diff mbox series

[2/9] perf symbols: Add support for x86 .plt.sec

Message ID	20230127170222.9895-3-adrian.hunter@intel.com
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; From: Adrian Hunter <adrian.hunter@intel.com> To: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>, Ian Rogers <irogers@google.com>, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH 2/9] perf symbols: Add support for x86 .plt.sec Date: Fri, 27 Jan 2023 19:02:15 +0200 Message-Id: <20230127170222.9895-3-adrian.hunter@intel.com> In-Reply-To: <20230127170222.9895-1-adrian.hunter@intel.com> References: <20230127170222.9895-1-adrian.hunter@intel.com> MIME-Version: 1.0 Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Content-Transfer-Encoding: 8bit Precedence: bulk
Series	perf symbols: Improve dso__synthesize_plt_symbols() for x86 \| [0/9] perf symbols: Improve dso__synthesize_plt_symbols() for x86 [1/9] perf symbols: Correct plt entry sizes for x86 [2/9] perf symbols: Add support for x86 .plt.sec [3/9] perf symbols: Sort plt relocations for x86 [4/9] perf symbols: Record whether a symbol is an alias for an IFUNC symbol [5/9] perf symbols: Add support for IFUNC symbols for x86_64 [6/9] perf symbols: Allow for .plt without header [7/9] perf symbols: Allow for static executables with .plt [8/9] perf symbols: Start adding support for .plt.got for x86 [9/9] perf symbols: Get symbols for .plt.got for x86-64

Commit Message

Adrian Hunter Jan. 27, 2023, 5:02 p.m. UTC

  The section .plt.sec was originally added for MPX and was first called
.plt.bnd. While MPX has been deprecated, .plt.sec is now also used for IBT.
On x86_64, IBT seems to be enabled by default, but can be switched off
using gcc option -fcf-protection=none. On 32-bit, option -z ibt will
enable IBT.

With .plt.sec, calls are made into .plt.sec instead of .plt, so it
makes more sense to put the symbols there instead of .plt. A notable
difference is that .plt.sec does not have a header entry.

For x86, when synthesizing symbols for plt, use offset and entry size of
.plt.sec instead of .plt when there is a .plt.sec section.

Example on Ubuntu 22.04 gcc 11.3:

  Before:

    $ cat tstpltlib.c
    void fn1(void) {}
    void fn2(void) {}
    void fn3(void) {}
    void fn4(void) {}
    $ cat tstplt.c
    void fn1(void);
    void fn2(void);
    void fn3(void);
    void fn4(void);

    int main()
    {
            fn4();
            fn1();
            fn2();
            fn3();
            return 0;
    }
    $ gcc --version
    gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
    Copyright (C) 2021 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions.  There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    $ gcc -Wall -Wextra -shared -o libtstpltlib.so tstpltlib.c
    $ gcc -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)
    $ readelf -SW tstplt | grep 'plt\|Name'
      [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
      [11] .rela.plt         RELA            0000000000000698 000698 000060 18  AI  6  24  8
      [13] .plt              PROGBITS        0000000000001020 001020 000050 10  AX  0   0 16
      [14] .plt.got          PROGBITS        0000000000001070 001070 000010 10  AX  0   0 16
      [15] .plt.sec          PROGBITS        0000000000001080 001080 000040 10  AX  0   0 16
    $ perf record -e intel_pt//u --filter 'filter main @ ./tstplt' ./tstplt
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.015 MB perf.data ]
    $ perf script --itrace=be --ns -F+flags,-event,+addr,-period,-comm,-tid,-cpu,-dso
    38970.522546686:   tr strt                               0 [unknown] =>     55fc222a81a9 main+0x0
    38970.522546686:   tr end  call               55fc222a81b1 main+0x8 =>     55fc222a80a0 [unknown]
    38970.522546687:   tr strt                               0 [unknown] =>     55fc222a81b6 main+0xd
    38970.522546687:   tr end  call               55fc222a81b6 main+0xd =>     55fc222a8080 [unknown]
    38970.522546688:   tr strt                               0 [unknown] =>     55fc222a81bb main+0x12
    38970.522546688:   tr end  call               55fc222a81bb main+0x12 =>     55fc222a80b0 [unknown]
    38970.522546688:   tr strt                               0 [unknown] =>     55fc222a81c0 main+0x17
    38970.522546688:   tr end  call               55fc222a81c0 main+0x17 =>     55fc222a8090 [unknown]
    38970.522546689:   tr strt                               0 [unknown] =>     55fc222a81c5 main+0x1c
    38970.522546894:   tr end  return             55fc222a81cb main+0x22 =>     7f3a4dc29d90 __libc_start_call_main+0x80

