On Wed, Aug 9, 2017 at 12:57 AM, Dmitry V. Levin <ldv@xxxxxxxxxxxx> wrote: > On Sun, Aug 06, 2017 at 06:44:05PM +0200, Mikko Rapeli wrote: >> Arnd Bergmann <arnd@xxxxxxxx> doubts that __kernel_size_t could be used here >> so trying to fall back to gcc's <stddef.h>. > > The only architecture where you cannot do this safely is x86 family > because of x32 exception. If there is no chance that the change will > affect x32, feel free to replace size_t with __kernel_size_t like I did > some time ago, see > http://lkml.kernel.org/r/20170302002022.GB27097@xxxxxxxxxxxx There is another problem: on some 32-bit architectures, size_t is defined as 'unsigned int', while '__kernel_size_t' is defined as 'unsigned long'. These obviously have the same size, but the man page explicitly defines it as 'size_t ss_size'. If a user space program accesses the field in a way requires an exact type match, it gets a warning or error, e.g. 1. printf("signal with %zd bytes\n", stack->ss_size); 2. size_t *pointer_to_size_t = &stack->ss_size; 3. assert(__builtin_types_compatible_p(size_t, typeof(stack->ss_size))) Not sure how important those are, but I think there is at least a risk of any of those showing up in user space. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
