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    Subject[PATCH v4] mips: Do not include hi and lo in clobber list for R6
    Date
    From: Romain Naour <romain.naour@gmail.com>

    From [1]
    "GCC 10 (PR 91233) won't silently allow registers that are not
    architecturally available to be present in the clobber list anymore,
    resulting in build failure for mips*r6 targets in form of:
    ...
    .../sysdep.h:146:2: error: the register ‘lo’ cannot be clobbered in ‘asm’ for the current target
    146 | __asm__ volatile ( \
    | ^~~~~~~

    This is because base R6 ISA doesn't define hi and lo registers w/o DSP
    extension. This patch provides the alternative clobber list for r6 targets
    that won't include those registers."

    Since kernel 5.4 and mips support for generic vDSO [2], the kernel fail to
    build for mips r6 cpus with gcc 10 for the same reason as glibc.

    [1] https://sourceware.org/git/?p=glibc.git;a=commit;h=020b2a97bb15f807c0482f0faee2184ed05bcad8
    [2] '24640f233b46 ("mips: Add support for generic vDSO")'

    Signed-off-by: Romain Naour <romain.naour@gmail.com>
    Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
    ---

    v4: [sudip] added macro VDSO_SYSCALL_CLOBBERS and fix checkpatch errors with commit message.
    v3 Avoid duplicate code (Maciej W. Rozycki)
    v2 use MIPS_ISA_REV instead of __mips_isa_rev (Alexander Lobakin)

    I have reused the original patch by Romain and have retained his s-o-b
    and author name as he is the original author of this patch. I have just
    added the macro. Build tested with gcc-10.3.1 and gcc-9.3.0.

    arch/mips/include/asm/vdso/gettimeofday.h | 26 ++++++++++++++++++-----
    1 file changed, 21 insertions(+), 5 deletions(-)

    diff --git a/arch/mips/include/asm/vdso/gettimeofday.h b/arch/mips/include/asm/vdso/gettimeofday.h
    index 2203e2d0ae2a..44a45f3fa4b0 100644
    --- a/arch/mips/include/asm/vdso/gettimeofday.h
    +++ b/arch/mips/include/asm/vdso/gettimeofday.h
    @@ -20,6 +20,12 @@

    #define VDSO_HAS_CLOCK_GETRES 1

    +#if MIPS_ISA_REV < 6
    +#define VDSO_SYSCALL_CLOBBERS "hi", "lo",
    +#else
    +#define VDSO_SYSCALL_CLOBBERS
    +#endif
    +
    static __always_inline long gettimeofday_fallback(
    struct __kernel_old_timeval *_tv,
    struct timezone *_tz)
    @@ -35,7 +41,9 @@ static __always_inline long gettimeofday_fallback(
    : "=r" (ret), "=r" (error)
    : "r" (tv), "r" (tz), "r" (nr)
    : "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
    - "$14", "$15", "$24", "$25", "hi", "lo", "memory");
    + "$14", "$15", "$24", "$25",
    + VDSO_SYSCALL_CLOBBERS
    + "memory");

    return error ? -ret : ret;
    }
    @@ -59,7 +67,9 @@ static __always_inline long clock_gettime_fallback(
    : "=r" (ret), "=r" (error)
    : "r" (clkid), "r" (ts), "r" (nr)
    : "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
    - "$14", "$15", "$24", "$25", "hi", "lo", "memory");
    + "$14", "$15", "$24", "$25",
    + VDSO_SYSCALL_CLOBBERS
    + "memory");

    return error ? -ret : ret;
    }
    @@ -83,7 +93,9 @@ static __always_inline int clock_getres_fallback(
    : "=r" (ret), "=r" (error)
    : "r" (clkid), "r" (ts), "r" (nr)
    : "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
    - "$14", "$15", "$24", "$25", "hi", "lo", "memory");
    + "$14", "$15", "$24", "$25",
    + VDSO_SYSCALL_CLOBBERS
    + "memory");

    return error ? -ret : ret;
    }
    @@ -105,7 +117,9 @@ static __always_inline long clock_gettime32_fallback(
    : "=r" (ret), "=r" (error)
    : "r" (clkid), "r" (ts), "r" (nr)
    : "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
    - "$14", "$15", "$24", "$25", "hi", "lo", "memory");
    + "$14", "$15", "$24", "$25",
    + VDSO_SYSCALL_CLOBBERS
    + "memory");

    return error ? -ret : ret;
    }
    @@ -125,7 +139,9 @@ static __always_inline int clock_getres32_fallback(
    : "=r" (ret), "=r" (error)
    : "r" (clkid), "r" (ts), "r" (nr)
    : "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
    - "$14", "$15", "$24", "$25", "hi", "lo", "memory");
    + "$14", "$15", "$24", "$25",
    + VDSO_SYSCALL_CLOBBERS
    + "memory");

    return error ? -ret : ret;
    }
    --
    2.30.2
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