  After:

    $ perf script --itrace=be --ns -F+flags,-event,+addr,-period,-comm,-tid,-cpu,-dso
    38970.522546686:   tr strt                               0 [unknown] =>     55fc222a81a9 main+0x0
    38970.522546686:   tr end  call               55fc222a81b1 main+0x8 =>     55fc222a80a0 fn4@plt+0x0
    38970.522546687:   tr strt                               0 [unknown] =>     55fc222a81b6 main+0xd
    38970.522546687:   tr end  call               55fc222a81b6 main+0xd =>     55fc222a8080 fn1@plt+0x0
    38970.522546688:   tr strt                               0 [unknown] =>     55fc222a81bb main+0x12
    38970.522546688:   tr end  call               55fc222a81bb main+0x12 =>     55fc222a80b0 fn2@plt+0x0
    38970.522546688:   tr strt                               0 [unknown] =>     55fc222a81c0 main+0x17
    38970.522546688:   tr end  call               55fc222a81c0 main+0x17 =>     55fc222a8090 fn3@plt+0x0
    38970.522546689:   tr strt                               0 [unknown] =>     55fc222a81c5 main+0x1c
    38970.522546894:   tr end  return             55fc222a81cb main+0x22 =>     7f3a4dc29d90 __libc_start_call_main+0x80

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 tools/perf/util/symbol-elf.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

Comments

Namhyung Kim Jan. 30, 2023, 5:34 p.m. UTC | #1

Hi Adrian,

On Fri, Jan 27, 2023 at 9:02 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> The section .plt.sec was originally added for MPX and was first called
> .plt.bnd. While MPX has been deprecated, .plt.sec is now also used for IBT.
> On x86_64, IBT seems to be enabled by default, but can be switched off
> using gcc option -fcf-protection=none. On 32-bit, option -z ibt will
> enable IBT.
>
> With .plt.sec, calls are made into .plt.sec instead of .plt, so it
> makes more sense to put the symbols there instead of .plt. A notable
> difference is that .plt.sec does not have a header entry.
>
> For x86, when synthesizing symbols for plt, use offset and entry size of
> .plt.sec instead of .plt when there is a .plt.sec section.
>
> Example on Ubuntu 22.04 gcc 11.3:
>
>   Before:
>
>     $ cat tstpltlib.c
>     void fn1(void) {}
>     void fn2(void) {}
>     void fn3(void) {}
>     void fn4(void) {}
>     $ cat tstplt.c
>     void fn1(void);
>     void fn2(void);
>     void fn3(void);
>     void fn4(void);
>
>     int main()
>     {
>             fn4();
>             fn1();
>             fn2();
>             fn3();
>             return 0;
>     }
>     $ gcc --version
>     gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
>     Copyright (C) 2021 Free Software Foundation, Inc.
>     This is free software; see the source for copying conditions.  There is NO
>     warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>     $ gcc -Wall -Wextra -shared -o libtstpltlib.so tstpltlib.c
>     $ gcc -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)
>     $ readelf -SW tstplt | grep 'plt\|Name'
>       [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
>       [11] .rela.plt         RELA            0000000000000698 000698 000060 18  AI  6  24  8
>       [13] .plt              PROGBITS        0000000000001020 001020 000050 10  AX  0   0 16
>       [14] .plt.got          PROGBITS        0000000000001070 001070 000010 10  AX  0   0 16
>       [15] .plt.sec          PROGBITS        0000000000001080 001080 000040 10  AX  0   0 16

On my machine, it's not enabled by default.  And it doesn't create .plt.sec
even if I pass -fcf-protection=full option.

