-Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.
There is currently an object (`tl`), at the beginning of multiple
structures, that contains a flexible structure (`struct nfp_dump_tl`),
for example:
struct nfp_dumpspec_csr {
struct nfp_dump_tl tl;
...
__be32 register_width; /* in bits */
};
So, in order to avoid ending up with flexible-array members in the
middle of multiple other structs, we use the `struct_group_tagged()`
helper to separate the flexible array from the rest of the members
in the flexible structure:
struct nfp_dump_tl {
struct_group_tagged(nfp_dump_tl_hdr, hdr,
... the rest of members
);
char data[];
};
With the change described above, we now declare objects of the type of
the tagged struct, in this case `struct nfp_dump_tl_hdr`, without
embedding flexible arrays in the middle of another struct:
struct nfp_dumpspec_csr {
struct nfp_dump_tl_hdr tl;
...
__be32 register_width; /* in bits */
};
Also, use `container_of()` whenever we need to retrieve a pointer to
the flexible structure, through which we can access the flexible
array if needed.
So, with these changes, fix 33 of the following warnings:
drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c:58:28: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c:64:28: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c:70:28: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c:78:28: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c:87:28: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c:92:28: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
Link: https://github.com/KSPP/linux/issues/202
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
.../netronome/nfp/nfp_net_debugdump.c | 41 +++++++++++--------
1 file changed, 25 insertions(+), 16 deletions(-)
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
index a614df095b08..2dd37557185e 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
@@ -34,8 +34,11 @@ enum nfp_dumpspec_type {
/* generic type plus length */
struct nfp_dump_tl {
- __be32 type;
- __be32 length; /* chunk length to follow, aligned to 8 bytes */
+ /* New members must be added within the struct_group() macro below. */
+ struct_group_tagged(nfp_dump_tl_hdr, hdr,
+ __be32 type;
+ __be32 length; /* chunk length to follow, aligned to 8 bytes */
+ );
char data[];
};
@@ -55,19 +58,19 @@ struct nfp_dump_common_cpp {
/* CSR dumpables */
struct nfp_dumpspec_csr {
- struct nfp_dump_tl tl;
+ struct nfp_dump_tl_hdr tl;
struct nfp_dump_common_cpp cpp;
__be32 register_width; /* in bits */
};
struct nfp_dumpspec_rtsym {
- struct nfp_dump_tl tl;
+ struct nfp_dump_tl_hdr tl;
char rtsym[];
};
/* header for register dumpable */
struct nfp_dump_csr {
- struct nfp_dump_tl tl;
+ struct nfp_dump_tl_hdr tl;
struct nfp_dump_common_cpp cpp;
__be32 register_width; /* in bits */
__be32 error; /* error code encountered while reading */
@@ -75,7 +78,7 @@ struct nfp_dump_csr {
};
struct nfp_dump_rtsym {
- struct nfp_dump_tl tl;
+ struct nfp_dump_tl_hdr tl;
struct nfp_dump_common_cpp cpp;
__be32 error; /* error code encountered while reading */
u8 padded_name_length; /* pad so data starts at 8 byte boundary */
@@ -84,12 +87,12 @@ struct nfp_dump_rtsym {
};
struct nfp_dump_prolog {
- struct nfp_dump_tl tl;
+ struct nfp_dump_tl_hdr tl;
__be32 dump_level;
};
struct nfp_dump_error {
- struct nfp_dump_tl tl;
+ struct nfp_dump_tl_hdr tl;
__be32 error;
char padding[4];
char spec[];
@@ -449,6 +452,8 @@ static int
nfp_dump_csr_range(struct nfp_pf *pf, struct nfp_dumpspec_csr *spec_csr,
struct nfp_dump_state *dump)
{
+ struct nfp_dump_tl *spec_csr_tl =
+ container_of(&spec_csr->tl, struct nfp_dump_tl, hdr);
struct nfp_dump_csr *dump_header = dump->p;
