Re: [dpdk-dev] [PATCH 3/4] net/ice/base: fix build with gcc11

["Wang, Haiyue" <haiyue.wang@intel.com>]

> -----Original Message-----
> From: Yigit, Ferruh <ferruh.yigit@intel.com>
> Sent: Tuesday, May 11, 2021 01:28
> To: Wang, Haiyue <haiyue.wang@intel.com>; Yang, Qiming <qiming.yang@intel.com>; Zhang, Qi Z
> <qi.z.zhang@intel.com>; Stillwell Jr, Paul M <paul.m.stillwell.jr@intel.com>; Lu, Wenzhuo
> <wenzhuo.lu@intel.com>; Rong, Leyi <leyi.rong@intel.com>; Shukla, Shivanshu
> <shivanshu.shukla@intel.com>
> Cc: dev@dpdk.org; stable@dpdk.org; Kevin Traynor <ktraynor@redhat.com>; Ajit Khaparde
> <ajit.khaparde@broadcom.com>
> Subject: Re: [dpdk-dev] [PATCH 3/4] net/ice/base: fix build with gcc11
> 
> On 5/10/2021 6:04 PM, Wang, Haiyue wrote:
> >> -----Original Message-----
> >> From: dev <dev-bounces@dpdk.org> On Behalf Of Ferruh Yigit
> >> Sent: Monday, May 10, 2021 23:03
> >> To: Yang, Qiming <qiming.yang@intel.com>; Zhang, Qi Z <qi.z.zhang@intel.com>; Stillwell Jr, Paul M
> >> <paul.m.stillwell.jr@intel.com>; Lu, Wenzhuo <wenzhuo.lu@intel.com>; Rong, Leyi
> <leyi.rong@intel.com>;
> >> Shukla, Shivanshu <shivanshu.shukla@intel.com>
> >> Cc: Yigit, Ferruh <ferruh.yigit@intel.com>; dev@dpdk.org; stable@dpdk.org; Kevin Traynor
> >> <ktraynor@redhat.com>; Ajit Khaparde <ajit.khaparde@broadcom.com>
> >> Subject: [dpdk-dev] [PATCH 3/4] net/ice/base: fix build with gcc11
> >>
> >> Reproduced with '--buildtype=debugoptimized' config,
> >> compiler version: gcc (GCC) 12.0.0 20210509 (experimental)
> >>
> >> There are multiple build errors, like:
> >> ../drivers/net/ice/base/ice_switch.c: In function ‘ice_add_marker_act’:
> >> ../drivers/net/ice/base/ice_switch.c:3727:15:
> >>       warning: array subscript ‘struct ice_aqc_sw_rules_elem[0]’
> >>       is partly outside array bounds of ‘unsigned char[52]’
> >>       [-Warray-bounds]
> >>  3727 |         lg_act->type = CPU_TO_LE16(ICE_AQC_SW_RULES_T_LG_ACT);
> >>       |               ^~
> >> In file included from ../drivers/net/ice/base/ice_type.h:52,
> >>                  from ../drivers/net/ice/base/ice_common.h:8,
> >>                  from ../drivers/net/ice/base/ice_switch.h:8,
> >>                  from ../drivers/net/ice/base/ice_switch.c:5:
> >> ../drivers/net/ice/base/ice_osdep.h:209:29:
> >>       note: referencing an object of size 52 allocated by ‘rte_zmalloc’
> >>   209 | #define ice_malloc(h, s)    rte_zmalloc(NULL, s, 0)
> >>       |                             ^~~~~~~~~~~~~~~~~~~~~~~
> >> ../drivers/net/ice/base/ice_switch.c:3720:50:
> >>       note: in expansion of macro ‘ice_malloc’
> >>   lg_act = (struct ice_aqc_sw_rules_elem *)ice_malloc(hw, rules_size);
> >>
> >> These errors are mainly because allocated memory is cast to
> >> "struct ice_aqc_sw_rules_elem *" but allocated size is less than the size
> >> of "struct ice_aqc_sw_rules_elem".
> >>
> >> "struct ice_aqc_sw_rules_elem" has multiple other structs has unions,
> >> based on which one is used allocated memory being less than the size of
> >> "struct ice_aqc_sw_rules_elem" is logically correct but compiler is
> >> complaining about it.
> >>
> >> As a solution making sure allocated memory size is at least size of
> >> "struct ice_aqc_sw_rules_elem".
> >> The function to use the struct is 'ice_aq_sw_rules()', and it already has
> >> parameter for size of the rule, allocating more than needed shouldn't
> >> cause any problem.
> >>
> >> Fixes: c7dd15931183 ("net/ice/base: add virtual switch code")
> >> Fixes: 02acdce2f553 ("net/ice/base: add MAC filter with marker and counter")
> >> Fixes: f89aa3affa9e ("net/ice/base: support removing advanced rule")
> >> Cc: stable@dpdk.org
> >>
> >> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> >> ---
> >> Cc: paul.m.stillwell.jr@intel.com
> >> Cc: qi.z.zhang@intel.com
> >> Cc: leyi.rong@intel.com
> >> Cc: Kevin Traynor <ktraynor@redhat.com>
> >> Cc: Ajit Khaparde <ajit.khaparde@broadcom.com>
> >> ---
> >>  drivers/net/ice/base/ice_switch.c | 30 +++++++++++++++++++++++-------
> >>  1 file changed, 23 insertions(+), 7 deletions(-)
> >
> > GCC bug ?
> >
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98266
> >
> > Bug 98266 - [11 Regression] bogus array subscript is partly outside array bounds on virtual
> inheritance
> >
> 
> I am not sure if this is a gcc defect.
> 
> Here there is a memory allocated and assigned to "struct ice_aqc_sw_rules_elem
> *", but allocated memory size is less than the struct size. As far as I
> understand this is the reason of compiler warning.
> 
> For this case it may not be problem logically since both who allocates memory
> and who uses the memory follows a contract, but there is a mismatch between
> pointer type and object. If some other function wants to access all fields of
> the struct, it will be out of bound access.
> 

That's why they are static function, not API. These functions are designed for
internally using to handle the compact memory layout with different types.

These XXX_SIZE is a helper to get the different memory type size. Of course,
this should be very careful, in other words, as you said: follows a contract. ;-)


#define DUMMY_ETH_HDR_LEN		16
#define ICE_SW_RULE_RX_TX_ETH_HDR_SIZE \
	(offsetof(struct ice_aqc_sw_rules_elem, pdata.lkup_tx_rx.hdr) + \
	 (DUMMY_ETH_HDR_LEN * \
	  sizeof(((struct ice_sw_rule_lkup_rx_tx *)0)->hdr[0])))
#define ICE_SW_RULE_RX_TX_NO_HDR_SIZE \
	(offsetof(struct ice_aqc_sw_rules_elem, pdata.lkup_tx_rx.hdr))
#define ICE_SW_RULE_LG_ACT_SIZE(n) \
	(offsetof(struct ice_aqc_sw_rules_elem, pdata.lg_act.act) + \
	 ((n) * sizeof(((struct ice_sw_rule_lg_act *)0)->act[0])))
#define ICE_SW_RULE_VSI_LIST_SIZE(n) \
	(offsetof(struct ice_aqc_sw_rules_elem, pdata.vsi_list.vsi) + \
	 ((n) * sizeof(((struct ice_sw_rule_vsi_list *)0)->vsi[0])))



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