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linux_dsm_epyc7002/include/uapi/linux/btf.h

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bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/* Copyright (c) 2018 Facebook */
#ifndef _UAPI__LINUX_BTF_H__
#define _UAPI__LINUX_BTF_H__
#include <linux/types.h>
#define BTF_MAGIC 0xeB9F
#define BTF_VERSION 1
struct btf_header {
__u16 magic;
__u8 version;
__u8 flags;
bpf: btf: Change how section is supported in btf_header There are currently unused section descriptions in the btf_header. Those sections are here to support future BTF use cases. For example, the func section (func_off) is to support function signature (e.g. the BPF prog function signature). Instead of spelling out all potential sections up-front in the btf_header. This patch makes changes to btf_header such that extending it (e.g. adding a section) is possible later. The unused ones can be removed for now and they can be added back later. This patch: 1. adds a hdr_len to the btf_header. It will allow adding sections (and other info like parent_label and parent_name) later. The check is similar to the existing bpf_attr. If a user passes in a longer hdr_len, the kernel ensures the extra tailing bytes are 0. 2. allows the section order in the BTF object to be different from its sec_off order in btf_header. 3. each sec_off is followed by a sec_len. It must not have gap or overlapping among sections. The string section is ensured to be at the end due to the 4 bytes alignment requirement of the type section. The above changes will allow enough flexibility to add new sections (and other info) to the btf_header later. This patch also removes an unnecessary !err check at the end of btf_parse(). Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:18 +07:00
__u32 hdr_len;
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* All offsets are in bytes relative to the end of this header */
__u32 type_off; /* offset of type section */
bpf: btf: Change how section is supported in btf_header There are currently unused section descriptions in the btf_header. Those sections are here to support future BTF use cases. For example, the func section (func_off) is to support function signature (e.g. the BPF prog function signature). Instead of spelling out all potential sections up-front in the btf_header. This patch makes changes to btf_header such that extending it (e.g. adding a section) is possible later. The unused ones can be removed for now and they can be added back later. This patch: 1. adds a hdr_len to the btf_header. It will allow adding sections (and other info like parent_label and parent_name) later. The check is similar to the existing bpf_attr. If a user passes in a longer hdr_len, the kernel ensures the extra tailing bytes are 0. 2. allows the section order in the BTF object to be different from its sec_off order in btf_header. 3. each sec_off is followed by a sec_len. It must not have gap or overlapping among sections. The string section is ensured to be at the end due to the 4 bytes alignment requirement of the type section. The above changes will allow enough flexibility to add new sections (and other info) to the btf_header later. This patch also removes an unnecessary !err check at the end of btf_parse(). Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:18 +07:00
__u32 type_len; /* length of type section */
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
__u32 str_off; /* offset of string section */
__u32 str_len; /* length of string section */
};
/* Max # of type identifier */
bpf: btf: Remove unused bits from uapi/linux/btf.h This patch does the followings: 1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can raise it later. 2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are currently encoded at the highest bit of a u32. It is because the current use case does not require supporting parent type (i.e type_id referring to a type in another BTF file). It also does not support referring to a string in ELF. The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are defined in btf.c instead of uapi/linux/btf.h. 3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough. There is unused bits headroom if we ever needed it later. 4. The root bit in BTF_INFO is also removed because it is not used in the current use case. 5. Remove BTF_INT_VARARGS since func type is not supported now. The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits. The above can be added back later because the verifier ensures the unused bits are zeros. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:20 +07:00
#define BTF_MAX_TYPE 0x0000ffff
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* Max offset into the string section */
bpf: btf: Remove unused bits from uapi/linux/btf.h This patch does the followings: 1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can raise it later. 2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are currently encoded at the highest bit of a u32. It is because the current use case does not require supporting parent type (i.e type_id referring to a type in another BTF file). It also does not support referring to a string in ELF. The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are defined in btf.c instead of uapi/linux/btf.h. 3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough. There is unused bits headroom if we ever needed it later. 4. The root bit in BTF_INFO is also removed because it is not used in the current use case. 5. Remove BTF_INT_VARARGS since func type is not supported now. The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits. The above can be added back later because the verifier ensures the unused bits are zeros. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:20 +07:00
