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btf: Add kind_flag support for btf_loader 

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@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Yonghong Song 2018-12-20 15:44:29 -08:00 committed by Arnaldo Carvalho de Melo
parent 472256d3c5
commit 2a82d593be
2 changed files with 37 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
btf_loader.c
View File

@ -1,4 +1,4 @@
/*
/*
* btf_loader.c
*
* Copyright (C) 2018 Arnaldo Carvalho de Melo <acme@kernel.org>
@ -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);

1
dwarves.h
View File

@ -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)