150 lines
4.8 KiB
C
150 lines
4.8 KiB
C
/****************************************************************************
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* mm/mm_heap/mm_sbrk.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <assert.h>
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#include <errno.h>
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#include <nuttx/arch.h>
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#include <nuttx/mm/mm.h>
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#include <nuttx/pgalloc.h>
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#ifdef CONFIG_BUILD_KERNEL
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mm_sbrk
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*
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* Description:
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* The sbrk() function is used to change the amount of space allocated
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* for the calling process. The change is made by resetting the process's
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* break value and allocating the appropriate amount of space. The amount
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* of allocated space increases as the break value increases.
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*
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* The sbrk() function adds 'incr' bytes to the break value and changes
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* the allocated space accordingly. If incr is negative, the amount of
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* allocated space is decreased by incr bytes. The current value of the
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* program break is returned by sbrk(0).
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*
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* Input Parameters:
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* heap - A reference to the data structure that defines this heap.
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* incr - Specifies the number of bytes to add or to remove from the
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* space allocated for the process.
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* maxbreak - The maximum permissible break address.
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*
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* Returned Value:
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* Upon successful completion, sbrk() returns the prior break value.
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* Otherwise, it returns (void *)-1 and sets errno to indicate the
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* error:
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*
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* ENOMEM - The requested change would allocate more space than
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* allowed under system limits.
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* EAGAIN - The total amount of system memory available for allocation
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* to this process is temporarily insufficient. This may occur even
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* though the space requested was less than the maximum data segment
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* size.
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*
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****************************************************************************/
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FAR void *mm_sbrk(FAR struct mm_heap_s *heap, intptr_t incr,
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uintptr_t maxbreak)
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{
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uintptr_t brkaddr;
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uintptr_t allocbase;
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unsigned int pgincr;
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size_t bytesize;
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int errcode;
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DEBUGASSERT(incr >= 0);
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if (incr < 0)
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{
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errcode = ENOSYS;
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goto errout;
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}
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/* Get the current break address (NOTE: assumes region 0). If
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* the memory manager is uninitialized, mm_brkaddr() will return
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* zero.
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*/
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brkaddr = (uintptr_t)mm_brkaddr(heap, 0);
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if (incr > 0)
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{
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/* Convert the increment to multiples of the page size */
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pgincr = MM_NPAGES(incr);
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/* Check if this increment would exceed the maximum break value */
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if ((brkaddr > 0) && ((maxbreak - brkaddr) < (pgincr << MM_PGSHIFT)))
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{
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errcode = ENOMEM;
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goto errout;
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}
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/* Allocate the requested number of pages and map them to the
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* break address. If we provide a zero brkaddr to pgalloc(), it
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* will create the first block in the correct virtual address
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* space and return the start address of that block.
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*/
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allocbase = pgalloc(brkaddr, pgincr);
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if (allocbase == 0)
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{
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errcode = EAGAIN;
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goto errout;
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}
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/* Has the been been initialized? brkaddr will be zero if the
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* memory manager has not yet been initialized.
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*/
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bytesize = pgincr << MM_PGSHIFT;
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if (brkaddr == 0)
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{
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/* No... then initialize it now */
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mm_initialize(heap, (FAR void *)allocbase, bytesize);
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}
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else
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{
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/* Extend the heap (region 0) */
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mm_extend(heap, (FAR void *)allocbase, bytesize, 0);
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}
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}
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return (FAR void *)brkaddr;
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errout:
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set_errno(errcode);
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return (FAR void *)-1;
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}
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#endif /* CONFIG_BUILD_KERNEL */
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