#define BTF_MAX_NAME_OFFSET 0x0000ffff
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* Max # of struct/union/enum members or func args */
#define BTF_MAX_VLEN 0xffff
struct btf_type {
bpf: btf: Clean up btf.h in uapi This patch cleans up btf.h in uapi: 1) Rename "name" to "name_off" to better reflect it is an offset to the string section instead of a char array. 2) Remove unused value BTF_FLAGS_COMPR and BTF_MAGIC_SWAP Suggested-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-21 23:48:23 +07:00
__u32 name_off;
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* "info" bits arrangement
* bits 0-15: vlen (e.g. # of struct's members)
* bits 16-23: unused
bpf: btf: Remove unused bits from uapi/linux/btf.h This patch does the followings: 1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can raise it later. 2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are currently encoded at the highest bit of a u32. It is because the current use case does not require supporting parent type (i.e type_id referring to a type in another BTF file). It also does not support referring to a string in ELF. The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are defined in btf.c instead of uapi/linux/btf.h. 3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough. There is unused bits headroom if we ever needed it later. 4. The root bit in BTF_INFO is also removed because it is not used in the current use case. 5. Remove BTF_INT_VARARGS since func type is not supported now. The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits. The above can be added back later because the verifier ensures the unused bits are zeros. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:20 +07:00
* bits 24-27: kind (e.g. int, ptr, array...etc)
bpf: btf: fix struct/union/fwd types with kind_flag This patch fixed two issues with BTF. One is related to struct/union bitfield encoding and the other is related to forward type. Issue #1 and solution: ====================== Current btf encoding of bitfield follows what pahole generates. For each bitfield, pahole will duplicate the type chain and put the bitfield size at the final int or enum type. Since the BTF enum type cannot encode bit size, pahole workarounds the issue by generating an int type whenever the enum bit size is not 32. For example, -bash-4.4$ cat t.c typedef int ___int; enum A { A1, A2, A3 }; struct t { int a[5]; ___int b:4; volatile enum A c:4; } g; -bash-4.4$ gcc -c -O2 -g t.c The current kernel supports the following BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t size=24 vlen=3 a type_id=5 bits_offset=0 b type_id=9 bits_offset=160 c type_id=11 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 [8] INT int size=1 bit_offset=0 nr_bits=4 encoding=(none) [9] TYPEDEF ___int type_id=8 [10] INT (anon) size=1 bit_offset=0 nr_bits=4 encoding=SIGNED [11] VOLATILE (anon) type_id=10 Two issues are in the above: . by changing enum type to int, we lost the original type information and this will not be ideal later when we try to convert BTF to a header file. . the type duplication for bitfields will cause BTF bloat. Duplicated types cannot be deduplicated later if the bitfield size is different. To fix this issue, this patch implemented a compatible change for BTF struct type encoding: . the bit 31 of struct_type->info, previously reserved, now is used to indicate whether bitfield_size is encoded in btf_member or not. . if bit 31 of struct_type->info is set, btf_member->offset will encode like: bit 0 - 23: bit offset bit 24 - 31: bitfield size if bit 31 is not set, the old behavior is preserved: bit 0 - 31: bit offset So if the struct contains a bit field, the maximum bit offset will be reduced to (2^24 - 1) instead of MAX_UINT. The maximum bitfield size will be 256 which is enough for today as maximum bitfield in compiler can be 128 where int128 type is supported. This kernel patch intends to support the new BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t kind_flag=1 size=24 vlen=3 a type_id=5 bitfield_size=0 bits_offset=0 b type_id=1 bitfield_size=4 bits_offset=160 c type_id=7 bitfield_size=4 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 Issue #2 and solution: ====================== Current forward type in BTF does not specify whether the original type is struct or union. This will not work for type pretty print and BTF-to-header-file conversion as struct/union must be specified. $ cat tt.c struct t; union u; int foo(struct t *t, union u *u) { return 0; } $ gcc -c -g -O2 tt.c $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t type_id=0 [3] PTR (anon) type_id=2 [4] FWD u type_id=0 [5] PTR (anon) type_id=4 To fix this issue, similar to issue #1, type->info bit 31 is used. If the bit is set, it is union type. Otherwise, it is a struct type. $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t kind_flag=0 type_id=0 [3] PTR (anon) kind_flag=0 type_id=2 [4] FWD u kind_flag=1 type_id=0 [5] PTR (anon) kind_flag=0 type_id=4 Pahole/LLVM change: =================== The new kind_flag functionality has been implemented in pahole and llvm: https://github.com/yonghong-song/pahole/tree/bitfield https://github.com/yonghong-song/llvm/tree/bitfield Note that pahole hasn't implemented func/func_proto kind and .BTF.ext. So to print function signature with bpftool, the llvm compiler should be used. Fixes: 69b693f0aefa ("bpf: btf: Introduce BPF Type Format (BTF)") Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-12-16 13:13:51 +07:00
* bits 28-30: unused
* bit 31: kind_flag, currently used by
* struct, union and fwd
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
*/
__u32 info;
/* "size" is used by INT, ENUM, STRUCT and UNION.
