For struct/union members, the struct/union type info kind_flag is
needed to calculate correct bitfield_size and bit_offset.
if (kind_flag) {
bitfield_size = BTF_MEMBER_BITFIELD_SIZE(member->offset);
bit_offset = BTF_MEMBER_BIT_OFFSET(member->offset);
} else {
bitfield_size = 0;
bit_offset = member->offset;
}
Note that bitfield_size and bit_offset will not depend on the
member type. The member type will help calculate correct
bitfield_offset, byte_size, byte_offset, bit_size.
For example, with the fix, we will be able to display
bit offset and bitfield size properly.
-bash-4.4$ cat t.c
struct t {
int a:2;
int b:3;
int c:2;
} g;
-bash-4.4$ gcc -c -O2 -g t.c
-bash-4.4$ pahole -JV t.o
File t.o:
[1] STRUCT t kind_flag=1 size=4 vlen=3
a type_id=2 bitfield_size=2 bits_offset=0
b type_id=2 bitfield_size=3 bits_offset=2
c type_id=2 bitfield_size=2 bits_offset=5
[2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
-bash-4.4$ pahole -F btf t.o
struct t {
int a:2; /* 0: 0 4 */
int b:3; /* 0: 2 4 */
int c:2; /* 0: 5 4 */
/* size: 4, cachelines: 1, members: 3 */
/* bit_padding: 25 bits */
/* last cacheline: 4 bytes */
};
Note that the above offset showing is different from the below dwarf as
BTF bitfield_offset is always the offset from the start of structure,
kindly like big endian encoding. This may need adjustment to be
conforming to the dwarf dump format.
-bash-4.4$ pahole -F dwarf t.o
struct t {
int a:2; /* 0:30 4 */
int b:3; /* 0:27 4 */
int c:2; /* 0:25 4 */
/* size: 4, cachelines: 1, members: 3 */
/* bit_padding: 25 bits */
/* last cacheline: 4 bytes */
};
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
btf_loader.c | 61 +++++++++++++++++++++++++++++++---------------------
dwarves.h | 1 +
2 files changed, 37 insertions(+), 25 deletions(-)
diff --git a/btf_loader.c b/btf_loader.c
index dae21d5..eeb0c8b 100644
--- a/btf_loader.c
+++ b/btf_loader.c
@@ -1,4 +1,4 @@
-/*
+/*
* btf_loader.c
*
* Copyright (C) 2018 Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
@@ -101,7 +101,7 @@ static struct base_type *base_type__new(strings_t name, uint32_t attrs,
}
static void type__init(struct type *type, uint16_t tag,
- strings_t name, size_t size)
+ strings_t name, size_t size, bool kflag)
{
INIT_LIST_HEAD(&type->node);
INIT_LIST_HEAD(&type->namespace.tags);
@@ -109,24 +109,26 @@ static void type__init(struct type *type, uint16_t tag,
type->namespace.tag.tag = tag;
type->namespace.name = name;
type->namespace.sname = 0;
+ type->flag = kflag;
}
-static struct type *type__new(uint16_t tag, strings_t name, size_t size)
+static struct type *type__new(uint16_t tag, strings_t name, size_t size,
+ bool kflag)
{
struct type *type = tag__alloc(sizeof(*type));
if (type != NULL)
- type__init(type, tag, name, size);
+ type__init(type, tag, name, size, kflag);
return type;
}
-static struct class *class__new(strings_t name, size_t size)
+static struct class *class__new(strings_t name, size_t size, bool kflag)
{
struct class *class = tag__alloc(sizeof(*class));
if (class != NULL) {
- type__init(&class->type, DW_TAG_structure_type, name, size);
+ type__init(&class->type, DW_TAG_structure_type, name, size, kflag);
INIT_LIST_HEAD(&class->vtable);
}
@@ -177,7 +179,8 @@ static int create_new_array(struct btf *btf, void *ptr, long id)
return sizeof(*ap);
}
-static int create_members(struct btf *btf, void *ptr, int vlen, struct type *class)
+static int create_members(struct btf *btf, void *ptr, int vlen, struct type *class,
+ bool kflag)
{
struct btf_member *mp = ptr;
int i;
@@ -193,8 +196,13 @@ static int create_members(struct btf *btf, void *ptr, int vlen, struct type *cla
member->tag.type = btf__get32(btf, &mp[i].type);
member->name = btf__get32(btf, &mp[i].name_off);
offset = btf__get32(btf, &mp[i].offset);
- member->bit_offset = BTF_MEMBER_BIT_OFFSET(offset);
- member->bitfield_size = BTF_MEMBER_BITFIELD_SIZE(offset);
+ if (kflag) {
+ member->bit_offset = BTF_MEMBER_BIT_OFFSET(offset);
+ member->bitfield_size = BTF_MEMBER_BITFIELD_SIZE(offset);
+ } else {
+ member->bit_offset = offset;
+ member->bitfield_size = 0;
+ }
/* sizes and offsets will be corrected at class__fixup_btf_bitfields */
type__add_member(class, member);
}
@@ -202,11 +210,13 @@ static int create_members(struct btf *btf, void *ptr, int vlen, struct type *cla
return sizeof(*mp);
}
-static int create_new_class(struct btf *btf, void *ptr, int vlen, struct btf_type *tp, uint64_t size, long id)
