Can you please attach a pre-processed file for an object that fails with objtool?

Assuming GCC 10.1 - you didn't specify.

(In reply to Richard Biener from comment #2)
> Assuming GCC 10.1 - you didn't specify.

In my env I can reproduce it on 8.3.0 / 9.2.0 / 9.3.0/ 10.1.0

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/8.3.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-8.3.0-r1/work/gcc-8.3.0/configure --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/8.3.0 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/8.3.0 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/8.3.0/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/8.3.0/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/g++-v8 --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/8.3.0/python --enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --disable-nls --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo Hardened 8.3.0-r1 p1.1' --enable-esp --enable-libstdcxx-time --disable-libstdcxx-pch --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --disable-multilib --with-multilib-list=m64 --disable-altivec --disable-fixed-point --enable-targets=all --enable-libgomp --disable-libmudflap --disable-libssp --disable-libmpx --disable-systemtap --enable-vtable-verify --enable-lto --without-isl --enable-default-pie --enable-default-ssp
Thread model: posix
gcc version 8.3.0 (Gentoo Hardened 8.3.0-r1 p1.1) 



Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/9.3.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-9.3.0/work/gcc-9.3.0/configure --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/9.3.0 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.3.0 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.3.0/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/9.3.0/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0/include/g++-v9 --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/9.3.0/python --enable-languages=c,c++ --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --disable-nls --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo Hardened 9.3.0 p2' --enable-esp --enable-libstdcxx-time --with-build-config=bootstrap-lto --disable-libstdcxx-pch --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --disable-multilib --with-multilib-list=m64 --disable-altivec --disable-fixed-point --enable-targets=all --enable-libgomp --disable-libmudflap --disable-libssp --disable-libada --disable-systemtap --enable-vtable-verify --disable-libquadmath --enable-lto --without-isl --enable-default-pie --enable-default-ssp
Thread model: posix
gcc version 9.3.0 (Gentoo Hardened 9.3.0 p2) 



built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/10.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-10.1.0-r1/work/gcc-10.1.0/configure --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/10.1.0 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/10.1.0 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/10.1.0/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/10.1.0/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/include/g++-v10 --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/10.1.0/python --enable-languages=c,c++ --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --disable-nls --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 10.1.0-r1 p2' --disable-esp --enable-libstdcxx-time --with-build-config=bootstrap-lto --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --disable-multilib --with-multilib-list=m64 --disable-fixed-point --enable-targets=all --enable-libgomp --disable-libmudflap --disable-libssp --disable-libada --disable-systemtap --enable-vtable-verify --with-zstd --disable-libquadmath --enable-lto --with-isl --disable-isl-version-check --enable-default-pie --enable-default-ssp
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.1.0 (Gentoo 10.1.0-r1 p2)

(In reply to Martin Liška from comment #1)
> Can you please attach a pre-processed file for an object that fails with
> objtool?

Heh... I'm afraid I need some howto for this... :(

But I made some minimal reproducible .config for kernel 5.7

$ tar xf linux-5.7.tar.xz
$ cd linux-5.7
$ curl https://raw.githubusercontent.com/graysky2/kernel_gcc_patch/master/enable_additional_cpu_optimizations_for_gcc_v9.1%2B_kernel_v5.7%2B.patch | patch -p1

$ copy .config10 .config
$ make oldconfig
$ make

I will attach my .config10

For me it fails:
  CC      arch/x86/entry/vdso/vma.o
  LDS     arch/x86/entry/vdso/vdso.lds
  AS      arch/x86/entry/vdso/vdso-note.o
  CC      arch/x86/entry/vdso/vclock_gettime.o
  CC      arch/x86/entry/vdso/vgetcpu.o
  VDSO    arch/x86/entry/vdso/vdso64.so.dbg
  OBJCOPY arch/x86/entry/vdso/vdso64.so
  HOSTCC  arch/x86/entry/vdso/vdso2c
  VDSO2C  arch/x86/entry/vdso/vdso-image-64.c
  CC      arch/x86/entry/vdso/vdso-image-64.o
  AR      arch/x86/entry/vdso/built-in.a
  CC      arch/x86/entry/vsyscall/vsyscall_64.o
arch/x86/entry/vsyscall/vsyscall_64.o: warning: objtool: emulate_vsyscall()+0x60: can't find jump dest instruction at .text+0x10a
make[3]: *** [scripts/Makefile.build:267: arch/x86/entry/vsyscall/vsyscall_64.o] Error 255
make[3]: *** Deleting file 'arch/x86/entry/vsyscall/vsyscall_64.o'
make[2]: *** [scripts/Makefile.build:488: arch/x86/entry/vsyscall] Error 2
make[1]: *** [scripts/Makefile.build:488: arch/x86/entry] Error 2
make: *** [Makefile:1729: arch/x86] Error 2

Created attachment 48732 [details]
some minimal config for kerknel 5.7 for reproduce

(In reply to Maxim Britov from comment #4)
> (In reply to Martin Liška from comment #1)
> > Can you please attach a pre-processed file for an object that fails with
> > objtool?
> 
> Heh... I'm afraid I need some howto for this... :(
> 

Add -E option to the compilation and attach the output file.

make arch/x86/entry/vsyscall/vsyscall_64.i

I've got a reduced test-case:

$ cat lbr.i
int a, c, d;
long b;

void
fn1() {
  for (; c; c++) {
    int e, f = 0;
    if (a) {
      e = !(d & 1ULL << 63);
      f = e;
    }
    d = fn1;
    b = f;
  }
}

