linux-kernel - [PATCH v3 0/8] scalable symbol flags with _

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Message-ID: <20251103161954.1351784-1-sidnayyar@google.com>
Date: Mon,  3 Nov 2025 16:19:46 +0000
From: Siddharth Nayyar <sidnayyar@...gle.com>
To: petr.pavlu@...e.com, corbet@....net
Cc: arnd@...db.de, linux-arch@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org, 
	mcgrof@...nel.org, nathan@...nel.org, nicolas.schier@...ux.dev, 
	samitolvanen@...gle.com, sidnayyar@...gle.com, maennich@...gle.com, 
	gprocida@...gle.com
Subject: [PATCH v3 0/8] scalable symbol flags with __kflagstab

This patch series implements a mechanism for scalable exported symbol
flags using a separate section called __kflagstab. The series introduces
__kflagstab support, removes *_gpl sections in favor of a GPL flag,
simplifies symbol resolution during module loading.

This series previously added symbol import protection which aims to
restrict the use of "protected symbol" exported by vmlinux, as a use
case for which __kflagstab is being introduced. Such symbols are only
allowed to be imported by signed modules when symbol protection is
enabled. This functionality requires more thought and discussion [1],
and therefore I will create a separate patch series for it. In the
meantime, this series now only focuses on introduction of __kflagstab
which right is an improvement to the module loader's code health [2].

Thank you Petr Pavlu and Jonathan Corbet for their valuable feedback.

---
Changes from v2:
- removed symbol import protection to spin off into its own series

v2:
https://lore.kernel.org/20251013153918.2206045-1-sidnayyar@google.com/

Changes from v1:
- added a check to ensure __kflagstab is present
- added warnings for the obsolete *_gpl sections
- moved protected symbol check before ref_module() call
- moved protected symbol check failure warning to issue detection point

v1:
https://lore.kernel.org/20250829105418.3053274-1-sidnayyar@google.com/

[1] https://lore.kernel.org/cac5ed5e-3320-4db0-99d8-ea5e97e56bfb@suse.com/
[2] https://lore.kernel.org/2bf54830-ea9c-4962-a7ef-653fbed8f8c0@suse.com/

Siddharth Nayyar (8):
  define kernel symbol flags
  linker: add kflagstab section to vmlinux and modules
  modpost: create entries for kflagstab
  module loader: use kflagstab instead of *_gpl sections
  modpost: put all exported symbols in ksymtab section
  module loader: remove references of *_gpl sections
  linker: remove *_gpl sections from vmlinux and modules
  remove references to *_gpl sections in documentation

 Documentation/kbuild/modules.rst  |  11 ++--
 include/asm-generic/vmlinux.lds.h |  21 ++----
 include/linux/export-internal.h   |  28 +++++---
 include/linux/module.h            |   4 +-
 include/linux/module_symbol.h     |   5 ++
 kernel/module/internal.h          |   4 +-
 kernel/module/main.c              | 102 ++++++++++++++----------------
 scripts/mod/modpost.c             |  16 +++--
 scripts/module.lds.S              |   3 +-
 9 files changed, 99 insertions(+), 95 deletions(-)

-- 
2.51.1.930.gacf6e81ea2-goog