On Sat, Oct 13, 2018 at 2:04 AM Edgecombe, Rick P <rick.p.edgecombe@xxxxxxxxx> wrote: > On Fri, 2018-10-12 at 19:22 +0200, Jann Horn wrote: > > On Fri, Oct 12, 2018 at 7:04 PM Edgecombe, Rick P > > <rick.p.edgecombe@xxxxxxxxx> wrote: > > > On Fri, 2018-10-12 at 02:35 +0200, Jann Horn wrote: > > > > Why all the rbtree stuff instead of stashing a pointer in struct > > > > vmap_area, or something like that? > > > > > > Since the tracking was not for all vmalloc usage, the intention was to not > > > bloat > > > the structure for other usages likes stacks. I thought usually there > > > wouldn't be > > > nearly as much module space allocations as there would be kernel stacks, but > > > I > > > didn't do any actual measurements on the tradeoffs. > > > > I imagine that one extra pointer in there - pointing to your struct > > mod_alloc_user - would probably not be terrible. 8 bytes more per > > kernel stack shouldn't be so bad? > > I looked into this and it starts to look a little messy. The nommu.c version of > vmalloc doesn't use or expose access to vmap_area or vm_struct. So it starts to > look like a bunch of IFDEFs to remove the rlimit in the nommu case or making a > stand in that maintains pretend vm struct's in nommu.c. I had actually > previously tried to at least pull the allocations size from vmalloc structs, but it broke on nommu. > > Thought I would check back and see. How important do you think this is? I don't think it's important - I just thought that it would be nice to avoid the extra complexity if it is easily avoidable.
