Hi Arnd, On 13.09.2018 17:59, Arnd Bergmann wrote: > There are only two 64-bit architecture ports that have a 32-bit > suseconds_t: sparc64 and parisc64. I've encountered a number of problems > with this, while trying to get a proper 64-bit time_t working on 32-bit > architectures. Having a 32-bit suseconds_t combined with a 64-bit time_t > means that we get extra padding in data structures that may leak kernel > stack data to user space, and it breaks all code that assumes that > timespec and timeval have the same layout. > > While we can't change sparc64, it seems that glibc on parisc64 has always > set suseconds_t to 'long', and the current version would give incorrect > results for gettimeofday() and many other interfaces: timestamps passed > from user space into the kernel result in tv_usec being always zero > (the lower bits contain the intended value but are ignored) while data > passed from the kernel to user space contains either zeroes or random > data in tv_usec. Should this wrong behavior be visible with 32-bit userspace or with 64-bit userspace (or both)? I didn't noticed such wrong behavior yet. Can you suggest some test programs to verify? LTP seems to be correct. > Based on that, it seems best to change the user API in the kernel in > an incompatible way to match what glibc expects. Basically that sounds the right way to go, but as said before, I didn't see such issues. > Note that the distros I could find (gentoo and debian) all just > have 32-bit user space, which does not suffer from this problem. That's correct. Kernel can be 32- or 64-bit, but userspace is currentl 32-bit only. So, breaking any 64-bit userspace is OK, since we don't have it yet. Breaking 32-bit userspace needs some thoughts... Helge > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > arch/parisc/include/uapi/asm/posix_types.h | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/arch/parisc/include/uapi/asm/posix_types.h b/arch/parisc/include/uapi/asm/posix_types.h > index 2785632c85e7..8dce56f5dcee 100644 > --- a/arch/parisc/include/uapi/asm/posix_types.h > +++ b/arch/parisc/include/uapi/asm/posix_types.h > @@ -16,9 +16,6 @@ typedef unsigned short __kernel_mode_t; > typedef unsigned short __kernel_ipc_pid_t; > #define __kernel_ipc_pid_t __kernel_ipc_pid_t > > -typedef int __kernel_suseconds_t; > -#define __kernel_suseconds_t __kernel_suseconds_t > - > typedef long long __kernel_off64_t; > typedef unsigned long long __kernel_ino64_t; > >
