Richard Henderson <[email protected]> writes:
> Coverity reports, in sve_zcr_get_valid_len, > > "Subtract operation overflows on operands > arm_cpu_vq_map_next_smaller(cpu, start_vq + 1U) and 1U" > > First, fix the aarch32 stub version to not return 0, but to > simply assert unreachable. Because that nonsense return value > does exactly what Coverity reports. > > Second, 1 is the minimum value that can be returned from the > aarch64 version of arm_cpu_vq_map_next_smaller, but that is > non-obvious from the set of asserts in the function. Begin by > asserting that 2 is the minimum input, and finish by asserting > that we did in fact find a set bit in the bitmap. Bit 0 is > always set, so we must be able to find that. > > Reported-by: Coverity (CID 1407217) > Signed-off-by: Richard Henderson <[email protected]> Reviewed-by: Alex Bennée <[email protected]> > --- > target/arm/cpu.h | 4 +++- > target/arm/cpu64.c | 11 +++++++++-- > 2 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/target/arm/cpu.h b/target/arm/cpu.h > index e1a66a2d1c..d89e727d7b 100644 > --- a/target/arm/cpu.h > +++ b/target/arm/cpu.h > @@ -190,7 +190,9 @@ uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, > uint32_t vq); > # define ARM_MAX_VQ 1 > static inline void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp) { } > static inline uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, uint32_t vq) > -{ return 0; } > +{ > + g_assert_not_reached(); > +} > #endif > > typedef struct ARMVectorReg { > diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c > index 68baf0482f..83ff8c8713 100644 > --- a/target/arm/cpu64.c > +++ b/target/arm/cpu64.c > @@ -466,11 +466,18 @@ uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, > uint32_t vq) > * We allow vq == ARM_MAX_VQ + 1 to be input because the caller may want > * to find the maximum vq enabled, which may be ARM_MAX_VQ, but this > * function always returns the next smaller than the input. > + * > + * Similarly, vq == 2 is the minimum input because 1 is the minimum > + * output that makes sense. > */ > - assert(vq && vq <= ARM_MAX_VQ + 1); > + assert(vq >= 2 && vq <= ARM_MAX_VQ + 1); > > bitnum = find_last_bit(cpu->sve_vq_map, vq - 1); > - return bitnum == vq - 1 ? 0 : bitnum + 1; > + > + /* We always have vq == 1 present in sve_vq_map. */ > + assert(bitnum < vq - 1); > + > + return bitnum + 1; > } > > static void cpu_max_get_sve_max_vq(Object *obj, Visitor *v, const char *name, -- Alex Bennée
