On Thu, Nov 17, 2022 at 12:50 AM Mike Rapoport <rppt@xxxxxxxxxx> wrote: > > On Mon, Nov 14, 2022 at 12:30:49PM -0800, Song Liu wrote: > > On Sun, Nov 13, 2022 at 2:35 AM Mike Rapoport <rppt@xxxxxxxxxx> wrote: > > > > > > My concern is that the proposed execmem_alloc() cannot be used for > > > centralized handling of loading text. I'm not familiar enough with > > > modules/ftrace/kprobes/BPF to clearly identify the potential caveats, but > > > my gut feeling is that the proposed execmem_alloc() won't be an improvement > > > but rather a hindrance for moving to centralized handling of loading text. > > > > I don't follow why this could ever be a hindrance. Luis is very excited about > > this, and I am very sure it works for ftrace, kprobe, and BPF. > > Again, it's a gut feeling. But for execmem_alloc() to be a unified place of > code allocation, it has to work for all architectures. If architectures > have to override it, then where is the unification? > > The implementation you propose if great for x86, but to see it as unified > solution it should be good at least for the major architectures. As I mentioned earlier, folks are working on using bpf_prog_pack for BPF JIT on powerpc. We will also work on something similar for ARM. I guess these are good enough for major architectures? > > > > It feels to me that a lot of ground work is needed to get to the point > > > where we can use centralized handling of loading text. > > > > Could you please be more specific on what is needed? > > The most obvious one to implement Peter's suggestion with VM_TOPDOWN_VMAP > so that execmem_alloc() can be actually used by modules. Current implementation is an alternative to VM_TOPDOWN_VMAP. I am very sure it works for modules just like VM_TOPDOWN_VMAP solution. Thanks, Song
