Tong Tiangen [Wed, 27 Oct 2021 11:18:22 +0000 (11:18 +0000)]
riscv, bpf: Add BPF exception tables
When a tracing BPF program attempts to read memory without using the
bpf_probe_read() helper, the verifier marks the load instruction with
the BPF_PROBE_MEM flag. Since the riscv JIT does not currently recognize
this flag it falls back to the interpreter.
Add support for BPF_PROBE_MEM, by appending an exception table to the
BPF program. If the load instruction causes a data abort, the fixup
infrastructure finds the exception table and fixes up the fault, by
clearing the destination register and jumping over the faulting
instruction.
A more generic solution would add a "handler" field to the table entry,
like on x86 and s390. The same issue in ARM64 is fixed in 800834285361
("bpf, arm64: Add BPF exception tables").
Several patches to improve parallel execution mode, updating vmtest.sh
and fixed two previously dropped patches according to feedback.
====================
Third patch replaces the u64 fields in struct bpf_prog_stats
with u64_stats_t ones to avoid possible sampling errors,
in case of load/store stearing.
====================
Joe Burton [Tue, 26 Oct 2021 22:35:28 +0000 (22:35 +0000)]
libbpf: Deprecate bpf_objects_list
Add a flag to `enum libbpf_strict_mode' to disable the global
`bpf_objects_list', preventing race conditions when concurrent threads
call bpf_object__open() or bpf_object__close().
bpf_object__next() will return NULL if this option is set.
Callers may achieve the same workflow by tracking bpf_objects in
application code.
Therefore, we cannot reliably use kallsyms_find_next() to find the end of
a function. Replace it with a simple guess (start + 128). This is good
enough for this test.
Song Liu [Tue, 26 Oct 2021 00:07:33 +0000 (17:07 -0700)]
selftests/bpf: Skip all serial_test_get_branch_snapshot in vm
Skipping the second half of the test is not enough to silent the warning
in dmesg. Skip the whole test before we can either properly silent the
warning in kernel, or fix LBR snapshot for VM.
v1: https://lore.kernel.org/bpf/20211021234653[email protected]/
v1 -> v2: Drop bpf_core_calc_field_relo() restructuring, split the
__BYTE_ORDER__ change (Andrii).
Hi,
this series fixes test failures in core_reloc on s390.
Patch 1 fixes an endianness bug with __BYTE_ORDER vs __BYTE_ORDER__.
Patches 2-5 make the rest of the code consistent in that respect.
Patch 6 fixes an endianness issue in test_core_reloc_mods.
Ilya Leoshkevich [Tue, 26 Oct 2021 01:08:26 +0000 (03:08 +0200)]
libbpf: Fix endianness detection in BPF_CORE_READ_BITFIELD_PROBED()
__BYTE_ORDER is supposed to be defined by a libc, and __BYTE_ORDER__ -
by a compiler. bpf_core_read.h checks __BYTE_ORDER == __LITTLE_ENDIAN,
which is true if neither are defined, leading to incorrect behavior on
big-endian hosts if libc headers are not included, which is often the
case.
Add libbpf APIs to access BPF program instructions. Both before and after
libbpf processing (before and after bpf_object__load()). This allows to
inspect what's going on with BPF program assembly instructions as libbpf
performs its processing magic.
But in more practical terms, this allows to do a no-brainer BPF program
cloning, which is something you need when working with fentry/fexit BPF
programs to be able to attach the same BPF program code to multiple kernel
functions. Currently, kernel needs multiple copies of BPF programs, each
loaded with its own target BTF ID. retsnoop is one such example that
previously had to rely on bpf_program__set_prep() API to hijack program
instructions ([0] for before and after).
Speaking of bpf_program__set_prep() API and the whole concept of
multiple-instance BPF programs in libbpf, all that is scheduled for
deprecation in v0.7. It doesn't work well, it's cumbersome, and it will become
more broken as libbpf adds more functionality. So deprecate and remove it in
libbpf 1.0. It doesn't seem to be used by anyone anyways (except for that
retsnoop hack, which is now much cleaner with new APIs as can be seen in [0]).
Andrii Nakryiko [Mon, 25 Oct 2021 22:45:31 +0000 (15:45 -0700)]
libbpf: Deprecate ambiguously-named bpf_program__size() API
The name of the API doesn't convey clearly that this size is in number
of bytes (there needed to be a separate comment to make this clear in
libbpf.h). Further, measuring the size of BPF program in bytes is not
exactly the best fit, because BPF programs always consist of 8-byte
instructions. As such, bpf_program__insn_cnt() is a better alternative
in pretty much any imaginable case.
So schedule bpf_program__size() deprecation starting from v0.7 and it
will be removed in libbpf 1.0.
Andrii Nakryiko [Mon, 25 Oct 2021 22:45:30 +0000 (15:45 -0700)]
libbpf: Deprecate multi-instance bpf_program APIs
Schedule deprecation of a set of APIs that are related to multi-instance
bpf_programs:
- bpf_program__set_prep() ([0]);
- bpf_program__{set,unset}_instance() ([1]);
- bpf_program__nth_fd().
These APIs are obscure, very niche, and don't seem to be used much in
practice. bpf_program__set_prep() is pretty useless for anything but the
simplest BPF programs, as it doesn't allow to adjust BPF program load
attributes, among other things. In short, it already bitrotted and will
bitrot some more if not removed.
With bpf_program__insns() API, which gives access to post-processed BPF
program instructions of any given entry-point BPF program, it's now
possible to do whatever necessary adjustments were possible with
set_prep() API before, but also more. Given any such use case is
automatically an advanced use case, requiring users to stick to
low-level bpf_prog_load() APIs and managing their own prog FDs is
reasonable.
