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  1. 11 3月, 2021 1 次提交
  3. 05 3月, 2021 1 次提交
  5. 04 2月, 2021 1 次提交
  7. 20 11月, 2020 1 次提交
  9. 30 9月, 2020 2 次提交
  11. 09 9月, 2020 1 次提交
    • T
      tools/libbpf: Avoid counting local symbols in ABI check · 746f534a
      由 Tony Ambardar 提交于 
      Encountered the following failure building libbpf from kernel 5.8.5 sources
with GCC 8.4.0 and binutils 2.34: (long paths shortened)

  Warning: Num of global symbols in sharedobjs/libbpf-in.o (234) does NOT
  match with num of versioned symbols in libbpf.so (236). Please make sure
  all LIBBPF_API symbols are versioned in libbpf.map.
  --- libbpf_global_syms.tmp    2020-09-02 07:30:58.920084380 +0000
  +++ libbpf_versioned_syms.tmp 2020-09-02 07:30:58.924084388 +0000
  @@ -1,3 +1,5 @@
  +_fini
  +_init
   bpf_btf_get_fd_by_id
   bpf_btf_get_next_id
   bpf_create_map
  make[4]: *** [Makefile:210: check_abi] Error 1

Investigation shows _fini and _init are actually local symbols counted
amongst global ones:

  $ readelf --dyn-syms --wide libbpf.so|head -10

  Symbol table '.dynsym' contains 343 entries:
     Num:    Value  Size Type    Bind   Vis      Ndx Name
       0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
       1: 00004098     0 SECTION LOCAL  DEFAULT   11
       2: 00004098     8 FUNC    LOCAL  DEFAULT   11 _init@@LIBBPF_0.0.1
       3: 00023040     8 FUNC    LOCAL  DEFAULT   14 _fini@@LIBBPF_0.0.1
       4: 00000000     0 OBJECT  GLOBAL DEFAULT  ABS LIBBPF_0.0.4
       5: 00000000     0 OBJECT  GLOBAL DEFAULT  ABS LIBBPF_0.0.1
       6: 0000ffa4     8 FUNC    GLOBAL DEFAULT   12 bpf_object__find_map_by_offset@@LIBBPF_0.0.1

A previous commit filtered global symbols in sharedobjs/libbpf-in.o. Do the
same with the libbpf.so DSO for consistent comparison.

Fixes: 306b267c ("libbpf: Verify versioned symbols")
Signed-off-by: NTony Ambardar <Tony.Ambardar@gmail.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200905214831.1565465-1-Tony.Ambardar@gmail.com
      746f534a
  13. 03 9月, 2020 1 次提交
  15. 28 8月, 2020 1 次提交
  17. 20 8月, 2020 1 次提交
    • A
      bpf: Add kernel module with user mode driver that populates bpffs. · d71fa5c9
      由 Alexei Starovoitov 提交于 
      Add kernel module with user mode driver that populates bpffs with
BPF iterators.

$ mount bpffs /my/bpffs/ -t bpf
$ ls -la /my/bpffs/
total 4
drwxrwxrwt  2 root root    0 Jul  2 00:27 .
drwxr-xr-x 19 root root 4096 Jul  2 00:09 ..
-rw-------  1 root root    0 Jul  2 00:27 maps.debug
-rw-------  1 root root    0 Jul  2 00:27 progs.debug

The user mode driver will load BPF Type Formats, create BPF maps, populate BPF
maps, load two BPF programs, attach them to BPF iterators, and finally send two
bpf_link IDs back to the kernel.
The kernel will pin two bpf_links into newly mounted bpffs instance under
names "progs.debug" and "maps.debug". These two files become human readable.

$ cat /my/bpffs/progs.debug
  id name            attached
  11 dump_bpf_map    bpf_iter_bpf_map
  12 dump_bpf_prog   bpf_iter_bpf_prog
  27 test_pkt_access
  32 test_main       test_pkt_access test_pkt_access
  33 test_subprog1   test_pkt_access_subprog1 test_pkt_access
  34 test_subprog2   test_pkt_access_subprog2 test_pkt_access
  35 test_subprog3   test_pkt_access_subprog3 test_pkt_access
  36 new_get_skb_len get_skb_len test_pkt_access
  37 new_get_skb_ifindex get_skb_ifindex test_pkt_access
  38 new_get_constant get_constant test_pkt_access

