On Thu, Sep 10, 2020 at 3:48 PM Elena Petrova <lenaptr@xxxxxxxxxx> wrote: > in_ubsan field of task_struct is only used in lib/ubsan.c, which in its > turn is used only `ifneq ($(CONFIG_UBSAN_TRAP),y)`. > > Removing unnecessary field from a task_struct will help preserve the > ABI between vanilla and CONFIG_UBSAN_TRAP'ed kernels. In particular, > this will help enabling bounds sanitizer transparently for Android's > GKI. The diff looks reasonable to me, but I'm curious about the justification in the commit message: Is the intent here that you want to be able to build a module without CONFIG_UBSAN and load it into a kernel that is built with CONFIG_UBSAN? Or the inverse? Does this mean that in the future, gating new exported functions, or new struct fields, on CONFIG_UBSAN (independent of whether CONFIG_UBSAN_TRAP is set) will break Android? If you really want to do this, and using alternatives to patch out the ubsan instructions is not an option, I wonder whether it would be more reasonable to at least add a configuration where CONFIG_UBSAN is enabled but the compiler flag is not actually set. Then you could unconditionally build that android kernel and its modules with that config option, and wouldn't have to worry about structure size issues, dependencies on undefined symbols and so on.
