On Wed, May 13, 2020 at 8:50 AM Kalle Valo <kvalo@xxxxxxxxxxxxxx> wrote: > > Kalle Valo <kvalo@xxxxxxxxxxxxxx> writes: > > > This motivated me to switch to using GCC 10.x and I noticed that you had > > already upgraded crosstool so it was a trivial thing to do, awesome :) > > > > https://mirrors.edge.kernel.org/pub/tools/crosstool/ > > And now I have a problem :) I first noticed that my x86 testbox is not > booting when I compile the kernel with GCC 10.1.0 from crosstool. I > didn't get any error messages so I just downgraded the compiler and the > kernel was booting fine again. Next I decided to try GCC 10.1 with my > x86 laptop and it also failed to boot, but this time I got kernel logs > and saw this: > > Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: start_secodary+0x178/0x180 > > Call Trace: > dump_stack > panic > ? _raw_spin_unlock_irqrestore > ? start_secondary > __stack_chk_fail > start_secondary > secondary_startup > > (I wrote the above messages manually from a picture so expect typos) > > Then also on my x86 laptop I downgraded the compiler to GCC 8.1.0 (from > crosstool), rebuilt the exactly same kernel version and the kernel > booted without issues. > > I'm using 5.7.0-rc4-wt-ath+ which is basically v5.7-rc4 plus latest > wireless patches, and I doubt the wireless patches are making any > difference this early in the boot. All compilers I use are prebuilt > binaries from kernel.org crosstool repo[1] with addition of ccache > v3.4.1 to speed up my builds. > > Any ideas? How should I debug this further? At least if it fails reproducibly, it's probably not too hard to drill down further. Some ideas: * I'd first try to reproduce it in qemu. Since you don't even need any user space or modules, I would simply try $ qemu-system-x86_64 -nographic -monitor none -append "console=ttyS0" -serial stdio -smp 4 -kernel arch/x86/boot/bzImage I tried it here with an x86 defconfig linux-next kernel but did not run into the problem you described. If you share your .config, I can try reproducing with that as well. Once there is a reproducer in qemu, it should be trivial to step through it using gdb. * There are still two prerelease compiler versions on kernel.org, from February and from April. You can try each one to see if this was a recent regression. It's also possible that there is a problem with my specific builds of gcc-10.1, and that the compiler is actually fine for others.The gcc-10 packages in Fedora/Debian/Ubuntu are probably better tested. Arnd
