On Wed, 4 Apr 2018 09:27:10 -0700 Kees Cook <keesc...@chromium.org> wrote:
> On Wed, Apr 4, 2018 at 12:49 AM, Peter Zijlstra <pet...@infradead.org> wrote: > > On Tue, Apr 03, 2018 at 05:06:12PM -0400, Steven Rostedt wrote: > >> If you are concerned about attack surface, I could make it a bit more > >> difficult to tweak by malicious software. What about the patch below? > >> It would be much more difficult to modify this knob from an attack > >> vector. > > > > Not if you build using clang, because that doesn't support asm-goto and > > thus falls back to a simple runtime variable, which is exactly what Kees > > didn't want. > > Nah, Clang will get asm-goto soon. I'm not worried about that. Besides > the "yay new target issue", I was concerned about Linus yelling about > seeing the knob added he specifically said he didn't want. :P > This isn't really a knob. It can only get enabled when trace_printk() is added, which requires a change to the kernel source code. It's just an easy way on doing it yourself and recompiling. No userspace can enable it, with the exception of adding a kernel module that has a trace_printk() in it. A kernel command line option wont even enable it. -- Steve
