kernel/linux.git/scripts/module.lds.S, branch v6.19.11

livepatch: Free klp_{object,func}_ext data after initialization

2026-02-05T16:00:45+00:00

The klp_object_ext and klp_func_ext data, which are stored in the __klp_objects and __klp_funcs sections, respectively, are not needed after they are used to create the actual klp_object and klp_func instances. This operation is implemented by the init function in scripts/livepatch/init.c. Prefix the two sections with ".init" so they are freed after the module is initializated. Signed-off-by: Petr Pavlu Acked-by: Joe Lawrence Acked-by: Miroslav Benes Reviewed-by: Aaron Tomlin Link: https://patch.msgid.link/20260123102825.3521961-3-petr.pavlu@suse.com Signed-off-by: Josh Poimboeuf

livepatch: Fix having __klp_objects relics in non-livepatch modules

2026-02-05T16:00:44+00:00

The linker script scripts/module.lds.S specifies that all input __klp_objects sections should be consolidated into an output section of the same name, and start/stop symbols should be created to enable scripts/livepatch/init.c to locate this data. This start/stop pattern is not ideal for modules because the symbols are created even if no __klp_objects input sections are present. Consequently, a dummy __klp_objects section also appears in the resulting module. This unnecessarily pollutes non-livepatch modules. Instead, since modules are relocatable files, the usual method for locating consolidated data in a module is to read its section table. This approach avoids the aforementioned problem. The klp_modinfo already stores a copy of the entire section table with the final addresses. Introduce a helper function that scripts/livepatch/init.c can call to obtain the location of the __klp_objects section from this data. Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files") Signed-off-by: Petr Pavlu Acked-by: Joe Lawrence Acked-by: Miroslav Benes Reviewed-by: Aaron Tomlin Link: https://patch.msgid.link/20260123102825.3521961-2-petr.pavlu@suse.com Signed-off-by: Josh Poimboeuf

objtool/klp: Introduce klp diff subcommand for diffing object files

2025-10-14T21:50:18+00:00

Add a new klp diff subcommand which performs a binary diff between two object files and extracts changed functions into a new object which can then be linked into a livepatch module. This builds on concepts from the longstanding out-of-tree kpatch [1] project which began in 2012 and has been used for many years to generate livepatch modules for production kernels. However, this is a complete rewrite which incorporates hard-earned lessons from 12+ years of maintaining kpatch. Key improvements compared to kpatch-build: - Integrated with objtool: Leverages objtool's existing control-flow graph analysis to help detect changed functions. - Works on vmlinux.o: Supports late-linked objects, making it compatible with LTO, IBT, and similar. - Simplified code base: ~3k fewer lines of code. - Upstream: No more out-of-tree #ifdef hacks, far less cruft. - Cleaner internals: Vastly simplified logic for symbol/section/reloc inclusion and special section extraction. - Robust __LINE__ macro handling: Avoids false positive binary diffs caused by the __LINE__ macro by introducing a fix-patch-lines script (coming in a later patch) which injects #line directives into the source .patch to preserve the original line numbers at compile time. Note the end result of this subcommand is not yet functionally complete. Livepatch needs some ELF magic which linkers don't like: - Two relocation sections (.rela*, .klp.rela*) for the same text section. - Use of SHN_LIVEPATCH to mark livepatch symbols. Unfortunately linkers tend to mangle such things. To work around that, klp diff generates a linker-compliant intermediate binary which encodes the relevant KLP section/reloc/symbol metadata. After module linking, a klp post-link step (coming soon) will clean up the mess and convert the linked .ko into a fully compliant livepatch module. Note this subcommand requires the diffed binaries to have been compiled with -ffunction-sections and -fdata-sections, and processed with 'objtool --checksum'. Those constraints will be handled by a klp-build script introduced in a later patch. Without '-ffunction-sections -fdata-sections', reliable object diffing would be infeasible due to toolchain limitations: - For intra-file+intra-section references, the compiler might occasionally generated hard-coded instruction offsets instead of relocations. - Section-symbol-based references can be ambiguous: - Overlapping or zero-length symbols create ambiguity as to which symbol is being referenced. - A reference to the end of a symbol (e.g., checking array bounds) can be misinterpreted as a reference to the next symbol, or vice versa. A potential future alternative to '-ffunction-sections -fdata-sections' would be to introduce a toolchain option that forces symbol-based (non-section) relocations. Acked-by: Petr Mladek Tested-by: Joe Lawrence Signed-off-by: Josh Poimboeuf