Andrii Nakryiko [Mon, 25 Oct 2021 22:45:29 +0000 (15:45 -0700)]
libbpf: Add ability to fetch bpf_program's underlying instructions
Add APIs providing read-only access to bpf_program BPF instructions ([0]).
This is useful for diagnostics purposes, but it also allows a cleaner
support for cloning BPF programs after libbpf did all the FD resolution
and CO-RE relocations, subprog instructions appending, etc. Currently,
cloning BPF program is possible only through hijacking a half-broken
bpf_program__set_prep() API, which doesn't really work well for anything
but most primitive programs. For instance, set_prep() API doesn't allow
adjusting BPF program load parameters which are necessary for loading
fentry/fexit BPF programs (the case where BPF program cloning is
a necessity if doing some sort of mass-attachment functionality).
Given bpf_program__set_prep() API is set to be deprecated, having
a cleaner alternative is a must. libbpf internally already keeps track
of linear array of struct bpf_insn, so it's not hard to expose it. The
only gotcha is that libbpf previously freed instructions array during
bpf_object load time, which would make this API much less useful overall,
because in between bpf_object__open() and bpf_object__load() a lot of
changes to instructions are done by libbpf.
So this patch makes libbpf hold onto prog->insns array even after BPF
program loading. I think this is a small price for added functionality
and improved introspection of BPF program code.
See retsnoop PR ([1]) for how it can be used in practice and code
savings compared to relying on bpf_program__set_prep().
Andrii Nakryiko [Tue, 26 Oct 2021 00:31:39 +0000 (17:31 -0700)]
Merge branch 'bpftool: Switch to libbpf's hashmap for referencing BPF objects'
Quentin Monnet says:
====================
When listing BPF objects, bpftool can print a number of properties about
items holding references to these objects. For example, it can show pinned
paths for BPF programs, maps, and links; or programs and maps using a given
BTF object; or the names and PIDs of processes referencing BPF objects. To
collect this information, bpftool uses hash maps (to be clear: the data
structures, inside bpftool - we are not talking of BPF maps). It uses the
implementation available from the kernel, and picks it up from
tools/include/linux/hashtable.h.
This patchset converts bpftool's hash maps to a distinct implementation
instead, the one coming with libbpf. The main motivation for this change is
that it should ease the path towards a potential out-of-tree mirror for
bpftool, like the one libbpf already has. Although it's not perfect to
depend on libbpf's internal components, bpftool is intimately tied with the
library anyway, and this looks better than depending too much on (non-UAPI)
kernel headers.
The first two patches contain preparatory work on the Makefile and on the
initialisation of the hash maps for collecting pinned paths for objects.
Then the transition is split into several steps, one for each kind of
properties for which the collection is backed by hash maps.
v2:
- Move hashmap cleanup for pinned paths for links from do_detach() to
do_show().
- Handle errors on hashmap__append() (in three of the patches).
- Rename bpftool_hash_fn() and bpftool_equal_fn() as hash_fn_for_key_id()
and equal_fn_for_key_id(), respectively.
- Add curly braces for hashmap__for_each_key_entry() { } in
show_btf_plain() and show_btf_json(), where the flow was difficult to
read.
====================
Quentin Monnet [Sat, 23 Oct 2021 20:51:54 +0000 (21:51 +0100)]
bpftool: Switch to libbpf's hashmap for PIDs/names references
In order to show PIDs and names for processes holding references to BPF
programs, maps, links, or BTF objects, bpftool creates hash maps to
store all relevant information. This commit is part of a set that
transitions from the kernel's hash map implementation to the one coming
with libbpf.
The motivation is to make bpftool less dependent of kernel headers, to
ease the path to a potential out-of-tree mirror, like libbpf has.
This is the third and final step of the transition, in which we convert
the hash maps used for storing the information about the processes
holding references to BPF objects (programs, maps, links, BTF), and at
last we drop the inclusion of tools/include/linux/hashtable.h.
Note: Checkpatch complains about the use of __weak declarations, and the
missing empty lines after the bunch of empty function declarations when
compiling without the BPF skeletons (none of these were introduced in
this patch). We want to keep things as they are, and the reports should
be safe to ignore.
Quentin Monnet [Sat, 23 Oct 2021 20:51:53 +0000 (21:51 +0100)]
bpftool: Switch to libbpf's hashmap for programs/maps in BTF listing
In order to show BPF programs and maps using BTF objects when the latter
are being listed, bpftool creates hash maps to store all relevant items.
This commit is part of a set that transitions from the kernel's hash map
implementation to the one coming with libbpf.
The motivation is to make bpftool less dependent of kernel headers, to
ease the path to a potential out-of-tree mirror, like libbpf has.
This commit focuses on the two hash maps used by bpftool when listing
BTF objects to store references to programs and maps, and convert them
to the libbpf's implementation.
Quentin Monnet [Sat, 23 Oct 2021 20:51:52 +0000 (21:51 +0100)]
bpftool: Switch to libbpf's hashmap for pinned paths of BPF objects
In order to show pinned paths for BPF programs, maps, or links when
listing them with the "-f" option, bpftool creates hash maps to store
all relevant paths under the bpffs. So far, it would rely on the
kernel implementation (from tools/include/linux/hashtable.h).
We can make bpftool rely on libbpf's implementation instead. The
motivation is to make bpftool less dependent of kernel headers, to ease
the path to a potential out-of-tree mirror, like libbpf has.
This commit is the first step of the conversion: the hash maps for
pinned paths for programs, maps, and links are converted to libbpf's
hashmap.{c,h}. Other hash maps used for the PIDs of process holding
references to BPF objects are left unchanged for now. On the build side,
this requires adding a dependency to a second header internal to libbpf,
and making it a dependency for the bootstrap bpftool version as well.
