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Message-ID: <20240813221221.GA798176@thelio-3990X>
Date: Tue, 13 Aug 2024 15:12:21 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Yury Norov <yury.norov@...il.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
Kees Cook <kees@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
Przemek Kitszel <przemyslaw.kitszel@...el.com>,
kernel test robot <lkp@...el.com>, llvm@...ts.linux.dev,
llvm-bugs@...ts.llvm.org
Subject: Re: lib/test_bitmap.c:1278:2: error: call to
'__compiletime_assert_127' declared with 'error' attribute: BUILD_BUG_ON
failed: !__builtin_constant_p(~var)
On Tue, Aug 13, 2024 at 12:47:27PM -0700, Yury Norov wrote:
> On Tue, Aug 13, 2024 at 04:38:10PM +0200, Alexander Lobakin wrote:
> > From: Kernel Test Robot <lkp@...el.com>
> > Date: Tue, 13 Aug 2024 17:00:56 +0800
> >
> > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > head: d74da846046aeec9333e802f5918bd3261fb5509
> > > commit: 7adaf37f7f104a7ee5f150af491674ccbbfc4114 lib/bitmap: add compile-time test for __assign_bit() optimization
> > > date: 4 months ago
> > > config: um-randconfig-r132-20240812 (https://download.01.org/0day-ci/archive/20240813/202408131601.Aj9JmK7K-lkp@intel.com/config)
> > > compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project f86594788ce93b696675c94f54016d27a6c21d18)
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240813/202408131601.Aj9JmK7K-lkp@intel.com/reproduce)
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@...el.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202408131601.Aj9JmK7K-lkp@intel.com/
> > >
> > > All errors (new ones prefixed by >>):
> > >
> > >>> lib/test_bitmap.c:1278:2: error: call to '__compiletime_assert_127' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(~var)
> > > 1278 | BUILD_BUG_ON(!__builtin_constant_p(~var));
> > > | ^
> > > include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
> > > 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> > > | ^
> > > include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
> > > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> > > | ^
> > > include/linux/compiler_types.h:460:2: note: expanded from macro 'compiletime_assert'
> > > 460 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > > | ^
> > > include/linux/compiler_types.h:448:2: note: expanded from macro '_compiletime_assert'
> > > 448 | __compiletime_assert(condition, msg, prefix, suffix)
> > > | ^
> > > include/linux/compiler_types.h:441:4: note: expanded from macro '__compiletime_assert'
> > > 441 | prefix ## suffix(); \
> > > | ^
> > > <scratch space>:193:1: note: expanded from here
> > > 193 | __compiletime_assert_127
> > > | ^
> > > 1 error generated.
> > >
> > >
> > > vim +1278 lib/test_bitmap.c
> > >
> > > 291f93ca339f5b Barry Song 2021-08-06 1227
> > > 2356d198d2b4dd Yury Norov 2023-07-17 1228 /*
> > > 2356d198d2b4dd Yury Norov 2023-07-17 1229 * FIXME: Clang breaks compile-time evaluations when KASAN and GCOV are enabled.
> > > 2356d198d2b4dd Yury Norov 2023-07-17 1230 * To workaround it, GCOV is force-disabled in Makefile for this configuration.
> > > 2356d198d2b4dd Yury Norov 2023-07-17 1231 */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1232 static void __init test_bitmap_const_eval(void)
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1233 {
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1234 DECLARE_BITMAP(bitmap, BITS_PER_LONG);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1235 unsigned long initvar = BIT(2);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1236 unsigned long bitopvar = 0;
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1237 unsigned long var = 0;
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1238 int res;
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1239
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1240 /*
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1241 * Compilers must be able to optimize all of those to compile-time
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1242 * constants on any supported optimization level (-O2, -Os) and any
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1243 * architecture. Otherwise, trigger a build bug.
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1244 * The whole function gets optimized out then, there's nothing to do
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1245 * in runtime.
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1246 */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1247
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1248 /* Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }` */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1249 bitmap_clear(bitmap, 0, BITS_PER_LONG);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1250 if (!test_bit(7, bitmap))
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1251 bitmap_set(bitmap, 5, 2);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1252
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1253 /* Equals to `unsigned long bitopvar = BIT(20)` */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1254 __change_bit(31, &bitopvar);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1255 bitmap_shift_right(&bitopvar, &bitopvar, 11, BITS_PER_LONG);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1256
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1257 /* Equals to `unsigned long var = BIT(25)` */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1258 var |= BIT(25);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1259 if (var & BIT(0))
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1260 var ^= GENMASK(9, 6);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1261
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1262 /* __const_hweight<32|64>(GENMASK(6, 5)) == 2 */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1263 res = bitmap_weight(bitmap, 20);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1264 BUILD_BUG_ON(!__builtin_constant_p(res));
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1265 BUILD_BUG_ON(res != 2);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1266
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1267 /* !(BIT(31) & BIT(18)) == 1 */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1268 res = !test_bit(18, &bitopvar);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1269 BUILD_BUG_ON(!__builtin_constant_p(res));
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1270 BUILD_BUG_ON(!res);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1271
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1272 /* BIT(2) & GENMASK(14, 8) == 0 */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1273 res = initvar & GENMASK(14, 8);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1274 BUILD_BUG_ON(!__builtin_constant_p(res));
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1275 BUILD_BUG_ON(res);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1276
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1277 /* ~BIT(25) */
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 @1278 BUILD_BUG_ON(!__builtin_constant_p(~var));
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1279 BUILD_BUG_ON(~var != ~BIT(25));
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1280
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1281 /* ~BIT(25) | BIT(25) == ~0UL */
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1282 bitmap_complement(&var, &var, BITS_PER_LONG);
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1283 __assign_bit(25, &var, true);
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1284
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1285 /* !(~(~0UL)) == 1 */
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1286 res = bitmap_full(&var, BITS_PER_LONG);
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1287 BUILD_BUG_ON(!__builtin_constant_p(res));
> > > 7adaf37f7f104a Alexander Lobakin 2024-03-27 1288 BUILD_BUG_ON(!res);
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1289 }
> > > dc34d5036692c6 Alexander Lobakin 2022-06-24 1290
> > >
> > > :::::: The code at line 1278 was first introduced by commit
> > > :::::: dc34d5036692c614eef23c1130ee42a201c316bf lib: test_bitmap: add compile-time optimization/evaluations assertions
> > >
> > > :::::: TO: Alexander Lobakin <alexandr.lobakin@...el.com>
> > > :::::: CC: Yury Norov <yury.norov@...il.com>
> >
> > + Cc Clang folks.
> >
> > clang-dev 20 issue?
> >
> > Thanks,
> > Olek
>
> Seems like that. Looping LLVM-bugs <llvm-bugs@...ts.llvm.org>.
It's not, I bisected it to a change in the 17 release. I think this only
shows up with this change because of '-fprofile-instr-generate', which
ARCH=um uses for GCOV, which was only added in commit 32a84cfc6caf
("arch: um: Add Clang coverage support") from 6.8.
I reported this upstream (I don't think llvm-bugs is really monitored
for traffic like this) and cc'd the author of the change that broke
this:
https://github.com/llvm/llvm-project/issues/103479
I think there is a tangential issue with ARCH=um doing its own thing
with the GCOV flags (such that it does not appear to respect
GCOV_PROFILE_... := n) but that just results in not being able to remove
the flags from test_bitmap.o's command.
Cheers,
Nathan
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