[PATCH] iommu/arm-smmu-v3: Fix endianness annotations

[Jean-Philippe Brucker]

On Fri, Sep 18, 2020 at 04:02:26PM +0100, Robin Murphy wrote:
> On 2020-09-18 15:18, Jean-Philippe Brucker wrote:
> > When building with C=1, sparse reports some issues regarding endianness
> > annotations:
> > 
> > arm-smmu-v3.c:221:26: warning: cast to restricted __le64
> > arm-smmu-v3.c:221:24: warning: incorrect type in assignment (different base types)
> > arm-smmu-v3.c:221:24:    expected restricted __le64 [usertype]
> > arm-smmu-v3.c:221:24:    got unsigned long long [usertype]
> > arm-smmu-v3.c:229:20: warning: incorrect type in argument 1 (different base types)
> > arm-smmu-v3.c:229:20:    expected restricted __le64 [usertype] *[assigned] dst
> > arm-smmu-v3.c:229:20:    got unsigned long long [usertype] *ent
> > arm-smmu-v3.c:229:25: warning: incorrect type in argument 2 (different base types)
> > arm-smmu-v3.c:229:25:    expected unsigned long long [usertype] *[assigned] src
> > arm-smmu-v3.c:229:25:    got restricted __le64 [usertype] *
> > arm-smmu-v3.c:396:20: warning: incorrect type in argument 1 (different base types)
> > arm-smmu-v3.c:396:20:    expected restricted __le64 [usertype] *[assigned] dst
> > arm-smmu-v3.c:396:20:    got unsigned long long *
> > arm-smmu-v3.c:396:25: warning: incorrect type in argument 2 (different base types)
> > arm-smmu-v3.c:396:25:    expected unsigned long long [usertype] *[assigned] src
> > arm-smmu-v3.c:396:25:    got restricted __le64 [usertype] *
> > arm-smmu-v3.c:1349:32: warning: invalid assignment: |=
> > arm-smmu-v3.c:1349:32:    left side has type restricted __le64
> > arm-smmu-v3.c:1349:32:    right side has type unsigned long
> > arm-smmu-v3.c:1396:53: warning: incorrect type in argument 3 (different base types)
> > arm-smmu-v3.c:1396:53:    expected restricted __le64 [usertype] *dst
> > arm-smmu-v3.c:1396:53:    got unsigned long long [usertype] *strtab
> > arm-smmu-v3.c:1424:39: warning: incorrect type in argument 1 (different base types)
> > arm-smmu-v3.c:1424:39:    expected unsigned long long [usertype] *[assigned] strtab
> > arm-smmu-v3.c:1424:39:    got restricted __le64 [usertype] *l2ptr
> > 
> > While harmless, they are incorrect and could hide actual errors during
> > development. Fix them.
> 
> Reviewed-by: Robin Murphy <robin.murphy at arm.com>

Thanks!

> > Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
> > ---
> > 
> > There is another false positive due to passing INT_MIN to cmpxchg, and
> > __cmpxchg* to truncate them to u8 and u16:
> > 
> > arch/arm64/include/asm/cmpxchg.h:172:1: warning: cast truncates bits from constant value (ffffffff80000000 becomes 0)
> > arch/arm64/include/asm/cmpxchg.h:172:1: warning: cast truncates bits from constant value (ffffffff80000000 becomes 0)
> > 
> > I haven't found a satisfying fix so far, except adding __force to
> > __cmpxchg_case* which could hide actual bugs.
> 
> I guess that's a general issue with the switch(sizeof()) idiom of sparse not
> being aware that those cases are unreachable?

Precisely. I wondered if _Generic could help, but it looks like the
problem is the same.

Thanks,
Jean