Messages in this thread | | | From | Namhyung Kim <> | Date | Mon, 30 Jan 2023 14:22:59 -0800 | Subject | Re: [PATCH 2/9] perf symbols: Add support for x86 .plt.sec |
| |
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
| |