That is the idiom for free its members and then free itself, 'free' is
just to free its members.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
So that we don't clash with libbpf's 'struct btf', in time more internal
state now in 'struct btf_elf' will refer to the equivalent internal
state in libbpf's 'struct btf', as they have lots in common.
Requested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Acked-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Martin Lau <kafai@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Now that libbpf is a submodule, we don't need to copy/paste btf.h header
with BTF type definitions.
This is a first step in migrating parts of libbtf, btf_encoder and
btf_loader to use libbpf and starting to use btf__dedup().
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
When dealing with BTF encoding of multiple CUs, special `void` type
should be handled explicitly.
This is already handled for all BTF types except recently added
FUNC_PROTO.
Without this fix, any `void` type directly referenced from FUNC_PROTO
will turn into last type from previous CU (see example below, for
FUNC_PROTO [4]).
$ cat test1.c
void (*foo)(void);
int main() {
return 0;
}
$ cat test2.c
void (*bar)(void);
$ cc -g test1.c test2.c -o test
Without fix:
$ LLVM_OBJCOPY=objcopy ~/local/pahole/build/pahole -JV /tmp/test
File /tmp/test:
[1] INT int size=4 bit_offset=0 nr_bits2 encoding=SIGNED
[2] FUNC_PROTO (anon) return=0 args=(void)
[3] PTR (anon) type_id=2
[4] FUNC_PROTO (anon) return=3 args=(void)
[5] PTR (anon) type_id=4
With fix:
$ LLVM_OBJCOPY=objcopy ~/local/pahole/build/pahole -JV /tmp/test
File /tmp/test:
[1] INT int size=4 bit_offset=0 nr_bits2 encoding=SIGNED
[2] FUNC_PROTO (anon) return=0 args=(void)
[3] PTR (anon) type_id=2
[4] FUNC_PROTO (anon) return=0 args=(void)
[5] PTR (anon) type_id=4
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-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
[ Applied patch by hand, came mangled ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Two new btf kinds, BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO,
have been added in kernel since
https://patchwork.ozlabs.org/cover/1000176/
to support better func introspection.
Currently, for a DW_TAG_subroutine_type dwarf type,
a simple "void *" is generated instead of real subroutine type.
This patch teaches pahole to generate BTF_KIND_FUNC_PROTO
properly. After this patch, pahole should have complete
type coverage for C frontend with types a bpf program cares.
For example,
$ cat t1.c
typedef int __int32;
struct t1 {
int a1;
int (*f1)(char p1, __int32 p2);
} g1;
$ cat t2.c
typedef int __int32;
struct t2 {
int a2;
int (*f2)(char q1, __int32 q2, ...);
int (*f3)();
} g2;
int main() { return 0; }
$ gcc -O2 -o t1 -g t1.c t2.c
$ pahole -JV t1
File t1:
[1] TYPEDEF __int32 type_id=2
[2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[3] STRUCT t1 kind_flag=0 size=16 vlen=2
a1 type_id=2 bits_offset=0
f1 type_id=6 bits_offset=64
[4] FUNC_PROTO (anon) return=2 args=(5 (anon), 1 (anon))
[5] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[6] PTR (anon) type_id=4
[7] TYPEDEF __int32 type_id=8
[8] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[9] STRUCT t2 kind_flag=0 size=24 vlen=3
a2 type_id=8 bits_offset=0
f2 type_id=12 bits_offset=64
f3 type_id=14 bits_offset=128
[10] FUNC_PROTO (anon) return=8 args=(11 (anon), 7 (anon), vararg)
[11] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[12] PTR (anon) type_id=10
[13] FUNC_PROTO (anon) return=8 args=(vararg)
[14] PTR (anon) type_id=13
$
In the above example, type [4], [10] and [13] represent the
func_proto types.
BTF_KIND_FUNC, which represents a real subprogram, is not generated in
this patch and will be considered later.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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,
commit b18354f64c ("btf: Generate correct struct bitfield
member types") workarounds the issue by generating
an int type whenever the enum bit size is not 32.
The above workaround is not ideal as we lost original type
in BTF. Another undesiable fact is the type duplication
as the pahole duplicates the type chain.
To fix this issue, this patch implemented a compatible
change for BTF struct type encoding:
. the bit 31 of 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 255 which is enough for today as maximum
bitfield in compiler can be 128 where int128 type is supported.
A new global, no_bitfield_type_recode, is introduced and which
will be set to true if BTF encoding is enabled. This global
will prevent pahole duplicating the bitfield types to avoid
type duplication in BTF.
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.
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.
