From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: bpf@vger.kernel.org,
Christophe Leroy <christophe.leroy@csgroup.eu>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/bpf: Use bctrl for making function calls
Date: Wed, 09 Jun 2021 18:41:10 +0530 [thread overview]
Message-ID: <1623243814.sye72m0d51.naveen@linux.ibm.com> (raw)
In-Reply-To: <4c371bd1-1fcf-54c1-d0a2-836d40887893@csgroup.eu>
Christophe Leroy wrote:
>
>
> Le 09/06/2021 à 11:00, Naveen N. Rao a écrit :
>> blrl corrupts the link stack. Instead use bctrl when making function
>> calls from BPF programs.
>
> What's the link stack ? Is it the PPC64 branch predictor stack ?
c974809a26a13e ("powerpc/vdso: Avoid link stack corruption in
__get_datapage()") has a good write up on the link stack.
>
>>
>> Reported-by: Anton Blanchard <anton@ozlabs.org>
>> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/include/asm/ppc-opcode.h | 1 +
>> arch/powerpc/net/bpf_jit_comp32.c | 4 ++--
>> arch/powerpc/net/bpf_jit_comp64.c | 12 ++++++------
>> 3 files changed, 9 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
>> index ac41776661e963..1abacb8417d562 100644
>> --- a/arch/powerpc/include/asm/ppc-opcode.h
>> +++ b/arch/powerpc/include/asm/ppc-opcode.h
>> @@ -451,6 +451,7 @@
>> #define PPC_RAW_MTLR(r) (0x7c0803a6 | ___PPC_RT(r))
>> #define PPC_RAW_MFLR(t) (PPC_INST_MFLR | ___PPC_RT(t))
>> #define PPC_RAW_BCTR() (PPC_INST_BCTR)
>> +#define PPC_RAW_BCTRL() (PPC_INST_BCTRL)
>
> Can you use the numeric value instead of the PPC_INST_BCTRL, to avoid conflict with
> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/4ca2bfdca2f47a293d05f61eb3c4e487ee170f1f.1621506159.git.christophe.leroy@csgroup.eu/
Sure. I'll post a v2.
- Naveen
next prev parent reply other threads:[~2021-06-09 13:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 9:00 [PATCH] powerpc/bpf: Use bctrl for making function calls Naveen N. Rao
2021-06-09 9:00 ` Naveen N. Rao
2021-06-09 9:42 ` Christophe Leroy
2021-06-09 13:11 ` Naveen N. Rao [this message]
2021-06-26 10:37 ` Michael Ellerman
2021-06-26 10:37 ` Michael Ellerman
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