$ gcc --version
gcc (Debian 12.2.0-10) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gcc -Wall -Wextra -shared -fcf-protection=full -o libtstplt.so tstpltlib.c
$ gcc -Wall -Wextra -fcf-protection=full -o tstplt tstplt.c -L.
-ltstpltlib -Wl,-rpath,$(pwd)
$ readelf -SW tstplt | grep 'plt\|Name'
   [Nr] Name              Type            Address          Off    Size
  ES Flg Lk Inf Al
   [11] .rela.plt         RELA            0000000000000688 000688
000060 18  AI  6  24  8
   [13] .plt              PROGBITS        0000000000001020 001020
000050 10  AX  0   0 16
   [14] .plt.got          PROGBITS        0000000000001070 001070
000008 08  AX  0   0  8
   [24] .got.plt          PROGBITS        0000000000003fe8 002fe8
000038 08  WA  0   0  8

Thanks,
Namhyung

Adrian Hunter Jan. 30, 2023, 6:35 p.m. UTC | #2

On 30/01/23 19:34, Namhyung Kim wrote:
> Hi Adrian,
> 
> On Fri, Jan 27, 2023 at 9:02 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> The section .plt.sec was originally added for MPX and was first called
>> .plt.bnd. While MPX has been deprecated, .plt.sec is now also used for IBT.
>> On x86_64, IBT seems to be enabled by default, but can be switched off
>> using gcc option -fcf-protection=none. On 32-bit, option -z ibt will
>> enable IBT.
>>
>> With .plt.sec, calls are made into .plt.sec instead of .plt, so it
>> makes more sense to put the symbols there instead of .plt. A notable
>> difference is that .plt.sec does not have a header entry.
>>
>> For x86, when synthesizing symbols for plt, use offset and entry size of
>> .plt.sec instead of .plt when there is a .plt.sec section.
>>
>> Example on Ubuntu 22.04 gcc 11.3:
>>
>>   Before:
>>
>>     $ cat tstpltlib.c
>>     void fn1(void) {}
>>     void fn2(void) {}
>>     void fn3(void) {}
>>     void fn4(void) {}
>>     $ cat tstplt.c
>>     void fn1(void);
>>     void fn2(void);
>>     void fn3(void);
>>     void fn4(void);
>>
>>     int main()
>>     {
>>             fn4();
>>             fn1();
>>             fn2();
>>             fn3();
>>             return 0;
>>     }
>>     $ gcc --version
>>     gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
>>     Copyright (C) 2021 Free Software Foundation, Inc.
>>     This is free software; see the source for copying conditions.  There is NO
>>     warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>>     $ gcc -Wall -Wextra -shared -o libtstpltlib.so tstpltlib.c
>>     $ gcc -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)
>>     $ readelf -SW tstplt | grep 'plt\|Name'
>>       [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
>>       [11] .rela.plt         RELA            0000000000000698 000698 000060 18  AI  6  24  8
>>       [13] .plt              PROGBITS        0000000000001020 001020 000050 10  AX  0   0 16
>>       [14] .plt.got          PROGBITS        0000000000001070 001070 000010 10  AX  0   0 16
>>       [15] .plt.sec          PROGBITS        0000000000001080 001080 000040 10  AX  0   0 16
> 
> On my machine, it's not enabled by default.  And it doesn't create .plt.sec
> even if I pass -fcf-protection=full option.
> 
> $ gcc --version
> gcc (Debian 12.2.0-10) 12.2.0
> Copyright (C) 2022 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
> $ gcc -Wall -Wextra -shared -fcf-protection=full -o libtstplt.so tstpltlib.c
> $ gcc -Wall -Wextra -fcf-protection=full -o tstplt tstplt.c -L.
> -ltstpltlib -Wl,-rpath,$(pwd)
> $ readelf -SW tstplt | grep 'plt\|Name'
>    [Nr] Name              Type            Address          Off    Size
>   ES Flg Lk Inf Al
>    [11] .rela.plt         RELA            0000000000000688 000688
> 000060 18  AI  6  24  8
>    [13] .plt              PROGBITS        0000000000001020 001020
> 000050 10  AX  0   0 16
>    [14] .plt.got          PROGBITS        0000000000001070 001070
> 000008 08  AX  0   0  8
>    [24] .got.plt          PROGBITS        0000000000003fe8 002fe8
> 000038 08  WA  0   0  8

That is interesting.  What does it say with -v i.e.

	gcc -v -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)

And what is the distribution?

