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test: the device runner refuses an image that runs past flash end

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A boot-linked image larger than its slot cannot execute on hardware, and
the naive copy smashed the heap beyond avr->flash — after which the
simulation misbehaved in ways that pointed everywhere but at the size:
phantom byte losses on the UART, garbage in SPMCSR, all downstream of
the overrun. The size gate had said it plainly; now the runner does too.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
BlackMark
2026-07-27 18:57:13 +02:00
parent aec430c2e1
commit a54075e526
2 changed files with 10 additions and 1 deletions
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9
test/device.c
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@@ -65,6 +65,15 @@ int main(int argc, char *argv[])
fprintf(stderr, "device: cannot read %s\n", argv[1]);
return 1;
}
// An image that runs past flash end cannot execute on hardware, and a
// naive copy of it would smash the heap beyond avr->flash — after which
// the simulation misbehaves in ways that point everywhere but here.
// Refuse it loudly instead.
if (boot_base + fw.flashsize > avr->flashend + 1) {
fprintf(stderr, "device: %u B at 0x%x runs past flash end 0x%x — image does not fit its slot\n",
(unsigned)fw.flashsize, boot_base, avr->flashend);
return 1;
}
memcpy(avr->flash + boot_base, fw.flash, fw.flashsize);
avr->pc = boot_base;
avr->codeend = avr->flashend;