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SubjectRe: [PATCH v3 2/2] powerpc/64: add stack protector support
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Snowpatch reports failure on pmac32_defconfig, as follows:

arch/powerpc/platforms/powermac/bootx_init.o: In function `bootx_printf':
/var/lib/jenkins-slave/workspace/snowpatch/snowpatch-linux-sparse/linux/arch/powerpc/platforms/powermac/bootx_init.c:88:
undefined reference to `__stack_chk_fail_local'
arch/powerpc/platforms/powermac/bootx_init.o: In function
`bootx_add_display_props':
/var/lib/jenkins-slave/workspace/snowpatch/snowpatch-linux-sparse/linux/arch/powerpc/platforms/powermac/bootx_init.c:211:
undefined reference to `__stack_chk_fail_local'
arch/powerpc/platforms/powermac/bootx_init.o: In function
`bootx_scan_dt_build_struct':
/var/lib/jenkins-slave/workspace/snowpatch/snowpatch-linux-sparse/linux/arch/powerpc/platforms/powermac/bootx_init.c:350:
undefined reference to `__stack_chk_fail_local'
arch/powerpc/platforms/powermac/bootx_init.o: In function `bootx_init':
/var/lib/jenkins-slave/workspace/snowpatch/snowpatch-linux-sparse/linux/arch/powerpc/platforms/powermac/bootx_init.c:598:
undefined reference to `__stack_chk_fail_local'
ld: .tmp_vmlinux1: hidden symbol `__stack_chk_fail_local' isn't defined
ld: final link failed: Bad value
Makefile:1040: recipe for target 'vmlinux' failed
make: *** [vmlinux] Error 1

I don't have this issue with GCC 8.1, bootx_init.o has references to
__stack_chk_fail, not to __stack_chk_fail_local

Looking online, it may be due to an old build and a lack of 'make
clean', could it be the case here ?

Otherwise, can you retry the build to see if it's happen again ?

Christophe

Le 24/09/2018 à 17:15, Christophe Leroy a écrit :
> On PPC64, as register r13 points to the paca_struct at all time,
> this patch adds a copy of the canary there, which is copied at
> task_switch.
> That new canary is then used by using the following GCC options:
> -mstack-protector-guard=tls
> -mstack-protector-guard-reg=r13
> -mstack-protector-guard-offset=offsetof(struct paca_struct, canary))
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> arch/powerpc/Kconfig | 2 +-
> arch/powerpc/Makefile | 8 ++++++++
> arch/powerpc/include/asm/paca.h | 3 +++
> arch/powerpc/include/asm/stackprotector.h | 3 +++
> arch/powerpc/kernel/asm-offsets.c | 3 +++
> arch/powerpc/kernel/entry_64.S | 4 ++++
> 6 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 3bcb05929931..602eea723624 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -180,7 +180,7 @@ config PPC
> select HAVE_ARCH_SECCOMP_FILTER
> select HAVE_ARCH_TRACEHOOK
> select HAVE_CBPF_JIT if !PPC64
> - select HAVE_STACKPROTECTOR if $(cc-option,-mstack-protector-guard=tls) && PPC32
> + select HAVE_STACKPROTECTOR if $(cc-option,-mstack-protector-guard=tls)
> select HAVE_CONTEXT_TRACKING if PPC64
> select HAVE_DEBUG_KMEMLEAK
> select HAVE_DEBUG_STACKOVERFLOW
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index 45b8eb4d8fe7..81552c7b46eb 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -113,7 +113,11 @@ KBUILD_ARFLAGS += --target=elf$(BITS)-$(GNUTARGET)
> endif
>
> cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard=tls
> +ifdef CONFIG_PPC64
> +cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard-reg=r13
> +else
> cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard-reg=r2
> +endif
>
> LDFLAGS_vmlinux-y := -Bstatic
> LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
> @@ -411,8 +415,12 @@ ifdef CONFIG_STACKPROTECTOR
> prepare: stack_protector_prepare
>
> stack_protector_prepare: prepare0
> +ifdef CONFIG_PPC64
> + $(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "PACA_CANARY") print $$3;}' include/generated/asm-offsets.h))
> +else
> $(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "TASK_CANARY") print $$3;}' include/generated/asm-offsets.h))
> endif
> +endif
>
> # 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.
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index 6d6b3706232c..98d883e58945 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -246,6 +246,9 @@ struct paca_struct {
> struct slb_entry *mce_faulty_slbs;
> u16 slb_save_cache_ptr;
> #endif /* CONFIG_PPC_BOOK3S_64 */
> +#ifdef CONFIG_STACKPROTECTOR
> + unsigned long canary;
> +#endif
> } ____cacheline_aligned;
>
> extern struct paca_struct **paca_ptrs;
> diff --git a/arch/powerpc/include/asm/stackprotector.h b/arch/powerpc/include/asm/stackprotector.h
> index 263e2aab1862..e81991955c0d 100644
> --- a/arch/powerpc/include/asm/stackprotector.h
> +++ b/arch/powerpc/include/asm/stackprotector.h
> @@ -29,6 +29,9 @@ static __always_inline void boot_init_stack_canary(void)
> canary ^= LINUX_VERSION_CODE;
>
> current->stack_canary = canary;
> +#ifdef CONFIG_PPC64
> + get_paca()->canary = canary;
> +#endif
> }
>
> #endif /* _ASM_STACKPROTECTOR_H */
> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
> index a992f7a53cf3..773dee55b3f6 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -81,6 +81,9 @@ int main(void)
> OFFSET(MM, task_struct, mm);
> #ifdef CONFIG_STACKPROTECTOR
> OFFSET(TASK_CANARY, task_struct, stack_canary);
> +#ifdef CONFIG_PPC64
> + OFFSET(PACA_CANARY, paca_struct, canary);
> +#endif
> #endif
> OFFSET(MMCONTEXTID, mm_struct, context.id);
> #ifdef CONFIG_PPC64
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 77a888bfcb53..573fa879d785 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -624,6 +624,10 @@ _GLOBAL(_switch)
>
> addi r6,r4,-THREAD /* Convert THREAD to 'current' */
> std r6,PACACURRENT(r13) /* Set new 'current' */
> +#if defined(CONFIG_STACKPROTECTOR)
> + ld r6, TASK_CANARY(r6)
> + std r6, PACA_CANARY(r13)
> +#endif
>
> ld r8,KSP(r4) /* new stack pointer */
> #ifdef CONFIG_PPC_BOOK3S_64
>

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