On Wed, Oct 30, 2024 at 6:01 PM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> Hi,
>
> Here's v5 of the DWARF modversions series. The main motivation is
> modversions support for Rust, which is important for distributions
> like Android that are about to ship Rust kernel modules. Per Luis'
> request [1], v2 dropped the Rust specific bits from the series and
> instead added the feature as an option for the entire kernel to
> make it easier to evaluate the benefits of this approach, and to
> get better test coverage. Matt is addressing Rust modversion_info
> compatibility issues in a separate patch set [2] that depends on this
> series, and actually allows modversions to be enabled with Rust.
>
> Short background: Unlike C, Rust source code doesn't have sufficient
> information about the final ABI, as the compiler has considerable
> freedom in adjusting structure layout, for example, which makes
> using a source code parser like genksyms a non-starter. Based on
> earlier feedback, this series uses DWARF debugging information for
> computing versions. DWARF is an established and a relatively stable
> format, which includes all the necessary ABI details, and adding a
> CONFIG_DEBUG_INFO dependency for Rust symbol versioning seems like a
> reasonable trade-off as most distributions already enable it.
>
> The first patch moves the genksyms CRC32 implementation to a shared
> header file to avoid code duplication and the next 15 patches add
> gendwarfksyms, a tool for computing symbol versions from DWARF. When
> passed a list of exported symbols and object files, the tool
> generates an expanded type string for each symbol and computes symbol
> CRCs similarly to genksyms. gendwarfksyms is written in C and uses
> libdw to process DWARF. Patch 17 ensures that debugging information
> is present where we need it, patch 18 adds gendwarfksyms as an
> alternative to genksyms, and the last patch adds documentation.
>
> v5 is based on v6.12-rc5 and for your convenience the series is also
> available here:
>
> https://github.com/samitolvanen/linux/commits/gendwarfksyms-v5
>
> If you also want to test the series with Rust modules, this branch
> adds Matt's latest modversion_info series:
>
> https://github.com/samitolvanen/linux/commits/rustmodversions-v5
>
> Sami
>
>
> [1] https://lore.kernel.org/lkml/ZnIZEtkkQWEIGf9n@bombadil.infradead.org/
> [2] https://lore.kernel.org/lkml/20240925233854.90072-1-mmaurer@google.com/
>
> ---
>
> v5:
> - Rebased on v6.12-rc5.
>
> - Fixed an issue with limiting structure expansion, and applied
> Petr's clean-up. (Patch 10)
>
> - Dropped an unnecessary return statement in error path. (Patch
> 12)
>
> - Addressed several other smaller issues Petr brought up. (Patches
> 13, 14, and 15)
>
> - Added a KBUILD_GENDWARFKSYMS_STABLE flag to enable --stable for
> the entire kernel build. (Patch 18)
>
Hi Sami,
perfect timing: Nathan uploaded SLIM LLVM toolchain v19.1.3
KBUILD_GENDWARFKSYMS_STABLE is to be set manually?
What value is recommended?
Thanks.
-Sedat-
> - Updated documentation to include KBUILD flags. (Patch 19)
>
> - Picked up Reviewed-by tags from v4.
>
> v4: https://lore.kernel.org/lkml/20241008183823.36676-21-samitolvanen@google.com/
> - Rebased on v6.12-rc2, which now includes all the prerequisites.
>
> - Dropped unnecessary name_only parameter for symbols.c::for_each
> and cleaned up error handling. (Patch 3)
>
> - Fixed anonymous scope handling to ensure unnamed DIEs don't get
> names. (Patch 4)
>
> - Added non-variant children to variant_type output, and included
> DW_AT_discr_value attributes for variants. (Patch 9)
>
> - Added another symbol pointer test case. (Patch 16)
>
> - Picked up (Acked|Reviewed)-by tags from v3.
>
>
> v3: https://lore.kernel.org/lkml/20240923181846.549877-22-samitolvanen@google.com/
> - Updated SPX license headers.
>
> - Squashed the first two patches in v2 and tried to reduce churn as
> much as reasonable.
>
> - Dropped patch 18 from v2 ("x86/asm-prototypes: Include
> <asm/ptrace.h>") as it's addressed by a separate patch.
>
> - Changed the error handling code to immediately terminate instead
> of propagating the errors back to main, which cleaned up the code
> quite a bit.
>
> - Switched to the list and hashtable implementations in scripts and
> dropped the remaining tools/include dependencies. Added a couple
> missing list macros. (patch 1)
>
> - Moved the genksyms CRC32 implementation to scripts/include and
> dropped the duplicate code. (patches 2 and 14)
>
> - Switched from ad-hoc command line parsing to getopt_long (patch 3).
>
> - Added structure member and function parameter names to the DIE
> output to match genksyms behavior, and tweaked the symtypes format
> to be more parser-friendly in general based on Petr's suggestions.
>
> - Replaced the declaration-only struct annotations with more generic
> kABI stability rules that allow source code annotations to be used
> where #ifndef __GENKSYMS__ was previously used. Added support for
> rules that can be used to exclude enumerators from versioning.
> (patch 16)
>
> - Per Miroslav's suggestion, added an option to hide structure
> members from versioning when they're added to existing alignment
> holes, for example. (patch 16)
>
> - Per Greg's request, added documentation and example macros for the
> --stable features, and a couple of test cases. (patches 15, 16, and
> 20)
>
> - Fixed making symtypes files, which need to depend on .o files with
> gendwarfksyms. (patch 19)
>
> - Addressed several other smaller issues that Petr and Masahiro
> kindly pointed out during the v2 review.
