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Sella, Iftach
ARM Emulator
Commits
b80ec766
Commit
b80ec766
authored
2 years ago
by
iftach
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added data processing instruction
parent
7ff087a5
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emulate.c
+90
-28
90 additions, 28 deletions
emulate.c
with
90 additions
and
28 deletions
emulate.c
+
90
−
28
View file @
b80ec766
...
...
@@ -17,7 +17,7 @@ struct ProcessorState
{
uint32_t
registers
[
17
];
// each uint32_t is 4 bytes large:
uint32_t
memory
[
MEMORY_SIZE
/
4
];
uint32_t
memory
[
MEMORY_SIZE
/
4
];
};
// Reads bits from source in the range [start, end] (inclusive). Returns an int32_t with the result as its least significant bits.
...
...
@@ -27,12 +27,25 @@ uint32_t getBits(uint32_t source, int start, int end)
return
(
source
&
((
2
<<
end
)
-
(
1
<<
start
)))
>>
start
;
}
void
setBit
(
uint32_t
*
source
,
int
index
,
bool
result
){
(
*
source
)
|=
(
1
<<
index
);
}
// Shorthand for getBits(source, index, index)
bool
isSet
(
uint32_t
source
,
int
index
)
{
return
(
source
&
(
1
<<
index
));
}
void
verifyAddress
(
unsigned
int
address
)
{
if
(
address
>
MEMORY_SIZE
/
8
||
address
%
4
!=
0
)
{
printf
(
"Invalid address! Exiting..."
);
exit
(
-
1
);
}
}
// Returns 1 if the condition code 'cond' is satisfied by the processor's current state, and 0 otherwise.
// Any condition code not listed in the spec will cause this to return 0.
bool
validCond
(
uint32_t
cond
,
struct
ProcessorState
*
processor
)
...
...
@@ -88,12 +101,13 @@ uint32_t barrelShift(bool immediate, uint32_t operand, bool *carry, struct Proce
// shifting an int32_t by 32 bits is undefined behaviour in C, and this if statement prevents it from happening later.
if
(
shiftCount
==
0
)
{
(
*
carry
)
=
0
;
return
operandVal
;
}
// set operandVal to the result after rotation
operandVal
=
(
operandVal
>>
(
2
*
shiftCount
))
|
(
operandVal
<<
(
32
-
2
*
shiftCount
));
// set c to the last bit of operandVal (the last bit to be rotated)
(
*
carry
)
=
isSet
(
operandVal
,
31
);
return
operandVal
;
...
...
@@ -108,7 +122,8 @@ uint32_t barrelShift(bool immediate, uint32_t operand, bool *carry, struct Proce
//*** shift using shift count stored in a register ***//
uint32_t
shiftReg
=
getBits
(
operand
,
8
,
11
);
// register should not be the PC
if
(
shiftReg
==
15
){
if
(
shiftReg
==
15
)
{
printf
(
"Invalid instruction: shift count cannot be stored in PC"
);
exit
(
-
1
);
}
...
...
@@ -186,8 +201,9 @@ uint32_t barrelShift(bool immediate, uint32_t operand, bool *carry, struct Proce
return
(
operandVal
>>
shiftCount
)
|
(
operandVal
<<
(
32
-
shiftCount
));
default:
// this should never happen (but gcc wants it)
return
0
;
// this should never happen (but gcc wants it)
printf
(
"Somehow, a 2-bit value has been interpreted as more than 3. Exiting..."
);
exit
(
-
1
);
};
}
...
...
@@ -229,9 +245,9 @@ int32_t applyOperation(int opcode, int32_t operand1, int32_t operand2, bool *car
case
3
:
// rsb
{
int32_t
swap
=
operand1
;
operand1
=
operand2
;
operand2
=
swap
;
int32_t
swap
=
operand1
;
operand1
=
operand2
;
operand2
=
swap
;
}
case
2
:
// sub
...
...
@@ -239,10 +255,10 @@ int32_t applyOperation(int opcode, int32_t operand1, int32_t operand2, bool *car
case
4
:
// add
{
uint32_t
result
=
operand1
+
operand2
;
// check for overflow (this should work in all cases):
(
*
carry
)
=
(
result
<
operand1
);
return
result
;
uint32_t
result
=
operand1
+
operand2
;
// check for overflow (this should work in all cases):
(
*
carry
)
=
(
result
<
operand1
);
return
result
;
}
case
13
:
...
...