The rest of the changes are a rather straightforward conversion.
Quentin Monnet [Sat, 23 Oct 2021 20:51:51 +0000 (21:51 +0100)]
bpftool: Do not expose and init hash maps for pinned path in main.c
BPF programs, maps, and links, can all be listed with their pinned paths
by bpftool, when the "-f" option is provided. To do so, bpftool builds
hash maps containing all pinned paths for each kind of objects.
These three hash maps are always initialised in main.c, and exposed
through main.h. There appear to be no particular reason to do so: we can
just as well make them static to the files that need them (prog.c,
map.c, and link.c respectively), and initialise them only when we want
to show objects and the "-f" switch is provided.
This may prevent unnecessary memory allocations if the implementation of
the hash maps was to change in the future.
Quentin Monnet [Sat, 23 Oct 2021 20:51:50 +0000 (21:51 +0100)]
bpftool: Remove Makefile dep. on $(LIBBPF) for $(LIBBPF_INTERNAL_HDRS)
The dependency is only useful to make sure that the $(LIBBPF_HDRS_DIR)
directory is created before we try to install locally the required
libbpf internal header. Let's create this directory properly instead.
This is in preparation of making $(LIBBPF_INTERNAL_HDRS) a dependency to
the bootstrap bpftool version, in which case we want no dependency on
$(LIBBPF).
Reduce amount of waiting time when running test_progs in parallel mode (-j) by
splitting bpf_verif_scale selftests into multiple tests. Previously it was
structured as a test with multiple subtests, but subtests are not easily
parallelizable with test_progs' infra. Also in practice each scale subtest is
really an independent test with nothing shared across all substest.
This patch set changes how test_progs test discovery works. Now it is possible
to define multiple tests within a single source code file. One of the patches
also marks tc_redirect selftests as serial, because it's extremely harmful to
the test system when run in parallel mode.
====================
Andrii Nakryiko [Fri, 22 Oct 2021 22:32:28 +0000 (15:32 -0700)]
selftests/bpf: Split out bpf_verif_scale selftests into multiple tests
Instead of using subtests in bpf_verif_scale selftest, turn each scale
sub-test into its own test. Each subtest is compltely independent and
just reuses a bit of common test running logic, so the conversion is
trivial. For convenience, keep all of BPF verifier scale tests in one
file.
This conversion shaves off a significant amount of time when running
test_progs in parallel mode. E.g., just running scale tests (-t verif_scale):
BEFORE
======
Summary: 24/0 PASSED, 0 SKIPPED, 0 FAILED
real 0m22.894s
user 0m0.012s
sys 0m22.797s
AFTER
=====
Summary: 24/0 PASSED, 0 SKIPPED, 0 FAILED
real 0m12.044s
user 0m0.024s
sys 0m27.869s
Ten second saving right there. test_progs -j is not yet ready to be
turned on by default, unfortunately, and some tests fail almost every
time, but this is a good improvement nevertheless. Ignoring few
failures, here is sequential vs parallel run times when running all
tests now:
Andrii Nakryiko [Fri, 22 Oct 2021 22:32:27 +0000 (15:32 -0700)]
selftests/bpf: Mark tc_redirect selftest as serial
It seems to cause a lot of harm to kprobe/tracepoint selftests. Yucong
mentioned before that it does manipulate sysfs, which might be the
reason. So let's mark it as serial, though ideally it would be less
intrusive on the system at test.
Andrii Nakryiko [Fri, 22 Oct 2021 22:32:26 +0000 (15:32 -0700)]
selftests/bpf: Support multiple tests per file
Revamp how test discovery works for test_progs and allow multiple test
entries per file. Any global void function with no arguments and
serial_test_ or test_ prefix is considered a test.
Andrii Nakryiko [Sat, 23 Oct 2021 00:31:57 +0000 (17:31 -0700)]
libbpf: Fix BTF header parsing checks
Original code assumed fixed and correct BTF header length. That's not
always the case, though, so fix this bug with a proper additional check.
And use actual header length instead of sizeof(struct btf_header) in
sanity checks.
Andrii Nakryiko [Sat, 23 Oct 2021 00:31:56 +0000 (17:31 -0700)]
libbpf: Fix overflow in BTF sanity checks
btf_header's str_off+str_len or type_off+type_len can overflow as they
are u32s. This will lead to bypassing the sanity checks during BTF
parsing, resulting in crashes afterwards. Fix by using 64-bit signed
integers for comparison.
Merge branch 'bpf: add support for BTF_KIND_DECL_TAG typedef'
Yonghong Song says:
====================
Latest upstream llvm-project added support for btf_decl_tag attributes
for typedef declarations ([1], [2]). Similar to other btf_decl_tag cases,
func/func_param/global_var/struct/union/field, btf_decl_tag with typedef
declaration can carry information from kernel source to clang compiler
and then to dwarf/BTF, for bpf verification or other use cases.
This patch set added kernel support for BTF_KIND_DECL_TAG to typedef
declaration (Patch 1). Additional selftests are added to cover
unit testing, dedup, or bpf program usage of btf_decl_tag with typedef.
(Patches 2, 3 and 4). The btf documentation is updated to include
BTF_KIND_DECL_TAG typedef (Patch 5).
Yonghong Song [Thu, 21 Oct 2021 19:56:43 +0000 (12:56 -0700)]
selftests/bpf: Add BTF_KIND_DECL_TAG typedef example in tag.c
Change value type in progs/tag.c to a typedef with a btf_decl_tag.
With `bpftool btf dump file tag.o`, we have
...
