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bpf: Add 64bit enum value support #3122

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bpf: Add 64bit enum value support #3122

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Pull request for series with
subject: bpf: Add 64bit enum value support
version: 5
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=647858

Kernel Patches Daemon and others added 18 commits June 6, 2022 23:30
adding ci files
d50c4a5
@yonghong-song
bpf: Add btf enum64 support
db22149 
Currently, BTF only supports upto 32bit enum value with BTF_KIND_ENUM.
But in kernel, some enum indeed has 64bit values, e.g.,
in uapi bpf.h, we have
  enum {
        BPF_F_INDEX_MASK                = 0xffffffffULL,
        BPF_F_CURRENT_CPU               = BPF_F_INDEX_MASK,
        BPF_F_CTXLEN_MASK               = (0xfffffULL << 32),
  };
In this case, BTF_KIND_ENUM will encode the value of BPF_F_CTXLEN_MASK
as 0, which certainly is incorrect.

This patch added a new btf kind, BTF_KIND_ENUM64, which permits
64bit value to cover the above use case. The BTF_KIND_ENUM64 has
the following three fields followed by the common type:
  struct bpf_enum64 {
    __u32 nume_off;
    __u32 val_lo32;
    __u32 val_hi32;
  };
Currently, btf type section has an alignment of 4 as all element types
are u32. Representing the value with __u64 will introduce a pad
for bpf_enum64 and may also introduce misalignment for the 64bit value.
Hence, two members of val_hi32 and val_lo32 are chosen to avoid these issues.

The kflag is also introduced for BTF_KIND_ENUM and BTF_KIND_ENUM64
to indicate whether the value is signed or unsigned. The kflag intends
to provide consistent output of BTF C fortmat with the original
source code. For example, the original BTF_KIND_ENUM bit value is 0xffffffff.
The format C has two choices, printing out 0xffffffff or -1 and current libbpf
prints out as unsigned value. But if the signedness is preserved in btf,
the value can be printed the same as the original source code.
The kflag value 0 means unsigned values, which is consistent to the default
by libbpf and should also cover most cases as well.

The new BTF_KIND_ENUM64 is intended to support the enum value represented as
64bit value. But it can represent all BTF_KIND_ENUM values as well.
The compiler ([1]) and pahole will generate BTF_KIND_ENUM64 only if the value has
to be represented with 64 bits.

In addition, a static inline function btf_kind_core_compat() is introduced which
will be used later when libbpf relo_core.c changed. Here the kernel shares the
same relo_core.c with libbpf.

  [1] https://reviews.llvm.org/D124641

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Permit 64bit relocation value
fde7f1c 
Currently, the libbpf limits the relocation value to be 32bit
since all current relocations have such a limit. But with
BTF_KIND_ENUM64 support, the enum value could be 64bit.
So let us permit 64bit relocation value in libbpf.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Fix an error in 64bit relocation value computation
506e9ab 
Currently, the 64bit relocation value in the instruction
is computed as follows:
  __u64 imm = insn[0].imm + ((__u64)insn[1].imm << 32)

Suppose insn[0].imm = -1 (0xffffffff) and insn[1].imm = 1.
With the above computation, insn[0].imm will first sign-extend
to 64bit -1 (0xffffffffFFFFFFFF) and then add 0x1FFFFFFFF,
producing incorrect value 0xFFFFFFFF. The correct value
should be 0x1FFFFFFFF.

Changing insn[0].imm to __u32 first will prevent 64bit sign
extension and fix the issue. Merging high and low 32bit values
also changed from '+' to '|' to be consistent with other
similar occurences in kernel and libbpf.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Refactor btf__add_enum() for future code sharing
2be4297 
Refactor btf__add_enum() function to create a separate
function btf_add_enum_common() so later the common function
can be used to add enum64 btf type. There is no functionality
change for this patch.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Add enum64 parsing and new enum64 public API
1e26da4 
Add enum64 parsing support and two new enum64 public APIs:
  btf__add_enum64
  btf__add_enum64_value

Also add support of signedness for BTF_KIND_ENUM. The
BTF_KIND_ENUM API signatures are not changed. The signedness
will be changed from unsigned to signed if btf__add_enum_value()
finds any negative values.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Add enum64 deduplication support
8ef0955 
Add enum64 deduplication support. BTF_KIND_ENUM64 handling
is very similar to BTF_KIND_ENUM.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Add enum64 support for btf_dump
66ddfe2 
Add enum64 btf dumping support. For long long and unsigned long long
dump, suffixes 'LL' and 'ULL' are added to avoid compilation errors
in some cases.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Add enum64 sanitization
da32807 
When old kernel does not support enum64 but user space btf
contains non-zero enum kflag or enum64, libbpf needs to
do proper sanitization so modified btf can be accepted
by the kernel.