The BPF program dump_bpf_prog() in iterators.bpf.c is printing this data about
all BPF programs currently loaded in the system. This information is unstable
and will change from kernel to kernel as ".debug" suffix conveys.
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200819042759.51280-4-alexei.starovoitov@gmail.com
      d71fa5c9
  19. 19 8月, 2020 3 次提交
  21. 02 6月, 2020 2 次提交
  23. 14 1月, 2020 1 次提交
  25. 10 1月, 2020 1 次提交
  27. 23 12月, 2019 1 次提交
  29. 18 12月, 2019 1 次提交
  31. 16 12月, 2019 2 次提交
    • A
      libbpf: Support libbpf-provided extern variables · 166750bc
      由 Andrii Nakryiko 提交于 
      Add support for extern variables, provided to BPF program by libbpf. Currently
the following extern variables are supported:
  - LINUX_KERNEL_VERSION; version of a kernel in which BPF program is
    executing, follows KERNEL_VERSION() macro convention, can be 4- and 8-byte
    long;
  - CONFIG_xxx values; a set of values of actual kernel config. Tristate,
    boolean, strings, and integer values are supported.

Set of possible values is determined by declared type of extern variable.
Supported types of variables are:
- Tristate values. Are represented as `enum libbpf_tristate`. Accepted values
  are **strictly** 'y', 'n', or 'm', which are represented as TRI_YES, TRI_NO,
  or TRI_MODULE, respectively.
- Boolean values. Are represented as bool (_Bool) types. Accepted values are
  'y' and 'n' only, turning into true/false values, respectively.
- Single-character values. Can be used both as a substritute for
  bool/tristate, or as a small-range integer:
  - 'y'/'n'/'m' are represented as is, as characters 'y', 'n', or 'm';
  - integers in a range [-128, 127] or [0, 255] (depending on signedness of
    char in target architecture) are recognized and represented with
    respective values of char type.
- Strings. String values are declared as fixed-length char arrays. String of
  up to that length will be accepted and put in first N bytes of char array,
  with the rest of bytes zeroed out. If config string value is longer than
  space alloted, it will be truncated and warning message emitted. Char array
  is always zero terminated. String literals in config have to be enclosed in
  double quotes, just like C-style string literals.
- Integers. 8-, 16-, 32-, and 64-bit integers are supported, both signed and
  unsigned variants. Libbpf enforces parsed config value to be in the
  supported range of corresponding integer type. Integers values in config can
  be:
  - decimal integers, with optional + and - signs;
  - hexadecimal integers, prefixed with 0x or 0X;
  - octal integers, starting with 0.

Config file itself is searched in /boot/config-$(uname -r) location with
fallback to /proc/config.gz, unless config path is specified explicitly
through bpf_object_open_opts' kernel_config_path option. Both gzipped and
plain text formats are supported. Libbpf adds explicit dependency on zlib
because of this, but this shouldn't be a problem, given libelf already depends
on zlib.

All detected extern variables, are put into a separate .extern internal map.
It, similarly to .rodata map, is marked as read-only from BPF program side, as
well as is frozen on load. This allows BPF verifier to track extern values as
constants and perform enhanced branch prediction and dead code elimination.
This can be relied upon for doing kernel version/feature detection and using
potentially unsupported field relocations or BPF helpers in a CO-RE-based BPF
program, while still having a single version of BPF program running on old and
new kernels. Selftests are validating this explicitly for unexisting BPF
helper.
Signed-off-by: NAndrii Nakryiko <andriin@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191214014710.3449601-3-andriin@fb.com
      166750bc
    • T
      libbpf: Fix readelf output parsing for Fedora · aa915931
      由 Thadeu Lima de Souza Cascardo 提交于 
      Fedora binutils has been patched to show "other info" for a symbol at the
end of the line. This was done in order to support unmaintained scripts
that would break with the extra info. [1]

[1] https://src.fedoraproject.org/rpms/binutils/c/b8265c46f7ddae23a792ee8306fbaaeacba83bf8

This in turn has been done to fix the build of ruby, because of checksec.
[2] Thanks Michael Ellerman for the pointer.

[2] https://bugzilla.redhat.com/show_bug.cgi?id=1479302

As libbpf Makefile is not unmaintained, we can simply deal with either
output format, by just removing the "other info" field, as it always comes
inside brackets.

