-
* volatile storage device. This distinction is made because up_allocpage()
* can probably be implemented in board-independent logic whereas up_fillpage()
* probably must be implemented as board-specific logic.
*
* NOTE 4: The initial mapping of vpage should be read-able and write-
* able (but not cached). No special actions will be required of
* up_fillpage() in order to write into this allocated page.
*
* Input Parameters:
* tcb - A reference to the task control block of the task that needs to
* have a page fill. Architecture-specific logic can retrieve page
* fault information from the architecture-specific context
* information in this TCB to perform the mapping.
*
* Returned Value:
* This function will return zero (OK) if the allocation was successful.
* A negated errno value may be returned if an error occurs. All errors,
* however, are fatal.
*
* Assumptions:
* - This function is called from the normal tasking context (but with
* interrupts disabled). The implementation must take whatever actions
* are necessary to assure that the operation is safe within this
* context.
*
****************************************************************************/
int up_allocpage(FAR _TCB *tcb, FAR void **vpage)
{
uintptr_t vaddr;
uintptr_t paddr;
uint32_t *pte;
unsigned int pgndx;
/* Since interrupts are disabled, we don't need to anything special. */
DEBUGASSERT(tcb && vpage);
/* Get the virtual address that caused the fault */
vaddr = tcb->xcp.far;
DEBUGASSERT(vaddr >= PG_PAGED_VBASE && vaddr < PG_PAGED_VEND);
/* Allocate page memory to back up the mapping. Start by getting the
* index of the next page that we are going to allocate.
*/
pgndx = g_pgndx++;
if (g_pgndx >= CONFIG_PAGING)
{
g_pgndx = 0;
g_pgwrap = true;
}
/* Was this physical page previously mapped? If so, then we need to un-map
* it.
*/
if (g_pgwrap)
{
/* Yes.. Get a pointer to the L2 entry corresponding to the previous
* mapping -- then zero it!
*/
uintptr_t oldvaddr = PG_POOL_NDX2VA(g_ptemap[pgndx]);
pte = up_va2pte(oldvaddr);
*pte = 0;
/* Invalidate the instruction TLB corresponding to the virtual address */
tlb_inst_invalidate_single(oldvaddr);
/* I do not believe that it is necessary to flush the I-Cache in this
* case: The I-Cache uses a virtual address index and, hence, since the
* NuttX address space is flat, the cached instruction value should be
* correct even if the page mapping is no longer in place.
*/
}
/* Then convert the index to a (physical) page address. */
paddr = PG_POOL_PGPADDR(pgndx);
/* Now setup up the new mapping. Get a pointer to the L2 entry
* corresponding to the new mapping. Then set it map to the newly
* allocated page address. The inital mapping is read/write but
* non-cached (MMU_L2_ALLOCFLAGS)
*/
pte = up_va2pte(vaddr);
*pte = (paddr | MMU_L2_ALLOCFLAGS);
/* And save the new L1 index */
g_ptemap[pgndx] = PG_POOL_VA2L2NDX(vaddr);
/* Finally, return the virtual address of allocated page */
*vpage = (void*)(vaddr & ~PAGEMASK);
return OK;
}
#endif /* CONFIG_PAGING */
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