* "size" tells the size of the type it is describing.
*
bpf: btf: Add BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO This patch adds BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO to support the function debug info. BTF_KIND_FUNC_PROTO must not have a name (i.e. !t->name_off) and it is followed by >= 0 'struct bpf_param' objects to describe the function arguments. The BTF_KIND_FUNC must have a valid name and it must refer back to a BTF_KIND_FUNC_PROTO. The above is the conclusion after the discussion between Edward Cree, Alexei, Daniel, Yonghong and Martin. By combining BTF_KIND_FUNC and BTF_LIND_FUNC_PROTO, a complete function signature can be obtained. It will be used in the later patches to learn the function signature of a running bpf program. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-11-20 06:29:08 +07:00
* "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
* FUNC and FUNC_PROTO.
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
* "type" is a type_id referring to another type.
*/
union {
__u32 size;
__u32 type;
};
};
bpf: btf: Remove unused bits from uapi/linux/btf.h This patch does the followings: 1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can raise it later. 2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are currently encoded at the highest bit of a u32. It is because the current use case does not require supporting parent type (i.e type_id referring to a type in another BTF file). It also does not support referring to a string in ELF. The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are defined in btf.c instead of uapi/linux/btf.h. 3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough. There is unused bits headroom if we ever needed it later. 4. The root bit in BTF_INFO is also removed because it is not used in the current use case. 5. Remove BTF_INT_VARARGS since func type is not supported now. The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits. The above can be added back later because the verifier ensures the unused bits are zeros. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:20 +07:00
#define BTF_INFO_KIND(info) (((info) >> 24) & 0x0f)
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
#define BTF_INFO_VLEN(info) ((info) & 0xffff)
bpf: btf: fix struct/union/fwd types with kind_flag This patch fixed two issues with BTF. One is related to struct/union bitfield encoding and the other is related to forward type. Issue #1 and solution: ====================== Current btf encoding of bitfield follows what pahole generates. For each bitfield, pahole will duplicate the type chain and put the bitfield size at the final int or enum type. Since the BTF enum type cannot encode bit size, pahole workarounds the issue by generating an int type whenever the enum bit size is not 32. For example, -bash-4.4$ cat t.c typedef int ___int; enum A { A1, A2, A3 }; struct t { int a[5]; ___int b:4; volatile enum A c:4; } g; -bash-4.4$ gcc -c -O2 -g t.c The current kernel supports the following BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t size=24 vlen=3 a type_id=5 bits_offset=0 b type_id=9 bits_offset=160 c type_id=11 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 [8] INT int size=1 bit_offset=0 nr_bits=4 encoding=(none) [9] TYPEDEF ___int type_id=8 [10] INT (anon) size=1 bit_offset=0 nr_bits=4 encoding=SIGNED [11] VOLATILE (anon) type_id=10 Two issues are in the above: . by changing enum type to int, we lost the original type information and this will not be ideal later when we try to convert BTF to a header file. . the type duplication for bitfields will cause BTF bloat. Duplicated types cannot be deduplicated later if the bitfield size is different. To fix this issue, this patch implemented a compatible change for BTF struct type encoding: . the bit 31 of