Fixes: 3464afdf (libbpf: Fix readelf output parsing on powerpc with recent binutils)
Reported-by: NJustin Forbes <jmforbes@linuxtx.org>
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NAndrii Nakryiko <andriin@fb.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Link: https://lore.kernel.org/bpf/20191213101114.GA3986@calabresa
      aa915931
  33. 05 12月, 2019 1 次提交
  35. 02 12月, 2019 1 次提交
  37. 28 11月, 2019 2 次提交
  39. 21 10月, 2019 1 次提交
  41. 13 10月, 2019 2 次提交
  43. 09 10月, 2019 2 次提交
  45. 06 10月, 2019 1 次提交
  47. 01 10月, 2019 1 次提交
    • Y
      libbpf: handle symbol versioning properly for libbpf.a · 1bd63524
      由 Yonghong Song 提交于 
      bcc uses libbpf repo as a submodule. It brings in libbpf source
code and builds everything together to produce shared libraries.
With latest libbpf, I got the following errors:
  /bin/ld: libbcc_bpf.so.0.10.0: version node not found for symbol xsk_umem__create@LIBBPF_0.0.2
  /bin/ld: failed to set dynamic section sizes: Bad value
  collect2: error: ld returned 1 exit status
  make[2]: *** [src/cc/libbcc_bpf.so.0.10.0] Error 1

In xsk.c, we have
  asm(".symver xsk_umem__create_v0_0_2, xsk_umem__create@LIBBPF_0.0.2");
  asm(".symver xsk_umem__create_v0_0_4, xsk_umem__create@@LIBBPF_0.0.4");
The linker thinks the built is for LIBBPF but cannot find proper version
LIBBPF_0.0.2/4, so emit errors.

I also confirmed that using libbpf.a to produce a shared library also
has issues:
  -bash-4.4$ cat t.c
  extern void *xsk_umem__create;
  void * test() { return xsk_umem__create; }
  -bash-4.4$ gcc -c -fPIC t.c
  -bash-4.4$ gcc -shared t.o libbpf.a -o t.so
  /bin/ld: t.so: version node not found for symbol xsk_umem__create@LIBBPF_0.0.2
  /bin/ld: failed to set dynamic section sizes: Bad value
  collect2: error: ld returned 1 exit status
  -bash-4.4$

Symbol versioning does happens in commonly used libraries, e.g., elfutils
and glibc. For static libraries, for a versioned symbol, the old definitions
will be ignored, and the symbol will be an alias to the latest definition.
For example, glibc sched_setaffinity is versioned.
  -bash-4.4$ readelf -s /usr/lib64/libc.so.6 | grep sched_setaffinity
     756: 000000000013d3d0    13 FUNC    GLOBAL DEFAULT   13 sched_setaffinity@GLIBC_2.3.3
     757: 00000000000e2e70   455 FUNC    GLOBAL DEFAULT   13 sched_setaffinity@@GLIBC_2.3.4
    1800: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS sched_setaffinity.c
    4228: 00000000000e2e70   455 FUNC    LOCAL  DEFAULT   13 __sched_setaffinity_new
    4648: 000000000013d3d0    13 FUNC    LOCAL  DEFAULT   13 __sched_setaffinity_old
    7338: 000000000013d3d0    13 FUNC    GLOBAL DEFAULT   13 sched_setaffinity@GLIBC_2
    7380: 00000000000e2e70   455 FUNC    GLOBAL DEFAULT   13 sched_setaffinity@@GLIBC_
  -bash-4.4$
For static library, the definition of sched_setaffinity aliases to the new definition.
  -bash-4.4$ readelf -s /usr/lib64/libc.a | grep sched_setaffinity
  File: /usr/lib64/libc.a(sched_setaffinity.o)
     8: 0000000000000000   455 FUNC    GLOBAL DEFAULT    1 __sched_setaffinity_new
    12: 0000000000000000   455 FUNC    WEAK   DEFAULT    1 sched_setaffinity

For both elfutils and glibc, additional macros are used to control different handling
of symbol versioning w.r.t static and shared libraries.
For elfutils, the macro is SYMBOL_VERSIONING
(https://sourceware.org/git/?p=elfutils.git;a=blob;f=lib/eu-config.h).
For glibc, the macro is SHARED
(https://sourceware.org/git/?p=glibc.git;a=blob;f=include/shlib-compat.h;hb=refs/heads/master)

This patch used SHARED as the macro name. After this patch, the libbpf.a has
  -bash-4.4$ readelf -s libbpf.a | grep xsk_umem__create
     372: 0000000000017145  1190 FUNC    GLOBAL DEFAULT    1 xsk_umem__create_v0_0_4
     405: 0000000000017145  1190 FUNC    GLOBAL DEFAULT    1 xsk_umem__create
     499: 00000000000175eb   103 FUNC    GLOBAL DEFAULT    1 xsk_umem__create_v0_0_2
  -bash-4.4$
No versioned symbols for xsk_umem__create.
The libbpf.a can be used to build a shared library succesfully.
  -bash-4.4$ cat t.c
  extern void *xsk_umem__create;
  void * test() { return xsk_umem__create; }
  -bash-4.4$ gcc -c -fPIC t.c
  -bash-4.4$ gcc -shared t.o libbpf.a -o t.so
  -bash-4.4$

