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Message-ID: <c4828c41-e46c-43c9-a73a-38ce8ab2c1c4@embeddedor.com>
Date: Wed, 30 Apr 2025 14:07:24 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Dan Williams <dan.j.williams@...el.com>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
Alison Schofield <alison.schofield@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>,
Ira Weiny <ira.weiny@...el.com>, "Rafael J. Wysocki" <rafael@...nel.org>,
Len Brown <lenb@...nel.org>
Cc: nvdimm@...ts.linux.dev, linux-acpi@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2][next] acpi: nfit: intel: Avoid multiple
-Wflex-array-member-not-at-end warnings
On 30/04/25 13:41, Gustavo A. R. Silva wrote:
>
>
> 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@...nel.org>
>>> ---
>>> 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),
> },
> });
>
Now, I can modify the helper like this:
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 69533e703be5..170d3cfe7ecc 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -404,7 +404,7 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
union { \
u8 bytes[struct_size_t(type, member, count)]; \
type obj; \
- } name##_u initializer; \
+ } name##_u = { .obj initializer }; \
type *name = (type *)&name##_u
/**
and then we can use the helper as follows:
_DEFINE_FLEX(struct nd_cmd_pkg, nd_cmd, nd_payload,
sizeof(struct nd_intel_get_security_state), = {
.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),
});
OK, I'll go and update the helper.
-Gustavo
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