Namhyung Kim Jan. 30, 2023, 10:22 p.m. UTC | #3

On Mon, Jan 30, 2023 at 10:35 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> On 30/01/23 19:34, Namhyung Kim wrote:
> > Hi Adrian,
> >
> > On Fri, Jan 27, 2023 at 9:02 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
> >>
> >> The section .plt.sec was originally added for MPX and was first called
> >> .plt.bnd. While MPX has been deprecated, .plt.sec is now also used for IBT.
> >> On x86_64, IBT seems to be enabled by default, but can be switched off
> >> using gcc option -fcf-protection=none. On 32-bit, option -z ibt will
> >> enable IBT.
> >>
> >> With .plt.sec, calls are made into .plt.sec instead of .plt, so it
> >> makes more sense to put the symbols there instead of .plt. A notable
> >> difference is that .plt.sec does not have a header entry.
> >>
> >> For x86, when synthesizing symbols for plt, use offset and entry size of
> >> .plt.sec instead of .plt when there is a .plt.sec section.
> >>
> >> Example on Ubuntu 22.04 gcc 11.3:
> >>
> >>   Before:
> >>
> >>     $ cat tstpltlib.c
> >>     void fn1(void) {}
> >>     void fn2(void) {}
> >>     void fn3(void) {}
> >>     void fn4(void) {}
> >>     $ cat tstplt.c
> >>     void fn1(void);
> >>     void fn2(void);
> >>     void fn3(void);
> >>     void fn4(void);
> >>
> >>     int main()
> >>     {
> >>             fn4();
> >>             fn1();
> >>             fn2();
> >>             fn3();
> >>             return 0;
> >>     }
> >>     $ gcc --version
> >>     gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
> >>     Copyright (C) 2021 Free Software Foundation, Inc.
> >>     This is free software; see the source for copying conditions.  There is NO
> >>     warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> >>     $ gcc -Wall -Wextra -shared -o libtstpltlib.so tstpltlib.c
> >>     $ gcc -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)
> >>     $ readelf -SW tstplt | grep 'plt\|Name'
> >>       [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
> >>       [11] .rela.plt         RELA            0000000000000698 000698 000060 18  AI  6  24  8
> >>       [13] .plt              PROGBITS        0000000000001020 001020 000050 10  AX  0   0 16
> >>       [14] .plt.got          PROGBITS        0000000000001070 001070 000010 10  AX  0   0 16
> >>       [15] .plt.sec          PROGBITS        0000000000001080 001080 000040 10  AX  0   0 16
> >
> > On my machine, it's not enabled by default.  And it doesn't create .plt.sec
> > even if I pass -fcf-protection=full option.
> >
> > $ gcc --version
> > gcc (Debian 12.2.0-10) 12.2.0
> > Copyright (C) 2022 Free Software Foundation, Inc.
> > This is free software; see the source for copying conditions.  There is NO
> > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> >
> > $ gcc -Wall -Wextra -shared -fcf-protection=full -o libtstplt.so tstpltlib.c
> > $ gcc -Wall -Wextra -fcf-protection=full -o tstplt tstplt.c -L.
> > -ltstpltlib -Wl,-rpath,$(pwd)
> > $ readelf -SW tstplt | grep 'plt\|Name'
> >    [Nr] Name              Type            Address          Off    Size
> >   ES Flg Lk Inf Al
> >    [11] .rela.plt         RELA            0000000000000688 000688
> > 000060 18  AI  6  24  8
> >    [13] .plt              PROGBITS        0000000000001020 001020
> > 000050 10  AX  0   0 16
> >    [14] .plt.got          PROGBITS        0000000000001070 001070
> > 000008 08  AX  0   0  8
> >    [24] .got.plt          PROGBITS        0000000000003fe8 002fe8
> > 000038 08  WA  0   0  8
>
> That is interesting.  What does it say with -v i.e.
>
