> On Sep 9, 2014, at 2:57 AM, Markus Trippelsdorf <mar...@trippelsdorf.de> > wrote: > >> On 2014.09.09 at 17:35 +0800, Arseny Solokha wrote: >> Hello, >> >> I've recently faced an issue I'm afraid I currently unable to debug. When >> building an arbitrary version of Linux kernel for powerpc-e500v2-linux-gnuspe >> target, it seems gcc prior to 5 produces a good image which boots just fine, >> and >> current gcc 5 snapshots (4.10.0-alpha20140810 for example) produce an image >> which hangs just after U-Boot hands over to the kernel. >> >> This behavior is well reproducible on real hardware as well as under qemu. >> I've >> prepared a minimal kernel config which is dysfunctional as is but still >> enough >> to demonstrate the problem in qemu. I believe the exact Linux version number >> doesn't actually matter here, but see the attachment for details. >> >> Compare the output produced by u-boot and this minified kernel build using >> gcc 4.9.1 and 4.10.0-alpha20140810 snapshot. >> >> I now have completely no idea what to do next to find a cause of (1) gcc 5 >> snapshots producing unbootable kernel, > > gcc trunk also miscompiles x86_64 kernels currently, but I haven't > looked deeper yet. > The best way to narrow down the issue is to use git (or svn) bisect to > find out which gcc revision causes the miscompile. Then you can md5sum > the kernel object files for the bad revision and for the first good > revision and compare the results. After that you can look at the > disassembly of the object files, for which md5sum differs, and try to > figure out the reason why.
I have a patch which I need to submit. Maybe by Friday I will do that. It fixes the kernel on arm64 but it is generic c front-end patch. > > -- > Markus
