[dpdk-stable] 回复: [PATCH v3] crypto/qat: fix uninitilized compiler warning

[Feifei Wang <Feifei.Wang2@arm.com>]

Hi, Ferruh

Thanks for your comments.
Please see below.

> -----邮件原件-----
> 发件人: Ferruh Yigit <ferruh.yigit@intel.com>
> 发送时间: 2021年5月19日 16:12
> 收件人: Feifei Wang <Feifei.Wang2@arm.com>; John Griffin
> <john.griffin@intel.com>; Fiona Trahe <fiona.trahe@intel.com>; Deepak
> Kumar Jain <deepak.k.jain@intel.com>; Jerin Jacob
> <jerin.jacob@caviumnetworks.com>; Herbert Guan
> <Herbert.Guan@arm.com>
> 抄送: dev@dpdk.org; david.marchand@redhat.com; nd <nd@arm.com>;
> stable@dpdk.org; Ruifeng Wang <Ruifeng.Wang@arm.com>
> 主题: Re: [dpdk-stable] [PATCH v3] crypto/qat: fix uninitilized compiler
> warning
> 
> On 5/17/2021 10:07 AM, Feifei Wang wrote:
> > In Arm platform, when "RTE_ARCH_ARM64_MEMCPY" is set as true,
> compiler
> > will report variable uninitilized warning:
> >
> > ../drivers/crypto/qat/qat_sym_session.c:
> > In function ‘partial_hash_compute’:
> > ../lib/eal/include/generic/rte_byteorder.h:241:24: warning:
> > ‘<U35a0>’ may be used uninitialized in this function
> > 	[-Wmaybe-uninitialized]
> > 	241 | #define rte_bswap32(x) __builtin_bswap32(x)
> > 	...
> >
> > This is because "digest" will be initialized by "rte_memcpy" function
> > rather than "memcpy" if "RTE_ARCH_ARM64_MEMCPY" is set as true.
> > However,
> 
> How 'digest' is initialized by 'rte_memcpy'?

Firstly, 'digest' is initialized by rte_memcpy in partial_hash_sha_x function :
'partial_hash_compute' -> 'partial_hash_sha_x' -> 'rte_memcpy'.

If "RTE_ARCH_ARM64_MEMCPY = false", rte_memcpy will be defined as
'memcpy' to initialize 'digest' in  lib\eal\arm\include\rte_memcpy_64.h: 364, 
and compiler can identify this.

However, if "RTE_ARCH_ARM64_MEMCPY = true", rte_memcpy will be a inline 
function, and finally it will initialize 'digest' with two steps by invoking rte_mov16:
rte_memcpy -> rte_memcpy_ge16_lt_128 ->
step 1: rte_mov16(dst,src )
 step 2: rte_mov16(dst - 16 + n, src - 16 + n)
And the compiler cannot identify this multi-step initialization, then it will report warning.
 
> 
> > compiler cannot know it is initialized by the function.
> >
> > To fix this, use "calloc" to initialize "digest".
> >
> > Fixes: cd7fc8a84b48 ("eal/arm64: optimize memcpy")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > ---
> > v2: add check and free for memory dynamic allocation (David Marchand)
> > v3: fix compiler error
> >
> >  drivers/crypto/qat/qat_sym_session.c | 27 ++++++++++++++++++---------
> >  1 file changed, 18 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/crypto/qat/qat_sym_session.c
> > b/drivers/crypto/qat/qat_sym_session.c
> > index 231b1640da..105a10957a 100644
> > --- a/drivers/crypto/qat/qat_sym_session.c
> > +++ b/drivers/crypto/qat/qat_sym_session.c
> > @@ -1190,8 +1190,7 @@ static int partial_hash_compute(enum
> icp_qat_hw_auth_algo hash_alg,
> >  			uint8_t *data_out)
> >  {
> >  	int digest_size;
> > -	uint8_t digest[qat_hash_get_digest_size(
> > -			ICP_QAT_HW_AUTH_ALGO_DELIMITER)];
> > +	uint8_t *digest;
> 
> Will a memset 'digest' work too? Although not sure which one is better.
Thanks for your meaningful comments, I try to use memset and it is ok to solve this warning.
I will update this in the next version.