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Date: Fri, 5 Nov 2021 13:21:33 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: kernel test robot <lkp@...el.com>
Cc: llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
linux-kernel@...r.kernel.org
Subject: Re: [peterz-queue:x86/wip.extable 1/22]
drivers/crypto/ccree/cc_driver.c:117:18: warning: result of comparison of
constant 18446744073709551615 with expression of type 'typeof
(_Generic((mask), char: (unsigned char)0, unsigned char: (unsigned char)0,
signed char: (unsigned char)0, unsigned shor...
On Fri, Nov 05, 2021 at 06:17:44PM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/wip.extable
> head: a4d149db054a77aa35b04bb088f749cbb9a2edea
> commit: 4b9e954553a4137f7504e068438851c27edc6b22 [1/22] bitfield.h: Fix "type of reg too small for mask" test
> config: riscv-randconfig-r032-20211105 (attached as .config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 847a6807332b13f43704327c2d30103ec0347c77)
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # install riscv cross compiling tool for clang build
> # apt-get install binutils-riscv64-linux-gnu
> # https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?id=4b9e954553a4137f7504e068438851c27edc6b22
> git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git
> git fetch --no-tags peterz-queue x86/wip.extable
> git checkout 4b9e954553a4137f7504e068438851c27edc6b22
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=riscv
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
> >> drivers/crypto/ccree/cc_driver.c:117:18: warning: result of comparison of constant 18446744073709551615 with expression of type 'typeof (_Generic((mask), char: (unsigned char)0, unsigned char: (unsigned char)0, signed char: (unsigned char)0, unsigned short: (unsigned short)0, short: (unsigned short)0, unsigned int: (unsigned int)0, int: (unsigned int)0, unsigned long: (unsigned long)0, long: (unsigned long)0, unsigned long long: (unsigned long long)0, long long: (unsigned long long)0, default: (mask)))' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
> cache_params |= FIELD_PREP(mask, val);
> ^~~~~~~~~~~~~~~~~~~~~
> include/linux/bitfield.h:111:3: note: expanded from macro 'FIELD_PREP'
> __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/linux/bitfield.h:68:53: note: expanded from macro '__BF_FIELD_CHECK'
> BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
> include/linux/build_bug.h:39:58: note: expanded from macro 'BUILD_BUG_ON_MSG'
> #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
> include/linux/compiler_types.h:322:22: note: expanded from macro 'compiletime_assert'
> _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/linux/compiler_types.h:310:23: note: expanded from macro '_compiletime_assert'
> __compiletime_assert(condition, msg, prefix, suffix)
> ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/linux/compiler_types.h:302:9: note: expanded from macro '__compiletime_assert'
> if (!(condition)) \
> ^~~~~~~~~
I'm confused here.. the code reads:
#define __scalar_type_to_unsigned_cases(type) \
unsigned type: (unsigned type)0, \
signed type: (unsigned type)0
#define __unsigned_scalar_typeof(x) typeof( \
_Generic((x), \
char: (unsigned char)0, \
__scalar_type_to_unsigned_cases(char), \
__scalar_type_to_unsigned_cases(short), \
__scalar_type_to_unsigned_cases(int), \
__scalar_type_to_unsigned_cases(long), \
__scalar_type_to_unsigned_cases(long long), \
default: (x)))
#define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \
({ \
BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
_pfx "mask is not constant"); \
BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \
BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
_pfx "value too large for the field"); \
BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
__bf_cast_unsigned(_reg, ~0ull), \
_pfx "type of reg too small for mask"); \
__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
(1ULL << __bf_shf(_mask))); \
})
#define FIELD_PREP(_mask, _val) \
({ \
__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
})
static void init_cc_cache_params(struct cc_drvdata *drvdata)
{
struct device *dev = drvdata_to_dev(drvdata);
u32 cache_params, ace_const, val, mask;
...
mask = CC_GENMASK(CC_AXIM_CACHE_PARAMS_AWCACHE); <-- *BOOM*
cache_params &= ~mask;
cache_params |= FIELD_PREP(mask, val);
...
}
So we're having "(unsigned int)mask > (unsigned long long)~0ull" as
a compile time constant input to the BUILD_BUG_ON_MSG(), and clang-14 is
now complaining it's a constant ?!?
It is that by design.
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