struct_type->info, previously reserved, now is used to indicate whether bitfield_size is encoded in btf_member or not. . if bit 31 of struct_type->info is set, btf_member->offset will encode like: bit 0 - 23: bit offset bit 24 - 31: bitfield size if bit 31 is not set, the old behavior is preserved: bit 0 - 31: bit offset So if the struct contains a bit field, the maximum bit offset will be reduced to (2^24 - 1) instead of MAX_UINT. The maximum bitfield size will be 256 which is enough for today as maximum bitfield in compiler can be 128 where int128 type is supported. This kernel patch intends to support the new BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t kind_flag=1 size=24 vlen=3 a type_id=5 bitfield_size=0 bits_offset=0 b type_id=1 bitfield_size=4 bits_offset=160 c type_id=7 bitfield_size=4 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 Issue #2 and solution: ====================== Current forward type in BTF does not specify whether the original type is struct or union. This will not work for type pretty print and BTF-to-header-file conversion as struct/union must be specified. $ cat tt.c struct t; union u; int foo(struct t *t, union u *u) { return 0; } $ gcc -c -g -O2 tt.c $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t type_id=0 [3] PTR (anon) type_id=2 [4] FWD u type_id=0 [5] PTR (anon) type_id=4 To fix this issue, similar to issue #1, type->info bit 31 is used. If the bit is set, it is union type. Otherwise, it is a struct type. $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t kind_flag=0 type_id=0 [3] PTR (anon) kind_flag=0 type_id=2 [4] FWD u kind_flag=1 type_id=0 [5] PTR (anon) kind_flag=0 type_id=4 Pahole/LLVM change: =================== The new kind_flag functionality has been implemented in pahole and llvm: https://github.com/yonghong-song/pahole/tree/bitfield https://github.com/yonghong-song/llvm/tree/bitfield Note that pahole hasn't implemented func/func_proto kind and .BTF.ext. So to print function signature with bpftool, the llvm compiler should be used. Fixes: 69b693f0aefa ("bpf: btf: Introduce BPF Type Format (BTF)") Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-12-16 13:13:51 +07:00
#define BTF_INFO_KFLAG(info) ((info) >> 31)
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
#define BTF_KIND_UNKN 0 /* Unknown */
#define BTF_KIND_INT 1 /* Integer */
#define BTF_KIND_PTR 2 /* Pointer */
#define BTF_KIND_ARRAY 3 /* Array */
#define BTF_KIND_STRUCT 4 /* Struct */
#define BTF_KIND_UNION 5 /* Union */
#define BTF_KIND_ENUM 6 /* Enumeration */
#define BTF_KIND_FWD 7 /* Forward */
#define BTF_KIND_TYPEDEF 8 /* Typedef */
#define BTF_KIND_VOLATILE 9 /* Volatile */
#define BTF_KIND_CONST 10 /* Const */
#define BTF_KIND_RESTRICT 11 /* Restrict */
bpf: btf: Add BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO This patch adds BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO to support the function debug info. BTF_KIND_FUNC_PROTO must not have a name (i.e. !t->name_off) and it is followed by >= 0 'struct bpf_param' objects to describe the function arguments. The BTF_KIND_FUNC must have a valid name and it must refer back to a BTF_KIND_FUNC_PROTO. The above is the conclusion after the discussion between Edward Cree, Alexei, Daniel, Yonghong and Martin. By combining BTF_KIND_FUNC and BTF_LIND_FUNC_PROTO, a complete function signature can be obtained. It will be used in the later patches to learn the function signature of a running bpf program. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-11-20 06:29:08 +07:00
#define BTF_KIND_FUNC 12 /* Function */
#define BTF_KIND_FUNC_PROTO 13 /* Function Proto */
#define BTF_KIND_MAX 13
#define NR_BTF_KINDS 14
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* For some specific BTF_KIND, "struct btf_type" is immediately
* followed by extra data.
