arm64: Remove system_uses_lse_atomics()

There are two variants of system_uses_lse_atomics(), depending on
CONFIG_ARM64_LSE_ATOMICS. The function isn't called anywhere when
CONFIG_ARM64_LSE_ATOMICS is disabled. It can be directly replaced
by alternative_has_cap_likely(ARM64_HAS_LSE_ATOMICS) when the kernel
option is enabled.

No need to keep system_uses_lse_atomics() and just remove it.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20231017005036.334067-1-gshan@redhat.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arm64: alternatives: use cpucap naming

To more clearly align the various users of the cpucap enumeration, this patch
changes the alternative code to use the term `cpucap` in favour of `feature`.
The alternative_has_feature_{likely,unlikely}() functions are renamed to
alternative_has_cap_<likely,unlikely}() to more clearly align with the
cpus_have_{const_,}cap() helpers.

At the same time remove the stale comment referring to the "ARM64_CB
bit", which is evidently a typo for ARM64_CB_PATCH, which was removed in
commit:

4c0bd995d73ed889 ("arm64: alternatives: have callbacks take a cap")

There should be no functional change as a result of this patch; this is
purely a renaming exercise.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230607164846.3967305-3-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arm64: atomics: lse: remove stale dependency on JUMP_LABEL

Currently CONFIG_ARM64_USE_LSE_ATOMICS depends upon CONFIG_JUMP_LABEL,
as the inline atomics were indirected with a static branch.

However, since commit:

21fb26bfb01ffe0d ("arm64: alternatives: add alternative_has_feature_*()")

... we use an alternative_branch (which is always available) rather than
a static branch, and hence the dependency is unnecessary.

Remove the stale dependency, along with the stale include. This will
allow the use of LSE atomics in kernels built with CONFIG_JUMP_LABEL=n,
and reduces the risk of circular header dependencies via <asm/lse.h>.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20221114125424.2998268-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

arm64: alternatives: add alternative_has_feature_*()

Currrently we use a mixture of alternative sequences and static branches
to handle features detected at boot time. For ease of maintenance we
generally prefer to use static branches in C code, but this has a few
downsides:

* Each static branch has metadata in the __jump_table section, which is
not discarded after features are finalized. This wastes some space,
and slows down the patching of other static branches.

* The static branches are patched at a different point in time from the
alternatives, so changes are not atomic. This leaves a transient
period where there could be a mismatch between the behaviour of
alternatives and static branches, which could be problematic for some
features (e.g. pseudo-NMI).

* More (instrumentable) kernel code is executed to patch each static
branch, which can be risky when patching certain features (e.g.
irqflags management for pseudo-NMI).

* When CONFIG_JUMP_LABEL=n, static branches are turned into a load of a
flag and a conditional branch. This means it isn't safe to use such
static branches in an alternative address space (e.g. the NVHE/PKVM
hyp code), where the generated address isn't safe to acccess.

To deal with these issues, this patch introduces new
alternative_has_feature_*() helpers, which work like static branches but
are patched using alternatives. This ensures the patching is performed
at the same time as other alternative patching, allows the metadata to
be freed after patching, and is safe for use in alternative address
spaces.

Note that all supported toolchains have asm goto support, and since
commit:

a0a12c3ed057af57 ("asm goto: eradicate CC_HAS_ASM_GOTO)"

... the CC_HAS_ASM_GOTO Kconfig symbol has been removed, so no feature
check is necessary, and we can always make use of asm goto.

Additionally, note that:

* This has no impact on cpus_have_cap(), which is a dynamic check.

* This has no functional impact on cpus_have_const_cap(). The branches
are patched slightly later than before this patch, but these branches
are not reachable until caps have been finalised.

* It is now invalid to use cpus_have_final_cap() in the window between
feature detection and patching. All existing uses are only expected
after patching anyway, so this should not be a problem.

* The LSE atomics will now be enabled during alternatives patching
rather than immediately before. As the LL/SC an LSE atomics are
functionally equivalent this should not be problematic.

When building defconfig with GCC 12.1.0, the resulting Image is 64KiB
smaller:

| % ls -al Image-*
| -rw-r--r-- 1 mark mark 37108224 Aug 23 09:56 Image-after
| -rw-r--r-- 1 mark mark 37173760 Aug 23 09:54 Image-before

According to bloat-o-meter.pl:

| add/remove: 44/34 grow/shrink: 602/1294 up/down: 39692/-61108 (-21416)
| Function old new delta
| [...]
| Total: Before=16618336, After=16596920, chg -0.13%
| add/remove: 0/2 grow/shrink: 0/0 up/down: 0/-1296 (-1296)
| Data old new delta
| arm64_const_caps_ready 16 - -16
| cpu_hwcap_keys 1280 - -1280
| Total: Before=8987120, After=8985824, chg -0.01%
| add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
| RO Data old new delta
| Total: Before=18408, After=18408, chg +0.00%

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220912162210.3626215-8-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arm64: atomics: remove redundant static branch

Due to a historical oversight, we emit a redundant static branch for
each atomic/atomic64 operation when CONFIG_ARM64_LSE_ATOMICS is
selected. We can safely remove this, making the kernel Image reasonably
smaller.

