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[158.174.22.223]) by smtp.gmail.com with ESMTPSA id z11sm2395073lfr.73.2021.05.10.15.52.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 May 2021 15:52:03 -0700 (PDT) From: Rikard Falkeborn X-Google-Original-From: Rikard Falkeborn Date: Tue, 11 May 2021 00:51:58 +0200 To: Andy Shevchenko Cc: Tetsuo Handa , Rikard Falkeborn , Yury Norov , Linux Kernel Mailing List , Andrew Morton , Rasmus Villemoes , linux-m68k , Linux-Arch , Linux-SH , Alexey Klimov , Andy Shevchenko , Arnd Bergmann , David Sterba , Dennis Zhou , Geert Uytterhoeven , Jianpeng Ma , Joe Perches , John Paul Adrian Glaubitz , Josh Poimboeuf , Rich Felker , Stefano Brivio , Wei Yang , Wolfram Sang , Yoshinori Sato Subject: Re: [PATCH 11/12] tools: sync lib/find_bit implementation Message-ID: References: <20210401003153.97325-1-yury.norov@gmail.com> <20210401003153.97325-12-yury.norov@gmail.com> <1ac7bbc2-45d9-26ed-0b33-bf382b8d858b@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org On Mon, May 10, 2021 at 06:44:44PM +0300, Andy Shevchenko wrote: > +Cc: Rikard > > On Mon, May 10, 2021 at 6:31 PM Tetsuo Handa > wrote: > > > > Commit eaae7841ba83bb42 ("tools: sync lib/find_bit implementation") broke > > build of 5.13-rc1 using gcc (GCC) 8.3.1 20190311 (Red Hat 8.3.1-3). > > > > DESCEND objtool > > CC /usr/src/linux/tools/objtool/exec-cmd.o > > CC /usr/src/linux/tools/objtool/help.o > > CC /usr/src/linux/tools/objtool/pager.o > > CC /usr/src/linux/tools/objtool/parse-options.o > > CC /usr/src/linux/tools/objtool/run-command.o > > CC /usr/src/linux/tools/objtool/sigchain.o > > CC /usr/src/linux/tools/objtool/subcmd-config.o > > LD /usr/src/linux/tools/objtool/libsubcmd-in.o > > AR /usr/src/linux/tools/objtool/libsubcmd.a > > CC /usr/src/linux/tools/objtool/arch/x86/special.o > > In file included from /usr/src/linux/tools/include/linux/kernel.h:8:0, > > from /usr/src/linux/tools/include/linux/list.h:7, > > from /usr/src/linux/tools/objtool/include/objtool/arch.h:10, > > from /usr/src/linux/tools/objtool/include/objtool/check.h:11, > > from /usr/src/linux/tools/objtool/include/objtool/special.h:10, > > from arch/x86/special.c:4: > > /usr/src/linux/tools/include/asm-generic/bitops/find.h: In function 'find_next_bit': > > /usr/src/linux/tools/include/linux/bits.h:24:21: error: first argument to '__builtin_choose_expr' not a constant > > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > ^ > > /usr/src/linux/tools/include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO' > > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) > > ^ > > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK' > > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h:32:17: note: in expansion of macro 'GENMASK' > > val = *addr & GENMASK(size - 1, offset); > > ^ > > /usr/src/linux/tools/include/linux/build_bug.h:16:51: error: bit-field '' width not an integer constant > > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) > > ^ > > /usr/src/linux/tools/include/linux/bits.h:24:3: note: in expansion of macro 'BUILD_BUG_ON_ZERO' > > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > ^ > > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK' > > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h:32:17: note: in expansion of macro 'GENMASK' > > val = *addr & GENMASK(size - 1, offset); > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h: In function 'find_next_and_bit': > > /usr/src/linux/tools/include/linux/bits.h:24:21: error: first argument to '__builtin_choose_expr' not a constant > > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > ^ > > /usr/src/linux/tools/include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO' > > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) > > ^ > > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK' > > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h:62:27: note: in expansion of macro 'GENMASK' > > val = *addr1 & *addr2 & GENMASK(size - 1, offset); > > ^ > > /usr/src/linux/tools/include/linux/build_bug.h:16:51: error: bit-field '' width not an integer constant > > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) > > ^ > > /usr/src/linux/tools/include/linux/bits.h:24:3: note: in expansion of macro 