Messages in this thread | | | Subject | Re: How to define some additional KBUILD_CFLAGS after building include/generated/asm-offsets.h ? | From | Christophe LEROY <> | Date | Mon, 24 Sep 2018 17:26:18 +0200 |
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Le 24/09/2018 à 14:10, Michael Ellerman a écrit : > Christophe Leroy <christophe.leroy@c-s.fr> writes: > >> I'm trying to implement TLS based stack protector in the Linux Kernel. >> For that I need to give to GCC the offset at which it will find the >> canary (register r2 is pointing to the current task struct). >> >> I have been able to do it with the below patch, but it only works when >> include/generated/asm-offsets.h already exists from the start of the build. >> >> Is there a way to evaluate CANARY_OFFSET and add the stack-protector >> flags to KBUILD_FLAGS only after include/generated/asm-offsets.h is built ? >> >> Or another way of add -mstack-protector-guard-offset=offsetof(struct >> task_struct, stack_canary) ? > > This seems to work, at least I see the value in CFLAGS: > > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile > index 07d9dce..39ee113 100644 > --- a/arch/powerpc/Makefile > +++ b/arch/powerpc/Makefile > @@ -404,6 +394,11 @@ archclean: > > archprepare: checkbin > > +prepare: stack_protector_prepare > + > +stack_protector_prepare: prepare0 > + $(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' include/generated/asm-offsets.h)) > +
Great, it works ! Thanks, I have sent v3 of the patches.
Christophe
> # Use the file '.tmp_gas_check' for binutils tests, as gas won't output > # to stdout and these checks are run even on install targets. > TOUT := .tmp_gas_check > > > cheers >
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