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dtc: Warning rather than error on possible truncation of cell values

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We always evaluate integer values in cell arrays as 64-bit quantities, then
truncate to the size of the array cells (32-bit by default).  However to
detect accidental truncation of meaningful values, we give an error if the
truncated portion isn't either all 0 or all 1 bits.  However, this can
still give counterintuitive errors.  For if the user is thinking in 2's
complement 32-bit arithmetic (which would be quite natural), then they'd
expect the expression (-0xffffffff-2) to evaluate to -1 (0xffffffff).
However in 64-bit it evaluates to 0xfffffffeffffffff which does truncate
to the expected value but trips this error message.

Because of this reduce the error to only a warnings, with a somewhat more
helpful message.

Fixes: https://github.com/dgibson/dtc/issues/74

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2022-11-21 14:18:44 +11:00
parent 55778a03df
commit 2cd89f862c
4 changed files with 27 additions and 3 deletions
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7
tests/cell-overflow-results.dts Normal file
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@ -0,0 +1,7 @@
/dts-v1/;
/ {
prop1 = < 0 >;
prop2 = < 0xffffffff >;
prop3 = < 0 >;
};

7
tests/cell-overflow.dts Normal file
View file

@ -0,0 +1,7 @@
/dts-v1/;
/ {
prop1 = < (-0xffffffff - 1) >;
prop2 = < (-0xffffffff - 2) >;
prop3 = < ((-0xffffffff - 1) * 2) >;
};

5
tests/run_tests.sh
View file

@ -518,6 +518,11 @@ libfdt_tests () {
## https://github.com/dgibson/dtc/issues/64
check_tests "$SRCDIR/phandle-args-overflow.dts" clocks_property
## https://github.com/dgibson/dtc/issues/74
run_dtc_test -I dts -O dtb -o cell-overflow-results.test.dtb cell-overflow-results.dts
run_dtc_test -I dts -O dtb -o cell-overflow.test.dtb cell-overflow.dts
run_test dtbs_equal_ordered cell-overflow.test.dtb cell-overflow-results.test.dtb
# check full tests
for good in test_tree1.dtb; do
run_test check_full $good