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Arnaldo Carvalho de Melo 979e9c9fc9 perf annotate bpf: Don't enclose non-debug code with an assert() 
In 616b14b47a ("perf build: Conditionally define NDEBUG") we
started using NDEBUG=1 when DEBUG=1 isn't present, so code that is
enclosed with assert() is not called.

In dd317df072 ("perf build: Make binutil libraries opt in") we
stopped linking against binutils-devel, for licensing reasons.

Recently people asked me why annotation of BPF programs wasn't working,
i.e. this:

  $ perf annotate bpf_prog_5280546344e3f45c_kfree_skb

was returning:

  case SYMBOL_ANNOTATE_ERRNO__NO_LIBOPCODES_FOR_BPF:
     scnprintf(buf, buflen, "Please link with binutils's libopcode to enable BPF annotation");

This was on a fedora rpm, so its new enough that I had to try to test by
rebuilding using BUILD_NONDISTRO=1, only to get it segfaulting on me.

This combination made this libopcode function not to be called:

        assert(bfd_check_format(bfdf, bfd_object));

Changing it to:

	if (!bfd_check_format(bfdf, bfd_object))
		abort();

Made it work, looking at this "check" function made me realize it
changes the 'bfdf' internal state, i.e. we better call it.

So stop using assert() on it, just call it and abort if it fails.

Probably it is better to propagate the error, etc, but it seems it is
unlikely to fail from the usage done so far and we really need to stop
using libopcodes, so do the quick fix above and move on.

With it we have BPF annotation back working when built with
BUILD_NONDISTRO=1:

  ⬢[acme@toolbox perf-tools-next]$ perf annotate --stdio2 bpf_prog_5280546344e3f45c_kfree_skb   | head
  No kallsyms or vmlinux with build-id 939bc71a1a51cdc434e60af93c7e734f7d5c0e7e was found
  Samples: 12  of event 'cpu-clock:ppp', 4000 Hz, Event count (approx.): 3000000, [percent: local period]
  bpf_prog_5280546344e3f45c_kfree_skb() bpf_prog_5280546344e3f45c_kfree_skb
  Percent      int kfree_skb(struct trace_event_raw_kfree_skb *args) {
                 nop
   33.33         xchg   %ax,%ax
                 push   %rbp
                 mov    %rsp,%rbp
                 sub    $0x180,%rsp
                 push   %rbx
                 push   %r13
  ⬢[acme@toolbox perf-tools-next]$

Fixes: 6987561c9e ("perf annotate: Enable annotation of BPF programs")
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mohamed Mahmoud <mmahmoud@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Dave Tucker <datucker@redhat.com>
Cc: Derek Barbosa <debarbos@redhat.com>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/lkml/ZMrMzoQBe0yqMek1@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
History 2023-08-03 17:01:28 -03:00
arch Xtensa fixes for v6.5: 2023-07-16 14:12:49 -07:00
block SCSI fixes on 20230714 2023-07-14 19:57:29 -07:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: algif_hash - Fix race between MORE and non-MORE sends 2023-07-08 22:48:42 +10:00
Documentation perf docs: Update metric usage for Alibaba's T-Head PMU driver (arm64) 2023-07-28 19:01:17 -03:00
drivers tpm,tpm_tis: Disable interrupts after 1000 unhandled IRQs 2023-07-17 19:40:27 +00:00
fs Five smb3 client fixes 2023-07-16 12:49:05 -07:00
include - Remove a cgroup from under a polling process properly 2023-07-16 13:22:08 -07:00
init Kbuild updates for v6.5 2023-07-01 09:24:31 -07:00
io_uring io_uring-6.5-2023-07-14 2023-07-14 19:46:54 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel Seven hotfixes, six of which are cc:stable and one of which addresses a 2023-07-18 14:19:42 -07:00
lib Seven hotfixes, six of which are cc:stable and one of which addresses a 2023-07-18 14:19:42 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/mlock: fix vma iterator conversion of apply_vma_lock_flags() 2023-07-17 12:53:21 -07:00
net A fix to prevent a potential buffer overrun in the messenger, marked 2023-07-14 09:05:15 -07:00
rust rust: error: impl Debug for Error with errname() integration 2023-06-13 01:24:42 +02:00
samples arm64: ftrace: Add direct call trampoline samples support 2023-07-10 17:51:54 -04:00
scripts kallsyms: strip LTO-only suffixes from promoted global functions 2023-07-12 15:39:34 -07:00
security security: keys: Modify mismatched function name 2023-07-17 19:40:27 +00:00
sound sound fixes for 6.5-rc1 2023-07-07 15:40:17 -07:00
tools perf annotate bpf: Don't enclose non-debug code with an assert() 2023-08-03 17:01:28 -03:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM64: 2023-07-03 15:32:22 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Revert ".gitignore: ignore *.cover and *.mbx" 2023-07-04 15:05:12 -07:00
.mailmap spi: Fixes for v6.5 2023-07-15 08:51:02 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS - Address -Wmissing-prototype warnings 2023-06-26 16:43:54 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Add git information for perf-tools and perf-tools-next trees/branches 2023-07-20 11:30:53 -03:00
Makefile Linux 6.5-rc2 2023-07-16 15:10:37 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.