When CONFIG_ARM64_LSE_ATOMICS is selected, every LSE atomic operation
has two preceding static branches with the same target, e.g.

b f7c <kernel_init_freeable+0xa4>
b f7c <kernel_init_freeable+0xa4>
mov w0, #0x1 // #1
ldadd w0, w0, [x19]

This is because the __lse_ll_sc_body() wrapper uses
system_uses_lse_atomics(), which checks both `arm64_const_caps_ready`
and `cpu_hwcap_keys[ARM64_HAS_LSE_ATOMICS]`, each of which emits a
static branch. This has been the case since commit:

addfc38672c73efd ("arm64: atomics: avoid out-of-line ll/sc atomics")

However, there was never a need to check `arm64_const_caps_ready`, which
was itself introduced in commit:

63a1e1c95e60e798 ("arm64/cpufeature: don't use mutex in bringup path")

... so that cpus_have_const_cap() could fall back to checking the
`cpu_hwcaps` bitmap prior to the static keys for individual caps
becoming enabled. As system_uses_lse_atomics() doesn't check
`cpu_hwcaps`, and doesn't need to as we can safely use the LL/SC atomics
prior to enabling the `ARM64_HAS_LSE_ATOMICS` static key, it doesn't
need to check `arm64_const_caps_ready`.

This patch removes the `arm64_const_caps_ready` check from
system_uses_lse_atomics(). As the arch_atomic_* routines are meant to be
safely usable in noinstr code, I've also marked
system_uses_lse_atomics() as __always_inline.

This results in one fewer static branch per atomic operation, with the
prior example becoming:

b f78 <kernel_init_freeable+0xa0>
mov w0, #0x1 // #1
ldadd w0, w0, [x19]

Each static branch consists of the branch itself and an associated
__jump_table entry. Removing these has a reasonable impact on the Image
size, with a GCC 11.1.0 defconfig v5.17-rc2 Image being reduced by
128KiB:

| [mark@lakrids:~/src/linux]% ls -al Image*
| -rw-r--r-- 1 mark mark 34619904 Feb 3 18:24 Image.baseline
| -rw-r--r-- 1 mark mark 34488832 Feb 3 18:33 Image.onebranch

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Suzuki Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220204104439.270567-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

arm64: lse: Fix LSE atomics with LLVM

Commit e0d5896bd356 ("arm64: lse: fix LSE atomics with LLVM's integrated
assembler") broke the build when clang is used in connjunction with the
binutils assembler ("-no-integrated-as"). This happens because
__LSE_PREAMBLE is defined as ".arch armv8-a+lse", which overrides the
version of the CPU architecture passed via the "-march" paramter to gas:

$ aarch64-none-linux-gnu-as -EL -I ./arch/arm64/include
-I ./arch/arm64/include/generated
-I ./include -I ./include
-I ./arch/arm64/include/uapi
-I ./arch/arm64/include/generated/uapi
-I ./include/uapi -I ./include/generated/uapi
-I ./init -I ./init
-march=armv8.3-a -o init/do_mounts.o
/tmp/do_mounts-d7992a.s
/tmp/do_mounts-d7992a.s: Assembler messages:
/tmp/do_mounts-d7992a.s:1959: Error: selected processor does not support `autiasp'
/tmp/do_mounts-d7992a.s:2021: Error: selected processor does not support `paciasp'
/tmp/do_mounts-d7992a.s:2157: Error: selected processor does not support `autiasp'
/tmp/do_mounts-d7992a.s:2175: Error: selected processor does not support `paciasp'
/tmp/do_mounts-d7992a.s:2494: Error: selected processor does not support `autiasp'

Fix the issue by replacing ".arch armv8-a+lse" with ".arch_extension lse".
Sami confirms that the clang integrated assembler does now support the
'.arch_extension' directive, so this change will be fine even for LTO
builds in future.

Fixes: e0d5896bd356cd ("arm64: lse: fix LSE atomics with LLVM's integrated assembler")
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Reported-by: Amit Kachhap <Amit.Kachhap@arm.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arm64: lse: fix LSE atomics with LLVM's integrated assembler

Unlike gcc, clang considers each inline assembly block to be independent
and therefore, when using the integrated assembler for inline assembly,
any preambles that enable features must be repeated in each block.

This change defines __LSE_PREAMBLE and adds it to each inline assembly
block that has LSE instructions, which allows them to be compiled also
with clang's assembler.

Link: https://github.com/ClangBuiltLinux/linux/issues/671
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Andrew Murray <andrew.murray@arm.com>
Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Will Deacon <will@kernel.org>

arm64: Move the LSE gas support detection to Kconfig

As the Kconfig syntax gained support for $(as-instr) tests, move the LSE
gas support detection from Makefile to the main arm64 Kconfig and remove
the additional CONFIG_AS_LSE definition and check.