Examples:
=========
-bash-4.4$ cat t.c
struct s;
union u;
typedef int ___int;
enum A { A1, A2, A3 };
struct t {
int a[5];
___int b:4;
volatile enum A c:4;
struct s *p1;
union u *p2;
} g;
-bash-4.4$ gcc -c -O2 -g t.c
Without this patch:
$ 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=40 vlen=5
a type_id=5 bits_offset=0
b type_id=13 bits_offset=160
c type_id=15 bits_offset=164
p1 type_id=9 bits_offset=192
p2 type_id=11 bits_offset=256
[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] FWD s type_id=0
[9] PTR (anon) type_id=8
[10] FWD u type_id=0
[11] PTR (anon) type_id=10
[12] INT int size=1 bit_offset=0 nr_bits=4 encoding=(none)
[13] TYPEDEF ___int type_id=12
[14] INT (anon) size=1 bit_offset=0 nr_bits=4 encoding=SIGNED
[15] VOLATILE (anon) type_id=14
With this patch:
$ pahole -JV t.o
File 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=40 vlen=5
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
p1 type_id=9 bitfield_size=0 bits_offset=192
p2 type_id=11 bitfield_size=0 bits_offset=256
[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] FWD s struct
[9] PTR (anon) type_id=8
[10] FWD u union
[11] PTR (anon) type_id=10
The fix removed the type duplication, preserved the enum type for the
bitfield, and have correct struct/union information for the forward
type.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Currently, the pahole dwarf->btf conversion only supports one
compilation unit. This is not ideal since we would like using pahole to
generate BTF for vmlinux which has a lot of compilation units.
This patch added support to process multiple compilation units per ELF
file. Multiple ELF files are also supported properly.
The following is a demonstration example:
-bash-4.4$ cat t1.c
struct t1 {
int a1;
} g1;
int main(void) { return 0; }
-bash-4.4$ cat t2.c
struct t2 {
char a2;
} g2;
int main() { return 0; }
-bash-4.4$ cat t3.c
struct t3 {
unsigned char a1:4;
} g1;
int main(void) { return 0; }
-bash-4.4$ cat t4.c
struct t4 {
volatile char a4;
} g2;
int main() { return 0; }
-bash-4.4$ gcc -O2 -o t1 -g t1.c t2.c
-bash-4.4$ gcc -O2 -o t3 -g t3.c t4.c
Note that both the binary "t1" and "t3" have two compilation units in
their respective dwarf debug_info sections. The following is the pahole
verbose output for BTF conversion for these two binaries.
-bash-4.4$ pahole -JV t1 t3
File t1:
[1] STRUCT t1 size=4 vlen=1
a1 type_id=2 bits_offset=0
[2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[3] STRUCT t2 size=1 vlen=1
a2 type_id=4 bits_offset=0
[4] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[5] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
File t3:
[1] STRUCT t3 size=1 vlen=1
a1 type_id=3 bits_offset=0
[2] INT unsigned char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[3] INT unsigned char size=1 bit_offset=0 nr_bits=4 encoding=(none)
[4] INT (anon) size=4 bit_offset=0 nr_bits=32 encoding=(none)
[5] STRUCT t4 size=1 vlen=1
a4 type_id=6 bits_offset=0
[6] VOLATILE (anon) type_id=7
[7] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[8] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
For int types, the correct type size will be generated. For enum types,
if the bit size is not 32, current BTF enum cannot represent it so a
signed int type will be generated.
For the following example:
$ cat test.c
enum A { A1, A2, A3 };
struct t {
enum A a:3;
volatile enum A b:4;
} g;
$ gcc -c -g -O2 test.c
Without this patch, we will have:
$ pahole -JV test.o
[1] ENUM A size=4 vlen=3
A1 val=0
A2 val=1
A3 val=2
[2] STRUCT t size=4 vlen=2
a type_id=4 bits_offset=0
b type_id=6 bits_offset=3
[3] VOLATILE (anon) type_id=1
[4] ENUM A size=1 vlen=3
A1 val=0
A2 val=1
A3 val=2
[5] ENUM A size=1 vlen=3
A1 val=0
A2 val=1
A3 val=2
[6] VOLATILE (anon) type_id=5
[7] INT (anon) size=4 bit_offset=0 nr_bits=32 encoding=(none)
There are two issues in the above. The struct "t" member "a" points to
type [4]. But the nr_bits is lost in type [4].
The same for type [5] which is for struct "t" member "b".
Since BTF ENUM type cannot encode nr_bits, this patch fixed the issue by
generating a BTF INT type if the ENUM type number of bits in pahole is
not 32.
With this patch, the incorrect member nr_bits issue is fixed as below:
$ pahole -JV test.o
[1] ENUM A size=4 vlen=3
A1 val=0
A2 val=1
A3 val=2
[2] STRUCT t size=4 vlen=2
a type_id=4 bits_offset=0
b type_id=6 bits_offset=3
[3] VOLATILE (anon) type_id=1
[4] INT (anon) size=1 bit_offset=0 nr_bits=3 encoding=SIGNED
[5] INT (anon) size=1 bit_offset=0 nr_bits=4 encoding=SIGNED
[6] VOLATILE (anon) type_id=5
[7] INT (anon) size=4 bit_offset=0 nr_bits=32 encoding=(none)
Signed-off-by: Yonghong Song <yhs@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The btf bitfield encoding is broken.