+static int create_new_class(struct btf *btf, void *ptr, int vlen,
+ struct btf_type *tp, uint64_t size, long id,
+ bool kflag)
{
strings_t name = btf__get32(btf, &tp->name_off);
- struct class *class = class__new(name, size);
- int member_size = create_members(btf, ptr, vlen, &class->type);
+ struct class *class = class__new(name, size, kflag);
+ int member_size = create_members(btf, ptr, vlen, &class->type, kflag);
if (member_size < 0)
goto out_free;
@@ -221,11 +231,12 @@ out_free:
static int create_new_union(struct btf *btf, void *ptr,
int vlen, struct btf_type *tp,
- uint64_t size, long id)
+ uint64_t size, long id,
+ bool kflag)
{
strings_t name = btf__get32(btf, &tp->name_off);
- struct type *un = type__new(DW_TAG_union_type, name, size);
- int member_size = create_members(btf, ptr, vlen, un);
+ struct type *un = type__new(DW_TAG_union_type, name, size, kflag);
+ int member_size = create_members(btf, ptr, vlen, un, kflag);
if (member_size < 0)
goto out_free;
@@ -259,7 +270,7 @@ static int create_new_enumeration(struct btf *btf, void *ptr,
uint16_t i;
struct type *enumeration = type__new(DW_TAG_enumeration_type,
btf__get32(btf, &tp->name_off),
- size ?: (sizeof(int) * 8));
+ size ?: (sizeof(int) * 8), false);
if (enumeration == NULL)
return -ENOMEM;
@@ -299,10 +310,11 @@ static int create_new_subroutine_type(struct btf *btf, void *ptr,
return vlen < 0 ? -ENOMEM : vlen;
}
-static int create_new_forward_decl(struct btf *btf, struct btf_type *tp, uint64_t size, long id)
+static int create_new_forward_decl(struct btf *btf, struct btf_type *tp,
+ uint64_t size, long id, bool kflag)
{
strings_t name = btf__get32(btf, &tp->name_off);
- struct class *fwd = class__new(name, size);
+ struct class *fwd = class__new(name, size, kflag);
if (fwd == NULL)
return -ENOMEM;
@@ -315,7 +327,7 @@ static int create_new_typedef(struct btf *btf, struct btf_type *tp, uint64_t siz
{
strings_t name = btf__get32(btf, &tp->name_off);
unsigned int type_id = btf__get32(btf, &tp->type);
- struct type *type = type__new(DW_TAG_typedef, name, size);
+ struct type *type = type__new(DW_TAG_typedef, name, size, false);
if (type == NULL)
return -ENOMEM;
@@ -377,6 +389,7 @@ static int btf__load_types(struct btf *btf)
int vlen = BTF_INFO_VLEN(val);
void *ptr = type_ptr;
uint32_t size = btf__get32(btf, &type_ptr->size);
+ bool kflag = BTF_INFO_KFLAG(val);
ptr += sizeof(struct btf_type);
@@ -385,13 +398,13 @@ static int btf__load_types(struct btf *btf)
} else if (type == BTF_KIND_ARRAY) {
vlen = create_new_array(btf, ptr, type_index);
} else if (type == BTF_KIND_STRUCT) {
- vlen = create_new_class(btf, ptr, vlen, type_ptr, size, type_index);
+ vlen = create_new_class(btf, ptr, vlen, type_ptr, size, type_index, kflag);
} else if (type == BTF_KIND_UNION) {
- vlen = create_new_union(btf, ptr, vlen, type_ptr, size, type_index);
+ vlen = create_new_union(btf, ptr, vlen, type_ptr, size, type_index, kflag);
} else if (type == BTF_KIND_ENUM) {
vlen = create_new_enumeration(btf, ptr, vlen, type_ptr, size, type_index);
} else if (type == BTF_KIND_FWD) {
- vlen = create_new_forward_decl(btf, type_ptr, size, type_index);
+ vlen = create_new_forward_decl(btf, type_ptr, size, type_index, kflag);
} else if (type == BTF_KIND_TYPEDEF) {
vlen = create_new_typedef(btf, type_ptr, size, type_index);
} else if (type == BTF_KIND_VOLATILE ||
@@ -442,7 +455,6 @@ static int class__fixup_btf_bitfields(struct tag *tag, struct cu *cu)
continue;
pos->bitfield_offset = 0;
- pos->bitfield_size = 0;
pos->byte_offset = pos->bit_offset / 8;
uint16_t type_bit_size;
@@ -484,13 +496,12 @@ static int class__fixup_btf_bitfields(struct tag *tag, struct cu *cu)
*/
pos->byte_size = integral_bit_size / 8;
- if (integral_bit_size == 0 || type_bit_size == integral_bit_size) {
+ if (integral_bit_size == 0) {
pos->bit_size = integral_bit_size;
continue;
}
pos->bitfield_offset = pos->bit_offset % integral_bit_size;
- pos->bitfield_size = type_bit_size;
pos->bit_size = type_bit_size;
pos->byte_offset = (((pos->bit_offset / integral_bit_size) *
integral_bit_size) / 8);
diff --git a/dwarves.h b/dwarves.h
index 156fa58..f800518 100644
--- a/dwarves.h
+++ b/dwarves.h
@@ -879,6 +879,7 @@ struct type {
uint8_t definition_emitted:1;
uint8_t fwd_decl_emitted:1;
uint8_t resized:1;
+ uint8_t flag:1;
};
static inline struct class *type__class(const struct type *type)
--
2.17.1