>         gcc -v -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/12/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian
12.2.0-10' --with-bugurl=file:///usr/share/doc/gcc-12/README.Bugs
--enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2
--prefix=/usr --with-gcc-major-version-only --program-suffix=-12
--program-prefix=x86_64-linux-gnu- --enable-shared
--enable-linker-build-id --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --libdir=/usr/lib
--enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new
--enable-gnu-unique-object --disable-vtable-verify --enable-plugin
--enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-12-hWCYKv/gcc-12-12.2.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-12-hWCYKv/gcc-12-12.2.0/debian/tmp-gcn/usr
--enable-offload-defaulted --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.2.0 (Debian 12.2.0-10)
COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt-'
 /usr/lib/gcc/x86_64-linux-gnu/12/cc1 -quiet -v -imultiarch
x86_64-linux-gnu tstplt.c -quiet -dumpdir tstplt- -dumpbase tstplt.c
-dumpbase-ext .c -mtune=generic -march=x86-64 -Wall -Wextra -version
-fcf-protection=full -fasynchronous-unwind-tables -o /tmp/ccKPWeTD.s
GNU C17 (Debian 12.2.0-10) version 12.2.0 (x86_64-linux-gnu)
    compiled by GNU C version 12.2.0, GMP version 6.2.1, MPFR version
4.1.0, MPC version 1.2.1, isl version isl-0.25-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/12/include-fixed"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-linux-gnu/12/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/x86_64-linux-gnu/12/include
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C17 (Debian 12.2.0-10) version 12.2.0 (x86_64-linux-gnu)
    compiled by GNU C version 12.2.0, GMP version 6.2.1, MPFR version
4.1.0, MPC version 1.2.1, isl version isl-0.25-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 0bf64a455b69fb48d1b44a013a099136
COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt-'
 as -v --64 -o /tmp/cc0IMyNr.o /tmp/ccKPWeTD.s
GNU assembler version 2.39.50 (x86_64-linux-gnu) using BFD version
(GNU Binutils for Debian) 2.39.50.20221208
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/12/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/12/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt.'
 /usr/lib/gcc/x86_64-linux-gnu/12/collect2 -plugin
/usr/lib/gcc/x86_64-linux-gnu/12/liblto_plugin.so
-plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/12/lto-wrapper
-plugin-opt=-fresolution=/tmp/ccU2c2jz.res
-plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s
-plugin-opt=-pass-through=-lc -plugin-opt=-pass-through=-lgcc
-plugin-opt=-pass-through=-lgcc_s --build-id --eh-frame-hdr -m
elf_x86_64 --hash-style=gnu --as-needed -dynamic-linker
/lib64/ld-linux-x86-64.so.2 -pie -o tstplt
/usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/Scrt1.o
/usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/crti.o
/usr/lib/gcc/x86_64-linux-gnu/12/crtbeginS.o -L.
-L/usr/lib/gcc/x86_64-linux-gnu/12
-L/usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu
-L/usr/lib/gcc/x86_64-linux-gnu/12/../../../../lib
-L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gnu
-L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/12/../../..
/tmp/cc0IMyNr.o -ltstpltlib -rpath=/home/namhyung/tmp/plt-test -lgcc
--push-state --as-needed -lgcc_s --pop-state -lc -lgcc --push-state
--as-needed -lgcc_s --pop-state
/usr/lib/gcc/x86_64-linux-gnu/12/crtendS.o
/usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/crtn.o
COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt.'


>
> And what is the distribution?

It's a Debian (Testing) with some customization.

