On Mon, 5 Nov 2018, Andy Lutomirski wrote:
> On Mon, Nov 5, 2018 at 11:25 AM Nadav Amit <na...@vmware.com> wrote:
> Linus, hpa, or Dave, a question for you: suppose I map some page
> writably, write to it, then upgrade permissions to allow execute.
> Must I force all CPUs that might execute from it without first
> serializing to serialize? I suspect this doesn't really affect user
> code, but it may affect the module loader.
>
> To be safe, shouldn't the module loader broadcast an IPI to
> sync_core() everywhere after loading a module and before making it
> runnable, regardless of alternative patching?
>
> IOW, the right sequence of events probably ought to me:
>
> 1. Allocate the memory and map it.
> 2. Copy in the text.
> 3. Patch alternatives, etc. This is logically just like (2) from an
> architectural perspective -- we're just writing to memory that won't
> be executed.
> 4. Serialize everything.
> 5. Run it!
I'd make that:
1. Allocate the memory and map it RW
2. Copy in the text.
3. Patch alternatives, etc. This is logically just like (2) from an
architectural perspective -- we're just writing to memory that won't
be executed.
4. Map it RX
5. Serialize everything.
6. Run it!
Thanks,
tglx