u32 reg_sz, header_size, total_size;
u32 cpp_rd_addr, max_rd_addr;
@@ -458,7 +463,7 @@ nfp_dump_csr_range(struct nfp_pf *pf, struct nfp_dumpspec_csr *spec_csr,
int err;
if (!nfp_csr_spec_valid(spec_csr))
- return nfp_dump_error_tlv(&spec_csr->tl, -EINVAL, dump);
+ return nfp_dump_error_tlv(spec_csr_tl, -EINVAL, dump);
reg_sz = be32_to_cpu(spec_csr->register_width) / BITS_PER_BYTE;
header_size = ALIGN8(sizeof(*dump_header));
@@ -466,7 +471,7 @@ nfp_dump_csr_range(struct nfp_pf *pf, struct nfp_dumpspec_csr *spec_csr,
ALIGN8(be32_to_cpu(spec_csr->cpp.dump_length));
dest = dump->p + header_size;
- err = nfp_add_tlv(be32_to_cpu(spec_csr->tl.type), total_size, dump);
+ err = nfp_add_tlv(be32_to_cpu(spec_csr_tl->type), total_size, dump);
if (err)
return err;
@@ -552,6 +557,8 @@ nfp_dump_indirect_csr_range(struct nfp_pf *pf,
struct nfp_dumpspec_csr *spec_csr,
struct nfp_dump_state *dump)
{
+ struct nfp_dump_tl *spec_csr_tl =
+ container_of(&spec_csr->tl, struct nfp_dump_tl, hdr);
struct nfp_dump_csr *dump_header = dump->p;
u32 reg_sz, header_size, total_size;
u32 cpp_rd_addr, max_rd_addr;
@@ -560,7 +567,7 @@ nfp_dump_indirect_csr_range(struct nfp_pf *pf,
int err;
if (!nfp_csr_spec_valid(spec_csr))
- return nfp_dump_error_tlv(&spec_csr->tl, -EINVAL, dump);
+ return nfp_dump_error_tlv(spec_csr_tl, -EINVAL, dump);
reg_sz = be32_to_cpu(spec_csr->register_width) / BITS_PER_BYTE;
header_size = ALIGN8(sizeof(*dump_header));
@@ -569,7 +576,7 @@ nfp_dump_indirect_csr_range(struct nfp_pf *pf,
total_size = header_size + ALIGN8(reg_data_length);
dest = dump->p + header_size;
- err = nfp_add_tlv(be32_to_cpu(spec_csr->tl.type), total_size, dump);
+ err = nfp_add_tlv(be32_to_cpu(spec_csr_tl->type), total_size, dump);
if (err)
return err;
@@ -597,6 +604,8 @@ static int
nfp_dump_single_rtsym(struct nfp_pf *pf, struct nfp_dumpspec_rtsym *spec,
struct nfp_dump_state *dump)
{
+ struct nfp_dump_tl *spec_tl =
+ container_of(&spec->tl, struct nfp_dump_tl, hdr);
struct nfp_dump_rtsym *dump_header = dump->p;
struct nfp_dumpspec_cpp_isl_id cpp_params;
struct nfp_rtsym_table *rtbl = pf->rtbl;
@@ -607,14 +616,14 @@ nfp_dump_single_rtsym(struct nfp_pf *pf, struct nfp_dumpspec_rtsym *spec,
void *dest;
int err;
- tl_len = be32_to_cpu(spec->tl.length);
+ tl_len = be32_to_cpu(spec_tl->length);
key_len = strnlen(spec->rtsym, tl_len);
if (key_len == tl_len)
- return nfp_dump_error_tlv(&spec->tl, -EINVAL, dump);
+ return nfp_dump_error_tlv(spec_tl, -EINVAL, dump);
sym = nfp_rtsym_lookup(rtbl, spec->rtsym);
if (!sym)
- return nfp_dump_error_tlv(&spec->tl, -ENOENT, dump);
+ return nfp_dump_error_tlv(spec_tl, -ENOENT, dump);
sym_size = nfp_rtsym_size(sym);
header_size =
@@ -622,7 +631,7 @@ nfp_dump_single_rtsym(struct nfp_pf *pf, struct nfp_dumpspec_rtsym *spec,
total_size = header_size + ALIGN8(sym_size);
dest = dump->p + header_size;
- err = nfp_add_tlv(be32_to_cpu(spec->tl.type), total_size, dump);
+ err = nfp_add_tlv(be32_to_cpu(spec_tl->type), total_size, dump);
if (err)
return err;
--
2.34.1
On Thu, 28 Mar 2024 19:17:10 -0600 Gustavo A. R. Silva wrote:
> --- a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
> +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
> @@ -34,8 +34,11 @@ enum nfp_dumpspec_type {
>
> /* generic type plus length */
> struct nfp_dump_tl {
> - __be32 type;
> - __be32 length; /* chunk length to follow, aligned to 8 bytes */
> + /* New members must be added within the struct_group() macro below. */
> + struct_group_tagged(nfp_dump_tl_hdr, hdr,
> + __be32 type;
> + __be32 length; /* chunk length to follow, aligned to 8 bytes */
> + );
> char data[];
> };
I counted 9 references to nfp_dump_tl->data.