Thanks,
Namhyung

Adrian Hunter Jan. 31, 2023, 10:14 a.m. UTC | #4

On 31/01/23 00:22, Namhyung Kim wrote:
> On Mon, Jan 30, 2023 at 10:35 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> On 30/01/23 19:34, Namhyung Kim wrote:
>>> Hi Adrian,
>>>
>>> On Fri, Jan 27, 2023 at 9:02 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>>>
>>>> The section .plt.sec was originally added for MPX and was first called
>>>> .plt.bnd. While MPX has been deprecated, .plt.sec is now also used for IBT.
>>>> On x86_64, IBT seems to be enabled by default, but can be switched off
>>>> using gcc option -fcf-protection=none. On 32-bit, option -z ibt will
>>>> enable IBT.
>>>>
>>>> With .plt.sec, calls are made into .plt.sec instead of .plt, so it
>>>> makes more sense to put the symbols there instead of .plt. A notable
>>>> difference is that .plt.sec does not have a header entry.
>>>>
>>>> For x86, when synthesizing symbols for plt, use offset and entry size of
>>>> .plt.sec instead of .plt when there is a .plt.sec section.
>>>>
>>>> Example on Ubuntu 22.04 gcc 11.3:
>>>>
>>>>   Before:
>>>>
>>>>     $ cat tstpltlib.c
>>>>     void fn1(void) {}
>>>>     void fn2(void) {}
>>>>     void fn3(void) {}
>>>>     void fn4(void) {}
>>>>     $ cat tstplt.c
>>>>     void fn1(void);
>>>>     void fn2(void);
>>>>     void fn3(void);
>>>>     void fn4(void);
>>>>
>>>>     int main()
>>>>     {
>>>>             fn4();
>>>>             fn1();
>>>>             fn2();
>>>>             fn3();
>>>>             return 0;
>>>>     }
>>>>     $ gcc --version
>>>>     gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
>>>>     Copyright (C) 2021 Free Software Foundation, Inc.
>>>>     This is free software; see the source for copying conditions.  There is NO
>>>>     warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>>>>     $ gcc -Wall -Wextra -shared -o libtstpltlib.so tstpltlib.c
>>>>     $ gcc -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)
>>>>     $ readelf -SW tstplt | grep 'plt\|Name'
>>>>       [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
>>>>       [11] .rela.plt         RELA            0000000000000698 000698 000060 18  AI  6  24  8
>>>>       [13] .plt              PROGBITS        0000000000001020 001020 000050 10  AX  0   0 16
>>>>       [14] .plt.got          PROGBITS        0000000000001070 001070 000010 10  AX  0   0 16
>>>>       [15] .plt.sec          PROGBITS        0000000000001080 001080 000040 10  AX  0   0 16
>>>
>>> On my machine, it's not enabled by default.  And it doesn't create .plt.sec
>>> even if I pass -fcf-protection=full option.
>>>
>>> $ gcc --version
>>> gcc (Debian 12.2.0-10) 12.2.0
>>> Copyright (C) 2022 Free Software Foundation, Inc.
>>> This is free software; see the source for copying conditions.  There is NO
>>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>>>
>>> $ gcc -Wall -Wextra -shared -fcf-protection=full -o libtstplt.so tstpltlib.c
>>> $ gcc -Wall -Wextra -fcf-protection=full -o tstplt tstplt.c -L.
>>> -ltstpltlib -Wl,-rpath,$(pwd)
>>> $ readelf -SW tstplt | grep 'plt\|Name'
>>>    [Nr] Name              Type            Address          Off    Size
>>>   ES Flg Lk Inf Al
>>>    [11] .rela.plt         RELA            0000000000000688 000688
>>> 000060 18  AI  6  24  8
>>>    [13] .plt              PROGBITS        0000000000001020 001020
>>> 000050 10  AX  0   0 16
>>>    [14] .plt.got          PROGBITS        0000000000001070 001070
>>> 000008 08  AX  0   0  8
>>>    [24] .got.plt          PROGBITS        0000000000003fe8 002fe8
>>> 000038 08  WA  0   0  8
>>
>> That is interesting.  What does it say with -v i.e.
>>
>>         gcc -v -Wall -Wextra -o tstplt tstplt.c -L . -ltstpltlib -Wl,-rpath=$(pwd)
> 
> Using built-in specs.
> COLLECT_GCC=gcc
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/12/lto-wrapper
> OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
> OFFLOAD_TARGET_DEFAULT=1
> Target: x86_64-linux-gnu
> Configured with: ../src/configure -v --with-pkgversion='Debian
> 12.2.0-10' --with-bugurl=file:///usr/share/doc/gcc-12/README.Bugs
> --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2
> --prefix=/usr --with-gcc-major-version-only --program-suffix=-12
> --program-prefix=x86_64-linux-gnu- --enable-shared
> --enable-linker-build-id --libexecdir=/usr/lib
> --without-included-gettext --enable-threads=posix --libdir=/usr/lib
> --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
