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7bdcedd5c8
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Tony Ambardar 7bdcedd5c8 bpf: Harden __bpf_kfunc tag against linker kfunc removal 
BPF kfuncs are often not directly referenced and may be inadvertently
removed by optimization steps during kernel builds, thus the __bpf_kfunc
tag mitigates against this removal by including the __used macro. However,
this macro alone does not prevent removal during linking, and may still
yield build warnings (e.g. on mips64el):

  [...]
    LD      vmlinux
    BTFIDS  vmlinux
  WARN: resolve_btfids: unresolved symbol bpf_verify_pkcs7_signature
  WARN: resolve_btfids: unresolved symbol bpf_lookup_user_key
  WARN: resolve_btfids: unresolved symbol bpf_lookup_system_key
  WARN: resolve_btfids: unresolved symbol bpf_key_put
  WARN: resolve_btfids: unresolved symbol bpf_iter_task_next
  WARN: resolve_btfids: unresolved symbol bpf_iter_css_task_new
  WARN: resolve_btfids: unresolved symbol bpf_get_file_xattr
  WARN: resolve_btfids: unresolved symbol bpf_ct_insert_entry
  WARN: resolve_btfids: unresolved symbol bpf_cgroup_release
  WARN: resolve_btfids: unresolved symbol bpf_cgroup_from_id
  WARN: resolve_btfids: unresolved symbol bpf_cgroup_acquire
  WARN: resolve_btfids: unresolved symbol bpf_arena_free_pages
    NM      System.map
    SORTTAB vmlinux
    OBJCOPY vmlinux.32
  [...]

Update the __bpf_kfunc tag to better guard against linker optimization by
including the new __retain compiler macro, which fixes the warnings above.

Verify the __retain macro with readelf by checking object flags for 'R':

  $ readelf -Wa kernel/trace/bpf_trace.o
  Section Headers:
    [Nr]  Name              Type     Address  Off  Size ES Flg Lk Inf Al
  [...]
    [178] .text.bpf_key_put PROGBITS 00000000 6420 0050 00 AXR  0   0  8
  [...]
  Key to Flags:
  [...]
    R (retain), D (mbind), p (processor specific)

Fixes: 57e7c169cd ("bpf: Add __bpf_kfunc tag for marking kernel functions as kfuncs")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Yonghong Song <yonghong.song@linux.dev>
Closes: https://lore.kernel.org/r/202401211357.OCX9yllM-lkp@intel.com/
Link: https://lore.kernel.org/bpf/ZlmGoT9KiYLZd91S@krava/T/
Link: https://lore.kernel.org/bpf/e9c64e9b5c073dabd457ff45128aabcab7630098.1717477560.git.Tony.Ambardar@gmail.com
2024-06-14 19:14:37 +02:00
arch ARM: 2024-06-05 08:43:41 -07:00
block blk-throttle: Fix incorrect display of io.max 2024-05-30 19:44:29 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto This push fixes a bug in the new ecc P521 code as well as a buggy 2024-05-20 08:47:54 -07:00
Documentation Including fixes from BPF and big collection of fixes for WiFi core 2024-06-06 09:55:27 -07:00
drivers net: stmmac: replace priv->speed with the portTransmitRate from the tc-cbs parameters 2024-06-11 19:58:18 -07:00
fs for-6.10-rc2-tag 2024-06-05 11:28:25 -07:00
include bpf: Harden __bpf_kfunc tag against linker kfunc removal 2024-06-14 19:14:37 +02:00
init Driver core changes for 6.10-rc1 2024-05-22 12:13:40 -07:00
io_uring io_uring/net: assign kmsg inq/flags before buffer selection 2024-05-30 14:04:37 -06:00
ipc Mainly singleton patches, documented in their respective changelogs. 2024-05-19 14:02:03 -07:00
kernel bpf: fix UML x86_64 compile failure 2024-06-13 11:24:45 -07:00
lib Including fixes from BPF and big collection of fixes for WiFi core 2024-06-06 09:55:27 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 16 hotfixes, 11 of which are cc:stable. 2024-05-25 15:10:33 -07:00
net bpf: Avoid splat in pskb_pull_reason 2024-06-14 17:20:21 +02:00
rust LoongArch changes for v6.10 2024-05-22 09:43:07 -07:00
samples tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
scripts dt-bindings: kbuild: Fix dt_binding_check on unconfigured build 2024-05-30 01:15:58 +09:00
security tomoyo: update project links 2024-06-03 22:43:11 +09:00
sound ALSA: seq: ump: Fix swapped song position pointer data 2024-05-31 09:51:44 +02:00
tools selftests/bpf: Add test coverage for reg_set_min_max handling 2024-06-13 11:16:01 -07:00
usr kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
virt The usual shower of singleton fixes and minor series all over MM, 2024-05-19 09:21:03 -07:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap MAINTAINERS: mailmap: Update Stanislav's email address 2024-06-12 17:58:36 -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 MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
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: mailmap: Update Stanislav's email address 2024-06-12 17:58:36 -07:00
Makefile Linux 6.10-rc2 2024-06-02 15:44:56 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.