scsi: fc: Avoid -Wflex-array-member-not-at-end warnings

-Wflex-array-member-not-at-end has been introduced in GCC-14, and we are
getting ready to enable it, globally.

So, in order to avoid ending up with a flexible-array member in the
middle of multiple other structs, we use the '__struct_group()' helper
to create a new tagged 'struct fc_df_desc_fpin_reg_hdr'.  This structure
groups together all the members of the flexible 'struct
fc_df_desc_fpin_reg' except the flexible array.

As a result, the array is effectively separated from the rest of the
members without modifying the memory layout of the flexible structure.
We then change the type of the middle struct members currently causing
trouble from 'struct fc_df_desc_fpin_reg' to 'struct
fc_df_desc_fpin_reg_hdr'.

We also want to ensure that in case new members need to be added to the
flexible structure, they are always included within the newly created
tagged struct. For this, we use '_Static_assert()'. This ensures that
the memory layout for both the flexible structure and the new tagged
struct is the same after any changes.

This approach avoids having to implement 'struct fc_df_desc_fpin_reg_hdr'
as a completely separate structure, thus preventing having to maintain
two independent but basically identical structures, closing the door
to potential bugs in the future.

The above is also done for flexible structures 'struct fc_els_rdf' and
'struct fc_els_rdf_resp'

So, with these changes, fix the following warnings:
drivers/scsi/lpfc/lpfc_hw4.h:4936:41: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/scsi/lpfc/lpfc_hw4.h:4942:41: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/scsi/lpfc/lpfc_hw4.h:4947:41: 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@kernel.org>
Link: https://lore.kernel.org/r/aK6hbQLyQlvlySf8@kspp
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/lpfc/lpfc_els.c b/drivers/scsi/lpfc/lpfc_els.c
index fca81e0c7c2e1a3cf6be4db6941fe2d8e0c28439..432761fb49de74b458905912f478f3a77adc4135 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_els.c
+++ b/drivers/scsi/lpfc/lpfc_els.c
@@ -3762,7 +3762,7 @@ lpfc_issue_els_rdf(struct lpfc_vport *vport, uint8_t retry)
        memset(prdf, 0, cmdsize);
        prdf->rdf.fpin_cmd = ELS_RDF;
        prdf->rdf.desc_len = cpu_to_be32(sizeof(struct lpfc_els_rdf_req) -
-                                        sizeof(struct fc_els_rdf));
+                                        sizeof(struct fc_els_rdf_hdr));
        prdf->reg_d1.reg_desc.desc_tag = cpu_to_be32(ELS_DTAG_FPIN_REGISTER);
        prdf->reg_d1.reg_desc.desc_len = cpu_to_be32(
                                FC_TLV_DESC_LENGTH_FROM_SZ(prdf->reg_d1));

diff --git a/drivers/scsi/lpfc/lpfc_hw4.h b/drivers/scsi/lpfc/lpfc_hw4.h
index bc709786e6af3fc2d1c8247503526f6a0cfc87fc..a7f7ed86d2b014d425a6ae289be7a1b9eb3b6f8c 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_hw4.h
+++ b/drivers/scsi/lpfc/lpfc_hw4.h
@@ -4909,18 +4909,18 @@ struct send_frame_wqe {
 
 #define ELS_RDF_REG_TAG_CNT            4
 struct lpfc_els_rdf_reg_desc {
-       struct fc_df_desc_fpin_reg      reg_desc;       /* descriptor header */
+       struct fc_df_desc_fpin_reg_hdr  reg_desc;       /* descriptor header */
        __be32                          desc_tags[ELS_RDF_REG_TAG_CNT];
                                                        /* tags in reg_desc */
 };
 
 struct lpfc_els_rdf_req {
-       struct fc_els_rdf               rdf;       /* hdr up to descriptors */
+       struct fc_els_rdf_hdr           rdf;       /* hdr up to descriptors */
        struct lpfc_els_rdf_reg_desc    reg_d1; /* 1st descriptor */
 };
 
 struct lpfc_els_rdf_rsp {
-       struct fc_els_rdf_resp          rdf_resp;  /* hdr up to descriptors */
+       struct fc_els_rdf_resp_hdr      rdf_resp;  /* hdr up to descriptors */
        struct lpfc_els_rdf_reg_desc    reg_d1; /* 1st descriptor */
 };
 

diff --git a/include/uapi/scsi/fc/fc_els.h b/include/uapi/scsi/fc/fc_els.h
index 16782c360de3c149263d10b45edb8fc718ff5840..019096beb179fa069469e9417392bf3b2e951eaf 100644 (file)
--- a/include/uapi/scsi/fc/fc_els.h
+++ b/include/uapi/scsi/fc/fc_els.h
@@ -11,6 +11,12 @@
 #include <linux/types.h>
 #include <asm/byteorder.h>
 
