Joanne Koong says:

====================

This patchset add a new helper, bpf_loop.

One of the complexities of using for loops in bpf programs is that the verifier
needs to ensure that in every possibility of the loop logic, the loop will always
terminate. As such, there is a limit on how many iterations the loop can do.

The bpf_loop helper moves the loop logic into the kernel and can thereby
guarantee that the loop will always terminate. The bpf_loop helper simplifies
a lot of the complexity the verifier needs to check, as well as removes the
constraint on the number of loops able to be run.

From the test results, we see that using bpf_loop in place
of the traditional for loop led to a decrease in verification time
and number of bpf instructions by ~99%. The benchmark results show
that as the number of iterations increases, the overhead per iteration
decreases.

The high-level overview of the patches -
Patch 1 - kernel-side + API changes for adding bpf_loop
Patch 2 - tests
Patch 3 - use bpf_loop in strobemeta + pyperf600 and measure verifier performance
Patch 4 - benchmark for throughput + latency of bpf_loop call

v3 -> v4:
~ Address nits: use usleep for triggering bpf programs, fix copyright style

v2 -> v3:
~ Rerun benchmarks on physical machine, update results
~ Propagate original error codes in the verifier

v1 -> v2:
~ Change helper name to bpf_loop (instead of bpf_for_each)
~ Set max nr_loops (~8 million loops) for bpf_loop call
~ Split tests + strobemeta/pyperf600 changes into two patches
~ Add new ops_report_final helper for outputting throughput and latency
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add benchmark to measure the throughput and latency of the bpf_loop
call.

Testing this on my dev machine on 1 thread, the data is as follows:

        nr_loops: 10
bpf_loop - throughput: 198.519 ± 0.155 M ops/s, latency: 5.037 ns/op

        nr_loops: 100
bpf_loop - throughput: 247.448 ± 0.305 M ops/s, latency: 4.041 ns/op

        nr_loops: 500
bpf_loop - throughput: 260.839 ± 0.380 M ops/s, latency: 3.834 ns/op

        nr_loops: 1000
bpf_loop - throughput: 262.806 ± 0.629 M ops/s, latency: 3.805 ns/op

        nr_loops: 5000
bpf_loop - throughput: 264.211 ± 1.508 M ops/s, latency: 3.785 ns/op

        nr_loops: 10000
bpf_loop - throughput: 265.366 ± 3.054 M ops/s, latency: 3.768 ns/op

        nr_loops: 50000
bpf_loop - throughput: 235.986 ± 20.205 M ops/s, latency: 4.238 ns/op

        nr_loops: 100000
bpf_loop - throughput: 264.482 ± 0.279 M ops/s, latency: 3.781 ns/op

        nr_loops: 500000
bpf_loop - throughput: 309.773 ± 87.713 M ops/s, latency: 3.228 ns/op

        nr_loops: 1000000
bpf_loop - throughput: 262.818 ± 4.143 M ops/s, latency: 3.805 ns/op

>From this data, we can see that the latency per loop decreases as the
number of loops increases. On this particular machine, each loop had an
overhead of about ~4 ns, and we were able to run ~250 million loops
per second.
Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211130030622.4131246-5-joannekoong@fb.com

This patch tests bpf_loop in pyperf and strobemeta, and measures the
verifier performance of replacing the traditional for loop
with bpf_loop.

The results are as follows:

~strobemeta~

Baseline
    verification time 6808200 usec
    stack depth 496
    processed 554252 insns (limit 1000000) max_states_per_insn 16
    total_states 15878 peak_states 13489  mark_read 3110
    #192 verif_scale_strobemeta:OK (unrolled loop)

Using bpf_loop
    verification time 31589 usec
    stack depth 96+400
    processed 1513 insns (limit 1000000) max_states_per_insn 2
    total_states 106 peak_states 106 mark_read 60
    #193 verif_scale_strobemeta_bpf_loop:OK

