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66 lines
2.0 KiB
66 lines
2.0 KiB
5 years ago
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; rt_memory.s: template for writing a memory model implementation
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;
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; Copyright 1999,2007 ARM Limited. All rights reserved.
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;
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; RCS $Revision: 172039 $
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; Checkin $Date: 2011-11-02 12:58:12 +0000 (Wed, 02 Nov 2011) $
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; Revising $Author: statham $
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; This module gives a framework for writing custom memory models
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; in. It actually implements a very simple memory model, in which:
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;
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; - the stack grows down from 0x80000000
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; - the heap is 128Kb and grows up from 0x60000000
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; - no extra memory is available for the heap
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IMPORT __rt_stackheap_storage
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AREA |.text|, CODE, READONLY
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; --------------------------------------------------
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; Initialisation function. This routine isn't required to
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; preserve any registers, although obviously it shouldn't
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; lose LR because it won't know where to return to. On
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; exit, SP should point to the top of the desired stack,
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; and [a1,a2) should be the initial block to use for the
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; heap.
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;
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; Returning a1==a2 is allowed.
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EXPORT __rt_stackheap_init
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__rt_stackheap_init
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; Set up some example values.
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MOV sp, #0x80000000
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MOV a1, #0x60000000
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ADD a2, a1, #0x20000
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MOV pc, lr
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; --------------------------------------------------
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; The heap extend function. This is called using the
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; ordinary ATPCS calling convention.
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;
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; On input: a1 is the minimum size of memory required
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; (guaranteed to be a multiple of 4)
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; a2 is a pointer to a word of memory, W, in which
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; to store the address of the block
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;
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; On exit: a1 is size of returned block
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; W contains base address of returned block
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; Or: a1 is zero
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; W has undefined contents
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EXPORT __rt_heap_extend
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__rt_heap_extend
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; Refuse all requests for extra heap space.
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MOV a1, #0
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LDMFD sp!, {pc}
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END
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