tjh.dev
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.
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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Current minimum required version of binutils is 2.30, which supports ENCLS
instruction mnemonic.
Replace the byte-wise specification of ENCLS with this proper mnemonic.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/20250616085716.158942-1-ubizjak@gmail.com
The Free Software Foundation does not reside in "675 Mass Ave, Cambridge"
anymore, so no need to mention that address in the source code here. But
instead of updating the address to their current location, just drop the
license boilerplate text and use a proper SPDX license identifier instead. The
text talks about the "GNU *Library* General Public License" and "any later
version", so LGPL-2.0+ is the right choice here.
[ bp: Massage commit message. ]
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250801084531.34089-1-thuth@redhat.com
Current minimum required version of binutils is 2.30, which supports RDPKRU and
WRPKRU instruction mnemonics.
Replace the byte-wise specification of RDPKRU and WRPKRU with these proper
mnemonics.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/20250616083611.157740-1-ubizjak@gmail.com
Current minimum required version of binutils is 2.30, which supports MONITORX
and MWAITX instruction mnemonics.
Replace the byte-wise specification of MONITORX and MWAITX with these proper
mnemonics.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250616083056.157460-1-ubizjak@gmail.com
Push __KERNEL_CS directly, rather than moving it into RAX and then
pushing RAX.
No functional changes.
Suggested-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250822071644.1405268-1-xin@zytor.com
Commit
5f5305dea066 ("raid6: skip avx512 checks")
and commit
bc23fe6dc172 ("crypto: x86 - Remove CONFIG_AS_AVX512 handling")
removed all uses of CONFIG_AS_AVX512.
Remove check for assembler support of AVX-512 instructions.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250819085855.333380-4-ubizjak@gmail.com
Current minimum required version of binutils is 2.30, which supports VPCLMULQDQ
instruction mnemonics.
Remove check for assembler support of VPCLMULQDQ instructions and all relevant
macros for conditional compilation.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/20250819085855.333380-3-ubizjak@gmail.com
Current minimum required version of binutils is 2.30, which supports VAES
instruction mnemonics.
Remove check for assembler support of VAES instructions and all relevant macros
for conditional compilation.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/20250819085855.333380-2-ubizjak@gmail.com
Current minimum required version of binutils is 2.30, which supports GFNI
instruction mnemonics.
Remove check for assembler support of GFNI instructions and all relevant
macros for conditional compilation.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/20250819085855.333380-1-ubizjak@gmail.com
As part of
38a4968b3190 ("x86/percpu/64: Remove INIT_PER_CPU macros"),
the only use of the config option X86_64_SMP in the kernel tree is removed. As
this config option X86_64_SMP is just equivalent to X86_64 && SMP, the source
code in the tree just uses that expression in the few places where needed. Note
further that this option cannot be explicitly enabled or disabled when
configuring the kernel build configuration.
Drop this needless and unused config option. No functional change.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250723071211.622802-1-lukas.bulwahn@redhat.com
Pull x86 fixes from Borislav Petkov:
- Remove a transitional asm/cpuid.h header which was added only as a
fallback during cpuid helpers reorg
- Initialize reserved fields in the SVSM page validation calls
structure to zero in order to allow for future structure extensions
- Have the sev-guest driver's buffers used in encryption operations be
in linear mapping space as the encryption operation can be offloaded
to an accelerator
- Have a read-only MSR write when in an AMD SNP guest trap to the
hypervisor as it is usually done. This makes the guest user
experience better by simply raising a #GP instead of terminating said
guest
- Do not output AVX512 elapsed time for kernel threads because the data
is wrong and fix a NULL pointer dereferencing in the process
- Adjust the SRSO mitigation selection to the new attack vectors
* tag 'x86_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/cpuid: Remove transitional <asm/cpuid.h> header
x86/sev: Ensure SVSM reserved fields in a page validation entry are initialized to zero
virt: sev-guest: Satisfy linear mapping requirement in get_derived_key()
x86/sev: Improve handling of writes to intercepted TSC MSRs
x86/fpu: Fix NULL dereference in avx512_status()
x86/bugs: Select best SRSO mitigation
Pull locking fixes from Borislav Petkov:
- Make sure sanity checks down in the mutex lock path happen on the
correct type of task so that they don't trigger falsely
- Use the write unsafe user access pairs when writing a futex value to
prevent an error on PowerPC which does user read and write accesses
differently
* tag 'locking_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking: Fix __clear_task_blocked_on() warning from __ww_mutex_wound() path
futex: Use user_write_access_begin/_end() in futex_put_value()
All CPUID call sites were updated at commit:
968e30006807 ("x86/cpuid: Set <asm/cpuid/api.h> as the main CPUID header")
to include <asm/cpuid/api.h> instead of <asm/cpuid.h>.
The <asm/cpuid.h> header was still retained as a wrapper, just in case
some new code in -next started using it. Now that everything is merged
to Linus' tree, remove the header.
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250815070227.19981-2-darwi@linutronix.de
Pull rust fixes from Miguel Ojeda:
- Workaround 'rustdoc' target modifiers bug in Rust >= 1.88.0. It will
be fixed in Rust 1.90.0 (expected 2025-09-18).
- Clean 'rustdoc' output before running it to avoid confusing the tool
when files from previous versions remain.
* tag 'rust-fixes-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux:
rust: kbuild: clean output before running `rustdoc`
rust: workaround `rustdoc` target modifiers bug
The __clear_task_blocked_on() helper added a number of sanity
checks ensuring we hold the mutex wait lock and that the task
we are clearing blocked_on pointer (if set) matches the mutex.
However, there is an edge case in the _ww_mutex_wound() logic
where we need to clear the blocked_on pointer for the task that
owns the mutex, not the task that is waiting on the mutex.
For this case the sanity checks aren't valid, so handle this
by allowing a NULL lock to skip the additional checks.
K Prateek Nayak and Maarten Lankhorst also pointed out that in
this case where we don't hold the owner's mutex wait_lock, we
need to be a bit more careful using READ_ONCE/WRITE_ONCE in both
the __clear_task_blocked_on() and __set_task_blocked_on()
implementations to avoid accidentally tripping WARN_ONs if two
instances race. So do that here as well.
This issue was easier to miss, I realized, as the test-ww_mutex
driver only exercises the wait-die class of ww_mutexes. I've
sent a patch[1] to address this so the logic will be easier to
test.
[1]: https://lore.kernel.org/lkml/20250801023358.562525-2-jstultz@google.com/
Fixes: a4f0b6fef4b0 ("locking/mutex: Add p->blocked_on wrappers for correctness checks")
Closes: https://lore.kernel.org/lkml/68894443.a00a0220.26d0e1.0015.GAE@google.com/
Reported-by: syzbot+602c4720aed62576cd79@syzkaller.appspotmail.com
Reported-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20250805001026.2247040-1-jstultz@google.com
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