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Bounds checking for LDI/SVI.

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Russell-S-Harper 2019-05-02 17:04:37 -04:00
parent 02a9fd15d4
commit 5b78dcbd82
4 changed files with 33 additions and 26 deletions
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15
common/common.asm
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@ -977,14 +977,23 @@ _CPR .( ; CPR pq 0c pq Rp <- Rq - copy register
_INILS .( ; common initialization for LDI and SVI
JSR _CPYI1 ; copy q to I1
LDA _I1+3 ; check for negative offsets
BMI _1
CLC ; add the allocated memory offset
LDA _ARL
LDA _ARLL
ADC _I1+1
STA _I1+1
LDA _ARH
LDA _ARLH
ADC _I1+2
STA _I1+2
RTS
CMP _ARUH ; compare against upper limit
BCC _2 ; for sure less
BNE _1 ; not equal, must be more
LDA _I1+1
CMP _ARUL
BCC _2 ; for sure less
_1 BRK ; accessing out of bounds, abort and call exception handler (TODO)
_2 RTS
.)
_LDI .( ; LDI pq 0d pq Rp <- (Rq:bbcc) - load indirect from memory

13
common/common.h
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@ -88,13 +88,12 @@ _F_N = 32 ; if Rr < 0.0 (after TST)
_F_O = 64 ; if overflow (after arithmetic operations)
_F_U = 128 ; if underflow (after arithmetic operations)
; register I7 maintains locations of code and allocated memory
_CRL = _I7 ; code low and high bytes
_CRH = _CRL + 1
_ARL = _CRH + 1 ; allocated low and high bytes
_ARH = _ARL + 1
_CR = _CRL ; code memory address
_AR = _ARL ; allocated memory address
; register I7 maintains locations of allocated memory
_ARLL = _I7 ; allocated low and high bytes
_ARLH = _ARLL + 1
_ARUL = _ARLH + 1 ; allocated upper limit
_ARUH = _ARUL + 1
_AR = _ARLL ; allocated memory address
; register I8 is reserved for future use, e.g. context switching

2
common/page6.src
View File

@ -8,7 +8,7 @@ CODE(DEMO)
START
CMN
SET(R0, 9.4662)
SET(R1, 2)
SET(R1, 5)
LDI(R7, R1)
MUL(R7, R7, R7)
SVI(R1, R0)

27
emulator/main.c
View File

@ -17,13 +17,12 @@
#define _F _PCH + 1 /* flags */
#define _PC _PCL /* program counter */
/* register I7 maintains locations of code and allocated memory */
#define _CRL _I7 /* code low and high bytes */
#define _CRH _CRL + 1
#define _ARL _CRH + 1 /* allocated low and high bytes */
#define _ARH _ARL + 1
#define _CR _CRL /* code memory address */
#define _AR _ARL /* allocated memory address */
/* register I7 maintains locations of allocated */
#define _ARLL _I7 /* allocated low and high bytes */
#define _ARLH _ARLL + 1
#define _ARUL _ARLH + 1 /* allocated upper limit */
#define _ARUH _ARUL + 1
#define _AR _ARLL /* allocated memory address */
/* section modifiers */
#define _SM_FXD 0x01
@ -91,8 +90,8 @@ int main() {
/* offset the starting address */
entity += index;
/* save the starting address */
memory[_CRL] = entity & 0xff;
memory[_CRH] = entity >> 8;
memory[_PCL] = entity & 0xff;
memory[_PCH] = entity >> 8;
/* advance to the end of the section */
index += length;
}
@ -102,18 +101,18 @@ int main() {
/* entity is the length of zeroed data, length is the length of preset data */
if (fread(memory + index, length, 1, stdin)) {
/* save the start of the data */
memory[_ARL] = index & 0xff;
memory[_ARH] = index >> 8;
memory[_ARLL] = index & 0xff;
memory[_ARLH] = index >> 8;
/* advance to the end of the section */
index += entity + length;
/* save the end of the data */
memory[_ARUL] = index & 0xff;
memory[_ARUH] = index >> 8;
}
break;
}
}
memory[_PCL] = memory[_CRL];
memory[_PCH] = memory[_CRH];
hookexternal(hook);
reset6502();