| Message ID | 20240328143051.1069575-8-arnd@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | address remaining -Wtautological-constant-out-of-range-compare | expand |
On Thu, Mar 28, 2024 at 7:32 AM Arnd Bergmann <arnd@kernel.org> wrote: > Add a cast to u32 in both cases, so it never warns about this. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Justin Stitt <justinstitt@google.com> > --- > drivers/infiniband/core/uverbs_ioctl.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/infiniband/core/uverbs_ioctl.c b/drivers/infiniband/core/uverbs_ioctl.c > index f80da6a67e24..e0cc3ddae71b 100644 > --- a/drivers/infiniband/core/uverbs_ioctl.c > +++ b/drivers/infiniband/core/uverbs_ioctl.c > @@ -90,7 +90,7 @@ void uapi_compute_bundle_size(struct uverbs_api_ioctl_method *method_elm, > ALIGN(bundle_size + 256, sizeof(*pbundle->internal_buffer)); > > /* Do not want order-2 allocations for this. */ > - WARN_ON_ONCE(method_elm->bundle_size > PAGE_SIZE); > + WARN_ON_ONCE((u32)method_elm->bundle_size > PAGE_SIZE); > } > > /** > @@ -636,7 +636,7 @@ long ib_uverbs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > if (err) > return -EFAULT; > > - if (hdr.length > PAGE_SIZE || > + if ((u32)hdr.length > PAGE_SIZE || > hdr.length != struct_size(&hdr, attrs, hdr.num_attrs)) > return -EINVAL; > > -- > 2.39.2 >
On Thu, Mar 28, 2024 at 03:30:45PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > clang warns for comparisons that are always true, which is the case > for these two page size checks on architectures with 64KB pages: > > drivers/infiniband/core/uverbs_ioctl.c:90:39: error: result of comparison of constant 65536 with expression of type 'u16' (aka 'unsigned short') is always false [-Werror,-Wtautological-constant-out-of-range-compare] > WARN_ON_ONCE(method_elm->bundle_size > PAGE_SIZE); > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~ > include/asm-generic/bug.h:104:25: note: expanded from macro 'WARN_ON_ONCE' > int __ret_warn_on = !!(condition); \ > ^~~~~~~~~ > drivers/infiniband/core/uverbs_ioctl.c:621:17: error: result of comparison of constant 65536 with expression of type '__u16' (aka 'unsigned short') is always false [-Werror,-Wtautological-constant-out-of-range-compare] > if (hdr.length > PAGE_SIZE || > ~~~~~~~~~~ ^ ~~~~~~~~~ > > Add a cast to u32 in both cases, so it never warns about this. But doesn't that hurt the codegen? Jason
On Wed, Apr 3, 2024, at 17:45, Jason Gunthorpe wrote: > On Thu, Mar 28, 2024 at 03:30:45PM +0100, Arnd Bergmann wrote: >> From: Arnd Bergmann <arnd@arndb.de> >> >> clang warns for comparisons that are always true, which is the case >> for these two page size checks on architectures with 64KB pages: >> >> drivers/infiniband/core/uverbs_ioctl.c:90:39: error: result of comparison of constant 65536 with expression of type 'u16' (aka 'unsigned short') is always false [-Werror,-Wtautological-constant-out-of-range-compare] >> WARN_ON_ONCE(method_elm->bundle_size > PAGE_SIZE); >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~ >> include/asm-generic/bug.h:104:25: note: expanded from macro 'WARN_ON_ONCE' >> int __ret_warn_on = !!(condition); \ >> ^~~~~~~~~ >> drivers/infiniband/core/uverbs_ioctl.c:621:17: error: result of comparison of constant 65536 with expression of type '__u16' (aka 'unsigned short') is always false [-Werror,-Wtautological-constant-out-of-range-compare] >> if (hdr.length > PAGE_SIZE || >> ~~~~~~~~~~ ^ ~~~~~~~~~ >> >> Add a cast to u32 in both cases, so it never warns about this. > > But doesn't that hurt the codegen? I just double-checked in the compiler explorer to confirm that this works as I expected: both gcc and clang are still able to optimize out the comparison for 64K pages, but clang no longer complains after my change that this is an obvious case. I also see that gcc still produces a -Wtype-limits warning, but that likely has to stay disabled because it produces too much output elsewhere and I don't see an easy way to shut it up. Arnd
diff --git a/drivers/infiniband/core/uverbs_ioctl.c b/drivers/infiniband/core/uverbs_ioctl.c index f80da6a67e24..e0cc3ddae71b 100644 --- a/drivers/infiniband/core/uverbs_ioctl.c +++ b/drivers/infiniband/core/uverbs_ioctl.c @@ -90,7 +90,7 @@ void uapi_compute_bundle_size(struct uverbs_api_ioctl_method *method_elm, ALIGN(bundle_size + 256, sizeof(*pbundle->internal_buffer)); /* Do not want order-2 allocations for this. */ - WARN_ON_ONCE(method_elm->bundle_size > PAGE_SIZE); + WARN_ON_ONCE((u32)method_elm->bundle_size > PAGE_SIZE); } /** @@ -636,7 +636,7 @@ long ib_uverbs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) if (err) return -EFAULT; - if (hdr.length > PAGE_SIZE || + if ((u32)hdr.length > PAGE_SIZE || hdr.length != struct_size(&hdr, attrs, hdr.num_attrs)) return -EINVAL;