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On Mon, 11 Jun 2018 14:50:24 +0200 Florian Weimer <fweimer@redhat.com> wrote: > On 06/11/2018 02:35 PM, Sergei Trofimovich wrote: > > On Mon, 11 Jun 2018 08:17:37 -0300 > > Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote: > > > >> On 11/06/2018 07:46, Florian Weimer wrote: > >>> On 06/11/2018 12:28 PM, Sergei Trofimovich wrote: > >>>> When glibc is built on armv7 with CFLAGS="-pipe -march=armv7-a -O2 -mfpu=neon" > >>>> rtld fails to link due to missing memcpy symbol. > >>>> > >>>> This happens because .c files are built with -mfpu=neon flag but .S/.s files > >>>> are built without it. Among other things -mfpu=neon defines __ARM_NEON__. > >>>> > >>>> To fix this mismatch CFLAGS should be passed consistently to .c and .S files. > >>> > >>> Please check if you can fix this by putting the architecture selection flags into the CC and CXX variables when invoking configure. > > > > I'm not sure just adding an arch flag is enough: > > https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/arm/armv7/multiarch/memcpy_neon.S;h=1a8d8bbe9e128618105be0652de42a34fbc52d73;hb=HEAD > > ... > > 2 #ifndef __ARM_NEON__ > > 3 # define memcpy __memcpy_neon > > Here memcpy_neon.S explicitly supports both neon-enabled and disabled flags. > > Does this mean your proposed patch fails to address the issue, too? My proposed patch fixes ld.so linkage (and ld.so seems to work). > The tricky part here is that the IFUNC selector is C, but the > alternative implementation is in assembler, so it's not a matter of > adding an #include for the rtld build. As I understand IFUNC selector is not used at all for -mfpu=neon target (due to "!defined (__ARM_NEON__)"): https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/arm/armv7/multiarch/memcpy.c;h=02776b6fe6ec9aa6aa7efb8c1770970d73fe50d5;hb=HEAD 22 #if IS_IN (libc) && !defined (__ARM_NEON__) ... 32 arm_libc_ifunc_redirected (__redirect_memcpy, memcpy, IFUNC_SELECTOR); 33 34 arm_libc_ifunc_hidden_def (__redirect_memcpy, memcpy); 35 #endif Or in other words how glibc seems to work today: - -mfpu=neon -> no IFUNC selection, memcpy_neon.S is supposed to define __memcpy - no -mfpu=neon -> IFUNC selection is used, memcpy_neon.S is supposed to define __memcpy_neon > I think a file > > sysdeps/arm/armv7/multiarch/rtld-memcpy.S > > with > > #ifdef __ARM_NEON__ > # include <sysdeps/arm/armv7/multiarch/memcpy_neon.S> > #else > # include <sysdeps/arm/armv7/multiarch/memcpy_noneon.S> > #endif > > might fix this, without affecting the IFUNCs in the libc.so build for > !__ARM_NEON__. Similarly for memchr. > > Thanks, > Florian -- Sergei
Attachment:
pgpIoB_S_XleF.pgp
Description: Цифровая подпись OpenPGP
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