vmlinux.lds: Unify TEXT_MAIN, DATA_MAIN, and related macros

2025-10-14T21:45:21+00:00

TEXT_MAIN, DATA_MAIN and friends are defined differently depending on whether certain config options enable -ffunction-sections and/or -fdata-sections. There's no technical reason for that beyond voodoo coding. Keeping the separate implementations adds unnecessary complexity, fragments the logic, and increases the risk of subtle bugs. Unify the macros by using the same input section patterns across all configs. This is a prerequisite for the upcoming livepatch klp-build tooling which will manually enable -ffunction-sections and -fdata-sections via KCFLAGS. Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Alexander Gordeev Acked-by: Petr Mladek Tested-by: Joe Lawrence Signed-off-by: Josh Poimboeuf

alloc_tag: remove empty module tag section

2025-07-10T05:42:03+00:00

The empty MOD_CODETAG_SECTIONS() macro added an incomplete .data section in module linker script, which caused symbol lookup tools like gdb to misinterpret symbol addresses e.g., __ib_process_cq incorrectly mapping to unrelated functions like below. (gdb) disas __ib_process_cq Dump of assembler code for function trace_event_fields_cq_schedule: Removing the empty section restores proper symbol resolution and layout, ensuring .data placement behaves as expected. Link: https://lkml.kernel.org/r/20250610162258.324645-1-cachen@purestorage.com Fixes: 0db6f8d7820a ("alloc_tag: load module tags into separate contiguous memory") 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling") Signed-off-by: Casey Chen Reviewed-by: Yuanyuan Zhong Acked-by: Suren Baghdasaryan Cc: Arnd Bergmann Cc: Kent Overstreet Cc: Luis Chamberalin Cc: Pasha Tatashin Signed-off-by: Andrew Morton

kbuild: keep symbols for symbol_get() even with CONFIG_TRIM_UNUSED_KSYMS

2025-02-05T16:08:58+00:00

Linus observed that the symbol_request(utf8_data_table) call fails when CONFIG_UNICODE=y and CONFIG_TRIM_UNUSED_KSYMS=y. symbol_get() relies on the symbol data being present in the ksymtab for symbol lookups. However, EXPORT_SYMBOL_GPL(utf8_data_table) is dropped due to CONFIG_TRIM_UNUSED_KSYMS, as no module references it in this case. Probably, this has been broken since commit dbacb0ef670d ("kconfig option for TRIM_UNUSED_KSYMS"). This commit addresses the issue by leveraging modpost. Symbol names passed to symbol_get() are recorded in the special .no_trim_symbol section, which is then parsed by modpost to forcibly keep such symbols. The .no_trim_symbol section is discarded by the linker scripts, so there is no impact on the size of the final vmlinux or modules. This commit cannot resolve the issue for direct calls to __symbol_get() because the symbol name is not known at compile-time. Although symbol_get() may eventually be deprecated, this workaround should be good enough meanwhile. Reported-by: Linus Torvalds Suggested-by: Linus Torvalds Signed-off-by: Masahiro Yamada

Merge tag 'modules-6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/modules/linux

2024-11-27T18:20:50+00:00

Pull modules updates from Luis Chamberlain: - The whole caching of module code into huge pages by Mike Rapoport is going in through Andrew Morton's tree due to some other code dependencies. That's really the biggest highlight for Linux kernel modules in this release. With it we share huge pages for modules, starting off with x86. Expect to see that soon through Andrew! - Helge Deller addressed some lingering low hanging fruit alignment enhancements by. It is worth pointing out that from his old patch series I dropped his vmlinux.lds.h change at Masahiro's request as he would prefer this to be specified in asm code [0]. [0] https://lore.kernel.org/all/20240129192644.3359978-5-mcgrof@kernel.org/T/#m9efef5e700fbecd28b7afb462c15eed8ba78ef5a - Matthew Maurer and Sami Tolvanen have been tag teaming to help get us closer to a modversions for Rust. In this cycle we take in quite a lot of the refactoring for ELF validation. I expect modversions for Rust will be merged by v6.14 as that code is mostly ready now. - Adds a new modules selftests: kallsyms which helps us tests find_symbol() and the limits of kallsyms on Linux today. - We have a realtime mailing list to kernel-ci testing for modules now which relies and combines patchwork, kpd and kdevops: https://patchwork.kernel.org/project/linux-modules/list/ https://github.com/linux-kdevops/kdevops/blob/main/docs/kernel-ci/README.md https://github.com/linux-kdevops/kdevops/blob/main/docs/kernel-ci/kernel-ci-kpd.md https://github.com/linux-kdevops/kdevops/blob/main/docs/kernel-ci/linux-modules-kdevops-ci.md If you want to help avoid Linux kernel modules regressions, now its simple, just add a new Linux modules sefltests under tools/testing/selftests/module/ That is it. All new selftests will be used and leveraged automatically by the CI. * tag 'modules-6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/modules/linux: tests/module/gen_test_kallsyms.sh: use 0 value for variables scripts: Remove export_report.pl selftests: kallsyms: add MODULE_DESCRIPTION selftests: add new kallsyms selftests module: Reformat struct for code style module: Additional validation in elf_validity_cache_strtab module: Factor out elf_validity_cache_strtab module: Group section index calculations together module: Factor out elf_validity_cache_index_str module: Factor out elf_validity_cache_index_sym module: Factor out elf_validity_cache_index_mod module: Factor out elf_validity_cache_index_info module: Factor out elf_validity_cache_secstrings module: Factor out elf_validity_cache_sechdrs module: Factor out elf_validity_ehdr module: Take const arg in validate_section_offset modules: Add missing entry for __ex_table modules: Ensure 64-bit alignment on __ksymtab_* sections