>
>
> v2: https://lore.kernel.org/lkml/20240815173903.4172139-21-samitolvanen@google.com/
> - Per Luis' request, dropped Rust-specific patches and added
> gendwarfksyms as an alternative to genksyms for the entire
> kernel.
>
> - Added support for missing DWARF features needed to handle
> also non-Rust code.
>
> - Changed symbol address matching to use the symbol table
> information instead of relying on addresses in DWARF.
>
> - Added __gendwarfksyms_ptr patches to ensure the compiler emits
> the necessary type information in DWARF even for symbols that
> are defined in other TUs.
>
> - Refactored debugging output and moved the more verbose output
> behind --dump* flags.
>
> - Added a --symtypes flag for generating a genksyms-style
> symtypes output based on Petr's feedback, and refactored
> symbol version calculations to be based on symtypes instead
> of raw --dump-dies output.
>
> - Based on feedback from Greg and Petr, added --stable flag and
> support for reserved data structure fields and declaration-onl
> structures. Also added examples for using these features.
>
> - Added a GENDWARFKSYMS option and hooked up kbuild support
> for both C and assembly code. Note that with gendwarfksyms,
> we have to actually build a temporary .o file for calculating
> assembly modversions.
>
> v1: https://lore.kernel.org/lkml/20240617175818.58219-17-samitolvanen@google.com/
>
> ---
>
> Sami Tolvanen (19):
> scripts: move genksyms crc32 implementation to a common include
> tools: Add gendwarfksyms
> gendwarfksyms: Add address matching
> gendwarfksyms: Expand base_type
> gendwarfksyms: Add a cache for processed DIEs
> gendwarfksyms: Expand type modifiers and typedefs
> gendwarfksyms: Expand subroutine_type
> gendwarfksyms: Expand array_type
> gendwarfksyms: Expand structure types
> gendwarfksyms: Limit structure expansion
> gendwarfksyms: Add die_map debugging
> gendwarfksyms: Add symtypes output
> gendwarfksyms: Add symbol versioning
> gendwarfksyms: Add support for kABI rules
> gendwarfksyms: Add support for reserved and ignored fields
> gendwarfksyms: Add support for symbol type pointers
> export: Add __gendwarfksyms_ptr_ references to exported symbols
> kbuild: Add gendwarfksyms as an alternative to genksyms
> Documentation/kbuild: Add DWARF module versioning
>
> Documentation/kbuild/gendwarfksyms.rst | 276 +++++
> Documentation/kbuild/index.rst | 1 +
> include/linux/export.h | 15 +
> kernel/module/Kconfig | 31 +
> scripts/Makefile | 3 +-
> scripts/Makefile.build | 41 +-
> scripts/gendwarfksyms/.gitignore | 2 +
> scripts/gendwarfksyms/Makefile | 12 +
> scripts/gendwarfksyms/cache.c | 44 +
> scripts/gendwarfksyms/die.c | 166 +++
> scripts/gendwarfksyms/dwarf.c | 1109 +++++++++++++++++++
> scripts/gendwarfksyms/examples/kabi.h | 141 +++
> scripts/gendwarfksyms/examples/kabi_ex0.c | 86 ++
> scripts/gendwarfksyms/examples/kabi_ex1.c | 89 ++
> scripts/gendwarfksyms/examples/kabi_ex2.c | 98 ++
> scripts/gendwarfksyms/examples/kabi_rules.c | 56 +
> scripts/gendwarfksyms/examples/symbolptr.c | 33 +
> scripts/gendwarfksyms/gendwarfksyms.c | 185 ++++
> scripts/gendwarfksyms/gendwarfksyms.h | 288 +++++
> scripts/gendwarfksyms/kabi.c | 263 +++++
> scripts/gendwarfksyms/symbols.c | 339 ++++++
> scripts/gendwarfksyms/types.c | 477 ++++++++
> scripts/genksyms/genksyms.c | 77 +-
> scripts/include/crc32.h | 93 ++
> 24 files changed, 3840 insertions(+), 85 deletions(-)
> create mode 100644 Documentation/kbuild/gendwarfksyms.rst
> create mode 100644 scripts/gendwarfksyms/.gitignore
> create mode 100644 scripts/gendwarfksyms/Makefile
> create mode 100644 scripts/gendwarfksyms/cache.c
> create mode 100644 scripts/gendwarfksyms/die.c
> create mode 100644 scripts/gendwarfksyms/dwarf.c
> create mode 100644 scripts/gendwarfksyms/examples/kabi.h
> create mode 100644 scripts/gendwarfksyms/examples/kabi_ex0.c
> create mode 100644 scripts/gendwarfksyms/examples/kabi_ex1.c
> create mode 100644 scripts/gendwarfksyms/examples/kabi_ex2.c
> create mode 100644 scripts/gendwarfksyms/examples/kabi_rules.c
> create mode 100644 scripts/gendwarfksyms/examples/symbolptr.c
> create mode 100644 scripts/gendwarfksyms/gendwarfksyms.c
> create mode 100644 scripts/gendwarfksyms/gendwarfksyms.h
> create mode 100644 scripts/gendwarfksyms/kabi.c
> create mode 100644 scripts/gendwarfksyms/symbols.c
> create mode 100644 scripts/gendwarfksyms/types.c
> create mode 100644 scripts/include/crc32.h
>
>
> base-commit: 81983758430957d9a5cb3333fe324fd70cf63e7e
> --
> 2.47.0.163.g1226f6d8fa-goog
>