diff options
| author | Peter Maydell <peter.maydell@linaro.org> | 2023-07-04 16:43:32 +0100 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2023-07-06 13:36:51 +0100 |
| commit | c41077235168140cdd4a34fce9bd95c3d30efe9c (patch) | |
| tree | 8bc11598b5de782ccd4abd40edb75e3f7076a439 | |
| parent | c74138c6c040b62e941326a4fbb25a93fdd35b72 (diff) | |
target/arm: Avoid over-length shift in arm_cpu_sve_finalize() error casepull-target-arm-20230706
If you build QEMU with the clang sanitizer enabled, you can see it
fire when running the arm-cpu-features test:
$ QTEST_QEMU_BINARY=./build/arm-clang/qemu-system-aarch64 ./build/arm-clang/tests/qtest/arm-cpu-features
[...]
../../target/arm/cpu64.c:125:19: runtime error: shift exponent 64 is too large for 64-bit type 'unsigned long long'
[...]
This happens because the user can specify some incorrect SVE
properties that result in our calculating a max_vq of 0. We catch
this and error out, but before we do that we calculate
vq_mask = MAKE_64BIT_MASK(0, max_vq);$
and the MAKE_64BIT_MASK() call is only valid for lengths that are
greater than zero, so we hit the undefined behaviour.
Change the logic so that if max_vq is 0 we specifically set vq_mask
to 0 without going via MAKE_64BIT_MASK(). This lets us drop the
max_vq check from the error-exit logic, because if max_vq is 0 then
vq_map must now be 0.
The UB only happens in the case where the user passed us an incorrect
set of SVE properties, so it's not a big problem in practice.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230704154332.3014896-1-peter.maydell@linaro.org
| -rw-r--r-- | target/arm/cpu64.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c index 6eaf8e32cf..6012e4ef54 100644 --- a/target/arm/cpu64.c +++ b/target/arm/cpu64.c @@ -122,10 +122,10 @@ void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp) vq = ctz32(tmp) + 1; max_vq = vq <= ARM_MAX_VQ ? vq - 1 : ARM_MAX_VQ; - vq_mask = MAKE_64BIT_MASK(0, max_vq); + vq_mask = max_vq > 0 ? MAKE_64BIT_MASK(0, max_vq) : 0; vq_map = vq_supported & ~vq_init & vq_mask; - if (max_vq == 0 || vq_map == 0) { + if (vq_map == 0) { error_setg(errp, "cannot disable sve%d", vq * 128); error_append_hint(errp, "Disabling sve%d results in all " "vector lengths being disabled.\n", |