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target/arm_simulator: fix undefined behaviour

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Shifting 32 bit unsigned variables by 32 bits is undefined behaviour

Change-Id: I846619a522c747f9c3b11a814a1864d1d51cfe87
Signed-off-by: Mark O'Donovan <shiftee@posteo.net>
Reviewed-on: https://review.openocd.org/c/openocd/+/9502
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
This commit is contained in:
Mark O'Donovan
2026-03-09 21:24:32 +00:00
committed by Antonio Borneo
parent 49e75c74d5
commit 231aa88ee5
1 changed files with 10 additions and 4 deletions
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14
src/target/arm_simulator.c
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@@ -27,25 +27,31 @@ static uint32_t arm_shift(uint8_t shift, uint32_t rm,
shift_amount &= 0xff; shift_amount &= 0xff;
if (shift == 0x0) { /* LSL */ if (shift == 0x0) { /* LSL */
if ((shift_amount > 0) && (shift_amount <= 32)) { if (shift_amount > 0 && shift_amount < 32) {
return_value = rm << shift_amount; return_value = rm << shift_amount;
*carry = rm >> (32 - shift_amount); *carry = rm >> (32 - shift_amount);
} else if (shift_amount == 32) {
return_value = 0x0;
*carry = rm & 0x1;
} else if (shift_amount > 32) { } else if (shift_amount > 32) {
return_value = 0x0; return_value = 0x0;
*carry = 0x0; *carry = 0x0;
} else /* (shift_amount == 0) */ } else /* (shift_amount == 0) */
return_value = rm; return_value = rm;
} else if (shift == 0x1) { /* LSR */ } else if (shift == 0x1) { /* LSR */
if ((shift_amount > 0) && (shift_amount <= 32)) { if (shift_amount > 0 && shift_amount < 32) {
return_value = rm >> shift_amount; return_value = rm >> shift_amount;
*carry = (rm >> (shift_amount - 1)) & 1; *carry = (rm >> (shift_amount - 1)) & 1;
} else if (shift_amount == 32) {
return_value = 0x0;
*carry = (rm >> 31) & 0x1;
} else if (shift_amount > 32) { } else if (shift_amount > 32) {
return_value = 0x0; return_value = 0x0;
*carry = 0x0; *carry = 0x0;
} else /* (shift_amount == 0) */ } else /* (shift_amount == 0) */
return_value = rm; return_value = rm;
} else if (shift == 0x2) { /* ASR */ } else if (shift == 0x2) { /* ASR */
if ((shift_amount > 0) && (shift_amount <= 32)) { if (shift_amount > 0 && shift_amount < 32) {
/* C right shifts of unsigned values are guaranteed to /* C right shifts of unsigned values are guaranteed to
* be logical (shift in zeroes); simulate an arithmetic * be logical (shift in zeroes); simulate an arithmetic
* shift (shift in signed-bit) by adding the sign bit * shift (shift in signed-bit) by adding the sign bit
@@ -54,7 +60,7 @@ static uint32_t arm_shift(uint8_t shift, uint32_t rm,
return_value = rm >> shift_amount; return_value = rm >> shift_amount;
if (rm & 0x80000000) if (rm & 0x80000000)
return_value |= 0xffffffff << (32 - shift_amount); return_value |= 0xffffffff << (32 - shift_amount);
} else if (shift_amount > 32) { } else if (shift_amount >= 32) {
if (rm & 0x80000000) { if (rm & 0x80000000) {
return_value = 0xffffffff; return_value = 0xffffffff;
*carry = 0x1; *carry = 0x1;