From: Adrian Hunter <adrian.hunter@intel.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>, Ian Rogers <irogers@google.com>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: Re: [PATCH 2/9] perf symbols: Add support for x86 .plt.sec
Date: Tue, 31 Jan 2023 12:14:30 +0200 [thread overview]
Message-ID: <aaeb7dc0-59e9-cd42-cf5b-e6a08b38670a@intel.com> (raw)
In-Reply-To: <CAM9d7ch2T1B_A_meyZi5A+kpwmzCY-eAKuZv5OVYGonBrhXqgQ@mail.gmail.com>
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.
next prev parent reply other threads:[~2023-01-31 10:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-27 17:02 [PATCH 0/9] perf symbols: Improve dso__synthesize_plt_symbols() for x86 Adrian Hunter
2023-01-27 17:02 ` [PATCH 1/9] perf symbols: Correct plt entry sizes " Adrian Hunter
2023-01-27 17:02 ` [PATCH 2/9] perf symbols: Add support for x86 .plt.sec Adrian Hunter
2023-01-30 17:34 ` Namhyung Kim
2023-01-30 18:35 ` Adrian Hunter
2023-01-30 22:22 ` Namhyung Kim
2023-01-31 10:14 ` Adrian Hunter [this message]
2023-01-27 17:02 ` [PATCH 3/9] perf symbols: Sort plt relocations for x86 Adrian Hunter
2023-01-27 17:02 ` [PATCH 4/9] perf symbols: Record whether a symbol is an alias for an IFUNC symbol Adrian Hunter
2023-01-27 17:02 ` [PATCH 5/9] perf symbols: Add support for IFUNC symbols for x86_64 Adrian Hunter
2023-01-27 17:02 ` [PATCH 6/9] perf symbols: Allow for .plt without header Adrian Hunter
2023-01-27 17:02 ` [PATCH 7/9] perf symbols: Allow for static executables with .plt Adrian Hunter
2023-01-27 17:02 ` [PATCH 8/9] perf symbols: Start adding support for .plt.got for x86 Adrian Hunter
2023-01-27 17:02 ` [PATCH 9/9] perf symbols: Get symbols for .plt.got for x86-64 Adrian Hunter
2023-01-30 23:26 ` Namhyung Kim
2023-01-31 10:17 ` Adrian Hunter
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aaeb7dc0-59e9-cd42-cf5b-e6a08b38670a@intel.com \
--to=adrian.hunter@intel.com \
--cc=acme@kernel.org \
--cc=irogers@google.com \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=namhyung@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.