Hi, When linking libswiftCore.so, gold linker with --warn-execstack option generates following messages. /usr/bin/ld.gold: warning: lib/swift/linux/x86_64/swift_begin.o: missing .note.GNU-stack section implies executable stack /usr/bin/ld.gold: warning: lib/swift/linux/x86_64/swift_end.o: missing .note.GNU-stack section implies executable stack
I found the web page about the GNU-stack section. http://en.chys.info/2010/12/note-gnu-stack/ After quick testing in my build system (Linux + execstack -q), I think we should append one line to stdlib/public/runtime/swift_sections.S, or pass the proper option to the linker. The line is .section .note.GNU-stack,"",@progbits and the option is '-z noexecstack' (or -Wl,-z -Wl,noexecstack for clang++). I don't know which method is better, to patch swift_section.S or to patch linking option. -Han Sangjin 2016-06-17 16:27 GMT+09:00 Dmitri Gribenko <griboz...@gmail.com>: > Hi, > > While there wight be an issue in WSL with executable stacks, Swift > does not really need one. If the binary is actually asking for one, > it would be great if we could figure out a way to ask the gold linker > to not mark stacks as executable. > > Dmitri > > On Thu, Jun 16, 2016 at 11:39 PM, Sangjin Han <tinysun....@gmail.com> > wrote: > > Hi, Kim. > > > > The test result is same on WSL build 14342. > > > > There is similar report in > > https://github.com/Microsoft/BashOnWindows/issues/286 . > > MS engineer recognized this and replied that give them feedback on the > > uservoice for prioritizing, currently it has only 3 votes. > > > > -Han Sangjin > > > > 2016-06-16 21:17 GMT+09:00 Jongsu Kim via swift-dev <swift-dev@swift.org > >: > >> > >> Hi, > >> > >>> This could have been caused by our switch from the BFD linker to gold. > >>> Could you try linking a hello world program using gold linker and > >>> running it in WSL? > >> > >> > >> I tried to build Swift by not using -fuse-gold option and the result was > >> same. > >> > >> > >>> Are you sure that PROT_GROWSDOWN is the flag that enables executable > >>> stack? I thought that's what PROT_EXEC is for. I'm not sure what > >>> PROT_GROWSDOWN actually changes, if I were to speculate, I'd say it > >>> could be a marker that means "this is a stack" or maybe even be just a > >>> performance hint. > >> > >> > >> You are right. The executable stack is enabled by PROT_EXEC. > >> > >> But Swift shared library's executable stack seems to set PROT_EXEC AND > >> PROT_GROWSDOWN according to strace. > >> > >> I don't know what causes Swift shared library to have executable stack > >> since Febrary 25 snapshot. Febrary 8 snapshot and Swift 2.X branches > have no > >> such executable stack shared library. > >> > >> Thanks, > >> > >> > >> -Kim, Jongsu > >> > >> _______________________________________________ > >> swift-dev mailing list > >> swift-dev@swift.org > >> https://lists.swift.org/mailman/listinfo/swift-dev > >> > > > > > > -- > main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if > (j){printf("%d\n",i);}}} /*Dmitri Gribenko <griboz...@gmail.com>*/ >
_______________________________________________ swift-dev mailing list swift-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-dev
