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Merge branch 'bpf-btf-type-fixes'

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Yonghong Song says:

====================
Commit 69b693f0ae ("bpf: btf: Introduce BPF Type Format (BTF)")
introduced BTF, a debug info format for BTF.

The original design has a couple of issues though.
First, the bitfield size is only encoded in int type.
If the struct member bitfield type is enum, pahole ([1])
or llvm is forced to replace enum with int type. As a result, the original
type information gets lost.

Second, the original BTF design does not envision the possibility of
BTF=>header_file conversion ([2]), hence does not encode "struct" or
"union" info for a forward type. Such information is necessary to
convert BTF to a header file.

This patch set fixed the issue by introducing kind_flag, using one bit
in type->info. When kind_flag, the struct/union btf_member->offset
will encode both bitfield_size and bit_offset, covering both
int and enum base types. The kind_flag is also used to indicate whether
the forward type is a union (when set) or a struct.

Patch #1 refactors function btf_int_bits_seq_show() so Patch #2
can reuse part of the function.
Patch #2 implemented kind_flag support for struct/union/fwd types.
Patch #3 added kind_flag support for cgroup local storage map pretty print.
Patch #4 syncs kernel uapi btf.h to tools directory.
Patch #5 added unit tests for kind_flag.
Patch #6 added tests for kernel bpffs based pretty print with kind_flag.
Patch #7 refactors function btf_dumper_int_bits() so Patch #8
can reuse part of the function.
Patch #8 added bpftool support of pretty print with kind_flag set.

  [1] https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=b18354f64cc215368c3bc0df4a7e5341c55c378c
  [2] https://lwn.net/SubscriberLink/773198/fe3074838f5c3f26/

Change logs:
  v2 -> v3:
    . Relocated comments about bitfield_size/bit_offset interpretation
      of the "offset" field right before the "offset" struct member.
    . Added missing byte alignment checking for non-bitfield enum
      member of a struct with kind_flag set.
    . Added two test cases in unit tests for struct type, kind_flag set,
      non-bitfield int/enum member, not-byte aligned bit offsets.
    . Added comments to help understand there is no overflow for
      total_bits_offset in bpftool function btf_dumper_int_bits().
    . Added explanation of typedef type dumping fix in Patch #8 commit
      message.