[14] TYPEDEF 'value_t' type_id=17
[15] DECL_TAG 'tag1' type_id=14 component_idx=-1
[16] DECL_TAG 'tag2' type_id=14 component_idx=-1
[17] STRUCT '(anon)' size=8 vlen=2
'a' type_id=2 bits_offset=0
'b' type_id=2 bits_offset=32
...
The btf_tag selftest also succeeded:
$ ./test_progs -t tag
#21 btf_tag:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
Yonghong Song [Thu, 21 Oct 2021 19:56:38 +0000 (12:56 -0700)]
selftests/bpf: Test deduplication for BTF_KIND_DECL_TAG typedef
Add unit tests for deduplication of BTF_KIND_DECL_TAG to typedef types.
Also changed a few comments from "tag" to "decl_tag" to match
BTF_KIND_DECL_TAG enum value name.
Andrii Nakryiko [Fri, 22 Oct 2021 23:50:56 +0000 (16:50 -0700)]
Merge branch 'libbpf: use func name when pinning programs with LIBBPF_STRICT_SEC_NAME'
Stanislav Fomichev says:
====================
Commit 15669e1dcd75 ("selftests/bpf: Normalize all the rest SEC() uses")
broke flow dissector tests. With the strict section names, bpftool isn't
able to pin all programs of the objects (all section names are the
same now). To bring it back to life let's do the following:
- teach libbpf to pin by func name with LIBBPF_STRICT_SEC_NAME
- enable strict mode in bpftool (breaking cli change)
- fix custom flow_dissector loader to use strict mode
- fix flow_dissector tests to use new pin names (func vs sec)
v5:
- get rid of error when retrying with '/' (Quentin Monnet)
v3:
- clarify program pinning in LIBBPF_STRICT_SEC_NAME,
for real this time (Andrii Nakryiko)
- fix possible segfault in __bpf_program__pin_name (Andrii Nakryiko)
Quentin Monnet [Fri, 22 Oct 2021 09:47:43 +0000 (10:47 +0100)]
bpftool: Avoid leaking the JSON writer prepared for program metadata
Bpftool creates a new JSON object for writing program metadata in plain
text mode, regardless of metadata being present or not. Then this writer
is freed if any metadata has been found and printed, but it leaks
otherwise. We cannot destroy the object unconditionally, because the
destructor prints an undesirable line break. Instead, make sure the
writer is created only after we have found program metadata to print.
Andrii Nakryiko [Fri, 22 Oct 2021 23:09:15 +0000 (16:09 -0700)]
Merge branch 'libbpf: Add btf__type_cnt() and btf__raw_data() APIs'
Hengqi Chen says:
====================
Add btf__type_cnt() and btf__raw_data() APIs and deprecate
btf__get_nr_type() and btf__get_raw_data() since the old APIs
don't follow libbpf naming convention. Also update tools/selftests
to use these new APIs. This is part of effort towards libbpf v1.0
v1->v2:
- Update commit message, deprecate the old APIs in libbpf v0.7 (Andrii)
- Separate changes in tools/ to individual patches (Andrii)
====================
Hengqi Chen [Fri, 22 Oct 2021 13:06:23 +0000 (21:06 +0800)]
selftests/bpf: Switch to new btf__type_cnt/btf__raw_data APIs
Replace the calls to btf__get_nr_types/btf__get_raw_data in
selftests with new APIs btf__type_cnt/btf__raw_data. The old
APIs will be deprecated in libbpf v0.7+.
Hengqi Chen [Fri, 22 Oct 2021 13:06:19 +0000 (21:06 +0800)]
libbpf: Add btf__type_cnt() and btf__raw_data() APIs
Add btf__type_cnt() and btf__raw_data() APIs and deprecate
btf__get_nr_type() and btf__get_raw_data() since the old APIs
don't follow the libbpf naming convention for getters which
omit 'get' in the name (see [0]). btf__raw_data() is just an
alias to the existing btf__get_raw_data(). btf__type_cnt()
now returns the number of all types of the BTF object
including 'void'.
Andrii Nakryiko [Fri, 22 Oct 2021 20:13:42 +0000 (13:13 -0700)]
selftests/bpf: Make perf_buffer selftests work on 4.9 kernel again
Recent change to use tp/syscalls/sys_enter_nanosleep for perf_buffer
selftests causes this selftest to fail on 4.9 kernel in libbpf CI ([0]):
libbpf: prog 'handle_sys_enter': failed to attach to perf_event FD 6: Invalid argument
libbpf: prog 'handle_sys_enter': failed to attach to tracepoint 'syscalls/sys_enter_nanosleep': Invalid argument
It's not exactly clear why, because perf_event itself is created for
this tracepoint, but I can't even compile 4.9 kernel locally, so it's
hard to figure this out. If anyone has better luck and would like to
help investigating this, I'd really appreciate this.
For now, unblock CI by switching back to raw_syscalls/sys_enter, but reduce
amount of unnecessary samples emitted by filter by process ID. Use
explicit ARRAY map for that to make it work on 4.9 as well, because
global data isn't yet supported there.
Andrii Nakryiko [Fri, 22 Oct 2021 19:25:02 +0000 (12:25 -0700)]
libbpf: Fix the use of aligned attribute
Building libbpf sources out of kernel tree (in Github repo) we run into
compilation error due to unknown __aligned attribute. It must be coming
from some kernel header, which is not available to Github sources. Use
explicit __attribute__((aligned(16))) instead.
Merge branch 'libbpf: support custom .rodata.*/.data.* sections'
Andrii Nakryiko says:
====================
This patch set refactors internals of libbpf to enable support for multiple
custom .rodata.* and .data.* sections. Each such section is backed by its own
BPF_MAP_TYPE_ARRAY, memory-mappable just like .rodata/.data. This is not
extended to .bss because .bss is not a great name, it is generated by compiler
with name that reflects completely irrelevant historical implementation
details. Given that users have to annotate their variables with
SEC(".data.my_sec") explicitly, standardizing on .rodata. and .data. prefixes
makes more sense and keeps things simpler.
