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Linux kernel source tree
ce4a262098
Introduce a Kconfig option for enabling the experimental option to normalize integer types. This ensures that integer types of the same size and signedness are considered compatible by the Control Flow Integrity sanitizer. The security impact of this flag is minimal. When Sami Tolvanen looked into it, he found that integer normalization reduced the number of unique type hashes in the kernel by ~1%, which is acceptable. This option exists for compatibility with Rust, as C and Rust do not have the same set of integer types. There are cases where C has two different integer types of the same size and signedness, but Rust only has one integer type of that size and signedness. When Rust calls into C functions using such types in their signature, this results in CFI failures. One example is 'unsigned long long' and 'unsigned long' which are both 64-bit on LP64 targets, so on those targets this flag will give both types the same CFI tag. This flag changes the ABI heavily. It is not applied automatically when CONFIG_RUST is turned on to make sure that the CONFIG_RUST option does not change the ABI of C code. For example, some build may need to make other changes atomically with toggling this flag. Having it be a separate option makes it possible to first turn on normalized integer tags, and then later turn on CONFIG_RUST. Similarly, when turning on CONFIG_RUST in a build, you may need a few attempts where the RUST=y commit gets reverted a few times. It is inconvenient if reverting RUST=y also requires reverting the changes you made to support normalized integer tags. To avoid having this flag impact builds that don't care about this, the next patch in this series will make CONFIG_RUST turn on this option using `select` rather than `depends on`. Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Gatlin Newhouse <gatlin.newhouse@gmail.com> Acked-by: Kees Cook <kees@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20240801-kcfi-v2-1-c93caed3d121@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.