| Message ID | 1395557744-25248-1-git-send-email-behanw@converseincode.com |
|---|---|
| State | New |
| Headers | show |
On 03/22/14 23:55, behanw@converseincode.com wrote: > From: Mark Charlebois <charlebm@gmail.com> > > Replaced non-standard C use of Variable Length Arrays In Structs (VLAIS) in > xt_repldata.h with a C99 compliant flexible array member and then calculated > offsets to the other struct members. These other members aren't referenced by > name in this code, however this patch maintains the same memory layout and > padding as was previously accomplished using VLAIS. > > Had the original structure been ordered differently, with the entries VLA at > the end, then it could have been a flexible member, and this patch would have > been a lot simpler. However since the data stored in this structure is > ultimately exported to userspace, the order of this structure can't be changed. > > This patch makes no attempt to change the existing behavior, merely the way in > which the current layout is accomplished using standard C99 constructs. As such > the code can now be compiled with either gcc or clang. > > This version of the patch removes the trailing alignment that the VLAIS > structure would allocate in order to simplify the patch. > > Author: Mark Charlebois <charlebm@gmail.com> > Signed-off-by: Mark Charlebois <charlebm@gmail.com> > Signed-off-by: Behan Webster <behanw@converseincode.com> > Signed-off-by: VinÃcius Tinti <viniciustinti@gmail.com> > --- > net/netfilter/xt_repldata.h | 22 +++++++++++++++++----- > 1 file changed, 17 insertions(+), 5 deletions(-) > > diff --git a/net/netfilter/xt_repldata.h b/net/netfilter/xt_repldata.h > index 6efe4e5..8fd3241 100644 > --- a/net/netfilter/xt_repldata.h > +++ b/net/netfilter/xt_repldata.h > @@ -5,23 +5,35 @@ > * they serve as the hanging-off data accessed through repl.data[]. > */ > > +/* tbl has the following structure equivalent, but is C99 compliant: > + * struct { > + * struct type##_replace repl; > + * struct type##_standard entries[nhooks]; > + * struct type##_error term; > + * } *tbl; > + */ > + > #define xt_alloc_initial_table(type, typ2) ({ \ > unsigned int hook_mask = info->valid_hooks; \ > unsigned int nhooks = hweight32(hook_mask); \ > unsigned int bytes = 0, hooknum = 0, i = 0; \ > struct { \ > struct type##_replace repl; \ > - struct type##_standard entries[nhooks]; \ > - struct type##_error term; \ > - } *tbl = kzalloc(sizeof(*tbl), GFP_KERNEL); \ > + struct type##_standard entries[]; \ > + } *tbl; \ > + struct type##_error *term; \ > + size_t term_offset = (offsetof(typeof(*tbl), entries[nhooks]) + \ > + __alignof__(*term) - 1) & ~(__alignof__(*term) - 1); \ > + tbl = kzalloc(term_offset + sizeof(*term), GFP_KERNEL); \ > if (tbl == NULL) \ > return NULL; \ > + term = (struct type##_error *)&(((char *)tbl)[term_offset]); \ > strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \ > - tbl->term = (struct type##_error)typ2##_ERROR_INIT; \ > + *term = (struct type##_error)typ2##_ERROR_INIT; \ > tbl->repl.valid_hooks = hook_mask; \ > tbl->repl.num_entries = nhooks + 1; \ > tbl->repl.size = nhooks * sizeof(struct type##_standard) + \ > - sizeof(struct type##_error); \ > + sizeof(struct type##_error); \ > for (; hook_mask != 0; hook_mask >>= 1, ++hooknum) { \ > if (!(hook_mask & 1)) \ > continue; \ Any further feedback about this patch? Behan
diff --git a/net/netfilter/xt_repldata.h b/net/netfilter/xt_repldata.h index 6efe4e5..8fd3241 100644 --- a/net/netfilter/xt_repldata.h +++ b/net/netfilter/xt_repldata.h @@ -5,23 +5,35 @@ * they serve as the hanging-off data accessed through repl.data[]. */ +/* tbl has the following structure equivalent, but is C99 compliant: + * struct { + * struct type##_replace repl; + * struct type##_standard entries[nhooks]; + * struct type##_error term; + * } *tbl; + */ + #define xt_alloc_initial_table(type, typ2) ({ \ unsigned int hook_mask = info->valid_hooks; \ unsigned int nhooks = hweight32(hook_mask); \ unsigned int bytes = 0, hooknum = 0, i = 0; \ struct { \ struct type##_replace repl; \ - struct type##_standard entries[nhooks]; \ - struct type##_error term; \ - } *tbl = kzalloc(sizeof(*tbl), GFP_KERNEL); \ + struct type##_standard entries[]; \ + } *tbl; \ + struct type##_error *term; \ + size_t term_offset = (offsetof(typeof(*tbl), entries[nhooks]) + \ + __alignof__(*term) - 1) & ~(__alignof__(*term) - 1); \ + tbl = kzalloc(term_offset + sizeof(*term), GFP_KERNEL); \ if (tbl == NULL) \ return NULL; \ + term = (struct type##_error *)&(((char *)tbl)[term_offset]); \ strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \ - tbl->term = (struct type##_error)typ2##_ERROR_INIT; \ + *term = (struct type##_error)typ2##_ERROR_INIT; \ tbl->repl.valid_hooks = hook_mask; \ tbl->repl.num_entries = nhooks + 1; \ tbl->repl.size = nhooks * sizeof(struct type##_standard) + \ - sizeof(struct type##_error); \ + sizeof(struct type##_error); \ for (; hook_mask != 0; hook_mask >>= 1, ++hooknum) { \ if (!(hook_mask & 1)) \ continue; \