+#ifdef __KERNEL__
+#include <linux/stddef.h>      /* for offsetof */
+#else
+#include <stddef.h>            /* for offsetof */
+#endif
+
 /*
  * Fibre Channel Switch - Enhanced Link Services definitions.
  * From T11 FC-LS Rev 1.2 June 7, 2005.
@@ -1109,12 +1115,15 @@ struct fc_els_fpin {
 
 /* Diagnostic Function Descriptor - FPIN Registration */
 struct fc_df_desc_fpin_reg {
-       __be32          desc_tag;       /* FPIN Registration (0x00030001) */
-       __be32          desc_len;       /* Length of Descriptor (in bytes).
-                                        * Size of descriptor excluding
-                                        * desc_tag and desc_len fields.
-                                        */
-       __be32          count;          /* Number of desc_tags elements */
+       /* New members MUST be added within the __struct_group() macro below. */
+       __struct_group(fc_df_desc_fpin_reg_hdr, __hdr, /* no attrs */,
+               __be32          desc_tag; /* FPIN Registration (0x00030001) */
+               __be32          desc_len; /* Length of Descriptor (in bytes).
+                                          * Size of descriptor excluding
+                                          * desc_tag and desc_len fields.
+                                          */
+               __be32          count;    /* Number of desc_tags elements */
+       );
        __be32          desc_tags[];    /* Array of Descriptor Tags.
                                         * Each tag indicates a function
                                         * supported by the N_Port (request)
@@ -1124,33 +1133,44 @@ struct fc_df_desc_fpin_reg {
                                         * See ELS_FN_DTAG_xxx for tag values.
                                         */
 };
+_Static_assert(offsetof(struct fc_df_desc_fpin_reg, desc_tags) == sizeof(struct fc_df_desc_fpin_reg_hdr),
+             "struct member likely outside of __struct_group()");
 
 /*
  * ELS_RDF - Register Diagnostic Functions
  */
 struct fc_els_rdf {
-       __u8            fpin_cmd;       /* command (0x19) */
-       __u8            fpin_zero[3];   /* specified as zero - part of cmd */
-       __be32          desc_len;       /* Length of Descriptor List (in bytes).
-                                        * Size of ELS excluding fpin_cmd,
-                                        * fpin_zero and desc_len fields.
-                                        */
+       /* New members MUST be added within the __struct_group() macro below. */
+       __struct_group(fc_els_rdf_hdr, __hdr, /* no attrs */,
+               __u8            fpin_cmd;       /* command (0x19) */
+               __u8            fpin_zero[3];   /* specified as zero - part of cmd */
+               __be32          desc_len;       /* Length of Descriptor List (in bytes).
+                                                * Size of ELS excluding fpin_cmd,
+                                                * fpin_zero and desc_len fields.
+                                                */
+       );
        struct fc_tlv_desc      desc[]; /* Descriptor list */
 };
+_Static_assert(offsetof(struct fc_els_rdf, desc) == sizeof(struct fc_els_rdf_hdr),
+              "struct member likely outside of __struct_group()");
 
 /*
  * ELS RDF LS_ACC Response.
  */
 struct fc_els_rdf_resp {
-       struct fc_els_ls_acc    acc_hdr;
-       __be32                  desc_list_len;  /* Length of response (in
-                                                * bytes). Excludes acc_hdr
-                                                * and desc_list_len fields.
-                                                */
-       struct fc_els_lsri_desc lsri;
+       /* New members MUST be added within the __struct_group() macro below. */
+       __struct_group(fc_els_rdf_resp_hdr, __hdr, /* no attrs */,
+               struct fc_els_ls_acc    acc_hdr;
+               __be32                  desc_list_len;  /* Length of response (in
+                                                        * bytes). Excludes acc_hdr
+                                                        * and desc_list_len fields.
+                                                        */
+               struct fc_els_lsri_desc lsri;
+       );
        struct fc_tlv_desc      desc[]; /* Supported Descriptor list */
 };
-
+_Static_assert(offsetof(struct fc_els_rdf_resp, desc) == sizeof(struct fc_els_rdf_resp_hdr),
+              "struct member likely outside of __struct_group()");
 
 /*
  * Diagnostic Capability Descriptors for EDC ELS