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Miguel Ojeda 4c353fca62 rust: kasan/kbuild: fix missing flags on first build 
commit 46e24a545c upstream.

If KASAN is enabled, and one runs in a clean repository e.g.:

    make LLVM=1 prepare
    make LLVM=1 prepare

Then the Rust code gets rebuilt, which should not happen.

The reason is some of the LLVM KASAN `rustc` flags are added in the
second run:

    -Cllvm-args=-asan-instrumentation-with-call-threshold=10000
    -Cllvm-args=-asan-stack=0
    -Cllvm-args=-asan-globals=1
    -Cllvm-args=-asan-kernel-mem-intrinsic-prefix=1

Further runs do not rebuild Rust because the flags do not change anymore.

Rebuilding like that in the second run is bad, even if this just happens
with KASAN enabled, but missing flags in the first one is even worse.

The root issue is that we pass, for some architectures and for the moment,
a generated `target.json` file. That file is not ready by the time `rustc`
gets called for the flag test, and thus the flag test fails just because
the file is not available, e.g.:

    $ ... --target=./scripts/target.json ... -Cllvm-args=...
    error: target file "./scripts/target.json" does not exist

There are a few approaches we could take here to solve this. For instance,
we could ensure that every time that the config is rebuilt, we regenerate
the file and recompute the flags. Or we could use the LLVM version to
check for these flags, instead of testing the flag (which may have other
advantages, such as allowing us to detect renames on the LLVM side).

However, it may be easier than that: `rustc` is aware of the `-Cllvm-args`
regardless of the `--target` (e.g. I checked that the list printed
is the same, plus that I can check for these flags even if I pass
a completely unrelated target), and thus we can just eliminate the
dependency completely.

Thus filter out the target.

This does mean that `rustc-option` cannot be used to test a flag that
requires the right target, but we don't have other users yet, it is a
minimal change and we want to get rid of custom targets in the future.

We could only filter in the case `target.json` is used, to make it work
in more cases, but then it would be harder to notice that it may not
work in a couple architectures.

Cc: Matthew Maurer <mmaurer@google.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: stable@vger.kernel.org
Fixes: e3117404b4 ("kbuild: rust: Enable KASAN support")
Tested-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250408220311.1033475-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-04-25 10:47:48 +02:00
arch riscv: KGDB: Remove ".option norvc/.option rvc" for kgdb_compiled_break 2025-04-25 10:47:48 +02:00
block block: fix resource leak in blk_register_queue() error path 2025-04-25 10:47:43 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Fix larval relookup type and mask 2025-04-10 14:39:20 +02:00
Documentation netlink: specs: rt-link: adjust mctp attribute naming 2025-04-25 10:47:45 +02:00
drivers net: ethernet: mtk_eth_soc: revise QDMA packet scheduler settings 2025-04-25 10:47:47 +02:00
fs ovl: remove unused forward declaration 2025-04-25 10:47:39 +02:00
include blk-mq: introduce blk_mq_map_hw_queues 2025-04-25 10:47:38 +02:00
init ARM: 9443/1: Require linker to support KEEP within OVERLAY for DCE 2025-04-10 14:39:40 +02:00
io_uring io_uring/kbuf: reject zero sized provided buffers 2025-04-20 10:15:40 +02:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel cpufreq/sched: Fix the usage of CPUFREQ_NEED_UPDATE_LIMITS 2025-04-25 10:47:48 +02:00
lib lib: scatterlist: fix sg_split_phys to preserve original scatterlist offsets 2025-04-20 10:15:45 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/hwpoison: introduce folio_contain_hwpoisoned_page() helper 2025-04-20 10:15:50 +02:00
net net: dsa: avoid refcount warnings when ds->ops->tag_8021q_vlan_del() fails 2025-04-25 10:47:46 +02:00
rust rust: Fix enabling Rust and building with GCC for LoongArch 2025-04-10 14:39:36 +02:00
samples rust: treewide: switch to the kernel Vec type 2025-03-13 13:01:46 +01:00
scripts rust: kasan/kbuild: fix missing flags on first build 2025-04-25 10:47:48 +02:00
security landlock: Prepare to add second errata 2025-04-20 10:15:56 +02:00
sound ASoC: cs42l43: Reset clamp override on jack removal 2025-04-25 10:47:40 +02:00
tools objtool/rust: add one more noreturn Rust function for Rust 1.86.0 2025-04-25 10:47:48 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow building irqbypass.ko as as module when kvm.ko is a module 2025-04-20 10:15:54 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2025-03-13 13:01:42 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add entry for the Rust alloc module 2025-03-13 13:01:47 +01:00
Makefile Linux 6.12.24 2025-04-20 10:16:02 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.