Additionally, this patch set makes it simpler to work with those special
internal maps by allowing to look them up by their full ELF section name.
Patch #1 is a preparatory patch that deprecates one libbpf API and moves
custom logic into libbpf.c, where it's used. This code is later refactored
with the rest of libbpf.c logic to support multiple data section maps.
See individual patches for all the details.
For new custom "dot maps", their full ELF section names are used as the names
that are sent into the kernel. Object name isn't prepended like for
.data/.rodata/.bss. The reason is that with longer custom names, there isn't
much space left for object name anyways. Also, if BTF is supported,
btf_value_type_id points to DATASEC BTF type, which contains full original ELF
name of the section, so tools like bpftool could use that to recover full
name. This patch set doesn't add this logic yet, this is left for follow up
patches.
One interesting possibility that is now open by these changes is that it's
possible to do:
and it will work as expected. I haven't updated libbpf-provided helpers in
bpf_helpers.h for snprintf, seq_printf, and printk, because using
`static const char ___fmt[] = fmt;` trick is still efficient and doesn't fill
out the buffer at runtime (no copying). But we might consider updating them in
the future, especially with the array check that Kumar proposed (see [0]).
Andrii Nakryiko [Thu, 21 Oct 2021 01:44:04 +0000 (18:44 -0700)]
selftests/bpf: Switch to ".bss"/".rodata"/".data" lookups for internal maps
Utilize libbpf's feature of allowing to lookup internal maps by their
ELF section names. No need to guess or calculate the exact truncated
prefix taken from the object name.
Andrii Nakryiko [Thu, 21 Oct 2021 01:44:03 +0000 (18:44 -0700)]
libbpf: Simplify look up by name of internal maps
Map name that's assigned to internal maps (.rodata, .data, .bss, etc)
consist of a small prefix of bpf_object's name and ELF section name as
a suffix. This makes it hard for users to "guess" the name to use for
looking up by name with bpf_object__find_map_by_name() API.
One proposal was to drop object name prefix from the map name and just
use ".rodata", ".data", etc, names. One downside called out was that
when multiple BPF applications are active on the host, it will be hard
to distinguish between multiple instances of .rodata and know which BPF
object (app) they belong to. Having few first characters, while quite
limiting, still can give a bit of a clue, in general.
Note, though, that btf_value_type_id for such global data maps (ARRAY)
points to DATASEC type, which encodes full ELF name, so tools like
bpftool can take advantage of this fact to "recover" full original name
of the map. This is also the reason why for custom .data.* and .rodata.*
maps libbpf uses only their ELF names and doesn't prepend object name at
all.
Another downside of such approach is that it is not backwards compatible
and, among direct use of bpf_object__find_map_by_name() API, will break
any BPF skeleton generated using bpftool that was compiled with older
libbpf version.
Instead of causing all this pain, libbpf will still generate map name
using a combination of object name and ELF section name, but it will
allow looking such maps up by their natural names, which correspond to
their respective ELF section names. This means non-truncated ELF section
names longer than 15 characters are going to be expected and supported.
With such set up, we get the best of both worlds: leave small bits of
a clue about BPF application that instantiated such maps, as well as
making it easy for user apps to lookup such maps at runtime. In this
sense it closes corresponding libbpf 1.0 issue ([0]).
BPF skeletons will continue using full names for lookups.
Andrii Nakryiko [Thu, 21 Oct 2021 01:44:01 +0000 (18:44 -0700)]
libbpf: Support multiple .rodata.* and .data.* BPF maps
Add support for having multiple .rodata and .data data sections ([0]).
.rodata/.data are supported like the usual, but now also
.rodata.<whatever> and .data.<whatever> are also supported. Each such
section will get its own backing BPF_MAP_TYPE_ARRAY, just like
.rodata and .data.
Multiple .bss maps are not supported, as the whole '.bss' name is
confusing and might be deprecated soon, as well as user would need to
specify custom ELF section with SEC() attribute anyway, so might as well
stick to just .data.* and .rodata.* convention.
User-visible map name for such new maps is going to be just their ELF
section names.
Andrii Nakryiko [Thu, 21 Oct 2021 01:44:00 +0000 (18:44 -0700)]
bpftool: Improve skeleton generation for data maps without DATASEC type
It can happen that some data sections (e.g., .rodata.cst16, containing
compiler populated string constants) won't have a corresponding BTF
DATASEC type. Now that libbpf supports .rodata.* and .data.* sections,
situation like that will cause invalid BPF skeleton to be generated that
won't compile successfully, as some parts of skeleton would assume
memory-mapped struct definitions for each special data section.
Fix this by generating empty struct definitions for such data sections.
Andrii Nakryiko [Thu, 21 Oct 2021 01:43:59 +0000 (18:43 -0700)]
bpftool: Support multiple .rodata/.data internal maps in skeleton
Remove the assumption about only single instance of each of .rodata and
.data internal maps. Nothing changes for '.rodata' and '.data' maps, but new
'.rodata.something' map will get 'rodata_something' section in BPF
skeleton for them (as well as having struct bpf_map * field in maps
section with the same field name).
Andrii Nakryiko [Thu, 21 Oct 2021 01:43:58 +0000 (18:43 -0700)]
libbpf: Remove assumptions about uniqueness of .rodata/.data/.bss maps
Remove internal libbpf assumption that there can be only one .rodata,
.data, and .bss map per BPF object. To achieve that, extend and
generalize the scheme that was used for keeping track of relocation ELF
sections. Now each ELF section has a temporary extra index that keeps
track of logical type of ELF section (relocations, data, read-only data,
BSS). Switch relocation to this scheme, as well as .rodata/.data/.bss
handling.
