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    SubjectRe: [PATCH 04/18] arm: implement nospec_ptr()
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    On 01/05/2018 05:10 PM, Dan Williams wrote:
    > From: Mark Rutland <mark.rutland@arm.com>
    >
    > This patch implements nospec_ptr() for arm, following the recommended
    > architectural sequences for the arm and thumb instruction sets.
    >

    Fedora picked up the series and it fails on arm:

    In file included from ./include/linux/compiler.h:242:0,
    from ./include/uapi/linux/swab.h:6,
    from ./include/linux/swab.h:5,
    from ./arch/arm/include/asm/opcodes.h:89,
    from ./arch/arm/include/asm/bug.h:7,
    from ./include/linux/bug.h:5,
    from ./include/linux/mmdebug.h:5,
    from ./include/linux/gfp.h:5,
    from ./include/linux/slab.h:15,
    from kernel/fork.c:14:
    ./include/linux/fdtable.h: In function '__fcheck_files':
    ./arch/arm/include/asm/barrier.h:112:41: error: expected declaration specifiers or '...' before numeric constant
    __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr); \
    ^
    ./arch/arm/include/asm/barrier.h:68:32: note: in definition of macro '__load_no_speculate_n'
    (typeof(*ptr)(unsigned long)(failval)); \
    ^~~~~~~
    ./arch/arm/include/asm/barrier.h:112:2: note: in expansion of macro '__load_no_speculate'
    __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr); \
    ^~~~~~~~~~~~~~~~~~~
    ./include/asm-generic/barrier.h:122:2: note: in expansion of macro 'nospec_ptr'
    nospec_ptr(__arr + __idx, __arr, __arr + __sz); \
    ^~~~~~~~~~
    ./include/linux/fdtable.h:86:13: note: in expansion of macro 'nospec_array_ptr'
    if ((fdp = nospec_array_ptr(fdt->fd, fd, fdt->max_fds)))
    ^~~~~~~~~~~~~~~~
    ./arch/arm/include/asm/barrier.h:112:41: error: expected declaration specifiers or '...' before numeric constant
    __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr); \
    ^
    ./arch/arm/include/asm/barrier.h:68:32: note: in definition of macro '__load_no_speculate_n'
    (typeof(*ptr)(unsigned long)(failval)); \
    ^~~~~~~
    ./arch/arm/include/asm/barrier.h:112:2: note: in expansion of macro '__load_no_speculate'
    __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr); \
    ^~~~~~~~~~~~~~~~~~~
    ./include/asm-generic/barrier.h:122:2: note: in expansion of macro 'nospec_ptr'
    nospec_ptr(__arr + __idx, __arr, __arr + __sz); \
    ^~~~~~~~~~
    ./include/linux/fdtable.h:86:13: note: in expansion of macro 'nospec_array_ptr'
    if ((fdp = nospec_array_ptr(fdt->fd, fd, fdt->max_fds)))
    ^~~~~~~~~~~~~~~~
    ./arch/arm/include/asm/barrier.h:112:41: error: expected declaration specifiers or '...' before numeric constant
    __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr); \
    ^
    ./arch/arm/include/asm/barrier.h:68:32: note: in definition of macro '__load_no_speculate_n'
    (typeof(*ptr)(unsigned long)(failval)); \
    ^~~~~~~
    ./arch/arm/include/asm/barrier.h:112:2: note: in expansion of macro '__load_no_speculate'
    __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr); \
    ^~~~~~~~~~~~~~~~~~~
    ./include/asm-generic/barrier.h:122:2: note: in expansion of macro 'nospec_ptr'
    nospec_ptr(__arr + __idx, __arr, __arr + __sz); \
    ^~~~~~~~~~
    ./include/linux/fdtable.h:86:13: note: in expansion of macro 'nospec_array_ptr'
    if ((fdp = nospec_array_ptr(fdt->fd, fd, fdt->max_fds)))

    I can't puzzle out what exactly is the problem here, except that it really
    does not seem to like that failval. Does the arm compiler not like doing
    the typeof with the __arr + __idx?