Cc: Will Deacon <will@kernel.org>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arm64: asm: Kill 'asm/atomic_arch.h'

The contents of 'asm/atomic_arch.h' can be split across some of our
other 'asm/' headers. Remove it.

Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arm64: lse: Remove unused 'alt_lse' assembly macro

The 'alt_lse' assembly macro has been unused since 7c8fc35dfc32
("locking/atomics/arm64: Replace our atomic/lock bitop implementations
with asm-generic").

Remove it.

Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arm64: atomics: avoid out-of-line ll/sc atomics

When building for LSE atomics (CONFIG_ARM64_LSE_ATOMICS), if the hardware
or toolchain doesn't support it the existing code will fallback to ll/sc
atomics. It achieves this by branching from inline assembly to a function
that is built with special compile flags. Further this results in the
clobbering of registers even when the fallback isn't used increasing
register pressure.

Improve this by providing inline implementations of both LSE and
ll/sc and use a static key to select between them, which allows for the
compiler to generate better atomics code. Put the LL/SC fallback atomics
in their own subsection to improve icache performance.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arm64: lse: Include compiler_types.h and export.h for out-of-line LL/SC

When the LL/SC atomics are moved out-of-line, they are annotated as
notrace and exported to modules. Ensure we pull in the relevant include
files so that these macros are defined when we need them.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arm64: do not trace atomic operations

Atomic operation function symbols are exported,when
CONFIG_ARM64_LSE_ATOMICS is defined. Prefix them with notrace, so that
an user can not trace these functions. Tracing these functions causes
kernel crash.

Signed-off-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arm64: Fix circular include of asm/lse.h through linux/jump_label.h

Commit efd9e03facd0 ("arm64: Use static keys for CPU features")
introduced support for static keys in asm/cpufeature.h, including
linux/jump_label.h. When CC_HAVE_ASM_GOTO is not defined, this causes a
circular dependency via linux/atomic.h, asm/lse.h and asm/cpufeature.h.

This patch moves the capability macros out out of asm/cpufeature.h into
a separate asm/cpucaps.h and modifies some of the #includes accordingly.

Fixes: efd9e03facd0 ("arm64: Use static keys for CPU features")
Reported-by: Artem Savkov <asavkov@redhat.com>
Tested-by: Artem Savkov <asavkov@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arm64: lse: deal with clobbered IP registers after branch via PLT

The LSE atomics implementation uses runtime patching to patch in calls
to out of line non-LSE atomics implementations on cores that lack hardware
support for LSE. To avoid paying the overhead cost of a function call even
if no call ends up being made, the bl instruction is kept invisible to the
compiler, and the out of line implementations preserve all registers, not
just the ones that they are required to preserve as per the AAPCS64.

However, commit fd045f6cd98e ("arm64: add support for module PLTs") added
support for routing branch instructions via veneers if the branch target
offset exceeds the range of the ordinary relative branch instructions.
Since this deals with jump and call instructions that are exposed to ELF
relocations, the PLT code uses x16 to hold the address of the branch target
when it performs an indirect branch-to-register, something which is
explicitly allowed by the AAPCS64 (and ordinary compiler generated code
does not expect register x16 or x17 to retain their values across a bl
instruction).

Since the lse runtime patched bl instructions don't adhere to the AAPCS64,
they don't deal with this clobbering of registers x16 and x17. So add them
to the clobber list of the asm() statements that perform the call
instructions, and drop x16 and x17 from the list of registers that are
callee saved in the out of line non-LSE implementations.

In addition, since we have given these functions two scratch registers,
they no longer need to stack/unstack temp registers.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
[will: factored clobber list into #define, updated Makefile comment]
Signed-off-by: Will Deacon <will.deacon@arm.com>

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arm64: lse: rename ARM64_CPU_FEAT_LSE_ATOMICS for consistency

Other CPU features follow an 'ARM64_HAS_*' naming scheme, so do the same
for the LSE atomics.

Signed-off-by: Will Deacon <will.deacon@arm.com>

arm64: bitops: patch in lse instructions when supported by the CPU

On CPUs which support the LSE atomic instructions introduced in ARMv8.1,
it makes sense to use them in preference to ll/sc sequences.

This patch introduces runtime patching of our bitops functions so that
LSE atomic instructions are used instead.

Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arm64: atomics: patch in lse instructions when supported by the CPU

On CPUs which support the LSE atomic instructions introduced in ARMv8.1,
it makes sense to use them in preference to ll/sc sequences.

This patch introduces runtime patching of atomic_t and atomic64_t
routines so that the call-site for the out-of-line ll/sc sequences is
patched with an LSE atomic instruction when we detect that
the CPU supports it.

If binutils is not recent enough to assemble the LSE instructions, then
the ll/sc sequences are inlined as though CONFIG_ARM64_LSE_ATOMICS=n.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>