We don't yet allow multiple .rodata, .data, and .bss sections, but no
libbpf internal code makes an assumption that there can be only one of
each and thus they can be explicitly referenced by a single index. Next
patches will actually allow multiple .rodata and .data sections.
Andrii Nakryiko [Thu, 21 Oct 2021 01:43:57 +0000 (18:43 -0700)]
libbpf: Use Elf64-specific types explicitly for dealing with ELF
Minimize the usage of class-agnostic gelf_xxx() APIs from libelf. These
APIs require copying ELF data structures into local GElf_xxx structs and
have a more cumbersome API. BPF ELF file is defined to be always 64-bit
ELF object, even when intended to be run on 32-bit host architectures,
so there is no need to do class-agnostic conversions everywhere. BPF
static linker implementation within libbpf has been using Elf64-specific
types since initial implementation.
Add two simple helpers, elf_sym_by_idx() and elf_rel_by_idx(), for more
succinct direct access to ELF symbol and relocation records within ELF
data itself and switch all the GElf_xxx usage into Elf64_xxx
equivalents. The only remaining place within libbpf.c that's still using
gelf API is gelf_getclass(), as there doesn't seem to be a direct way to
get underlying ELF bitness.
Andrii Nakryiko [Thu, 21 Oct 2021 01:43:55 +0000 (18:43 -0700)]
libbpf: Deprecate btf__finalize_data() and move it into libbpf.c
There isn't a good use case where anyone but libbpf itself needs to call
btf__finalize_data(). It was implemented for internal use and it's not
clear why it was made into public API in the first place. To function, it
requires active ELF data, which is stored inside bpf_object for the
duration of opening phase only. But the only BTF that needs bpf_object's
ELF is that bpf_object's BTF itself, which libbpf fixes up automatically
during bpf_object__open() operation anyways. There is no need for any
additional fix up and no reasonable scenario where it's useful and
appropriate.
Thus, btf__finalize_data() is just an API atavism and is better removed.
So this patch marks it as deprecated immediately (v0.6+) and moves the
code from btf.c into libbpf.c where it's used in the context of
bpf_object opening phase. Such code co-location allows to make code
structure more straightforward and remove bpf_object__section_size() and
bpf_object__variable_offset() internal helpers from libbpf_internal.h,
making them static. Their naming is also adjusted to not create
a wrong illusion that they are some sort of method of bpf_object. They
are internal helpers and are called appropriately.
Jiri Olsa [Thu, 21 Oct 2021 11:41:32 +0000 (13:41 +0200)]
selftests/bpf: Use nanosleep tracepoint in perf buffer test
The perf buffer tests triggers trace with nanosleep syscall,
but monitors all syscalls, which results in lot of data in the
buffer and makes it harder to debug. Let's lower the trace
traffic and monitor just nanosleep syscall.
If the offline cpu is from the middle of the possible set,
we get mismatch with possible and online cpu buffers.
The perf buffer test calls perf_buffer__consume_buffer for
all 'possible' cpus, but the library holds only 'online'
cpu buffers and perf_buffer__consume_buffer returns them
based on index.
Adding extra (online) index to keep track of online buffers,
we need the original (possible) index to trigger trace on
proper cpu.
Andrii Nakryiko [Thu, 21 Oct 2021 22:51:48 +0000 (15:51 -0700)]
Merge branch 'bpf: keep track of verifier insn_processed'
Dave Marchevsky says:
====================
This is a followup to discussion around RFC patchset "bpf: keep track of
prog verification stats" [0]. The RFC elaborates on my usecase, but to
summarize: keeping track of verifier stats for programs as they - and
the kernels they run on - change over time can help developers of
individual programs and BPF kernel folks.
The RFC added a verif_stats to the uapi which contained most of the info
which verifier prints currently. Feedback here was to avoid polluting
uapi with stats that might be meaningless after major changes to the
verifier, but that insn_processed or conceptually similar number would
exist in the long term and was safe to expose.
So let's expose just insn_processed via bpf_prog_info and fdinfo for now
and explore good ways of getting more complicated stats in the future.
v2->v3:
* Remove unnecessary check in patch 2's test [Andrii]
* Go back to adding new u32 in bpf_prog_info (vs using spare bits) [Andrii]
* Rebase + add acks [Andrii, John]
v1->v2:
* Rename uapi field from insn_processed to verified_insns [Daniel]
* use 31 bits of existing bitfield space in bpf_prog_info [Daniel]
* change underlying type from 64-> 32 bits [Daniel]
====================
Dave Marchevsky [Wed, 20 Oct 2021 07:48:18 +0000 (00:48 -0700)]
selftests/bpf: Add verif_stats test
verified_insns field was added to response of bpf_obj_get_info_by_fd
call on a prog. Confirm that it's being populated by loading a simple
program and asking for its info.
Dave Marchevsky [Wed, 20 Oct 2021 07:48:17 +0000 (00:48 -0700)]
bpf: Add verified_insns to bpf_prog_info and fdinfo
This stat is currently printed in the verifier log and not stored
anywhere. To ease consumption of this data, add a field to bpf_prog_aux
so it can be exposed via BPF_OBJ_GET_INFO_BY_FD and fdinfo.
Ilya Leoshkevich [Thu, 21 Oct 2021 10:46:58 +0000 (12:46 +0200)]
libbpf: Fix ptr_is_aligned() usages
Currently ptr_is_aligned() takes size, and not alignment, as a
parameter, which may be overly pessimistic e.g. for __i128 on s390,
which must be only 8-byte aligned. Fix by using btf__align_of().
