Michael Ellerman [mich...@ellerman.id.au] wrote: | > | make: *** [tests/attr.o] Error 1 | > | | > | i386 compiles fine | > | > __u64 is 'unsigned long long' on x86 and PRIu64 is 'llu' which is fine. | > | > __u64 is 'unsigned long' on Power and PRIu64 is 'lu' which is again fine. | > | > But __u64 is 'unsigned long long' on x86_64, but PRIu64 is '%lu' bc __WORDSIZE | > is 64. | | | This is a bit of a mess, but let me see if I can help explain it.
Yes it is :-) thanks for explaining it. | | The root of the problem is that you're mixing up the kernel type __u64, | with the userspace format specifier PRIu64. struct perf_event_attr is shared with user space and is using __u64. Should it use uint64_t instead ? | | PRIu64 is the format specifier for printing a uint64_t, it _may_ also be | the right specifier for a __u64, but there's no guarantee of that - as | you have discovered. | | Inside the kernel both x86 and powerpc use unsigned long long always, in | 32-bit and 64-bit code. That means in the kernel we can always use %llu. | | On x86 that definition is also exported to userspace, so on x86 __u64 is | always unsigned long long. As you noticed this potentially differs from | uint64_t, which can be confusing. However it means in x86 userspace code | you can always print a __u64 with %llu. | | On powerpc we default to using definitions that match userspace, so | __u64 changes depending on your wordsize, and so you must use PRIu64 | etc. to print them. Well, using __u64 and PRIu64 seems breaks x86-64... | | There is however support in recent powerpc kernels to switch to using | unsigned long long even on 64-bit. See commit 2c9c6ce. | | You need to define __SANE_USERSPACE_TYPES__ before including types.h. | Then you can always use %llu to print __u64. but __SANE_USERSPACE_TYPES__ with __u64 and %llu seems to work on x86, x86-64, powerpc. Will modify my patch to add __SANE_USERSPACE_TYPES__ but leave the %llu as is. Sukadev _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
