On Wed, Jun 19, 2013 at 5:59 AM, BERTRAND Joël <joel.bertrand@xxxxxxxxxxx> wrote: > > If I rebuild the same kernel with the same options, it just runs as > expected. I have no idea to investigate. Unfortunately, neither do we. You know more about the kernel than we do. Debugging failed-boot problems is indeed among the hardest of compiler problems to track down. This could of course be a compiler bug, but the more common cause is that improved compiler optimization has found some bug in the kernel code where the kernel relies on undefined behaviour. Or, something has changed in the way that asm statements work. Or, the kernel is relying on specific inlining semantics that have changed. Some steps you can try are: compile the kernel without optimization. Compile the kernel with optimization but with the -fno-strict-aliasing option. Boot the kernel in a VM where you can trace the instruction sequence; compare the sequence for a working and non-working kernel and look for where it goes wrong. Ian