~pyperf600~

Baseline
    verification time 29702486 usec
    stack depth 368
    processed 626838 insns (limit 1000000) max_states_per_insn 7
    total_states 30368 peak_states 30279 mark_read 748
    #182 verif_scale_pyperf600:OK (unrolled loop)

Using bpf_loop
    verification time 148488 usec
    stack depth 320+40
    processed 10518 insns (limit 1000000) max_states_per_insn 10
    total_states 705 peak_states 517 mark_read 38
    #183 verif_scale_pyperf600_bpf_loop:OK

Using the bpf_loop helper led to approximately a 99% decrease
in the verification time and in the number of instructions.
Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211130030622.4131246-4-joannekoong@fb.com

Add test for bpf_loop testing a variety of cases:
various nr_loops, null callback ctx, invalid flags, nested callbacks.
Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211130030622.4131246-3-joannekoong@fb.com

This patch adds the kernel-side and API changes for a new helper
function, bpf_loop:

long bpf_loop(u32 nr_loops, void *callback_fn, void *callback_ctx,
u64 flags);

where long (*callback_fn)(u32 index, void *ctx);

bpf_loop invokes the "callback_fn" **nr_loops** times or until the
callback_fn returns 1. The callback_fn can only return 0 or 1, and
this is enforced by the verifier. The callback_fn index is zero-indexed.

A few things to please note:
~ The "u64 flags" parameter is currently unused but is included in
case a future use case for it arises.
~ In the kernel-side implementation of bpf_loop (kernel/bpf/bpf_iter.c),
bpf_callback_t is used as the callback function cast.
~ A program can have nested bpf_loop calls but the program must
still adhere to the verifier constraint of its stack depth (the stack depth
cannot exceed MAX_BPF_STACK))
~ Recursive callback_fns do not pass the verifier, due to the call stack
for these being too deep.
~ The next patch will include the tests and benchmark
Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211130030622.4131246-2-joannekoong@fb.com

filter.rst starts out documenting the classic BPF and then spills into
introducing and documentating eBPF.  Move the eBPF documentation into
rwo new files under Documentation/bpf/ for the instruction set and
the verifier and link to the BPF documentation from filter.rst.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de

Move the general maps documentation into the maps.rst file from the
overall networking filter documentation and add a link instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211119163215.971383-5-hch@lst.de

The eBPF name has completely taken over from eBPF in general usage for
the actual eBPF representation, or BPF for any general in-kernel use.
Prune all remaining references to "internal BPF".
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211119163215.971383-4-hch@lst.de

The comment telling that the prog_free helper is freeing the program is
not exactly useful, so just remove it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211119163215.971383-3-hch@lst.de

Don't bother mentioning the file name as it is implied, and remove the
reference to internal BPF.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211119163215.971383-2-hch@lst.de

There is a same action when load_attr.attach_btf_id is initialized.
Signed-off-by: Mehrdad Arshad Rad <arshad.rad@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211128193337.10628-1-arshad.rad@gmail.com

When compiling libbpf with gcc 4.8.5, we see:

  CC       staticobjs/btf_dump.o
btf_dump.c: In function ‘btf_dump_dump_type_data.isra.24’:
btf_dump.c:2296:5: error: ‘err’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  if (err < 0)
     ^
cc1: all warnings being treated as errors
make: *** [staticobjs/btf_dump.o] Error 1

While gcc 4.8.5 is too old to build the upstream kernel, it's possible it
could be used to build standalone libbpf which suffers from the same problem.
Silence the error by initializing 'err' to 0.  The warning/error seems to be
a false positive since err is set early in the function.  Regardless we
shouldn't prevent libbpf from building for this.

