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Message-ID: <30fb4e6b-0981-c53c-a1db-94138eaad268@c-s.fr>
Date: Wed, 26 Sep 2018 09:58:30 +0200
From: Christophe LEROY <christophe.leroy@....fr>
To: Segher Boessenkool <segher@...nel.crashing.org>
Cc: Russell Currey <ruscur@...sell.cc>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Andrew Donnellan <andrew.donnellan@....ibm.com>,
linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] powerpc/64: add stack protector support
Segher, any idea about this problem ?
Christophe
Le 26/09/2018 à 09:05, Russell Currey a écrit :
> On Tue, 2018-09-25 at 17:56 +0200, Christophe LEROY wrote:
>> 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 ?
>
> We do make mrproper AND clean, just to be sure :)
>
>>
>> Otherwise, can you retry the build to see if it's happen again ?
>
> I've retried the build and the same thing happens. Our build environment is using
> GCC 7.3 on Ubuntu 18.04. Reproduced on a different machine too, running the same
> OS and compiler.
>
> You can see exactly what gets run here:
> https://github.com/ajdlinux/openpower.xyz-snowpatch/blob/master/kernel-build-sparse.sh
>
> - Russell
>
>>
>> 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@....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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