*/
/* BTF_KIND_INT is followed by a u32 and the following
* is the 32 bits arrangement:
*/
bpf: btf: Remove unused bits from uapi/linux/btf.h This patch does the followings: 1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can raise it later. 2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are currently encoded at the highest bit of a u32. It is because the current use case does not require supporting parent type (i.e type_id referring to a type in another BTF file). It also does not support referring to a string in ELF. The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are defined in btf.c instead of uapi/linux/btf.h. 3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough. There is unused bits headroom if we ever needed it later. 4. The root bit in BTF_INFO is also removed because it is not used in the current use case. 5. Remove BTF_INT_VARARGS since func type is not supported now. The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits. The above can be added back later because the verifier ensures the unused bits are zeros. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:20 +07:00
#define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24)
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
#define BTF_INT_OFFSET(VAL) (((VAL & 0x00ff0000)) >> 16)
bpf: btf: Clean up BTF_INT_BITS() in uapi btf.h This patch shrinks the BTF_INT_BITS() mask. The current btf_int_check_meta() ensures the nr_bits of an integer cannot exceed 64. Hence, it is mostly an uapi cleanup. The actual btf usage (i.e. seq_show()) is also modified to use u8 instead of u16. The verification (e.g. btf_int_check_meta()) path stays as is to deal with invalid BTF situation. Fixes: 69b693f0aefa ("bpf: btf: Introduce BPF Type Format (BTF)") Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-07-20 12:14:31 +07:00
#define BTF_INT_BITS(VAL) ((VAL) & 0x000000ff)
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* Attributes stored in the BTF_INT_ENCODING */
bpf: btf: Remove unused bits from uapi/linux/btf.h This patch does the followings: 1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can raise it later. 2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are currently encoded at the highest bit of a u32. It is because the current use case does not require supporting parent type (i.e type_id referring to a type in another BTF file). It also does not support referring to a string in ELF. The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are defined in btf.c instead of uapi/linux/btf.h. 3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough. There is unused bits headroom if we ever needed it later. 4. The root bit in BTF_INFO is also removed because it is not used in the current use case. 5. Remove BTF_INT_VARARGS since func type is not supported now. The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits. The above can be added back later because the verifier ensures the unused bits are zeros. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-05-23 04:57:20 +07:00
#define BTF_INT_SIGNED (1 << 0)
#define BTF_INT_CHAR (1 << 1)
#define BTF_INT_BOOL (1 << 2)
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
/* BTF_KIND_ENUM is followed by multiple "struct btf_enum".
* The exact number of btf_enum is stored in the vlen (of the
* info in "struct btf_type").
*/
struct btf_enum {
bpf: btf: Clean up btf.h in uapi This patch cleans up btf.h in uapi: 1) Rename "name" to "name_off" to better reflect it is an offset to the string section instead of a char array. 2) Remove unused value BTF_FLAGS_COMPR and BTF_MAGIC_SWAP Suggested-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-21 23:48:23 +07:00
__u32 name_off;
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
__s32 val;
};
/* BTF_KIND_ARRAY is followed by one "struct btf_array" */
struct btf_array {
__u32 type;
__u32 index_type;
__u32 nelems;
};
/* BTF_KIND_STRUCT and BTF_KIND_UNION are followed
* by multiple "struct btf_member". The exact number
* of btf_member is stored in the vlen (of the info in
* "struct btf_type").
*/
struct btf_member {
bpf: btf: Clean up btf.h in uapi This patch cleans up btf.h in uapi: 1) Rename "name" to "name_off" to better reflect it is an offset to the string section instead of a char array. 2) Remove unused value BTF_FLAGS_COMPR and BTF_MAGIC_SWAP Suggested-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-21 23:48:23 +07:00
__u32 name_off;
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
