On Wed, 13 May 2020 19:43:24 -0700 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Wed, May 13, 2020 at 6:00 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > > But we should likely at least disallow it entirely on platforms where > > > we really can't - or pick one hardcoded choice. On sparc, you really > > > _have_ to specify one or the other. > > > > OK. BTW, is there any way to detect the kernel/user space overlap on > > memory layout statically? If there, I can do it. (I don't like > > "if (CONFIG_X86)" thing....) > > Or, maybe we need CONFIG_ARCH_OVERLAP_ADDRESS_SPACE? > > I think it would be better to have a CONFIG variable that > architectures can just 'select' to show that they are ok with separate > kernel and user addresses. > > Because I don't think we have any way to say that right now as-is. You > can probably come up with hacky ways to approximate it, ie something > like > > if (TASK_SIZE_MAX > PAGE_OFFSET) > .... they overlap .. > > which would almost work, but.. It seems TASK_SIZE_MAX is defined only on x86 and s390, what about comparing STACK_TOP_MAX with PAGE_OFFSET ? Anyway, I agree that the best way is introducing a CONFIG. Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