Fixes: 10d30e30 ("libbpf: add flags to umem config")
Cc: Kevin Laatz <kevin.laatz@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Acked-by: NAndrii Nakryiko <andriin@fb.com>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      1bd63524
  49. 30 9月, 2019 1 次提交
  51. 31 8月, 2019 1 次提交
  53. 21 8月, 2019 1 次提交
  55. 16 8月, 2019 1 次提交
    • A
      libbpf: make libbpf.map source of truth for libbpf version · dadb81d0
      由 Andrii Nakryiko 提交于 
      Currently libbpf version is specified in 2 places: libbpf.map and
Makefile. They easily get out of sync and it's very easy to update one,
but forget to update another one. In addition, Github projection of
libbpf has to maintain its own version which has to be remembered to be
kept in sync manually, which is very error-prone approach.

This patch makes libbpf.map a source of truth for libbpf version and
uses shell invocation to parse out correct full and major libbpf version
to use during build. Now we need to make sure that once new release
cycle starts, we need to add (initially) empty section to libbpf.map
with correct latest version.

This also will make it possible to keep Github projection consistent
with kernel sources version of libbpf by adopting similar parsing of
version from libbpf.map.

v2->v3:
- grep -o + sort -rV (Andrey);

v1->v2:
- eager version vars evaluation (Jakub);
- simplified version regex (Andrey);

Cc: Andrey Ignatov <rdna@fb.com>
Signed-off-by: NAndrii Nakryiko <andriin@fb.com>
Acked-by: NAndrey Ignatov <rdna@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      dadb81d0
  57. 28 5月, 2019 1 次提交
  59. 23 5月, 2019 1 次提交
  61. 05 5月, 2019 1 次提交
  63. 10 4月, 2019 1 次提交
    • D
      bpf, libbpf: support global data/bss/rodata sections · d859900c
      由 Daniel Borkmann 提交于 
      This work adds BPF loader support for global data sections
to libbpf. This allows to write BPF programs in more natural
C-like way by being able to define global variables and const
data.

Back at LPC 2018 [0] we presented a first prototype which
implemented support for global data sections by extending BPF
syscall where union bpf_attr would get additional memory/size
pair for each section passed during prog load in order to later
add this base address into the ldimm64 instruction along with
the user provided offset when accessing a variable. Consensus
from LPC was that for proper upstream support, it would be
more desirable to use maps instead of bpf_attr extension as
this would allow for introspection of these sections as well
as potential live updates of their content. This work follows
this path by taking the following steps from loader side:

 1) In bpf_object__elf_collect() step we pick up ".data",
    ".rodata", and ".bss" section information.

 2) If present, in bpf_object__init_internal_map() we add
    maps to the obj's map array that corresponds to each
    of the present sections. Given section size and access
    properties can differ, a single entry array map is
    created with value size that is corresponding to the
    ELF section size of .data, .bss or .rodata. These
    internal maps are integrated into the normal map
    handling of libbpf such that when user traverses all
    obj maps, they can be differentiated from user-created
    ones via bpf_map__is_internal(). In later steps when
    we actually create these maps in the kernel via
    bpf_object__create_maps(), then for .data and .rodata
    sections their content is copied into the map through
    bpf_map_update_elem(). For .bss this is not necessary
    since array map is already zero-initialized by default.
    Additionally, for .rodata the map is frozen as read-only
    after setup, such that neither from program nor syscall
    side writes would be possible.

 3) In bpf_program__collect_reloc() step, we record the
    corresponding map, insn index, and relocation type for
    the global data.

 4) And last but not least in the actual relocation step in
    bpf_program__relocate(), we mark the ldimm64 instruction
    with src_reg = BPF_PSEUDO_MAP_VALUE where in the first
    imm field the map's file descriptor is stored as similarly
    done as in BPF_PSEUDO_MAP_FD, and in the second imm field
    (as ldimm64 is 2-insn wide) we store the access offset
    into the section. Given these maps have only single element
    ldimm64's off remains zero in both parts.