    Thanks,
    Laura

    > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
    > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    > ---
    > arch/arm/include/asm/barrier.h | 75 ++++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 75 insertions(+)
    >
    > diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h
    > index 40f5c410fd8c..6384c90e4b72 100644
    > --- a/arch/arm/include/asm/barrier.h
    > +++ b/arch/arm/include/asm/barrier.h
    > @@ -37,6 +37,81 @@
    > #define dmb(x) __asm__ __volatile__ ("" : : : "memory")
    > #endif
    >
    > +#ifdef CONFIG_THUMB2_KERNEL
    > +#define __load_no_speculate_n(ptr, lo, hi, failval, cmpptr, sz) \
    > +({ \
    > + typeof(*ptr) __nln_val; \
    > + typeof(*ptr) __failval = \
    > + (typeof(*ptr)(unsigned long)(failval)); \
    > + \
    > + asm volatile ( \
    > + " cmp %[c], %[l]\n" \
    > + " it hs\n" \
    > + " cmphs %[h], %[c]\n" \
    > + " blo 1f\n" \
    > + " ld" #sz " %[v], %[p]\n" \
    > + "1: it lo\n" \
    > + " movlo %[v], %[f]\n" \
    > + " .inst 0xf3af8014 @ CSDB\n" \
    > + : [v] "=&r" (__nln_val) \
    > + : [p] "m" (*(ptr)), [l] "r" (lo), [h] "r" (hi), \
    > + [f] "r" (__failval), [c] "r" (cmpptr) \
    > + : "cc"); \
    > + \
    > + __nln_val; \
    > +})
    > +#else
    > +#define __load_no_speculate_n(ptr, lo, hi, failval, cmpptr, sz) \
    > +({ \
    > + typeof(*ptr) __nln_val; \
    > + typeof(*ptr) __failval = \
    > + (typeof(*ptr)(unsigned long)(failval)); \
    > + \
    > + asm volatile ( \
    > + " cmp %[c], %[l]\n" \
    > + " cmphs %[h], %[c]\n" \
    > + " ldr" #sz "hi %[v], %[p]\n" \
    > + " movls %[v], %[f]\n" \
    > + " .inst 0xe320f014 @ CSDB\n" \
    > + : [v] "=&r" (__nln_val) \
    > + : [p] "m" (*(ptr)), [l] "r" (lo), [h] "r" (hi), \
    > + [f] "r" (__failval), [c] "r" (cmpptr) \
    > + : "cc"); \
    > + \
    > + __nln_val; \
    > +})
    > +#endif
    > +
    > +#define __load_no_speculate(ptr, lo, hi, failval, cmpptr) \
    > +({ \
    > + typeof(*(ptr)) __nl_val; \
    > + \
    > + switch (sizeof(__nl_val)) { \
    > + case 1: \
    > + __nl_val = __load_no_speculate_n(ptr, lo, hi, failval, \
    > + cmpptr, b); \
    > + break; \
    > + case 2: \
    > + __nl_val = __load_no_speculate_n(ptr, lo, hi, failval, \
    > + cmpptr, h); \
    > + break; \
    > + case 4: \
    > + __nl_val = __load_no_speculate_n(ptr, lo, hi, failval, \
    > + cmpptr, ); \
    > + break; \
    > + default: \
    > + BUILD_BUG(); \
    > + } \
    > + \
    > + __nl_val; \
    > +})
    > +
    > +#define nospec_ptr(ptr, lo, hi) \
    > +({ \
    > + typeof(ptr) __np_ptr = (ptr); \
    > + __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr); \
    > +})
    > +
    > #ifdef CONFIG_ARM_HEAVY_MB
    > extern void (*soc_mb)(void);
    > extern void arm_heavy_mb(void);
    >

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