$ gcc lbr.i -c -O2 -march=bdver2 -c && ~/Programming/linux/tools/objtool/objtool check --uaccess lbr.o
lbr.i: In function ‘fn1’:
lbr.i:12:7: warning: assignment to ‘int’ from ‘void (*)()’ makes integer from pointer without a cast [-Wint-conversion]
   12 |     d = fn1;
      |       ^
lbr.o: warning: objtool: fn1()+0x26: can't find jump dest instruction at .text+0x36

disassembly:
  26:	74 0e                	je     36 <fn1+0x36>
  28:	48 0f ba fa 1f       	btc    $0x1f,%rdx
  2d:	8f ea f8 10 ca 1f 01 	bextr  $0x11f,%rdx,%rcx
  34:	00 00 
  36:	ff c0                	inc    %eax

It seems to me bextr is not supported (parsed) by objtool?

Created attachment 48733 [details]
gcc -E ...

I believe attachment is what you aksed. I did

gcc -E -Wp,-MD,arch/x86/entry/vsyscall/.vsyscall_64.o.d -nostdinc -isystem /usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/include -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE -Werror=implicit-function-declaration -Werror=implicit-int -Wno-format-security -std=gnu89 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup -march=bdver2 -mno-red-zone -mcmodel=kernel -Wno-sign-compare -fno-asynchronous-unwind-tables -fno-delete-null-pointer-checks -Wno-frame-address -Wno-format-truncation -Wno-format-overflow -Wno-address-of-packed-member -O2 -fno-allow-store-data-races -Wframe-larger-than=2048 -fno-stack-protector -Wno-unused-but-set-variable -Wimplicit-fallthrough -Wno-unused-const-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -Wno-stringop-truncation -Wno-zero-length-bounds -Wno-array-bounds -Wno-stringop-overflow -Wno-restrict -Wno-maybe-uninitialized -fno-strict-overflow -fno-merge-all-constants -fmerge-constants -fno-stack-check -fconserve-stack -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -fmacro-prefix-map=./= -Wno-packed-not-aligned    -DKBUILD_MODFILE='"arch/x86/entry/vsyscall/vsyscall_64"' -DKBUILD_BASENAME='"vsyscall_64"' -DKBUILD_MODNAME='"vsyscall_64"' -c -o arch/x86/entry/vsyscall/vsyscall_64.o arch/x86/entry/vsyscall/vsyscall_64.c


Fail was:

make -f ./scripts/Makefile.build obj=arch/x86/entry/vsyscall \
 \
need-builtin=1 \
need-modorder=1
  gcc -Wp,-MD,arch/x86/entry/vsyscall/.vsyscall_64.o.d -nostdinc -isystem /usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/include -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE -Werror=implicit-function-declaration -Werror=implicit-int -Wno-format-security -std=gnu89 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup -march=bdver2 -mno-red-zone -mcmodel=kernel -Wno-sign-compare -fno-asynchronous-unwind-tables -fno-delete-null-pointer-checks -Wno-frame-address -Wno-format-truncation -Wno-format-overflow -Wno-address-of-packed-member -O2 -fno-allow-store-data-races -Wframe-larger-than=2048 -fno-stack-protector -Wno-unused-but-set-variable -Wimplicit-fallthrough -Wno-unused-const-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -Wno-stringop-truncation -Wno-zero-length-bounds -Wno-array-bounds -Wno-stringop-overflow -Wno-restrict -Wno-maybe-uninitialized -fno-strict-overflow -fno-merge-all-constants -fmerge-constants -fno-stack-check -fconserve-stack -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -fmacro-prefix-map=./= -Wno-packed-not-aligned    -DKBUILD_MODFILE='"arch/x86/entry/vsyscall/vsyscall_64"' -DKBUILD_BASENAME='"vsyscall_64"' -DKBUILD_MODNAME='"vsyscall_64"' -c -o arch/x86/entry/vsyscall/vsyscall_64.o arch/x86/entry/vsyscall/vsyscall_64.c
   ./tools/objtool/objtool check  --uaccess arch/x86/entry/vsyscall/vsyscall_64.o
arch/x86/entry/vsyscall/vsyscall_64.o: warning: objtool: emulate_vsyscall()+0x60: can't find jump dest instruction at .text+0xca
make[3]: *** [scripts/Makefile.build:267: arch/x86/entry/vsyscall/vsyscall_64.o] Error 255
make[3]: *** Deleting file 'arch/x86/entry/vsyscall/vsyscall_64.o'
make[2]: *** [scripts/Makefile.build:488: arch/x86/entry/vsyscall] Error 2
make[1]: *** [scripts/Makefile.build:488: arch/x86/entry] Error 2
make: *** [Makefile:1729: arch/x86] Error 2

Yep, I've already created a reduced-testcase myself:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95671#c6

That is clearly a kernel/objtool bug.
Seems it has its own x86_64 instruction decoder and has some VEX decoding code, but either not well tested or not working in this particular case.
Kernel doesn't normally use floating point or SIMD instructions, therefore I'd expect that it only rarely uses VEX encoded instructions, and BEXTR is one of the few general purpose instructions that are VEX encoded.

Please report it to kernel bugzilla or whatever objtool has bugtracker.
https://bugs.gentoo.org/642924
is very likely exactly the same thing, but not sure if they have reported it upstream.

New report https://bugzilla.kernel.org/show_bug.cgi?id=208187

Thanks!