fbd8961be1
In sim65, simulator memory access to a 64 KB array is implemented via functions defined in src/sim65/memory.h and src/sim65/memory.c. In the old version, the types for both content bytes (8 bits), content words (16 bits), regular addresses (16 bits), and zero-page addresses (8 bits) were all given as bare 'unsigned'. This lead to several cases of address overrun (e.g., when an instruction wraps around from address 0xffff to 0x0000) when running the simulator against a stress test (specifically, the 65x02 test suite). To protect from this, and to more properly express the bit width of the types involved which is a good idea anyway, we start using the fixed-width types provided by 'stdint.h'. In the process, we also change the MemReadByte macro to a full function call. This may impact performance (by a small amount), but it improves memory safety, as cases where the address is accidentally expressed as a value exceeding 0xffff are handled by wrap-around (as it is in the actual hardware), rather than causing access outside of the Mem[] array where the 64 KB of simulated RAM resides. The reason for this patch is twofold. (1) It is a partial patch for issue #2539. Several issues brought to the surface by running the 65x02 testsuite are eliminated by these changes. In the discussion about this issue, it was concluded that it is a Good Idea to use the stdint-types, both for the simulated CPU registers and for the memory. This patch addresses the memory-part of that change. (2) It is a precursor patch for issue #2355. For that issue, we will implement a memory-mapped timer register. This will make handling of memory access in the simulator a bit more complex. Having proper functions with the proper types in place will help to make the timer register patch easier.
75 lines
3.4 KiB
C
75 lines
3.4 KiB
C
/*****************************************************************************/
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/* */
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/* memory.h */
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/* */
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/* Memory subsystem for the 6502 simulator */
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/* */
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/* */
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/* */
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/* (C) 2002-2012, Ullrich von Bassewitz */
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/* Roemerstrasse 52 */
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/* D-70794 Filderstadt */
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/* EMail: uz@cc65.org */
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/* */
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/* */
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/* This software is provided 'as-is', without any expressed or implied */
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/* warranty. In no event will the authors be held liable for any damages */
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/* arising from the use of this software. */
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/* */
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/* Permission is granted to anyone to use this software for any purpose, */
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/* including commercial applications, and to alter it and redistribute it */
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/* freely, subject to the following restrictions: */
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/* */
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/* 1. The origin of this software must not be misrepresented; you must not */
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/* claim that you wrote the original software. If you use this software */
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/* in a product, an acknowledgment in the product documentation would be */
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/* appreciated but is not required. */
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/* 2. Altered source versions must be plainly marked as such, and must not */
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/* be misrepresented as being the original software. */
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/* 3. This notice may not be removed or altered from any source */
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/* distribution. */
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/* */
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/*****************************************************************************/
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#ifndef MEMORY_H
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#define MEMORY_H
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#include <stdint.h>
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extern uint8_t Mem[0x10000];
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/*****************************************************************************/
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/* Code */
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/*****************************************************************************/
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void MemWriteByte (uint16_t Addr, uint8_t Val);
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/* Write a byte to a memory location */
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void MemWriteWord (uint16_t Addr, uint16_t Val);
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/* Write a word to a memory location */
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uint8_t MemReadByte (uint16_t Addr);
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/* Read a byte from a memory location */
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uint16_t MemReadWord (uint16_t Addr);
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/* Read a word from a memory location */
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uint16_t MemReadZPWord (uint8_t Addr);
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/* Read a word from the zero page. This function differs from MemReadWord in that
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** the read will always be in the zero page, even in case of an address
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** overflow.
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*/
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void MemInit (void);
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/* Initialize the memory subsystem */
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/* End of memory.h */
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#endif
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