Pu Lehui [Thu, 21 Oct 2021 12:39:13 +0000 (20:39 +0800)]
samples: bpf: Suppress readelf stderr when probing for BTF support
When compiling bpf samples, the following warning appears:
readelf: Error: Missing knowledge of 32-bit reloc types used in DWARF
sections of machine number 247
readelf: Warning: unable to apply unsupported reloc type 10 to section
.debug_info
readelf: Warning: unable to apply unsupported reloc type 1 to section
.debug_info
readelf: Warning: unable to apply unsupported reloc type 10 to section
.debug_info
Same problem was mentioned in commit 2f0921262ba9 ("selftests/bpf:
suppress readelf stderr when probing for BTF support"), let's use
readelf that supports btf.
Ilya Leoshkevich [Wed, 13 Oct 2021 16:09:01 +0000 (18:09 +0200)]
libbpf: Fix dumping non-aligned __int128
Non-aligned integers are dumped as bitfields, which is supported for at
most 64-bit integers. Fix by using the same trick as
btf_dump_float_data(): copy non-aligned values to the local buffer.
Ilya Leoshkevich [Wed, 13 Oct 2021 16:09:00 +0000 (18:09 +0200)]
libbpf: Fix dumping big-endian bitfields
On big-endian arches not only bytes, but also bits are numbered in
reverse order (see e.g. S/390 ELF ABI Supplement, but this is also true
for other big-endian arches as well).
Ilya Leoshkevich [Wed, 13 Oct 2021 16:08:59 +0000 (18:08 +0200)]
selftests/bpf: Use cpu_number only on arches that have it
cpu_number exists only on Intel and aarch64, so skip the test involing
it on other arches. An alternative would be to replace it with an
exported non-ifdefed primitive-typed percpu variable from the common
code, but there appears to be none.
Quentin Monnet [Wed, 20 Oct 2021 09:48:26 +0000 (10:48 +0100)]
bpftool: Remove useless #include to <perf-sys.h> from map_perf_ring.c
The header is no longer needed since the event_pipe implementation
was updated to rely on libbpf's perf_buffer. This makes bpftool free of
dependencies to perf files, and we can update the Makefile accordingly.
Wan Jiabing [Tue, 12 Oct 2021 02:32:30 +0000 (10:32 +0800)]
selftests/bpf: Remove duplicated include in cgroup_helpers
Fix following checkincludes.pl warning:
./scripts/checkincludes.pl tools/testing/selftests/bpf/cgroup_helpers.c
tools/testing/selftests/bpf/cgroup_helpers.c: unistd.h is included more
than once.
Quentin Monnet [Wed, 20 Oct 2021 09:46:47 +0000 (10:46 +0100)]
bpf/preload: Clean up .gitignore and "clean-files" target
kernel/bpf/preload/Makefile was recently updated to have it install
libbpf's headers locally instead of pulling them from tools/lib/bpf. But
two items still need to be addressed.
First, the local .gitignore file was not adjusted to ignore the files
generated in the new kernel/bpf/preload/libbpf output directory.
Second, the "clean-files" target is now incorrect. The old artefacts
names were not removed from the target, while the new ones were added
incorrectly. This is because "clean-files" expects names relative to
$(obj), but we passed the absolute path instead. This results in the
output and header-destination directories for libbpf (and their
contents) not being removed from kernel/bpf/preload on "make clean" from
the root of the repository.
This commit fixes both issues. Note that $(userprogs) needs not be added
to "clean-files", because the cleaning infrastructure already accounts
for it.
Cleaning the files properly also prevents make from printing the
following message, for builds coming after a "make clean":
"make[4]: Nothing to be done for 'install_headers'."
bpf: Silence Coverity warning for find_kfunc_desc_btf
The helper function returns a pointer that in the failure case encodes
an error in the struct btf pointer. The current code lead to Coverity
warning about the use of the invalid pointer:
Daniel suggested the use of ERR_CAST so that the intended use is clear
to Coverity, but on closer look it seems that we never return NULL from
the helper. Andrii noted that since __find_kfunc_desc_btf already logs
errors for all cases except btf_get_by_fd, it is much easier to add
logging for that and remove the IS_ERR check altogether, returning
directly from it.
Andrii Nakryiko [Tue, 19 Oct 2021 23:38:16 +0000 (16:38 -0700)]
Merge branch 'fixes for bpftool's Makefile'
Quentin Monnet says:
====================
This set contains one fix for bpftool's Makefile, to make sure that the
headers internal to libbpf are installed properly even if we add more
headers to the relevant Makefile variable in the future (although we'd like
to avoid that if possible).
The other patches aim at cleaning up the output from the Makefile, in
particular when running the command "make" another time after bpftool is
built.
====================
Quentin Monnet [Sat, 9 Oct 2021 21:03:41 +0000 (22:03 +0100)]
bpftool: Turn check on zlib from a phony target into a conditional error
One of bpftool's object files depends on zlib. To make sure we do not
attempt to build that object when the library is not available, commit d66fa3c70e59 ("tools: bpftool: add feature check for zlib") introduced a
feature check to detect whether zlib is present.
This check comes as a rule for which the target ("zdep") is a
nonexistent file (phony target), which means that the Makefile always
attempts to rebuild it. It is mostly harmless. However, one side effect
is that, on running again once bpftool is already built, make considers
that "something" (the recipe for zdep) was executed, and does not print
the usual message "make: Nothing to be done for 'all'", which is a
user-friendly indicator that the build went fine.
Before, with some level of debugging information:
$ make --debug=m
[...]
Reading makefiles...
Auto-detecting system features:
... libbfd: [ on ]
... disassembler-four-args: [ on ]
... zlib: [ on ]
... libcap: [ on ]
... clang-bpf-co-re: [ on ]
Updating makefiles....