@@ -254,6 +270,45 @@ int32_t applyOperation(int opcode, int32_t operand1, int32_t operand2, bool *car
};
}
//*** INSTRUCTIONS ***///
void
dataProcessingInstr
(
struct
ProcessorState
*
processor
,
int
address
)
{
// Check if address is valid
verifyAddress
(
address
);
uint32_t
instr
=
processor
->
memory
[
address
];
// Check if the instruction should be executed according to its condition codes
if
(
!
validCond
(
getBits
(
instr
,
28
,
31
),
processor
)){
return
;
}
// Get the shifted second operand
bool
carry
;
uint32_t
operand2
=
barrelShift
(
isSet
(
instr
,
25
),
getBits
(
instr
,
0
,
11
),
&
carry
,
processor
);
// Execute the instruction
bool
store
;
uint32_t
result
=
applyOperation
(
getBits
(
instr
,
21
,
24
),
processor
->
registers
[
getBits
(
instr
,
16
,
19
)],
operand2
,
&
carry
,
&
store
);
// Store the result
if
(
store
){
processor
->
registers
[
getBits
(
instr
,
12
,
15
)]
=
result
;
}
// Set the CPSR flags
if
(
isSet
(
instr
,
20
)){
uint32_t
*
cprs
=
processor
->
registers
[
16
];
// C
setBit
(
cprs
,
29
,
carry
);
// Z (I think this should be set to 0 if the result isn't all zeros, but the spec is a little unclear)
setBit
(
cprs
,
30
,
result
==
0
);
// N
setBit
(
cprs
,
31
,
isSet
(
result
,
31
));
}
}
//*** TESTING FUNCTIONS ***//
/* testing helper function (similar to the one in the slides) */
...
...
@@ -264,12 +319,15 @@ void test(bool pass, char *testname)
/* converts string representing a binary number to a number.
for testing - doesn't check validity. ignores leading zeros and any spaces*/
uint32_t
bin
(
char
*
number
){
uint32_t
bin
(
char
*
number
)
{
uint32_t
result
=
0
;
int
end
=
strlen
(
number
)
-
1
;
int
spaceCount
=
0
;
for
(
int
i
=
end
;
i
>=
0
;
i
--
){
if
(
number
[
i
]
==
' '
){
for
(
int
i
=
end
;
i
>=
0
;
i
--
)
{
if
(
number
[
i
]
==
' '
)
{
spaceCount
++
;
continue
;
}
...
...
@@ -278,7 +336,8 @@ uint32_t bin(char* number){
return
result
;
}
void
testBitGetters
(
void
){
void
testBitGetters
(
void
)
{
printf
(
"*** getBits() tests ***
\n
"
);
test
(
getBits
(
bin
(
"11000000000000000000000101101110"
),
28
,
31
)
==
12
,
"leftmost bits"
);
test
(
getBits
(
bin
(
"11000000000000000000000101101110"
),
8
,
20
)
==
1
,
"middle bits"
);
...
...
@@ -290,19 +349,10 @@ void testBitGetters(void){
test
(
isSet
(
bin
(
"11000000000000000000000101101110"
),
8
),
"middle bit"
);
test
(
!
isSet
(
bin
(
"11000000000000000000000101101110"
),
0
),
"rightmost bit"
);
printf
(
"
\n
"
);
}
/* creates a new processor, setting all registers to 0. Dynamically allocated - call free()! */
struct
ProcessorState
*
makeProcessor
(
void
){
struct
ProcessorState
*
processor
=
(
struct
ProcessorState
*
)
malloc
(
sizeof
(
struct
ProcessorState
));
for
(
int
i
=
0
;
i
<
17
;
i
++
){
processor
->
registers
[
i
]
=
0
;
}
return
processor
;
}
void
testBarrelShifter
(
void
){
void
testBarrelShifter
(
void
)
{
printf
(
"*** barrelShifter() tests ***
\n
"
);
struct
ProcessorState
*
processor
=
makeProcessor
();
processor
->
registers
[
0
]
=
bin
(
"10110100000000000000000000000000"
);
...
...
@@ -328,7 +378,19 @@ void testBarrelShifter(void){
free
(
processor
);
}
int
main
(
void
){
/* creates a new processor, setting all registers to 0. Dynamically allocated - call free()! */
struct
ProcessorState
*
makeProcessor
(
void
)
{
struct
ProcessorState
*
processor
=
(
struct
ProcessorState
*
)
malloc
(
sizeof
(
struct
ProcessorState
));
for
(
int
i
=
0
;
i
<
17
;
i
++
)
{
processor
->
registers
[
i
]
=
0
;
}
return
processor
;
}
int
main
(
void
)
{
testBitGetters
();
printf
(
"
\n
"
);
testBarrelShifter
();
...
...
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