linux-kernel - [PATCH v3 0/5] linkage: better symbol aliasing

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Date:   Fri, 11 Feb 2022 15:14:40 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org
Cc:     acme@...hat.com, ardb@...nel.org, bp@...en8.de, broonie@...nel.org,
        catalin.marinas@....com, dave.hansen@...ux.intel.com,
        jpoimboe@...hat.com, jslaby@...e.cz,
        linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
        mingo@...hat.com, ndesaulniers@...gle.com, peterz@...radead.org,
        tglx@...utronix.de, will@...nel.org
Subject: [PATCH v3 0/5] linkage: better symbol aliasing

This series aims to make symbol aliasing simpler and more consistent.
The basic idea is to replace SYM_FUNC_START_ALIAS(alias) and
SYM_FUNC_END_ALIAS(alias) with a new SYM_FUNC_ALIAS(alias, name), so
that e.g.

    SYM_FUNC_START(func)
    SYM_FUNC_START_ALIAS(alias1)
    SYM_FUNC_START_ALIAS(alias2)
        ... asm insns ...
    SYM_FUNC_END(func)
    SYM_FUNC_END_ALIAS(alias1)
    SYM_FUNC_END_ALIAS(alias2)
    EXPORT_SYMBOL(alias1)
    EXPORT_SYMBOL(alias2)

... can become:

    SYM_FUNC_START(name)
        ... asm insns ...
    SYM_FUNC_END(name)

    SYM_FUNC_ALIAS(alias1, func)
    EXPORT_SYMBOL(alias1)

    SYM_FUNC_ALIAS(alias2, func)
    EXPORT_SYMBOL(alias2)

This avoids repetition and hopefully make it easier to ensure
consistency (e.g. so each function has a single canonical name and
associated metadata).

I've build-tested the following with both GCC 10.3.0 and LLVM 13.0.0
without issues (ignoring any existing warnings):

* arm omap1_defconfig (v2 broke with LLVM here)
* arm multi_v7_defconfig
* arm64 defconfig
* i386 defconfig
* x86_64 defconfig

I've boot-tested the arm64 Images.

I've pushed the series to my `linkage/alias-rework` branch on git.kernel.org,
atop v5.17-rc2:

  git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git linkage/alias-rework
  https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=linkage/alias-rework

Since RFCv1 [1]:
* Drop arm64 dma alias removal (taken via arm64 for v5.17-rc1)
* Rename SYM_FUNC_LOCAL_ALIAS() -> SYM_FUNC_ALIAS_LOCAL()
* Update the tools/ copies of x86 routines
* Add preparatory fix for 32-bit arm
* Rebase to v5.17-rc1

Since v2 [2]:
* Rework to be LLVM-compatible
  - Drop SYM_ENTRY_AT() / SYM_END_AT()
  - Drop unnecessary local symbols
  - Calculate size in SYM_END()
  - Use common SYM_ALIAS()
* Drop newly redundant arch/arm changes
* Clarify commit message wording
* Fix typos

[1] https://lore.kernel.org/r/20211206124715.4101571-1-mark.rutland@arm.com/
[2] https://lore.kernel.org/r/20220125113200.3829108-1-mark.rutland@arm.com/

Thanks,
Mark.

Mark Rutland (5):
  linkage: add SYM_FUNC_ALIAS{,_LOCAL,_WEAK}()
  arm64: clean up symbol aliasing
  x86: clean up symbol aliasing
  linkage: remove SYM_FUNC_{START,END}_ALIAS()
  tools: update x86 string routines

 Documentation/asm-annotations.rst       | 11 ++--
 arch/arm64/include/asm/linkage.h        | 24 ---------
 arch/arm64/kvm/hyp/nvhe/cache.S         |  5 +-
 arch/arm64/lib/clear_page.S             |  5 +-
 arch/arm64/lib/copy_page.S              |  5 +-
 arch/arm64/lib/memchr.S                 |  5 +-
 arch/arm64/lib/memcmp.S                 |  6 +--
 arch/arm64/lib/memcpy.S                 | 21 ++++----
 arch/arm64/lib/memset.S                 | 12 +++--
 arch/arm64/lib/strchr.S                 |  6 ++-
 arch/arm64/lib/strcmp.S                 |  6 +--
 arch/arm64/lib/strlen.S                 |  6 +--
 arch/arm64/lib/strncmp.S                |  6 +--
 arch/arm64/lib/strnlen.S                |  6 ++-
 arch/arm64/lib/strrchr.S                |  5 +-
 arch/arm64/mm/cache.S                   | 35 +++++++------
 arch/x86/boot/compressed/head_32.S      |  3 +-
 arch/x86/boot/compressed/head_64.S      |  3 +-
 arch/x86/crypto/aesni-intel_asm.S       |  4 +-
 arch/x86/lib/memcpy_64.S                | 10 ++--
 arch/x86/lib/memmove_64.S               |  4 +-
 arch/x86/lib/memset_64.S                |  6 +--
 include/linux/linkage.h                 | 67 +++++++++++++------------
 tools/arch/x86/lib/memcpy_64.S          | 10 ++--
 tools/arch/x86/lib/memset_64.S          |  6 +--
 tools/perf/util/include/linux/linkage.h | 46 ++++++++++++-----
 26 files changed, 169 insertions(+), 154 deletions(-)

-- 
2.30.2