On 5/14/20 11:44 AM, Masami Hiramatsu wrote:
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.
Agree, CONFIG knob that archs can select feels cleanest. Fwiw, I've cooked
up fixes for bpf side locally here and finishing up testing, will push out
later today.
Thanks,
Daniel
