Messages in this thread Patch in this message | | | Date | Mon, 16 Mar 2020 14:04:14 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86: fix early boot crash on gcc-10 |
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On Sat, Mar 14, 2020 at 04:44:51PM +0000, Sergei Trofimovich wrote: > The change fixes boot failure on physical machine where kernel > is built with gcc-10 with stack-protector enabled by default:
> This happens because `start_secondary()` is responsible for setting > up initial stack canary value in `smpboot.c`, but nothing prevents > gcc from inserting stack canary into `start_secondary()` itself > before `boot_init_stack_canary()` call.
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile > index 9b294c13809a..da9f4ea9bf4c 100644 > --- a/arch/x86/kernel/Makefile > +++ b/arch/x86/kernel/Makefile > @@ -11,6 +11,12 @@ extra-y += vmlinux.lds > > CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE) > > +# smpboot's init_secondary initializes stack canary. > +# Make sure we don't emit stack checks before it's > +# initialized. > +nostackp := $(call cc-option, -fno-stack-protector) > +CFLAGS_smpboot.o := $(nostackp)
What makes GCC10 insert this while GCC9 does not. Also, I would much rather GCC10 add a function attrbute to kill this:
__attribute__((no_stack_protect))
Then we can explicitly clear this one function and keep it on for the rest of the file.
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