Re: [PATCH v2][next] acpi: nfit: intel: Avoid multiple -Wflex-array-member-not-at-end warnings

["Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx>]

On 27/03/25 08:03, Dan Williams wrote:
> Gustavo A. R. Silva wrote:
> > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> > getting ready to enable it, globally.
> >
> > Use the `DEFINE_RAW_FLEX()` helper for on-stack definitions of
> > a flexible structure where the size of the flexible-array member
> > is known at compile-time, and refactor the rest of the code,
> > accordingly.
> >
> > So, with these changes, fix a dozen of the following warnings:
> >
> > drivers/acpi/nfit/intel.c:692:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> >
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> > ---
> > Changes in v2:
> >   - Use DEFINE_RAW_FLEX() instead of __struct_group().
> >
> > v1:
> >   - Link: https://lore.kernel.org/linux-hardening/Z618ILbAR8YAvTkd@kspp/
> >
> >   drivers/acpi/nfit/intel.c | 388 ++++++++++++++++++--------------------
> >   1 file changed, 179 insertions(+), 209 deletions(-)
> >
> > diff --git a/drivers/acpi/nfit/intel.c b/drivers/acpi/nfit/intel.c
> > index 3902759abcba..114d5b3bb39b 100644
> > --- a/drivers/acpi/nfit/intel.c
> > +++ b/drivers/acpi/nfit/intel.c
> > @@ -55,21 +55,17 @@ static unsigned long intel_security_flags(struct nvdimm *nvdimm,
> >   {
> >   	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> >   	unsigned long security_flags = 0;
> > -	struct {
> > -		struct nd_cmd_pkg pkg;
> > -		struct nd_intel_get_security_state cmd;
> > -	} nd_cmd = {
> > -		.pkg = {
> > -			.nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,
> > -			.nd_family = NVDIMM_FAMILY_INTEL,
> > -			.nd_size_out =
> > -				sizeof(struct nd_intel_get_security_state),
> > -			.nd_fw_size =
> > -				sizeof(struct nd_intel_get_security_state),
> > -		},
> > -	};
> > +	DEFINE_RAW_FLEX(struct nd_cmd_pkg, nd_cmd, nd_payload,
> > +			sizeof(struct nd_intel_get_security_state));
> > +	struct nd_intel_get_security_state *cmd =
> > +			(struct nd_intel_get_security_state *)nd_cmd->nd_payload;
> >   	int rc;
> >   
> > +	nd_cmd->nd_command = NVDIMM_INTEL_GET_SECURITY_STATE;
> > +	nd_cmd->nd_family = NVDIMM_FAMILY_INTEL;
> > +	nd_cmd->nd_size_out = sizeof(struct nd_intel_get_security_state);
> > +	nd_cmd->nd_fw_size = sizeof(struct nd_intel_get_security_state);
>
> Can this keep the C99 init-style with something like (untested):
>
> _DEFINE_FLEX(struct nd_cmd_pkg, nd_cmd, nd_payload,
>               sizeof(struct nd_intel_get_security_state), {
> 		.pkg = {
> 		        .nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,
> 		        .nd_family = NVDIMM_FAMILY_INTEL,
> 		        .nd_size_out =
> 		                sizeof(struct nd_intel_get_security_state),
> 		        .nd_fw_size =
> 		                sizeof(struct nd_intel_get_security_state),
> 		},
> 	});
> 	
>
> ?

The code below works - however, notice that in this case we should
go through 'obj', which is an object defined in _DEFINE_FLEX().

        _DEFINE_FLEX(struct nd_cmd_pkg, nd_cmd, nd_payload,
                        sizeof(struct nd_intel_get_security_state), = {
                .obj = {
                        .nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,
                        .nd_family = NVDIMM_FAMILY_INTEL,
                        .nd_size_out =
                                sizeof(struct nd_intel_get_security_state),
                        .nd_fw_size =
                                sizeof(struct nd_intel_get_security_state),
                },
        });

Thanks
-Gustavo