Updating goal targets....
File 'all' does not exist.
File 'zdep' does not exist.
Must remake target 'zdep'.
File 'all' does not exist.
Must remake target 'all'.
Successfully remade target file 'all'.
After the patch:
$ make --debug=m
[...]
Auto-detecting system features:
... libbfd: [ on ]
... disassembler-four-args: [ on ]
... zlib: [ on ]
... libcap: [ on ]
... clang-bpf-co-re: [ on ]
Updating makefiles....
Updating goal targets....
File 'all' does not exist.
Must remake target 'all'.
Successfully remade target file 'all'.
make: Nothing to be done for 'all'.
(Note the last line, which is not part of make's debug information.)
Quentin Monnet [Sat, 9 Oct 2021 21:03:40 +0000 (22:03 +0100)]
bpftool: Do not FORCE-build libbpf
In bpftool's Makefile, libbpf has a FORCE dependency, to make sure we
rebuild it in case its source files changed. Let's instead make the
rebuild depend on the source files directly, through a call to the
"$(wildcard ...)" function. This avoids descending into libbpf's
directory if there is nothing to update.
Do the same for the bootstrap libbpf version.
This results in a slightly faster operation and less verbose output when
running make a second time in bpftool's directory.
Before:
Auto-detecting system features:
... libbfd: [ on ]
... disassembler-four-args: [ on ]
... zlib: [ on ]
... libcap: [ on ]
... clang-bpf-co-re: [ on ]
make[1]: Entering directory '/root/dev/linux/tools/lib/bpf'
make[1]: Entering directory '/root/dev/linux/tools/lib/bpf'
make[1]: Nothing to be done for 'install_headers'.
make[1]: Leaving directory '/root/dev/linux/tools/lib/bpf'
make[1]: Leaving directory '/root/dev/linux/tools/lib/bpf'
After:
Auto-detecting system features:
... libbfd: [ on ]
... disassembler-four-args: [ on ]
... zlib: [ on ]
... libcap: [ on ]
... clang-bpf-co-re: [ on ]
Other ways to clean up the output could be to pass the "-s" option, or
to redirect the output to >/dev/null, when calling make recursively to
descend into libbpf's directory. However, this would suppress some
useful output if something goes wrong during the build. A better
alternative would be to pass "--no-print-directory" to the recursive
make, but that would still leave us with some noise for
"install_headers". Skipping the descent into libbpf's directory if no
source file has changed works best, and seems the most logical option
overall.
Quentin Monnet [Sat, 9 Oct 2021 21:03:39 +0000 (22:03 +0100)]
bpftool: Fix install for libbpf's internal header(s)
We recently updated bpftool's Makefile to make it install the headers
from libbpf, instead of pulling them directly from libbpf's directory.
There is also an additional header, internal to libbpf, that needs be
installed. The way that bpftool's Makefile installs that particular
header is currently correct, but would break if we were to modify
$(LIBBPF_INTERNAL_HDRS) to make it point to more than one header.
Use a static pattern rule instead, so that the Makefile can withstand
the addition of other headers to install.
The objective is simply to make the Makefile more robust. It should
_not_ be read as an invitation to import more internal headers from
libbpf into bpftool.
Quentin Monnet [Sun, 10 Oct 2021 00:25:28 +0000 (01:25 +0100)]
libbpf: Remove Makefile warnings on out-of-sync netlink.h/if_link.h
Although relying on some definitions from the netlink.h and if_link.h
headers copied into tools/include/uapi/linux/, libbpf does not need
those headers to stay entirely up-to-date with their original versions,
and the warnings emitted by the Makefile when it detects a difference
are usually just noise. Let's remove those warnings.
Yonghong Song [Tue, 12 Oct 2021 16:48:38 +0000 (09:48 -0700)]
bpf: Rename BTF_KIND_TAG to BTF_KIND_DECL_TAG
Patch set [1] introduced BTF_KIND_TAG to allow tagging
declarations for struct/union, struct/union field, var, func
and func arguments and these tags will be encoded into
dwarf. They are also encoded to btf by llvm for the bpf target.
After BTF_KIND_TAG is introduced, we intended to use it
for kernel __user attributes. But kernel __user is actually
a type attribute. Upstream and internal discussion showed
it is not a good idea to mix declaration attribute and
type attribute. So we proposed to introduce btf_type_tag
as a type attribute and existing btf_tag renamed to
btf_decl_tag ([2]).
This patch renamed BTF_KIND_TAG to BTF_KIND_DECL_TAG and some
other declarations with *_tag to *_decl_tag to make it clear
the tag is for declaration. In the future, BTF_KIND_TYPE_TAG
might be introduced per [3].
Fixes: b5ea834dde6b ("bpf: Support for new btf kind BTF_KIND_TAG") Fixes: 5b84bd10363e ("libbpf: Add support for BTF_KIND_TAG") Fixes: 5c07f2fec003 ("bpftool: Add support for BTF_KIND_TAG") Signed-off-by: Yonghong Song <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
selftests/bpf: Skip verifier tests that fail to load with ENOTSUPP
The verifier tests added in commit c48e51c8b07a ("bpf: selftests: Add
selftests for module kfunc support") fail on s390, since the JIT does
not support calling kernel functions. This is most likely an issue for
all the other non-Intel arches, as well as on Intel with
!CONFIG_DEBUG_INFO_BTF or !CONFIG_BPF_JIT.
Trying to check for messages from all the possible add_kfunc_call()
failure cases in test_verifier looks pointless, so do a much simpler
thing instead: just like it's already done in do_prog_test_run(), skip
the tests that fail to load with ENOTSUPP.
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