pahole: Introduce --fixup_silly_bitfields

$ pahole -C acpi_device_perf_flags ac.o
struct acpi_device_perf_flags {
	u8          reserved:8;           /*     0: 0  1 */

	/* size: 1, cachelines: 1, members: 1 */
	/* last cacheline: 1 bytes */
};
$ pahole --fixup_silly_bitfields -C acpi_device_perf_flags ac.o
struct acpi_device_perf_flags {
	u8          reserved;             /*     0     1 */

	/* size: 1, cachelines: 1, members: 1 */
	/* last cacheline: 1 bytes */
};
$

Used in ctfdwdiff as in CTF land we can't express such sillyness.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

ctfdwdiff

@@ -8,10 +8,12 @@ ctf=$dir/$obj.ctf.c
 dwarf=$dir/$obj.dwarf.c
 pahole -Z $obj
 pahole -F ctf $obj > $ctf
-pahole --flat_arrays --show_private_classes -F dwarf $obj > $dwarf
+pahole --flat_arrays \
+       --show_private_classes \
+       --fixup_silly_bitfields -F dwarf $obj > $dwarf
 diff -up $ctf $dwarf > $diff
 if [ -s $diff ] ; then
-	# vim $dir/$obj.diff
+	[ $# -gt 1 ] && vim $dir/$obj.diff
 	exit 0
 else
 	rm -f $diff $ctf $dwarf

dwarf_loader.c

@@ -1715,9 +1715,10 @@ static void die__process(Dwarf_Die *die, struct cu *cu)
 }
 
 static int class_member__cache_byte_size(struct tag *self, struct cu *cu,
-					 void *cookie __unused)
+					 void *cookie)
 {
 	if (self->tag == DW_TAG_member || self->tag == DW_TAG_inheritance) {
+		struct conf_load *conf_load = cookie;
 		struct class_member *member;
 
 		if (member->bitfield_size != 0) {
@@ -1742,8 +1743,15 @@ static int class_member__cache_byte_size(struct tag *self, struct cu *cu,
 			 */
 			member->byte_size = integral_bit_size / 8;
 
-			if (integral_bit_size == 0 || type_bit_size == integral_bit_size) {
+			if (integral_bit_size == 0)
+				return 0;
+
+			if (type_bit_size == integral_bit_size) {
 				member->bit_size = integral_bit_size;
+				if (conf_load && conf_load->fixup_silly_bitfields) {
+					member->bitfield_size = 0;
+					member->bitfield_offset = 0;
+				}
 				return 0;
 			}
 
@@ -1785,7 +1793,7 @@ static int cus__load_module(struct cus *self, struct conf_load *conf,
 		cu->extra_dbg_info = conf ? conf->extra_dbg_info : 0;
 		die__process(cu_die, cu);
 		base_type_name_to_size_table__init();
-		cu__for_all_tags(cu, class_member__cache_byte_size, NULL);
+		cu__for_all_tags(cu, class_member__cache_byte_size, conf);
 		off = noff;
 		if (conf && conf->steal) {
 			switch (conf->steal(cu, conf)) {

dwarves.h

@@ -32,13 +32,15 @@ enum load_steal_kind {
 /** struct conf_load - load configuration
  * @extra_dbg_info - keep original debugging format extra info
  *		     (e.g. DWARF's decl_{line,file}, id, etc)
+ * @fixup_silly_bitfields - Fixup silly things such as "int foo:32;"
  */
 struct conf_load {
-	bool			extra_dbg_info;
 	enum load_steal_kind	(*steal)(struct cu *self,
 					 struct conf_load *conf);
 	void			*cookie;
 	char			*format_path;
+	bool			extra_dbg_info;
+	bool			fixup_silly_bitfields;
 };
 
 /** struct conf_fprintf - hints to the __fprintf routines

man-pages/pahole.1

@@ -165,6 +165,10 @@ Flatten arrays, so that array[10][2] becomes array[20].
 Useful when generating from both CTF and DWARF encodings
 for the same binary for testing purposes.
 
+.TP
+.B     \-\-fixup_silly_bitfields
+Converts silly bitfields such as "int foo:32" to plain "int foo".
+
 .TP
 .B \-V, \-\-verbose
 be verbose

pahole.c

@@ -704,8 +704,9 @@ static void print_containers(const struct cu *cu, uint16_t type, int ident)
 /* Name and version of program.  */
 ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
 
-#define ARGP_flat_arrays	  300
+#define ARGP_flat_arrays	   300
-#define ARGP_show_private_classes 301
+#define ARGP_show_private_classes  301
+#define ARGP_fixup_silly_bitfields 302
 
 static const struct argp_option pahole__options[] = {
 	{
@@ -914,6 +915,11 @@ static const struct argp_option pahole__options[] = {
 		.key  = ARGP_show_private_classes,
 		.doc  = "Show classes that are defined inside other classes or in functions",
 	},
+	{
+		.name = "fixup_silly_bitfields",
+		.key  = ARGP_fixup_silly_bitfields,
+		.doc  = "Fix silly bitfields such as int foo:32",
+	},
 	{
 		.name = NULL,
 	}
@@ -986,6 +992,8 @@ static error_t pahole__options_parser(int key, char *arg,
 	case ARGP_flat_arrays: conf.flat_arrays = 1;	break;
 	case ARGP_show_private_classes:
 		show_private_classes = true;		break;
+	case ARGP_fixup_silly_bitfields:
+		conf_load.fixup_silly_bitfields = 1;	break;
 	default:
 		return ARGP_ERR_UNKNOWN;
 	}