Fixes: 920d16af ("libbpf: BTF dumper support for typed data")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1638180040-8037-1-git-send-email-alan.maguire@oracle.com

Hengqi Chen says:

====================

Make libbpf support static initialization of BPF_MAP_TYPE_PROG_ARRAY
with a syntax similar to map-in-map initialization:

    SEC("socket")
    int tailcall_1(void *ctx)
    {
        return 0;
    }

    struct {
        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
        __uint(max_entries, 2);
        __uint(key_size, sizeof(__u32));
        __array(values, int (void *));
    } prog_array_init SEC(".maps") = {
        .values = {
            [1] = (void *)&tailcall_1,
        },
    };

v1->v2:
  - Add stricter checks on relos collect, some renamings (Andrii)
  - Update selftest to check tailcall result (Andrii)
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Add testcase for BPF_MAP_TYPE_PROG_ARRAY static initialization.
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211128141633.502339-3-hengqi.chen@gmail.com

Support static initialization of BPF_MAP_TYPE_PROG_ARRAY with a
syntax similar to map-in-map initialization ([0]):

    SEC("socket")
    int tailcall_1(void *ctx)
    {
        return 0;
    }

    struct {
        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
        __uint(max_entries, 2);
        __uint(key_size, sizeof(__u32));
        __array(values, int (void *));
    } prog_array_init SEC(".maps") = {
        .values = {
            [1] = (void *)&tailcall_1,
        },
    };

Here's the relevant part of libbpf debug log showing what's
going on with prog-array initialization:

libbpf: sec '.relsocket': collecting relocation for section(3) 'socket'
libbpf: sec '.relsocket': relo #0: insn #2 against 'prog_array_init'
libbpf: prog 'entry': found map 0 (prog_array_init, sec 4, off 0) for insn #0
libbpf: .maps relo #0: for 3 value 0 rel->r_offset 32 name 53 ('tailcall_1')
libbpf: .maps relo #0: map 'prog_array_init' slot [1] points to prog 'tailcall_1'
libbpf: map 'prog_array_init': created successfully, fd=5
libbpf: map 'prog_array_init': slot [1] set to prog 'tailcall_1' fd=6

  [0] Closes: https://github.com/libbpf/libbpf/issues/354Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211128141633.502339-2-hengqi.chen@gmail.com

Add the __NR_bpf definitions to fix the following build errors for mips:

  $ cd tools/bpf/bpftool
  $ make
  [...]
  bpf.c:54:4: error: #error __NR_bpf not defined. libbpf does not support your arch.
   #  error __NR_bpf not defined. libbpf does not support your arch.
      ^~~~~
  bpf.c: In function ‘sys_bpf’:
  bpf.c:66:17: error: ‘__NR_bpf’ undeclared (first use in this function); did you mean ‘__NR_brk’?
    return syscall(__NR_bpf, cmd, attr, size);
                   ^~~~~~~~
                   __NR_brk
  [...]
  In file included from gen_loader.c:15:0:
  skel_internal.h: In function ‘skel_sys_bpf’:
  skel_internal.h:53:17: error: ‘__NR_bpf’ undeclared (first use in this function); did you mean ‘__NR_brk’?
    return syscall(__NR_bpf, cmd, attr, size);
                   ^~~~~~~~
                   __NR_brk

We can see the following generated definitions:

  $ grep -r "#define __NR_bpf" arch/mips
  arch/mips/include/generated/uapi/asm/unistd_o32.h:#define __NR_bpf (__NR_Linux + 355)
  arch/mips/include/generated/uapi/asm/unistd_n64.h:#define __NR_bpf (__NR_Linux + 315)
  arch/mips/include/generated/uapi/asm/unistd_n32.h:#define __NR_bpf (__NR_Linux + 319)

The __NR_Linux is defined in arch/mips/include/uapi/asm/unistd.h:

  $ grep -r "#define __NR_Linux" arch/mips
  arch/mips/include/uapi/asm/unistd.h:#define __NR_Linux	4000
  arch/mips/include/uapi/asm/unistd.h:#define __NR_Linux	5000
  arch/mips/include/uapi/asm/unistd.h:#define __NR_Linux	6000

That is to say, __NR_bpf is:

  4000 + 355 = 4355 for mips o32,
  6000 + 319 = 6319 for mips n32,
  5000 + 315 = 5315 for mips n64.

