On 19.06.2024 18:31, Andrew Cooper wrote: > Gitlab CI reports an ARM32 randconfig failure as follows: > > In file included from common/livepatch.c:9: > common/livepatch.c: In function ‘livepatch_list’: > ./include/xen/guest_access.h:130:25: error: cast to pointer from integer of > different size [-Werror=int-to-pointer-cast] > 130 | __raw_copy_to_guest((void *)(d_ + (off) * sizeof(*_s)), \ > | ^ > common/livepatch.c:1283:18: note: in expansion of macro > ‘__copy_to_guest_offset’ > 1283 | if ( __copy_to_guest_offset(list->name, name_offset, > | ^~~~~~~~~~~~~~~~~~~~~~ > ./include/xen/guest_access.h:130:25: error: cast to pointer from integer of > different size [-Werror=int-to-pointer-cast] > 130 | __raw_copy_to_guest((void *)(d_ + (off) * sizeof(*_s)), \ > | ^ > common/livepatch.c:1287:17: note: in expansion of macro > ‘__copy_to_guest_offset’ > 1287 | __copy_to_guest_offset(list->metadata, > metadata_offset, > | ^~~~~~~~~~~~~~~~~~~~~~ > > This isn't specific to ARM32; it's LIVEPATCH on any 32bit build of Xen. > > Both name_offset and metadata_offset are uint64_t, meaning that the > expression: > > (d_ + (off) * sizeof(*(hnd).p) > > gets promoted to uint64_t, and is too wide to cast back to a pointer in 32bit > builds. The expression needs casting through (unsigned long) before it can be > cast to (void *).
I disagree. Instead I'd like to raise the question why these two local variables are uint64_t in the first place. They accumulate buffer size, and hence ought to have been size_t from the beginning. I'll make an alternative patch (first making sure I test livepatch building not only for x86 and arm64). > @@ -65,7 +65,7 @@ > /* Check that the handle is not for a const type */ \ > void *__maybe_unused _t = (hnd).p; \ > (void)((hnd).p == _s); \ > - raw_copy_to_guest((void *)(d_ + (off) * sizeof(*_s)), \ > + raw_copy_to_guest(_p(d_ + (off) * sizeof(*_s)), \ It's also from an abstract perspective that I disagree with using _p() like this. We'd rather keep this as straightforward as possible, to keep down the risk of hiding bugs by excess casting. Jan
