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Bugfix #560: false positive crash on out-of-bounds memory writes #561

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Merged
gatk555 merged 1 commit into from
Oct 13, 2025
Merged

Bugfix #560: false positive crash on out-of-bounds memory writes #561

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25 changes: 13 additions & 12 deletions simavr/sim/sim_core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -227,17 +227,15 @@ void _call_sram_irqs(avr_t *avr, uint16_t addr) {
void avr_core_watch_write(avr_t *avr, uint16_t addr, uint8_t v)
{
if (addr > avr->ramend) {
uint16_t ramstart = avr->ioend + 1;
uint16_t ramsize = avr->ramend - ramstart + 1;
uint16_t wrapped_addr = ramstart + ((addr - ramstart) % ramsize);
AVR_LOG(avr, LOG_WARNING,
"CORE: *** Wrapping write address "
"PC=%04x SP=%04x O=%04x v=%02x Address %04x %% %04x --> %04x\n",
avr->pc, _avr_sp_get(avr), _avr_flash_read16le(avr, avr->pc), v, addr, (avr->ramend + 1), addr % (avr->ramend + 1));
addr = addr % (avr->ramend + 1);
}
if (addr < 32) {
AVR_LOG(avr, LOG_ERROR,
"%sCORE: *** Invalid write address PC=%04x SP=%04x O=%04x Address %04x=%02x low registers%s\n",
simavr_font.red, avr->pc, _avr_sp_get(avr), _avr_flash_read16le(avr, avr->pc), addr, v, simavr_font.normal);
crash(avr);
"PC=%04x SP=%04x O=%04x Address %04x --> %04x (ramstart=%04x, ramend=%04x)\n",
avr->pc, _avr_sp_get(avr), _avr_flash_read16le(avr, avr->pc),
addr, wrapped_addr, ramstart, avr->ramend);
addr = wrapped_addr;
}
#if AVR_STACK_WATCH
/*
Expand All @@ -264,12 +262,15 @@ void avr_core_watch_write(avr_t *avr, uint16_t addr, uint8_t v)
uint8_t avr_core_watch_read(avr_t *avr, uint16_t addr)
{
if (addr > avr->ramend) {
uint16_t ramstart = avr->ioend + 1;
uint16_t ramsize = avr->ramend - ramstart + 1;
uint16_t wrapped_addr = ramstart + ((addr - ramstart) % ramsize);
AVR_LOG(avr, LOG_WARNING,
"CORE: *** Wrapping read address "
"PC=%04x SP=%04x O=%04x Address %04x %% %04x --> %04x\n",
"PC=%04x SP=%04x O=%04x Address %04x --> %04x (ramstart=%04x, ramend=%04x)\n",
avr->pc, _avr_sp_get(avr), _avr_flash_read16le(avr, avr->pc),
addr, (avr->ramend + 1), addr % (avr->ramend + 1));
addr = addr % (avr->ramend + 1);
addr, wrapped_addr, ramstart, avr->ramend);
addr = wrapped_addr;
}

if (avr->gdb) {
Expand Down