So use the GCC pre-defined macro _ABIO32, _ABIN32 and _ABI64 [1] to define
the corresponding __NR_bpf.

This patch is similar with commit bad1926d ("bpf, s390: fix build for
libbpf and selftest suite").

  [1] https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/mips/mips.h#l549Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/1637804167-8323-1-git-send-email-yangtiezhu@loongson.cn

Similar to previous patch, just copy over necessary struct into local
stack variable before checking its fields.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-14-andrii@kernel.org

Construct packet buffer explicitly for each packet to avoid unaligned
memory accesses.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-13-andrii@kernel.org

Buf can be not zero-terminated leading to strstr() to access data beyond
the intended buf[] array. Fix by forcing zero termination.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-12-andrii@kernel.org

Copy over iphdr into a local variable before accessing its fields.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-11-andrii@kernel.org

Perfbuf doesn't guarantee 8-byte alignment of the data like BPF ringbuf
does, so struct get_stack_trace_t can arrive not properly aligned for
subsequent u64 accesses. Easiest fix is to just copy data locally.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-10-andrii@kernel.org

Prevent sanitizer from complaining about passing NULL into memcpy(),
even if it happens with zero size.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-9-andrii@kernel.org

Test is using __int128 variable as unsigned and highest order bit can be
set to 1 after bit shift. Use unsigned __int128 explicitly and prevent
UBSan from complaining.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-8-andrii@kernel.org

add_dst_sec() can invalidate bpf_linker's section index making
dst_symtab pointer pointing into unallocated memory. Reinitialize
dst_symtab pointer on each iteration to make sure it's always valid.

Fixes: faf6ed32 ("libbpf: Add BPF static linker APIs")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-7-andrii@kernel.org

glob_syms array wasn't freed on bpf_link__free(). Fix that.

Fixes: a4634922 ("libbpf: Add linker extern resolution support for functions and global variables")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-6-andrii@kernel.org

Sanitizer complains about qsort(), bsearch(), and memcpy() being called
with NULL pointer. This can only happen when the associated number of
elements is zero, so no harm should be done. But still prevent this from
happening to keep sanitizer runs clean from extra noise.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-5-andrii@kernel.org

Perform a memory copy before we do the sanity checks of btf_ext_hdr.
This prevents misaligned memory access if raw btf_ext data is not 4-byte
aligned ([0]).

While at it, also add missing const qualifier.

  [0] Closes: https://github.com/libbpf/libbpf/issues/391

Fixes: 2993e051 ("tools/bpf: add support to read .BTF.ext sections")
Reported-by: Evgeny Vereshchagin <evvers@ya.ru>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-3-andrii@kernel.org

Fix one case where we don't do explicit clean up.

Fixes: fbbb68de ("bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-2-andrii@kernel.org

Conversion is straightforward for most cases. In few cases tests are
using mutable map_flags and attribute structs, but bpf_map_create_opts
can be used in the similar fashion, so there were no problems. Just lots
of repetitive conversions.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124193233.3115996-5-andrii@kernel.org

xsk.c is using own APIs that are marked for deprecation internally.
Given xsk.c and xsk.h will be gone in libbpf 1.0, there is no reason to
do public vs internal function split just to avoid deprecation warnings.
So just add a pragma to silence deprecation warnings (until the code is
removed completely).
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124193233.3115996-4-andrii@kernel.org

Remove all the remaining uses of to-be-deprecated bpf_create_map*() APIs.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124193233.3115996-3-andrii@kernel.org

Mark the entire zoo of low-level map creation APIs for deprecation in
libbpf 0.7 ([0]) and introduce a new bpf_map_create() API that is
OPTS-based (and thus future-proof) and matches the BPF_MAP_CREATE
command name.

While at it, ensure that gen_loader sends map_extra field. Also remove
now unneeded btf_key_type_id/btf_value_type_id logic that libbpf is
doing anyways.

