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Diffstat (limited to 'docs/PROJECTS.md')
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diff --git a/docs/PROJECTS.md b/docs/PROJECTS.md index eae860b..fe6c2a8 100644 --- a/docs/PROJECTS.md +++ b/docs/PROJECTS.md @@ -335,6 +335,20 @@ Worth knowing: a correctly-chosen 32-bit ARM database also lets IDA's own auto-analysis find Thumb functions — `experiments/fibonacci.bin` yields 54 functions on load with `arm:ARMv7-A` and none with `arm`. +### Thumb entry points from a vector table + +`Shift+T` scans forward from the cursor for **odd pointers** — an ARM function +pointer carries the mode in bit 0, so a Cortex-M vector table is a list of Thumb +entry points. IDA won't follow them on a headerless image, because nothing tells +it those words are pointers at all: + + 3 Thumb entries found, 3 disassembled + +A word only counts when it is odd, lands inside a loaded segment, and its target +is executable and not already data. The even words in a vector table (the initial +stack pointer) fail the first test, which is the point — marking a data word as +code corrupts the listing, so a false positive costs more than a miss. + ### When analysis finds nothing Zero functions is what a raw image described wrongly looks like — right file, |