 5) On kernel side, this special marked BPF_PSEUDO_MAP_VALUE
    load will then store the actual target address in order
    to have a 'map-lookup'-free access. That is, the actual
    map value base address + offset. The destination register
    in the verifier will then be marked as PTR_TO_MAP_VALUE,
    containing the fixed offset as reg->off and backing BPF
    map as reg->map_ptr. Meaning, it's treated as any other
    normal map value from verification side, only with
    efficient, direct value access instead of actual call to
    map lookup helper as in the typical case.

Currently, only support for static global variables has been
added, and libbpf rejects non-static global variables from
loading. This can be lifted until we have proper semantics
for how BPF will treat multi-object BPF loads. From BTF side,
libbpf will set the value type id of the types corresponding
to the ".bss", ".data" and ".rodata" names which LLVM will
emit without the object name prefix. The key type will be
left as zero, thus making use of the key-less BTF option in
array maps.

Simple example dump of program using globals vars in each
section:

  # bpftool prog
  [...]
  6784: sched_cls  name load_static_dat  tag a7e1291567277844  gpl
        loaded_at 2019-03-11T15:39:34+0000  uid 0
        xlated 1776B  jited 993B  memlock 4096B  map_ids 2238,2237,2235,2236,2239,2240

  # bpftool map show id 2237
  2237: array  name test_glo.bss  flags 0x0
        key 4B  value 64B  max_entries 1  memlock 4096B
  # bpftool map show id 2235
  2235: array  name test_glo.data  flags 0x0
        key 4B  value 64B  max_entries 1  memlock 4096B
  # bpftool map show id 2236
  2236: array  name test_glo.rodata  flags 0x80
        key 4B  value 96B  max_entries 1  memlock 4096B

  # bpftool prog dump xlated id 6784
  int load_static_data(struct __sk_buff * skb):
  ; int load_static_data(struct __sk_buff *skb)
     0: (b7) r6 = 0
  ; test_reloc(number, 0, &num0);
     1: (63) *(u32 *)(r10 -4) = r6
     2: (bf) r2 = r10
  ; int load_static_data(struct __sk_buff *skb)
     3: (07) r2 += -4
  ; test_reloc(number, 0, &num0);
     4: (18) r1 = map[id:2238]
     6: (18) r3 = map[id:2237][0]+0    <-- direct addr in .bss area
     8: (b7) r4 = 0
     9: (85) call array_map_update_elem#100464
    10: (b7) r1 = 1
  ; test_reloc(number, 1, &num1);
  [...]
  ; test_reloc(string, 2, str2);
   120: (18) r8 = map[id:2237][0]+16   <-- same here at offset +16
   122: (18) r1 = map[id:2239]
   124: (18) r3 = map[id:2237][0]+16
   126: (b7) r4 = 0
   127: (85) call array_map_update_elem#100464
   128: (b7) r1 = 120
  ; str1[5] = 'x';
   129: (73) *(u8 *)(r9 +5) = r1
  ; test_reloc(string, 3, str1);
   130: (b7) r1 = 3
   131: (63) *(u32 *)(r10 -4) = r1
   132: (b7) r9 = 3
   133: (bf) r2 = r10
  ; int load_static_data(struct __sk_buff *skb)
   134: (07) r2 += -4
  ; test_reloc(string, 3, str1);
   135: (18) r1 = map[id:2239]
   137: (18) r3 = map[id:2235][0]+16   <-- direct addr in .data area
   139: (b7) r4 = 0
   140: (85) call array_map_update_elem#100464
   141: (b7) r1 = 111
  ; __builtin_memcpy(&str2[2], "hello", sizeof("hello"));
   142: (73) *(u8 *)(r8 +6) = r1       <-- further access based on .bss data
   143: (b7) r1 = 108
   144: (73) *(u8 *)(r8 +5) = r1
  [...]

For Cilium use-case in particular, this enables migrating configuration
constants from Cilium daemon's generated header defines into global
data sections such that expensive runtime recompilations with LLVM can
be avoided altogether. Instead, the ELF file becomes effectively a
"template", meaning, it is compiled only once (!) and the Cilium daemon
will then rewrite relevant configuration data from the ELF's .data or
.rodata sections directly instead of recompiling the program. The
updated ELF is then loaded into the kernel and atomically replaces
the existing program in the networking datapath. More info in [0].

Based upon recent fix in LLVM, commit c0db6b6bd444 ("[BPF] Don't fail
for static variables").

  [0] LPC 2018, BPF track, "ELF relocation for static data in BPF",
      http://vger.kernel.org/lpc-bpf2018.html#session-3Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAndrii Nakryiko <andriin@fb.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      d859900c