  [0] Closes: https://github.com/libbpf/libbpf/issues/282Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124193233.3115996-2-andrii@kernel.org

Add selftest that combines two BPF programs within single BPF object
file such that one of the programs is using global variables, but can be
skipped at runtime on old kernels that don't support global data.
Another BPF program is written with the goal to be runnable on very old
kernels and only relies on explicitly accessed BPF maps.

Such test, run against old kernels (e.g., libbpf CI will run it against 4.9
kernel that doesn't support global data), allows to test the approach
and ensure that libbpf doesn't make unnecessary assumption about
necessary kernel features.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211123200105.387855-2-andrii@kernel.org

Load global data maps lazily, if kernel is too old to support global
data. Make sure that programs are still correct by detecting if any of
the to-be-loaded programs have relocation against any of such maps.

This allows to solve the issue ([0]) with bpf_printk() and Clang
generating unnecessary and unreferenced .rodata.strX.Y sections, but it
also goes further along the CO-RE lines, allowing to have a BPF object
in which some code can work on very old kernels and relies only on BPF
maps explicitly, while other BPF programs might enjoy global variable
support. If such programs are correctly set to not load at runtime on
old kernels, bpf_object will load and function correctly now.

  [0] https://lore.kernel.org/bpf/CAK-59YFPU3qO+_pXWOH+c1LSA=8WA1yabJZfREjOEXNHAqgXNg@mail.gmail.com/

Fixes: aed65917 ("libbpf: Support multiple .rodata.* and .data.* BPF maps")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211123200105.387855-1-andrii@kernel.org

Fix trivial typo in comment from 'oveflow' to 'overflow'.
Reported-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211122070528.837806-1-dfustini@baylibre.com

bpf_program__set_extra_flags has just been introduced so we can still
change it without breaking users.

This new interface is a bit more flexible (for example if someone wants
to clear a flag).
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211119180035.1396139-1-revest@chromium.org

Add an artificial minimal example simulating compilers producing two
different types within a single CU that correspond to identical struct
definitions.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211117194114.347675-2-andrii@kernel.org

According to [0], compilers sometimes might produce duplicate DWARF
definitions for exactly the same struct/union within the same
compilation unit (CU). We've had similar issues with identical arrays
and handled them with a similar workaround in 6b6e6b1d ("libbpf:
Accomodate DWARF/compiler bug with duplicated identical arrays"). Do the
same for struct/union by ensuring that two structs/unions are exactly
the same, down to the integer values of field referenced type IDs.

Solving this more generically (allowing referenced types to be
equivalent, but using different type IDs, all within a single CU)
requires a huge complexity increase to handle many-to-many mappings
between canonidal and candidate type graphs. Before we invest in that,
let's see if this approach handles all the instances of this issue in
practice. Thankfully it's pretty rare, it seems.

  [0] https://lore.kernel.org/bpf/YXr2NFlJTAhHdZqq@krava/Reported-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211117194114.347675-1-andrii@kernel.org

Libbpf provided LIBBPF_MAJOR_VERSION and LIBBPF_MINOR_VERSION macros to
check libbpf version at compilation time. This doesn't cover all the
needs, though, because version of libbpf that application is compiled
against doesn't necessarily match the version of libbpf at runtime,
especially if libbpf is used as a shared library.

Add libbpf_major_version() and libbpf_minor_version() returning major
and minor versions, respectively, as integers. Also add a convenience
libbpf_version_string() for various tooling using libbpf to print out
libbpf version in a human-readable form. Currently it will return
"v0.6", but in the future it can contains some extra information, so the
format itself is not part of a stable API and shouldn't be relied upon.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20211118174054.2699477-1-andrii@kernel.org

[1] added s390 support to libbpf CI and added an ${ARCH} prefix to a
number of paths and identifiers in libbpf GitHub repo, which vmtest.sh
relies upon. Update these and make use of the new s390 support.

[1] https://github.com/libbpf/libbpf/pull/204Co-developed-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211118115225.1349726-1-iii@linux.ibm.com