> --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new
> --enable-gnu-unique-object --disable-vtable-verify --enable-plugin
> --enable-default-pie --with-system-zlib
> --enable-libphobos-checking=release --with-target-system-zlib=auto
> --enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet
> --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
> --enable-multilib --with-tune=generic
> --enable-offload-targets=nvptx-none=/build/gcc-12-hWCYKv/gcc-12-12.2.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-12-hWCYKv/gcc-12-12.2.0/debian/tmp-gcn/usr
> --enable-offload-defaulted --without-cuda-driver
> --enable-checking=release --build=x86_64-linux-gnu
> --host=x86_64-linux-gnu --target=x86_64-linux-gnu
> Thread model: posix
> Supported LTO compression algorithms: zlib zstd
> gcc version 12.2.0 (Debian 12.2.0-10)
> COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
> 'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt-'
>  /usr/lib/gcc/x86_64-linux-gnu/12/cc1 -quiet -v -imultiarch
> x86_64-linux-gnu tstplt.c -quiet -dumpdir tstplt- -dumpbase tstplt.c
> -dumpbase-ext .c -mtune=generic -march=x86-64 -Wall -Wextra -version
> -fcf-protection=full -fasynchronous-unwind-tables -o /tmp/ccKPWeTD.s
> GNU C17 (Debian 12.2.0-10) version 12.2.0 (x86_64-linux-gnu)
>     compiled by GNU C version 12.2.0, GMP version 6.2.1, MPFR version
> 4.1.0, MPC version 1.2.1, isl version isl-0.25-GMP
> 
> GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
> ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
> ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/12/include-fixed"
> ignoring nonexistent directory
> "/usr/lib/gcc/x86_64-linux-gnu/12/../../../../x86_64-linux-gnu/include"
> #include "..." search starts here:
> #include <...> search starts here:
>  /usr/lib/gcc/x86_64-linux-gnu/12/include
>  /usr/local/include
>  /usr/include/x86_64-linux-gnu
>  /usr/include
> End of search list.
> GNU C17 (Debian 12.2.0-10) version 12.2.0 (x86_64-linux-gnu)
>     compiled by GNU C version 12.2.0, GMP version 6.2.1, MPFR version
> 4.1.0, MPC version 1.2.1, isl version isl-0.25-GMP
> 
> GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
> Compiler executable checksum: 0bf64a455b69fb48d1b44a013a099136
> COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
> 'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt-'
>  as -v --64 -o /tmp/cc0IMyNr.o /tmp/ccKPWeTD.s
> GNU assembler version 2.39.50 (x86_64-linux-gnu) using BFD version
> (GNU Binutils for Debian) 2.39.50.20221208
> COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/
> LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/12/:/usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/12/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/12/../../../:/lib/:/usr/lib/
> COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
> 'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt.'
>  /usr/lib/gcc/x86_64-linux-gnu/12/collect2 -plugin
> /usr/lib/gcc/x86_64-linux-gnu/12/liblto_plugin.so
> -plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/12/lto-wrapper
> -plugin-opt=-fresolution=/tmp/ccU2c2jz.res
> -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s
> -plugin-opt=-pass-through=-lc -plugin-opt=-pass-through=-lgcc
> -plugin-opt=-pass-through=-lgcc_s --build-id --eh-frame-hdr -m
> elf_x86_64 --hash-style=gnu --as-needed -dynamic-linker
> /lib64/ld-linux-x86-64.so.2 -pie -o tstplt
> /usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/Scrt1.o
> /usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/crti.o
> /usr/lib/gcc/x86_64-linux-gnu/12/crtbeginS.o -L.
> -L/usr/lib/gcc/x86_64-linux-gnu/12
> -L/usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu
> -L/usr/lib/gcc/x86_64-linux-gnu/12/../../../../lib
> -L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gnu
> -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/12/../../..
> /tmp/cc0IMyNr.o -ltstpltlib -rpath=/home/namhyung/tmp/plt-test -lgcc
> --push-state --as-needed -lgcc_s --pop-state -lc -lgcc --push-state
> --as-needed -lgcc_s --pop-state
> /usr/lib/gcc/x86_64-linux-gnu/12/crtendS.o
> /usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/crtn.o
> COLLECT_GCC_OPTIONS='-Wall' '-Wextra' '-fcf-protection=full' '-v' '-o'
> 'tstplt' '-L.' '-mtune=generic' '-march=x86-64' '-dumpdir' 'tstplt.'
> 
> 
>>
>> And what is the distribution?
> 
> It's a Debian (Testing) with some customization.

