linux-toradex.git/include/linux/kernel.h, branch v6.4-rc1

kernel.h: split the hexadecimal related helpers to hex.h

2023-04-08T20:45:38+00:00

For the sake of cleaning up the kernel.h split the hexadecimal related
helpers to own header called 'hex.h'.

Link: https://lkml.kernel.org/r/20230323155029.40000-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko 
Cc: Rasmus Villemoes 
Signed-off-by: Andrew Morton

tracing: Always use canonical ftrace path

2023-02-18T19:34:09+00:00

The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Many comments and Kconfig help messages in the tracing code still refer
to this older debugfs path, so let's update them to avoid confusion.

Link: https://lore.kernel.org/linux-trace-kernel/20230215223350.2658616-2-zwisler@google.com

Acked-by: Masami Hiramatsu (Google) 
Reviewed-by: Mukesh Ojha 
Signed-off-by: Ross Zwisler 
Signed-off-by: Steven Rostedt (Google)

hex2bin: make the function hex_to_bin constant-time

2022-04-27T17:57:33+00:00

The function hex2bin is used to load cryptographic keys into device
mapper targets dm-crypt and dm-integrity.  It should take constant time
independent on the processed data, so that concurrently running
unprivileged code can't infer any information about the keys via
microarchitectural convert channels.

This patch changes the function hex_to_bin so that it contains no
branches and no memory accesses.

Note that this shouldn't cause performance degradation because the size
of the new function is the same as the size of the old function (on
x86-64) - and the new function causes no branch misprediction penalties.

I compile-tested this function with gcc on aarch64 alpha arm hppa hppa64
i386 ia64 m68k mips32 mips64 powerpc powerpc64 riscv sh4 s390x sparc32
sparc64 x86_64 and with clang on aarch64 arm hexagon i386 mips32 mips64
powerpc powerpc64 s390x sparc32 sparc64 x86_64 to verify that there are
no branches in the generated code.

Signed-off-by: Mikulas Patocka 
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds

block: move lower_48_bits() to block

2022-04-12T01:18:27+00:00

The function is not generally applicable enough to be included in the core
kernel header. Move it to block since it's the only subsystem using it.

Suggested-by: Linus Torvalds 
Signed-off-by: Keith Busch 
Link: https://lore.kernel.org/r/20220327173316.315-1-kbusch@kernel.org
Signed-off-by: Jens Axboe

Merge tag 'for-5.18/64bit-pi-2022-03-25' of git://git.kernel.dk/linux-block

2022-03-26T19:01:35+00:00

Pull block layer 64-bit data integrity support from Jens Axboe:
 "This adds support for 64-bit data integrity in the block layer and in
  NVMe"

* tag 'for-5.18/64bit-pi-2022-03-25' of git://git.kernel.dk/linux-block:
  crypto: fix crc64 testmgr digest byte order
  nvme: add support for enhanced metadata
  block: add pi for extended integrity
  crypto: add rocksoft 64b crc guard tag framework
  lib: add rocksoft model crc64
  linux/kernel: introduce lower_48_bits function
  asm-generic: introduce be48 unaligned accessors
  nvme: allow integrity on extended metadata formats
  block: support pi with extended metadata

linux/kernel: introduce lower_48_bits function

2022-03-07T19:48:35+00:00

Recent data integrity field enhancements allow reference tags to be up
to 48 bits. Introduce an inline helper function since this will be a
repeated operation.

Suggested-by: Bart Van Assche 
Signed-off-by: Keith Busch 
Reviewed-by: Bart Van Assche 
Link: https://lore.kernel.org/r/20220303201312.3255347-5-kbusch@kernel.org
Signed-off-by: Jens Axboe

sched/preempt: Add PREEMPT_DYNAMIC using static keys

2022-02-19T10:11:08+00:00

Where an architecture selects HAVE_STATIC_CALL but not
HAVE_STATIC_CALL_INLINE, each static call has an out-of-line trampoline
which will either branch to a callee or return to the caller.

On such architectures, a number of constraints can conspire to make
those trampolines more complicated and potentially less useful than we'd
like. For example:

* Hardware and software control flow integrity schemes can require the
  addition of "landing pad" instructions (e.g. `BTI` for arm64), which
  will also be present at the "real" callee.

* Limited branch ranges can require that trampolines generate or load an
  address into a register and perform an indirect branch (or at least
  have a slow path that does so). This loses some of the benefits of
  having a direct branch.

* Interaction with SW CFI schemes can be complicated and fragile, e.g.
  requiring that we can recognise idiomatic codegen and remove
  indirections understand, at least until clang proves more helpful
  mechanisms for dealing with this.