__u32 type;
bpf: btf: fix struct/union/fwd types with kind_flag This patch fixed two issues with BTF. One is related to struct/union bitfield encoding and the other is related to forward type. Issue #1 and solution: ====================== Current btf encoding of bitfield follows what pahole generates. For each bitfield, pahole will duplicate the type chain and put the bitfield size at the final int or enum type. Since the BTF enum type cannot encode bit size, pahole workarounds the issue by generating an int type whenever the enum bit size is not 32. For example, -bash-4.4$ cat t.c typedef int ___int; enum A { A1, A2, A3 }; struct t { int a[5]; ___int b:4; volatile enum A c:4; } g; -bash-4.4$ gcc -c -O2 -g t.c The current kernel supports the following BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t size=24 vlen=3 a type_id=5 bits_offset=0 b type_id=9 bits_offset=160 c type_id=11 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 [8] INT int size=1 bit_offset=0 nr_bits=4 encoding=(none) [9] TYPEDEF ___int type_id=8 [10] INT (anon) size=1 bit_offset=0 nr_bits=4 encoding=SIGNED [11] VOLATILE (anon) type_id=10 Two issues are in the above: . by changing enum type to int, we lost the original type information and this will not be ideal later when we try to convert BTF to a header file. . the type duplication for bitfields will cause BTF bloat. Duplicated types cannot be deduplicated later if the bitfield size is different. To fix this issue, this patch implemented a compatible change for BTF struct type encoding: . the bit 31 of struct_type->info, previously reserved, now is used to indicate whether bitfield_size is encoded in btf_member or not. . if bit 31 of struct_type->info is set, btf_member->offset will encode like: bit 0 - 23: bit offset bit 24 - 31: bitfield size if bit 31 is not set, the old behavior is preserved: bit 0 - 31: bit offset So if the struct contains a bit field, the maximum bit offset will be reduced to (2^24 - 1) instead of MAX_UINT. The maximum bitfield size will be 256 which is enough for today as maximum bitfield in compiler can be 128 where int128 type is supported. This kernel patch intends to support the new BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t kind_flag=1 size=24 vlen=3 a type_id=5 bitfield_size=0 bits_offset=0 b type_id=1 bitfield_size=4 bits_offset=160 c type_id=7 bitfield_size=4 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 Issue #2 and solution: ====================== Current forward type in BTF does not specify whether the original type is struct or union. This will not work for type pretty print and BTF-to-header-file conversion as struct/union must be specified. $ cat tt.c struct t; union u; int foo(struct t *t, union u *u) { return 0; } $ gcc -c -g -O2 tt.c $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t type_id=0 [3] PTR (anon) type_id=2 [4] FWD u type_id=0 [5] PTR (anon) type_id=4 To fix this issue, similar to issue #1, type->info bit 31 is used. If the bit is set, it is union type. Otherwise, it is a struct type. $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t kind_flag=0 type_id=0 [3] PTR (anon) kind_flag=0 type_id=2 [4] FWD u kind_flag=1 type_id=0 [5] PTR (anon) kind_flag=0 type_id=4 Pahole/LLVM change: =================== The new kind_flag functionality has been implemented in pahole and llvm: https://github.com/yonghong-song/pahole/tree/bitfield https://github.com/yonghong-song/llvm/tree/bitfield Note that pahole hasn't implemented func/func_proto kind and .BTF.ext. So to print function signature with bpftool, the llvm compiler should be used. Fixes: 69b693f0aefa ("bpf: btf: Introduce BPF Type Format (BTF)") Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-12-16 13:13:51 +07:00
/* 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;
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
};
bpf: btf: fix struct/union/fwd types with kind_flag This patch fixed two issues with BTF. One is related to struct/union bitfield encoding and the other is related to forward type. Issue #1 and solution: ====================== Current btf encoding of bitfield follows what pahole generates. For each bitfield, pahole will duplicate the type chain and put the bitfield size at the final int or enum type. Since the BTF enum type cannot encode bit size, pahole workarounds the issue by generating an int type whenever the enum bit size is not 32. For example, -bash-4.4$ cat t.c typedef int ___int; enum A { A1, A2, A3 }; struct t { int a[5]; ___int b:4; volatile enum A c:4; } g; -bash-4.4$ gcc -c -O2 -g t.c The current kernel supports the following BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t size=24 vlen=3 a type_id=5 bits_offset=0 b type_id=9 bits_offset=160 c type_id=11 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 [8] INT int size=1 bit_offset=0 nr_bits=4 encoding=(none) [9] TYPEDEF ___int type_id=8 [10] INT (anon) size=1 bit_offset=0 nr_bits=4 encoding=SIGNED [11] VOLATILE (anon) type_id=10 Two issues are in the above: . by changing enum type to int, we lost the original type information and this will not be ideal later when we try to convert BTF to a header file. . the type duplication for bitfields will cause BTF bloat. Duplicated types cannot be deduplicated later if the bitfield size is different. To fix this issue, this patch implemented a compatible