  v1 -> v2:
    . If kind_flag is set for a structure, ensure an int member,
      whether it is a bitfield or not, is a regular int type.
    . Added support so cgroup local storage map pretty print
      works with kind_flag.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Daniel Borkmann
2018-12-18 01:12:00 +01:00
parent 6c4fc209fc 8772c8bc09
commit 37c7b1caea
7 changed files with 1046 additions and 91 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/btf.h
+4 -1
View File
@@ -7,6 +7,7 @@
#include <linux/types.h>
struct btf;
struct btf_member;
struct btf_type;
union bpf_attr;
@@ -46,7 +47,9 @@ void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m);
int btf_get_fd_by_id(u32 id);
u32 btf_id(const struct btf *btf);
bool btf_type_is_reg_int(const struct btf_type *t, u32 expected_size);
bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
const struct btf_member *m,
u32 expected_offset, u32 expected_size);
#ifdef CONFIG_BPF_SYSCALL
const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);
include/uapi/linux/btf.h
+18 -2
View File
@@ -34,7 +34,9 @@ struct btf_type {
* bits 0-15: vlen (e.g. # of struct's members)
* bits 16-23: unused
* bits 24-27: kind (e.g. int, ptr, array...etc)
* bits 28-31: unused
* bits 28-30: unused
* bit 31: kind_flag, currently used by
* struct, union and fwd
*/
__u32 info;
/* "size" is used by INT, ENUM, STRUCT and UNION.
@@ -52,6 +54,7 @@ struct btf_type {
#define BTF_INFO_KIND(info) (((info) >> 24) & 0x0f)
#define BTF_INFO_VLEN(info) ((info) & 0xffff)
#define BTF_INFO_KFLAG(info) ((info) >> 31)
#define BTF_KIND_UNKN 0 /* Unknown */
#define BTF_KIND_INT 1 /* Integer */
@@ -110,9 +113,22 @@ struct btf_array {
struct btf_member {
__u32 name_off;
__u32 type;
__u32 offset; /* offset in bits */
/* If the type info kind_flag is set, the btf_member offset
* contains both member bitfield size and bit offset. The
* bitfield size is set for bitfield members. If the type
* info kind_flag is not set, the offset contains only bit
* offset.
*/
__u32 offset;
};
/* If the struct/union type info kind_flag is set, the
* following two macros are used to access bitfield_size
* and bit_offset from btf_member.offset.
*/
#define BTF_MEMBER_BITFIELD_SIZE(val) ((val) >> 24)
#define BTF_MEMBER_BIT_OFFSET(val) ((val) & 0xffffff)
/* BTF_KIND_FUNC_PROTO is followed by multiple "struct btf_param".
* The exact number of btf_param is stored in the vlen (of the
* info in "struct btf_type").
kernel/bpf/btf.c
+309 -43
View File
File diff suppressed because it is too large Load Diff
kernel/bpf/local_storage.c
+4 -13
View File
@@ -315,9 +315,8 @@ static int cgroup_storage_check_btf(const struct bpf_map *map,
const struct btf_type *key_type,
const struct btf_type *value_type)
{
const struct btf_type *t;
struct btf_member *m;
u32 id, size;
u32 offset, size;
/* Key is expected to be of struct bpf_cgroup_storage_key type,
* which is:
@@ -338,25 +337,17 @@ static int cgroup_storage_check_btf(const struct bpf_map *map,
* The first field must be a 64 bit integer at 0 offset.
*/
m = (struct btf_member *)(key_type + 1);
if (m->offset)
return -EINVAL;
id = m->type;
t = btf_type_id_size(btf, &id, NULL);
size = FIELD_SIZEOF(struct bpf_cgroup_storage_key, cgroup_inode_id);
if (!t || !btf_type_is_reg_int(t, size))
if (!btf_member_is_reg_int(btf, key_type, m, 0, size))
return -EINVAL;
/*
* The second field must be a 32 bit integer at 64 bit offset.
*/
m++;
if (m->offset != offsetof(struct bpf_cgroup_storage_key, attach_type) *
BITS_PER_BYTE)
return -EINVAL;
id = m->type;
t = btf_type_id_size(btf, &id, NULL);
offset = offsetof(struct bpf_cgroup_storage_key, attach_type);
size = FIELD_SIZEOF(struct bpf_cgroup_storage_key, attach_type);
if (!t || !btf_type_is_reg_int(t, size))
if (!btf_member_is_reg_int(btf, key_type, m, offset, size))
return -EINVAL;
return 0;
tools/bpf/bpftool/btf_dumper.c
+46 -15
View File
@@ -73,20 +73,17 @@ static int btf_dumper_array(const struct btf_dumper *d, __u32 type_id,
return ret;
}
static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
static void btf_dumper_bitfield(__u32 nr_bits, __u8 bit_offset,
const void *data, json_writer_t *jw,
bool is_plain_text)
{
int left_shift_bits, right_shift_bits;
int nr_bits = BTF_INT_BITS(int_type);
int total_bits_offset;
int bytes_to_copy;
int bits_to_copy;
__u64 print_num;
total_bits_offset = bit_offset + BTF_INT_OFFSET(int_type);
data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