For PREEMPT_DYNAMIC, we don't need the full power of static calls, as we
really only need to enable/disable specific preemption functions. We can
achieve the same effect without a number of the pain points above by
using static keys to fold early returns into the preemption functions
themselves rather than in an out-of-line trampoline, effectively
inlining the trampoline into the start of the function.

For arm64, this results in good code generation. For example, the
dynamic_cond_resched() wrapper looks as follows when enabled. When
disabled, the first `B` is replaced with a `NOP`, resulting in an early
return.

| :
|        bti     c
|        b            // or `nop`
|        mov     w0, #0x0
|        ret
|        mrs     x0, sp_el0
|        ldr     x0, [x0, #8]
|        cbnz    x0, 
|        paciasp
|        stp     x29, x30, [sp, #-16]!
|        mov     x29, sp
|        bl      
|        mov     w0, #0x1
|        ldp     x29, x30, [sp], #16
|        autiasp
|        ret

... compared to the regular form of the function:

| <__cond_resched>:
|        bti     c
|        mrs     x0, sp_el0
|        ldr     x1, [x0, #8]
|        cbz     x1, <__cond_resched+0x18>
|        mov     w0, #0x0
|        ret
|        paciasp
|        stp     x29, x30, [sp, #-16]!
|        mov     x29, sp
|        bl      
|        mov     w0, #0x1
|        ldp     x29, x30, [sp], #16
|        autiasp
|        ret

Any architecture which implements static keys should be able to use this
to implement PREEMPT_DYNAMIC with similar cost to non-inlined static
calls. Since this is likely to have greater overhead than (inlined)
static calls, PREEMPT_DYNAMIC is only defaulted to enabled when
HAVE_PREEMPT_DYNAMIC_CALL is selected.

Signed-off-by: Mark Rutland 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Ard Biesheuvel 
Acked-by: Frederic Weisbecker 
Link: https://lore.kernel.org/r/20220214165216.2231574-6-mark.rutland@arm.com

Merge branch 'akpm' (patches from Andrew)

2022-01-20T08:41:01+00:00

Merge more updates from Andrew Morton:
 "55 patches.

  Subsystems affected by this patch series: percpu, procfs, sysctl,
  misc, core-kernel, get_maintainer, lib, checkpatch, binfmt, nilfs2,
  hfs, fat, adfs, panic, delayacct, kconfig, kcov, and ubsan"

* emailed patches from Andrew Morton : (55 commits)
  lib: remove redundant assignment to variable ret
  ubsan: remove CONFIG_UBSAN_OBJECT_SIZE
  kcov: fix generic Kconfig dependencies if ARCH_WANTS_NO_INSTR
  lib/Kconfig.debug: make TEST_KMOD depend on PAGE_SIZE_LESS_THAN_256KB
  btrfs: use generic Kconfig option for 256kB page size limit
  arch/Kconfig: split PAGE_SIZE_LESS_THAN_256KB from PAGE_SIZE_LESS_THAN_64KB
  configs: introduce debug.config for CI-like setup
  delayacct: track delays from memory compact
  Documentation/accounting/delay-accounting.rst: add thrashing page cache and direct compact
  delayacct: cleanup flags in struct task_delay_info and functions use it
  delayacct: fix incomplete disable operation when switch enable to disable
  delayacct: support swapin delay accounting for swapping without blkio
  panic: remove oops_id
  panic: use error_report_end tracepoint on warnings
  fs/adfs: remove unneeded variable make code cleaner
  FAT: use io_schedule_timeout() instead of congestion_wait()
  hfsplus: use struct_group_attr() for memcpy() region
  nilfs2: remove redundant pointer sbufs
  fs/binfmt_elf: use PT_LOAD p_align values for static PIE
  const_structs.checkpatch: add frequently used ops structs
  ...

kernel.h: include a note to discourage people from including it in headers

2022-01-20T06:52:53+00:00

Include a note at the top to discourage people from including it in
headers.

Link: https://lkml.kernel.org/r/20211209150803.4473-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

exit: Rename complete_and_exit to kthread_complete_and_exit

2021-12-13T18:04:45+00:00

Update complete_and_exit to call kthread_exit instead of do_exit.

Change the name to reflect this change in functionality.  All of the
users of complete_and_exit are causing the current kthread to exit so
this change makes it clear what is happening.

Move the implementation of kthread_complete_and_exit from
kernel/exit.c to to kernel/kthread.c.  As this function is kthread
specific it makes most sense to live with the kthread functions.

There are no functional change.

Signed-off-by: "Eric W. Biederman"