change for BTF struct type encoding: . the bit 31 of struct_type->info, previously reserved, now is used to indicate whether bitfield_size is encoded in btf_member or not. . if bit 31 of struct_type->info is set, btf_member->offset will encode like: bit 0 - 23: bit offset bit 24 - 31: bitfield size if bit 31 is not set, the old behavior is preserved: bit 0 - 31: bit offset So if the struct contains a bit field, the maximum bit offset will be reduced to (2^24 - 1) instead of MAX_UINT. The maximum bitfield size will be 256 which is enough for today as maximum bitfield in compiler can be 128 where int128 type is supported. This kernel patch intends to support the new BTF encoding: $ pahole -JV t.o [1] TYPEDEF ___int type_id=2 [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [3] ENUM A size=4 vlen=3 A1 val=0 A2 val=1 A3 val=2 [4] STRUCT t kind_flag=1 size=24 vlen=3 a type_id=5 bitfield_size=0 bits_offset=0 b type_id=1 bitfield_size=4 bits_offset=160 c type_id=7 bitfield_size=4 bits_offset=164 [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5 [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none) [7] VOLATILE (anon) type_id=3 Issue #2 and solution: ====================== Current forward type in BTF does not specify whether the original type is struct or union. This will not work for type pretty print and BTF-to-header-file conversion as struct/union must be specified. $ cat tt.c struct t; union u; int foo(struct t *t, union u *u) { return 0; } $ gcc -c -g -O2 tt.c $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t type_id=0 [3] PTR (anon) type_id=2 [4] FWD u type_id=0 [5] PTR (anon) type_id=4 To fix this issue, similar to issue #1, type->info bit 31 is used. If the bit is set, it is union type. Otherwise, it is a struct type. $ pahole -JV tt.o [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED [2] FWD t kind_flag=0 type_id=0 [3] PTR (anon) kind_flag=0 type_id=2 [4] FWD u kind_flag=1 type_id=0 [5] PTR (anon) kind_flag=0 type_id=4 Pahole/LLVM change: =================== The new kind_flag functionality has been implemented in pahole and llvm: https://github.com/yonghong-song/pahole/tree/bitfield https://github.com/yonghong-song/llvm/tree/bitfield Note that pahole hasn't implemented func/func_proto kind and .BTF.ext. So to print function signature with bpftool, the llvm compiler should be used. Fixes: 69b693f0aefa ("bpf: btf: Introduce BPF Type Format (BTF)") Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-12-16 13:13:51 +07:00
/* 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)
bpf: btf: Add BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO This patch adds BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO to support the function debug info. BTF_KIND_FUNC_PROTO must not have a name (i.e. !t->name_off) and it is followed by >= 0 'struct bpf_param' objects to describe the function arguments. The BTF_KIND_FUNC must have a valid name and it must refer back to a BTF_KIND_FUNC_PROTO. The above is the conclusion after the discussion between Edward Cree, Alexei, Daniel, Yonghong and Martin. By combining BTF_KIND_FUNC and BTF_LIND_FUNC_PROTO, a complete function signature can be obtained. It will be used in the later patches to learn the function signature of a running bpf program. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-11-20 06:29:08 +07:00
/* 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").
*/
struct btf_param {
__u32 name_off;
__u32 type;
};
bpf: btf: Introduce BPF Type Format (BTF) This patch introduces BPF type Format (BTF). BTF (BPF Type Format) is the meta data format which describes the data types of BPF program/map. Hence, it basically focus on the C programming language which the modern BPF is primary using. The first use case is to provide a generic pretty print capability for a BPF map. BTF has its root from CTF (Compact C-Type format). To simplify the handling of BTF data, BTF removes the differences between small and big type/struct-member. Hence, BTF consistently uses u32 instead of supporting both "one u16" and "two u32 (+padding)" in describing type and struct-member. It also raises the number of types (and functions) limit from 0x7fff to 0x7fffffff. Due to the above changes, the format is not compatible to CTF. Hence, BTF starts with a new BTF_MAGIC and version number. This patch does the first verification pass to the BTF. The first pass checks: 1. meta-data size (e.g. It does not go beyond the total btf's size) 2. name_offset is valid 3. Each BTF_KIND (e.g. int, enum, struct....) does its own check of its meta-data. Some other checks, like checking a struct's member is referring to a valid type, can only be done in the second pass. The second verification pass will be implemented in the next patch. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-04-19 05:55:57 +07:00
#endif /* _UAPI__LINUX_BTF_H__ */
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