For the following example:
-bash-4.2$ cat t.c
struct t {
int a:2;
int b:1;
int :3;
int c:1;
int d;
char e:1;
char f:1;
int g;
};
void test(struct t *t) {
return;
}
-bash-4.2$ clang -S -g -emit-llvm t.c
The output for bpf "little and big" endian results with pahole dwarf2btf
conversion:
-bash-4.2$ llc -march=bpfel -mattr=dwarfris -filetype=obj t.ll
-bash-4.2$ pahole -JV t.o
[1] PTR (anon) type_id=2
[2] STRUCT t size=16 vlen=7
a type_id=5 bits_offset=30
b type_id=6 bits_offset=29
c type_id=6 bits_offset=25
d type_id=3 bits_offset=32
e type_id=7 bits_offset=71
f type_id=7 bits_offset=70
g type_id=3 bits_offset=96
[3] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[4] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[5] INT int size=1 bit_offset=0 nr_bits=2 encoding=(none)
[6] INT int size=1 bit_offset=0 nr_bits=1 encoding=(none)
[7] INT char size=1 bit_offset=0 nr_bits=1 encoding=(none)
-bash-4.2$ llc -march=bpfeb -mattr=dwarfris -filetype=obj t.ll
-bash-4.2$ pahole -JV t.o
[1] PTR (anon) type_id=2
[2] STRUCT t size=16 vlen=7
a type_id=5 bits_offset=0
b type_id=6 bits_offset=2
c type_id=6 bits_offset=6
d type_id=3 bits_offset=32
e type_id=7 bits_offset=64
f type_id=7 bits_offset=65
g type_id=3 bits_offset=96
[3] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[4] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[5] INT int size=1 bit_offset=0 nr_bits=2 encoding=(none)
[6] INT int size=1 bit_offset=0 nr_bits=1 encoding=(none)
[7] INT char size=1 bit_offset=0 nr_bits=1 encoding=(none)
The BTF struct member bits_offset counts bits from the beginning of the
containing entity regardless of endianness, similar to what
DW_AT_bit_offset from DWARF4 does. Such counting is equivalent to the
big endian conversion in the above.
But the little endian conversion is not correct since dwarf generates
DW_AT_bit_offset based on actual bit position in the little endian
architecture. For example, for the above struct member "a", the dwarf
would generate DW_AT_bit_offset=30 for little endian, and
DW_AT_bit_offset=0 for big endian.
This patch fixed the little endian structure member bits_offset problem
with proper calculation based on dwarf attributes.
With the fix, we get:
-bash-4.2$ llc -march=bpfel -mattr=dwarfris -filetype=obj t.ll
-bash-4.2$ pahole -JV t.o
[1] STRUCT t size=16 vlen=7
a type_id=5 bits_offset=0
b type_id=6 bits_offset=2
c type_id=6 bits_offset=6
d type_id=2 bits_offset=32
e type_id=7 bits_offset=64
f type_id=7 bits_offset=65
g type_id=2 bits_offset=96
[2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[3] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[4] PTR (anon) type_id=1
[5] INT int size=1 bit_offset=0 nr_bits=2 encoding=(none)
[6] INT int size=1 bit_offset=0 nr_bits=1 encoding=(none)
[7] INT char size=1 bit_offset=0 nr_bits=1 encoding=(none)
-bash-4.2$ llc -march=bpfeb -mattr=dwarfris -filetype=obj t.ll
-bash-4.2$ pahole -JV t.o
[1] PTR (anon) type_id=2
[2] STRUCT t size=16 vlen=7
a type_id=5 bits_offset=0
b type_id=6 bits_offset=2
c type_id=6 bits_offset=6
d type_id=3 bits_offset=32
e type_id=7 bits_offset=64
f type_id=7 bits_offset=65
g type_id=3 bits_offset=96
[3] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[4] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[5] INT int size=1 bit_offset=0 nr_bits=2 encoding=(none)
[6] INT int size=1 bit_offset=0 nr_bits=1 encoding=(none)
[7] INT char size=1 bit_offset=0 nr_bits=1 encoding=(none)
-bash-4.2$
For both little endian and big endian, we have correct and
same bits_offset for struct members.
We could fix pos->bit_offset, but pos->bit_offset will be inconsistent
to pos->bitfield_offset in the meaning and pos->bitfield_offset is used
to print out pahole data structure:
-bash-4.2$ llc -march=bpfel -mattr=dwarfris -filetype=obj t.ll
-bash-4.2$ /bin/pahole t.o
struct t {
int a:2; /* 0:30 4 */
int b:1; /* 0:29 4 */
int c:1; /* 0:25 4 */
.....
So this patch just made the change in btf specific routines.
Signed-off-by: Yonghong Song <yhs@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Andrii Nakryiko
Arnaldo Carvalho de Melo
Martin Lau
Domenico Andreoli
Yonghong Song