bit_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
data += BITS_ROUNDDOWN_BYTES(bit_offset);
bit_offset = BITS_PER_BYTE_MASKED(bit_offset);
bits_to_copy = bit_offset + nr_bits;
bytes_to_copy = BITS_ROUNDUP_BYTES(bits_to_copy);
@@ -109,6 +106,22 @@ static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
jsonw_printf(jw, "%llu", print_num);
}
static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
const void *data, json_writer_t *jw,
bool is_plain_text)
{
int nr_bits = BTF_INT_BITS(int_type);
int total_bits_offset;
/* bits_offset is at most 7.
* BTF_INT_OFFSET() cannot exceed 64 bits.
*/
total_bits_offset = bit_offset + BTF_INT_OFFSET(int_type);
btf_dumper_bitfield(nr_bits, total_bits_offset, data, jw,
is_plain_text);
}
static int btf_dumper_int(const struct btf_type *t, __u8 bit_offset,
const void *data, json_writer_t *jw,
bool is_plain_text)
@@ -180,6 +193,7 @@ static int btf_dumper_struct(const struct btf_dumper *d, __u32 type_id,
const struct btf_type *t;
struct btf_member *m;
const void *data_off;
int kind_flag;
int ret = 0;
int i, vlen;
@@ -187,18 +201,32 @@ static int btf_dumper_struct(const struct btf_dumper *d, __u32 type_id,
if (!t)
return -EINVAL;
kind_flag = BTF_INFO_KFLAG(t->info);
vlen = BTF_INFO_VLEN(t->info);
jsonw_start_object(d->jw);
m = (struct btf_member *)(t + 1);
for (i = 0; i < vlen; i++) {
data_off = data + BITS_ROUNDDOWN_BYTES(m[i].offset);
__u32 bit_offset = m[i].offset;
__u32 bitfield_size = 0;
if (kind_flag) {
bitfield_size = BTF_MEMBER_BITFIELD_SIZE(bit_offset);
bit_offset = BTF_MEMBER_BIT_OFFSET(bit_offset);
}
jsonw_name(d->jw, btf__name_by_offset(d->btf, m[i].name_off));
ret = btf_dumper_do_type(d, m[i].type,
BITS_PER_BYTE_MASKED(m[i].offset),
data_off);
if (ret)
break;
if (bitfield_size) {
btf_dumper_bitfield(bitfield_size, bit_offset,
data, d->jw, d->is_plain_text);
} else {
data_off = data + BITS_ROUNDDOWN_BYTES(bit_offset);
ret = btf_dumper_do_type(d, m[i].type,
BITS_PER_BYTE_MASKED(bit_offset),
data_off);
if (ret)
break;
}
}
jsonw_end_object(d->jw);
@@ -285,6 +313,7 @@ static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id,
switch (BTF_INFO_KIND(t->info)) {
case BTF_KIND_INT:
case BTF_KIND_TYPEDEF:
BTF_PRINT_ARG("%s ", btf__name_by_offset(btf, t->name_off));
break;
case BTF_KIND_STRUCT:
@@ -308,10 +337,11 @@ static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id,
BTF_PRINT_TYPE(t->type);
BTF_PRINT_ARG("* ");
break;
case BTF_KIND_UNKN:
case BTF_KIND_FWD:
case BTF_KIND_TYPEDEF:
return -1;
BTF_PRINT_ARG("%s %s ",
BTF_INFO_KFLAG(t->info) ? "union" : "struct",
btf__name_by_offset(btf, t->name_off));
break;
case BTF_KIND_VOLATILE:
BTF_PRINT_ARG("volatile ");
BTF_PRINT_TYPE(t->type);
@@ -335,6 +365,7 @@ static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id,
if (pos == -1)
return -1;
break;
case BTF_KIND_UNKN:
default:
return -1;
}
tools/include/uapi/linux/btf.h
+18 -2
View File
@@ -34,7 +34,9 @@ struct btf_type {
* bits 0-15: vlen (e.g. # of struct's members)
* bits 16-23: unused
* bits 24-27: kind (e.g. int, ptr, array...etc)
* bits 28-31: unused
* bits 28-30: unused
* bit 31: kind_flag, currently used by
* struct, union and fwd
*/
__u32 info;
/* "size" is used by INT, ENUM, STRUCT and UNION.
@@ -52,6 +54,7 @@ struct btf_type {
#define BTF_INFO_KIND(info) (((info) >> 24) & 0x0f)
#define BTF_INFO_VLEN(info) ((info) & 0xffff)
#define BTF_INFO_KFLAG(info) ((info) >> 31)
#define BTF_KIND_UNKN 0 /* Unknown */
#define BTF_KIND_INT 1 /* Integer */
@@ -110,9 +113,22 @@ struct btf_array {
struct btf_member {
__u32 name_off;
__u32 type;
__u32 offset; /* offset in bits */
/* If the type info kind_flag is set, the btf_member offset
* contains both member bitfield size and bit offset. The
* bitfield size is set for bitfield members. If the type
* info kind_flag is not set, the offset contains only bit
* offset.
*/
__u32 offset;
};
/* If the struct/union type info kind_flag is set, the
* following two macros are used to access bitfield_size
* and bit_offset from btf_member.offset.
*/
#define BTF_MEMBER_BITFIELD_SIZE(val) ((val) >> 24)
#define BTF_MEMBER_BIT_OFFSET(val) ((val) & 0xffffff)
/* BTF_KIND_FUNC_PROTO is followed by multiple "struct btf_param".
* The exact number of btf_param is stored in the vlen (of the
* info in "struct btf_type").
tools/testing/selftests/bpf/test_btf.c
+647 -15
View File
File diff suppressed because it is too large Load Diff