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Message-ID: <CAA8EJpo3X5Ljdf5w8pj+WPQZaqab4mD53VXdAxfLFqsU4mNoPQ@mail.gmail.com> Date: Wed, 21 Feb 2024 22:37:30 +0200 From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org> To: Lucas De Marchi <lucas.demarchi@...el.com> Cc: Yury Norov <yury.norov@...il.com>, linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Jani Nikula <jani.nikula@...ux.intel.com>, intel-xe@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org, Jani Nikula <jani.nikula@...el.com> Subject: Re: [PATCH v3 1/3] bits: introduce fixed-type genmasks On Wed, 21 Feb 2024 at 22:30, Dmitry Baryshkov <dmitry.baryshkov@...aro.org> wrote: > > On Thu, 8 Feb 2024 at 09:45, Lucas De Marchi <lucas.demarchi@...el.com> wrote: > > > > From: Yury Norov <yury.norov@...il.com> > > > > Generalize __GENMASK() to support different types, and implement > > fixed-types versions of GENMASK() based on it. The fixed-type version > > allows more strict checks to the min/max values accepted, which is > > useful for defining registers like implemented by i915 and xe drivers > > with their REG_GENMASK*() macros. > > > > The strict checks rely on shift-count-overflow compiler check to > > fail the build if a number outside of the range allowed is passed. > > Example: > > > > #define FOO_MASK GENMASK_U32(33, 4) > > > > will generate a warning like: > > > > ../include/linux/bits.h:41:31: error: left shift count >= width of type [-Werror=shift-count-overflow] > > 41 | (((t)~0ULL - ((t)(1) << (l)) + 1) & \ > > | ^~ > > > > Signed-off-by: Yury Norov <yury.norov@...il.com> > > Signed-off-by: Lucas De Marchi <lucas.demarchi@...el.com> > > Acked-by: Jani Nikula <jani.nikula@...el.com> > > --- > > include/linux/bitops.h | 1 - > > include/linux/bits.h | 32 ++++++++++++++++++++++---------- > > 2 files changed, 22 insertions(+), 11 deletions(-) > > > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h > > index 2ba557e067fe..1db50c69cfdb 100644 > > --- a/include/linux/bitops.h > > +++ b/include/linux/bitops.h > > @@ -15,7 +15,6 @@ > > # define aligned_byte_mask(n) (~0xffUL << (BITS_PER_LONG - 8 - 8*(n))) > > #endif > > > > -#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) > > #define BITS_TO_LONGS(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(long)) > > #define BITS_TO_U64(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u64)) > > #define BITS_TO_U32(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u32)) > > diff --git a/include/linux/bits.h b/include/linux/bits.h > > index 7c0cf5031abe..bd56f32de44e 100644 > > --- a/include/linux/bits.h > > +++ b/include/linux/bits.h > > @@ -6,6 +6,8 @@ > > #include <vdso/bits.h> > > #include <asm/bitsperlong.h> > > > > +#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) > > + > > #define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG)) > > #define BIT_WORD(nr) ((nr) / BITS_PER_LONG) > > #define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG)) > > @@ -30,16 +32,26 @@ > > #define GENMASK_INPUT_CHECK(h, l) 0 > > #endif > > > > -#define __GENMASK(h, l) \ > > - (((~UL(0)) - (UL(1) << (l)) + 1) & \ > > - (~UL(0) >> (BITS_PER_LONG - 1 - (h)))) > > -#define GENMASK(h, l) \ > > - (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) > > +/* > > + * Generate a mask for the specified type @t. Additional checks are made to > > + * guarantee the value returned fits in that type, relying on > > + * shift-count-overflow compiler check to detect incompatible arguments. > > + * For example, all these create build errors or warnings: > > + * > > + * - GENMASK(15, 20): wrong argument order > > + * - GENMASK(72, 15): doesn't fit unsigned long > > + * - GENMASK_U32(33, 15): doesn't fit in a u32 > > + */ > > +#define __GENMASK(t, h, l) \ > > + (GENMASK_INPUT_CHECK(h, l) + \ > > + (((t)~0ULL - ((t)(1) << (l)) + 1) & \ > > + ((t)~0ULL >> (BITS_PER_TYPE(t) - 1 - (h))))) > > > > -#define __GENMASK_ULL(h, l) \ > > - (((~ULL(0)) - (ULL(1) << (l)) + 1) & \ > > - (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h)))) > > -#define GENMASK_ULL(h, l) \ > > - (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l)) > > +#define GENMASK(h, l) __GENMASK(unsigned long, h, l) > > +#define GENMASK_ULL(h, l) __GENMASK(unsigned long long, h, l) > > +#define GENMASK_U8(h, l) __GENMASK(u8, h, l) > > +#define GENMASK_U16(h, l) __GENMASK(u16, h, l) > > +#define GENMASK_U32(h, l) __GENMASK(u32, h, l) > > +#define GENMASK_U64(h, l) __GENMASK(u64, h, l) > > This breaks drm-tip on arm64 architecture: > Excuse me, it seems a c&p from gitlab didn't work as expected. arch/arm64/kernel/entry-fpsimd.S: Assembler messages: arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:271: Error: unexpected characters following instruction at operand 3 -- `bic x2,x1,(0+(((unsigned long)~0ULL-((unsigned long)(1)<<(0))+1)&((unsigned long)~0ULL>>((sizeof(unsigned long)*8)-1-(3)))))' arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')' arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here arch/arm64/kernel/entry-fpsimd.S:282: Error: unexpected characters following instruction at operand 3 -- `bic x2,x1,(0+(((unsigned long)~0ULL-((unsigned long)(1)<<(0))+1)&((unsigned long)~0ULL>>((sizeof(unsigned long)*8)-1-(3)))))' arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here make[4]: *** [scripts/Makefile.build:361: arch/arm64/kernel/entry-fpsimd.o] Error 1 make[3]: *** [scripts/Makefile.build:481: arch/arm64/kernel] Error 2 make[2]: *** [scripts/Makefile.build:481: arch/arm64] Error 2 make[2]: *** Waiting for unfinished jobs... -- With best wishes Dmitry
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