Seems to need also options -z ibt and/or -z ibtplt

I will send a V2 with updated examples.

diff mbox series

Patch

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 9328c162d68f..bb1b5cb3ff12 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -379,6 +379,11 @@  static bool get_plt_sizes(struct dso *dso, GElf_Ehdr *ehdr, GElf_Shdr *shdr_plt,
 	return false;
 }
 
+static bool machine_is_x86(GElf_Half e_machine)
+{
+	return e_machine == EM_386 || e_machine == EM_X86_64;
+}
+
 /*
  * We need to check if we have a .dynsym, so that we can handle the
  * .plt, synthesizing its symbols, that aren't on the symtabs (be it
@@ -391,8 +396,8 @@  int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss)
 	uint32_t nr_rel_entries, idx;
 	GElf_Sym sym;
 	u64 plt_offset, plt_header_size, plt_entry_size;
-	GElf_Shdr shdr_plt;
-	struct symbol *f;
+	GElf_Shdr shdr_plt, plt_sec_shdr;
+	struct symbol *f, *plt_sym;
 	GElf_Shdr shdr_rel_plt, shdr_dynsym;
 	Elf_Data *syms, *symstrs;
 	Elf_Scn *scn_plt_rel, *scn_symstrs, *scn_dynsym;
@@ -422,10 +427,23 @@  int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss)
 		return 0;
 
 	/* Add a symbol for .plt header */
-	f = symbol__new(shdr_plt.sh_offset, plt_header_size, STB_GLOBAL, STT_FUNC, ".plt");
-	if (!f)
+	plt_sym = symbol__new(shdr_plt.sh_offset, plt_header_size, STB_GLOBAL, STT_FUNC, ".plt");
+	if (!plt_sym)
 		goto out_elf_end;
-	symbols__insert(&dso->symbols, f);
+	symbols__insert(&dso->symbols, plt_sym);
+
+	/* Only x86 has .plt.sec */
+	if (machine_is_x86(ehdr.e_machine) &&
+	    elf_section_by_name(elf, &ehdr, &plt_sec_shdr, ".plt.sec", NULL)) {
+		if (!get_plt_sizes(dso, &ehdr, &plt_sec_shdr, &plt_header_size, &plt_entry_size))
+			return 0;
+		/* Extend .plt symbol to entire .plt */
+		plt_sym->end = plt_sym->start + shdr_plt.sh_size;
+		/* Use .plt.sec offset */
+		plt_offset = plt_sec_shdr.sh_offset;
+	} else {
+		plt_offset = shdr_plt.sh_offset + plt_header_size;
+	}
 
 	scn_dynsym = ss->dynsym;
 	shdr_dynsym = ss->dynshdr;
@@ -474,8 +492,6 @@  int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss)
 		goto out_elf_end;
 
 	nr_rel_entries = shdr_rel_plt.sh_size / shdr_rel_plt.sh_entsize;
-	plt_offset = shdr_plt.sh_offset;
-	plt_offset += plt_header_size;
 
 	ri.is_rela = shdr_rel_plt.sh_type == SHT_RELA;