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    Subject[PATCH 5.4 271/411] Kconfig: add config option for asm goto w/ outputs
    Date
    From: Nick Desaulniers <ndesaulniers@google.com>

    commit 587f17018a2c6c414e41a312b002faaef60cf423 upstream.

    This allows C code to make use of compilers with support for output
    variables along the fallthrough path via preprocessor define:

    CONFIG_CC_HAS_ASM_GOTO_OUTPUT

    [ This is not used anywhere yet, and currently released compilers don't
    support this yet, but it's coming, and I have some local experimental
    patches to take advantage of it when it does - Linus ]

    Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    init/Kconfig | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/init/Kconfig
    +++ b/init/Kconfig
    @@ -38,6 +38,10 @@ config CC_HAS_ASM_GOTO_TIED_OUTPUT
    # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
    def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)

    +config CC_HAS_ASM_GOTO_OUTPUT
    + depends on CC_HAS_ASM_GOTO
    + def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
    +
    config TOOLS_SUPPORT_RELR
    def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)


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