Better to add:
static void *nfp_dump_tl_data(struct nfp_dump_tl *spec)
{
return &spec[1];
}
and delete the flex array completely.
--
pw-bot: cr
On 01/04/24 22:24, Jakub Kicinski wrote:
> On Thu, 28 Mar 2024 19:17:10 -0600 Gustavo A. R. Silva wrote:
>> --- a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
>> +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
>> @@ -34,8 +34,11 @@ enum nfp_dumpspec_type {
>>
>> /* generic type plus length */
>> struct nfp_dump_tl {
>> - __be32 type;
>> - __be32 length; /* chunk length to follow, aligned to 8 bytes */
>> + /* New members must be added within the struct_group() macro below. */
>> + struct_group_tagged(nfp_dump_tl_hdr, hdr,
>> + __be32 type;
>> + __be32 length; /* chunk length to follow, aligned to 8 bytes */
>> + );
>> char data[];
>> };
>
> I counted 9 references to nfp_dump_tl->data.
> Better to add:
>
> static void *nfp_dump_tl_data(struct nfp_dump_tl *spec)
> {
> return &spec[1];
> }
Unfortunately, that's out-of-bounds for the compiler, and well, basically
the reason why flex-array members were created in the first place.
I was looking into implementing two separate structs:
struct nfp_dump_tl_hdr {
__be32 type;
__be32 length; /* chunk length to follow, aligned to 8 bytes */
};
struct nfp_dump_tl {
__be32 type;
__be32 length; /* chunk length to follow, aligned to 8 bytes */
char data[];
};
and at least for structs nfp_dumpspec_csr, nfp_dumpspec_rtsym, nfp_dump_csr, and
nfp_dump_rtsym it'd be a clean change (no need for container_of()), but not for
structs nfp_dumpspec_csr and nfp_dumpspec_rtsym because of some casts from
the flex struct:
nfp_add_tlv_size():
case NFP_DUMPSPEC_TYPE_ME_CSR:
spec_csr = (struct nfp_dumpspec_csr *)tl;
if (!nfp_csr_spec_valid(spec_csr))
...
case NFP_DUMPSPEC_TYPE_INDIRECT_ME_CSR:
spec_csr = (struct nfp_dumpspec_csr *)tl;
if (!nfp_csr_spec_valid(spec_csr))
...
case NFP_DUMPSPEC_TYPE_RTSYM:
spec_rtsym = (struct nfp_dumpspec_rtsym *)tl;
err = nfp_dump_single_rtsym(pf, spec_rtsym, dump);
nfp_calc_rtsym_dump_sz():
spec_rtsym = (struct nfp_dumpspec_rtsym *)spec;
At least for those two structs, it's probably more straightforward to use
struct_group_tagged() and container_of().
--
Gustavo
Hello:
This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <[email protected]>:
On Thu, 28 Mar 2024 19:17:10 -0600 you wrote:
> -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
> ready to enable it globally.
>
> There is currently an object (`tl`), at the beginning of multiple
> structures, that contains a flexible structure (`struct nfp_dump_tl`),
> for example:
>
> [...]
Here is the summary with links:
- [next] nfp: Avoid -Wflex-array-member-not-at-end warnings
https://git.kernel.org/netdev/net-next/c/d88cabfd9abc
You are awesome, thank you!
--
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