alloc_tag: load module tags into separate contiguous memory

2024-11-07T22:25:16+00:00

When a module gets unloaded there is a possibility that some of the allocations it made are still used and therefore the allocation tags corresponding to these allocations are still referenced. As such, the memory for these tags can't be freed. This is currently handled as an abnormal situation and module's data section is not being unloaded. To handle this situation without keeping module's data in memory, allow codetags with longer lifespan than the module to be loaded into their own separate memory. The in-use memory areas and gaps after module unloading in this separate memory are tracked using maple trees. Allocation tags arrange their separate memory so that it is virtually contiguous and that will allow simple allocation tag indexing later on in this patchset. The size of this virtually contiguous memory is set to store up to 100000 allocation tags. [surenb@google.com: fix empty codetag module section handling] Link: https://lkml.kernel.org/r/20241101000017.3856204-1-surenb@google.com [akpm@linux-foundation.org: update comment, per Dan] Link: https://lkml.kernel.org/r/20241023170759.999909-4-surenb@google.com Signed-off-by: Suren Baghdasaryan Reviewed-by: Pasha Tatashin Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Borislav Petkov (AMD) Cc: Christoph Hellwig Cc: Daniel Gomez Cc: David Hildenbrand Cc: Davidlohr Bueso Cc: David Rientjes Cc: Dennis Zhou Cc: Johannes Weiner Cc: John Hubbard Cc: Jonathan Corbet Cc: Joonsoo Kim Cc: Kalesh Singh Cc: Kees Cook Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Luis Chamberlain Cc: Matthew Wilcox Cc: Michal Hocko Cc: Mike Rapoport (Microsoft) Cc: Minchan Kim Cc: Paul E. McKenney Cc: Petr Pavlu Cc: Roman Gushchin Cc: Sami Tolvanen Cc: Sourav Panda Cc: Steven Rostedt (Google) Cc: Thomas Gleixner Cc: Thomas Huth Cc: Uladzislau Rezki (Sony) Cc: Vlastimil Babka Cc: Xiongwei Song Cc: Yu Zhao Cc: Dan Carpenter Signed-off-by: Andrew Morton

modules: Add missing entry for __ex_table

2024-10-19T20:40:42+00:00

The entry for __ex_table was missing, which may make __ex_table become 1- or 2-byte aligned in modules. Add the entry to ensure it gets 32-bit aligned. As per unaligned-memory-access [0] "unaligned memory accesses [...] will not work correctly on certain platforms and will cause performance problems on others", so fix this. Signed-off-by: Helge Deller [mcgrof: added unaligned-memory-access justification] Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/core-api/unaligned-memory-access.rst # [0] Signed-off-by: Luis Chamberlain

modules: Ensure 64-bit alignment on __ksymtab_* sections

2024-10-19T20:35:24+00:00

On 64-bit architectures without CONFIG_HAVE_ARCH_PREL32_RELOCATIONS (e.g. ppc64, ppc64le, parisc, s390x,...) the __KSYM_REF() macro stores 64-bit pointers into the __ksymtab* sections. Make sure that those sections will be correctly aligned at module link time, otherwise unaligned memory accesses may happen at runtime. As per unaligned-memory-access [0] "unaligned memory accesses [...] will not work correctly on certain platforms and will cause performance problems on others", so fix this. The __kcrctab* sections store 32-bit entities, so use ALIGN(4) for those. Signed-off-by: Helge Deller [mcgrof: added unaligned-memory-access justification] Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/core-api/unaligned-memory-access.rst # [0] Signed-off-by: Luis Chamberlain