| Message ID | 20240923181846.549877-22-samitolvanen@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Implement DWARF modversions | expand |
On Mon, Sep 23, 2024 at 2:19 PM Sami Tolvanen <samitolvanen@google.com> wrote: > > Hi, > > Here's v3 of the DWARF modversions series [1][2]. The main > motivation remains modversions support for Rust, which is important > for distributions like Android that are eager to ship Rust kernel > modules. Per Luis' request [3], v2 dropped the Rust specific bits > from the series and instead added the feature as an option for > the entire kernel. Matt is still addressing Rust modversion_info > compatibility issues in a separate series [4], and we'll follow up > with a patch to actually allow CONFIG_MODVERSIONS with Rust once > everything else has been sorted out. > > A short background recap: 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 Matt's suggestion and previous feedback from > maintainers, 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. > > The first two patches add more list macros to scripts/include and > move the genksyms CRC32 implementation to a shared header file. 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 18 ensures > that debugging information is present where we need it, patch 19 > adds gendwarfksyms as an alternative to genksyms, and the last patch > adds documentation. > > Note that v3 is based on next-20240923 as it depends on Masahiro's > scripts/include changes. For x86, we also need a separate small > patch to include asm/ptrace.h in asm/ftrace.h. [5] For your > convenience, you can find this series with all the prerequisites > here: > > https://github.com/samitolvanen/linux/commits/gendwarfksyms-v3 > > If you also want to test the series with Rust modules, this branch > adds Matt's modversion_info series and a small patch to enable Rust > modversions: > > https://github.com/samitolvanen/linux/commits/rustmodversions-v3 > > Looking forward to hearing your thoughts! > > Sami > > > [1] v1: https://lore.kernel.org/lkml/20240617175818.58219-17-samitolvanen@google.com/ > [2] v2: https://lore.kernel.org/lkml/20240815173903.4172139-21-samitolvanen@google.com/ > [3] https://lore.kernel.org/lkml/ZnIZEtkkQWEIGf9n@bombadil.infradead.org/ > [4] https://lore.kernel.org/lkml/20240806212106.617164-1-mmaurer@google.com/ > [5] https://lore.kernel.org/lkml/20240916221557.846853-2-samitolvanen@google.com/ > > --- > > Changes in v3: > - 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. [5] > > - 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. > > Changes in v2: > - 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. > > --- > > Sami Tolvanen (20): > scripts: import more list macros > 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 | 274 +++++ > Documentation/kbuild/index.rst | 1 + > include/linux/export.h | 15 + > kernel/module/Kconfig | 31 + > scripts/Makefile | 3 +- > scripts/Makefile.build | 39 +- > scripts/gendwarfksyms/.gitignore | 2 + > scripts/gendwarfksyms/Makefile | 12 + > scripts/gendwarfksyms/cache.c | 44 + > scripts/gendwarfksyms/die.c | 166 +++ > scripts/gendwarfksyms/dwarf.c | 1085 +++++++++++++++++++ > 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 | 29 + > scripts/gendwarfksyms/gendwarfksyms.c | 195 ++++ > scripts/gendwarfksyms/gendwarfksyms.h | 351 ++++++ > scripts/gendwarfksyms/kabi.c | 214 ++++ > scripts/gendwarfksyms/symbols.c | 317 ++++++ > scripts/gendwarfksyms/types.c | 477 ++++++++ > scripts/genksyms/genksyms.c | 77 +- > scripts/include/crc32.h | 93 ++ > scripts/include/list.h | 50 + > 25 files changed, 3860 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: ef545bc03a65438cabe87beb1b9a15b0ffcb6ace > -- > 2.46.0.792.g87dc391469-goog > This patch set looks fairly reasonable. Acked-by: Neal Gompa <neal@gompa.dev>
Hi, Here's v3 of the DWARF modversions series [1][2]. The main motivation remains modversions support for Rust, which is important for distributions like Android that are eager to ship Rust kernel modules. Per Luis' request [3], v2 dropped the Rust specific bits from the series and instead added the feature as an option for the entire kernel. Matt is still addressing Rust modversion_info compatibility issues in a separate series [4], and we'll follow up with a patch to actually allow CONFIG_MODVERSIONS with Rust once everything else has been sorted out. A short background recap: 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 Matt's suggestion and previous feedback from maintainers, 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. The first two patches add more list macros to scripts/include and move the genksyms CRC32 implementation to a shared header file. 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 18 ensures that debugging information is present where we need it, patch 19 adds gendwarfksyms as an alternative to genksyms, and the last patch adds documentation. Note that v3 is based on next-20240923 as it depends on Masahiro's scripts/include changes. For x86, we also need a separate small patch to include asm/ptrace.h in asm/ftrace.h. [5] For your convenience, you can find this series with all the prerequisites here: https://github.com/samitolvanen/linux/commits/gendwarfksyms-v3 If you also want to test the series with Rust modules, this branch adds Matt's modversion_info series and a small patch to enable Rust modversions: https://github.com/samitolvanen/linux/commits/rustmodversions-v3 Looking forward to hearing your thoughts! Sami [1] v1: https://lore.kernel.org/lkml/20240617175818.58219-17-samitolvanen@google.com/ [2] v2: https://lore.kernel.org/lkml/20240815173903.4172139-21-samitolvanen@google.com/ [3] https://lore.kernel.org/lkml/ZnIZEtkkQWEIGf9n@bombadil.infradead.org/ [4] https://lore.kernel.org/lkml/20240806212106.617164-1-mmaurer@google.com/ [5] https://lore.kernel.org/lkml/20240916221557.846853-2-samitolvanen@google.com/ --- Changes in v3: - 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. [5] - 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. Changes in v2: - 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. --- Sami Tolvanen (20): scripts: import more list macros 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 | 274 +++++ Documentation/kbuild/index.rst | 1 + include/linux/export.h | 15 + kernel/module/Kconfig | 31 + scripts/Makefile | 3 +- scripts/Makefile.build | 39 +- scripts/gendwarfksyms/.gitignore | 2 + scripts/gendwarfksyms/Makefile | 12 + scripts/gendwarfksyms/cache.c | 44 + scripts/gendwarfksyms/die.c | 166 +++ scripts/gendwarfksyms/dwarf.c | 1085 +++++++++++++++++++ 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 | 29 + scripts/gendwarfksyms/gendwarfksyms.c | 195 ++++ scripts/gendwarfksyms/gendwarfksyms.h | 351 ++++++ scripts/gendwarfksyms/kabi.c | 214 ++++ scripts/gendwarfksyms/symbols.c | 317 ++++++ scripts/gendwarfksyms/types.c | 477 ++++++++ scripts/genksyms/genksyms.c | 77 +- scripts/include/crc32.h | 93 ++ scripts/include/list.h | 50 + 25 files changed, 3860 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: ef545bc03a65438cabe87beb1b9a15b0ffcb6ace