'BUILD_BUG_ON_ZERO' > > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > ^ > > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK' > > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h:62:27: note: in expansion of macro 'GENMASK' > > val = *addr1 & *addr2 & GENMASK(size - 1, offset); > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h: In function 'find_next_zero_bit': > > /usr/src/linux/tools/include/linux/bits.h:24:21: error: first argument to '__builtin_choose_expr' not a constant > > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > ^ > > /usr/src/linux/tools/include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO' > > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) > > ^ > > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK' > > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h:90:18: note: in expansion of macro 'GENMASK' > > val = *addr | ~GENMASK(size - 1, offset); > > ^ > > /usr/src/linux/tools/include/linux/build_bug.h:16:51: error: bit-field '' width not an integer constant > > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) > > ^ > > /usr/src/linux/tools/include/linux/bits.h:24:3: note: in expansion of macro 'BUILD_BUG_ON_ZERO' > > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > ^ > > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK' > > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) > > ^ > > /usr/src/linux/tools/include/asm-generic/bitops/find.h:90:18: note: in expansion of macro 'GENMASK' > > val = *addr | ~GENMASK(size - 1, offset); > > ^ > > make[5]: *** [/usr/src/linux/tools/objtool/arch/x86/special.o] Error 1 > > make[4]: *** [arch/x86] Error 2 > > make[3]: *** [/usr/src/linux/tools/objtool/objtool-in.o] Error 2 > > make[2]: *** [objtool] Error 2 > > make[1]: *** [tools/objtool] Error 2 > > make: *** [__sub-make] Error 2 > > > > Some background: when I added the input check to GENMASK there was originally a check that disabled the input check if gcc versions earlier than 4.9, since for old compilers, there was a bug [1] where for some constructs, __builtin_constant_p() did not evaluate to a constant. This was supposedly fixed in gcc 4.9, but apparently there are newer gcc versions which suffer from this too. [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449 > > > > Applying below diff seems to solve the build failure. > > It will desynchronize this implementation with the mother's one (i.e. > in bits.h). > > > Do we need to use BUILD_BUG_ON_ZERO() here? > > Rikard? Yes, (as Yury pointed out), GENMASK is used in for example structure initializers where BUIlD_BUG() can not be used. > > > > > diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h > > index 7f475d59a097..0aba9294f29d 100644 > > --- a/tools/include/linux/bits.h > > +++ b/tools/include/linux/bits.h > > @@ -21,8 +21,7 @@ > > #if !defined(__ASSEMBLY__) > > #include > > #define GENMASK_INPUT_CHECK(h, l) \ > > - (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > - __builtin_constant_p((l) > (h)), (l) > (h), 0))) > > + ({ BUILD_BUG_ON(__builtin_constant_p((l) > (h)) && ((l) > (h))); 0; }) > > #else > > /* > > * BUILD_BUG_ON_ZERO is not available in h files included from asm files, Does the following work for you? For simplicity, I copied__is_constexpr from include/linux/minmax.h (which isn't available in tools/). A proper patch would reuse __is_constexpr (possibly refactoring it to a separate header since bits.h including minmax.h for that only seems smelly) and fix bits.h in the kernel header as well, to keep the files in sync. diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h index 7f475d59a097..7bc4c31a7df0 100644 --- a/tools/include/linux/bits.h +++ b/tools/include/linux/bits.h @@ -19,10 +19,13 @@ * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000. */ #if !defined(__ASSEMBLY__) + +#define __is_constexpr(x) \ + (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) #include #define GENMASK_INPUT_CHECK(h, l) \ (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ - __builtin_constant_p((l) > (h)), (l) > (h), 0))) + __is_constexpr((l) > (h)), (l) > (h), 0))) #else /* * BUILD_BUG_ON_ZERO is not available in h files included from asm files, I think any solution which results in using __GENMASK to avoid the input check will just result in similar reports in the future. Rikard