Sanitization for enum kflag can be achieved by clearing
the kflag bit. For enum64, the type is replaced with an
union of integer member types and the integer member size
must be smaller than enum64 size. If such an integer
type cannot be found, a new type is created and used
for union members.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Add enum64 support for bpf linking
bfec46e 
Add BTF_KIND_ENUM64 support for bpf linking, which is
very similar to BTF_KIND_ENUM.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
libbpf: Add enum64 relocation support
b66278a 
The enum64 relocation support is added. The bpf local type
could be either enum or enum64 and the remote type could be
either enum or enum64 too. The all combinations of local enum/enum64
and remote enum/enum64 are supported.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
bpftool: Add btf enum64 support
2963c6d 
Add BTF_KIND_ENUM64 support.
For example, the following enum is defined in uapi bpf.h.
  $ cat core.c
  enum A {
        BPF_F_INDEX_MASK                = 0xffffffffULL,
        BPF_F_CURRENT_CPU               = BPF_F_INDEX_MASK,
        BPF_F_CTXLEN_MASK               = (0xfffffULL << 32),
  } g;
Compiled with
  clang -target bpf -O2 -g -c core.c
Using bpftool to dump types and generate format C file:
  $ bpftool btf dump file core.o
  ...
  [1] ENUM64 'A' encoding=UNSIGNED size=8 vlen=3
        'BPF_F_INDEX_MASK' val=4294967295ULL
        'BPF_F_CURRENT_CPU' val=4294967295ULL
        'BPF_F_CTXLEN_MASK' val=4503595332403200ULL
  $ bpftool btf dump file core.o format c
  ...
  enum A {
        BPF_F_INDEX_MASK = 4294967295ULL,
        BPF_F_CURRENT_CPU = 4294967295ULL,
        BPF_F_CTXLEN_MASK = 4503595332403200ULL,
  };
  ...

Note that for raw btf output, the encoding (UNSIGNED or SIGNED)
is printed out as well. The 64bit value is also represented properly
in BTF and C dump.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
selftests/bpf: Fix selftests failure
a5d538b 
The kflag is supported now for BTF_KIND_ENUM.
So remove the test which tests verifier failure
due to existence of kflag.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
selftests/bpf: Test new enum kflag and enum64 API functions
89880c0 
Add tests to use the new enum kflag and enum64 API functions
in selftest btf_write.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
selftests/bpf: Add BTF_KIND_ENUM64 unit tests
b24e460 
Add unit tests for basic BTF_KIND_ENUM64 encoding.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
selftests/bpf: Test BTF_KIND_ENUM64 for deduplication
2204ff7 
Add a few unit tests for BTF_KIND_ENUM64 deduplication.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
selftests/bpf: Add a test for enum64 value relocations
a6dc34c 
Add a test for enum64 value relocations.
The test will be skipped if clang version is 14 or lower
since enum64 is only supported from version 15.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@yonghong-song
docs/bpf: Update documentation for BTF_KIND_ENUM64 support
5fb2040 
Add BTF_KIND_ENUM64 documentation in btf.rst.
Also fixed a typo for section number for BTF_KIND_TYPE_TAG
from 2.2.17 to 2.2.18, and fixed a type size issue for
BTF_KIND_ENUM.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
@kernel-patches-bot
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Master branch: 02f4afe
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=647858
version: 5

@kernel-patches-bot
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Master branch: d352bd8
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=647858
version: 5

Pull request is NOT updated. Failed to apply https://patchwork.kernel.org/project/netdevbpf/list/?series=647858
error message:

Cmd('git') failed due to: exit code(128)
  cmdline: git am -3
  stdout: 'Applying: bpf: Add btf enum64 support
Using index info to reconstruct a base tree...
M	include/linux/btf.h
M	include/uapi/linux/btf.h
M	kernel/bpf/btf.c
M	kernel/bpf/verifier.c
M	tools/include/uapi/linux/btf.h
Falling back to patching base and 3-way merge...
No changes -- Patch already applied.
Applying: libbpf: Permit 64bit relocation value
Using index info to reconstruct a base tree...
M	tools/lib/bpf/relo_core.c
M	tools/lib/bpf/relo_core.h
Falling back to patching base and 3-way merge...
Auto-merging tools/lib/bpf/relo_core.c
No changes -- Patch already applied.
Applying: libbpf: Fix an error in 64bit relocation value computation
Using index info to reconstruct a base tree...
M	tools/lib/bpf/relo_core.c
Falling back to patching base and 3-way merge...
Auto-merging tools/lib/bpf/relo_core.c
No changes -- Patch already applied.
Applying: libbpf: Refactor btf__add_enum() for future code sharing
Using index info to reconstruct a base tree...
M	tools/lib/bpf/btf.c
Falling back to patching base and 3-way merge...
Auto-merging tools/lib/bpf/btf.c
CONFLICT (content): Merge conflict in tools/lib/bpf/btf.c
Patch failed at 0004 libbpf: Refactor btf__add_enum() for future code sharing
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".'
  stderr: 'error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch'

conflict:

diff --cc tools/lib/bpf/btf.c
index ae1520f7e1b0,1972d0c65e0c..000000000000
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@@ -2188,10 -2176,6 +2188,13 @@@ static int btf_add_enum_common(struct b
   */
  int btf__add_enum(struct btf *btf, const char *name, __u32 byte_sz)
  {
++<<<<<<< HEAD
 +	/*
 +	 * set the signedness to be unsigned, it will change to signed
 +	 * if any later enumerator is negative.
 +	 */
++=======
++>>>>>>> libbpf: Refactor btf__add_enum() for future code sharing
  	return btf_add_enum_common(btf, name, byte_sz, false, BTF_KIND_ENUM);
  }

@kernel-patches-bot
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=647858 irrelevant now. Closing PR.

@kernel-patches-bot kernel-patches-bot deleted the series/637423=>bpf-next branch June 7, 2022 17:45
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