On Fri, 2020-03-06 at 11:02 -0800, Dave Hansen wrote: > On 3/6/20 10:37 AM, Yu-cheng Yu wrote: > > We used to do this for CET instructions, but after adding kernel-mode > > instructions and inserting ENDBR's, the code becomes cluttered. I also > > found an earlier discussion on the ENDBR: > > > > https://lore.kernel.org/lkml/CALCETrVRH8LeYoo7V1VBPqg4WS0Enxtizt=T7dPvgoeWfJrdzA@xxxxxxxxxxxxxx/ > > > > It makes sense to let the user know early on that the system cannot support > > CET and cannot build a CET-enabled kernel. > > > > One thing we can do is to disable CET in Kconfig and not in kernel > > build, which I will do in the next version. > > I'll go on the record and say I think we should allow building > CET-enabled kernels on old toolchains. We need it for build test > coverage. We can spit out a warning, but we need to allow building it. The build test will go through (assembler or .byte), once the opcode patch is applied [1]. Also, when we enable kernel-mode CET, it is difficult to build IBT code without the right tool chain. Yu-cheng [1] opcode patch: https://lore.kernel.org/lkml/20200204171425.28073-1-yu-cheng.yu@xxxxxxxxx/
