On Mon, Jul 17, 2017 at 9:02 PM, Alan Modra <amo...@gmail.com> wrote: > On Mon, Jul 17, 2017 at 06:01:47AM -0700, H.J. Lu wrote: >> On Mon, Jul 17, 2017 at 5:33 AM, Alan Modra <amo...@gmail.com> wrote: >> > On Sat, Jul 15, 2017 at 06:32:40AM -0700, H.J. Lu wrote: >> >> On Thu, Jun 22, 2017 at 8:28 AM, Alan Modra <amo...@gmail.com> wrote: >> >> > PR80044 notes that -static and -pie together behave differently when >> >> > gcc is configured with --enable-default-pie as compared to configuring >> >> > without (or --disable-default-pie). This patch removes that >> >> > difference. In both cases you now will have -static completely >> >> > overriding -pie. >> >> > >> >> > Fixing this wasn't quite as simple as you'd expect, due to poor >> >> > separation of functionality. PIE_SPEC didn't just mean that -pie was >> >> > on explicitly or by default, but also -r and -shared were *not* on. >> >> > Fortunately the three files touched by this patch are the only places >> >> > PIE_SPEC and NO_PIE_SPEC are used, so it isn't too hard to see that >> >> > the reason PIE_SPEC and NO_PIE_SPEC are not inverses is the use of >> >> > PIE_SPEC in LINK_PIE_SPEC. So, move the inelegant symmetry breaking >> >> > addition, to LINK_PIE_SPEC where it belongs. Doing that showed >> >> > another problem in gnu-user.h, with PIE_SPEC and NO_PIE_SPEC selection >> >> > of crtbegin*.o not properly hooked into a chain of if .. elseif .. >> >> > conditions, which required both PIE_SPEC and NO_PIE_SPEC to exclude >> >> > -static and -shared. Fixing that particular problem finally allows >> >> > PIE_SPEC to serve just one purpose, and NO_PIE_SPEC to disappear. >> >> > >> >> > Bootstrapped and regression tested powerpc64le-linux c,c++. No >> >> > regressions and a bunch of --enable-default-pie failures squashed. >> >> > OK mainline and active branches? >> >> > >> >> > Incidentally, there is a fairly strong case to be made for adding >> >> > -static to the -shared, -pie, -no-pie chain of RejectNegative's in >> >> > common.opt. Since git 0d6378a9e (svn r48039) 2001-11-15, -static has >> >> > done more than just the traditional "prevent linking with dynamic >> >> > libraries", as -static selects crtbeginT.o rather than crtbegin.o >> >> > on GNU systems. Realizing this is what led me to close pr80044, which >> >> > I'd opened with the aim of making -pie -static work together (with the >> >> > traditional meaning of -static). I don't that is worth doing, but >> >> > mention pr80044 in the changelog due to fixing the insane output >> >> > produced by -pie -static with --disable-default-pie. >> >> > >> >> >> >> On x86-64, without --enable-default-pie, "-static -pie" and "-pie -static" >> >> never worked since both -static and -pie are passed to linker, which >> >> uses libc.a to build PIE. >> > >> > Yes, it's broken. >> >> This behavior may be useful for static PIE when libc.a is compiled with >> -fPIE. > > Building a PIE from static archives using -static -pie or -pie -static > right now is broken, even if the archives are compiled -fpie/PIE. > I've looked into fixing it, and decided it wasn't worth the effort. > There are multiple problems. See > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80044#c1 > > One reason why I believe it isn't worth fixing is that the meaning of > -static has changed over the years, from "link using static archives" > to "produce a static executable", and most certainly the meaning of > -static and -pie together is not clear. I'll cite gold behaviour as > evidence: -static with -pie results in an error from gold. See > https://sourceware.org/ml/binutils/2012-02/msg00119.html and following > discussion. > >> >> With --enable-default-pie, -static and -pie >> >> override each other. >> > >> > No they don't. -static overrides -pie. >> > >> >> What does your patch do on x86-64? Make >> >> with and without --enable-default-pie behave the same? >> > >> > Yes, as I said in my original post first paragraph. >> > >> >> Does it >> >> mean that both fail to create executable? >> > >> > I try to leave that sort of patch to those better qualified. >> > Bootstrap and regression testing on x86_64-linux both >> > --enable-default-pie and --disable-default-pie was complete June 23. >> > >> >> What is the new behavior? The old --disable-default-pie or old >> --enable-default-pie? > > You are asking questions to which the answer is given in the very > first paragraph posted in this thread, if you knew the current > --enable-default-pie behaviour. -static overrides -pie. ie. current > --enable-default-pie behaviour is unchanged. > >> Will static PIE be supported if libc is >> compiled with -fPIE by default? > > I covered this above, if you're asking about -static and -pie > together. Unsupported both before and after my patch. You *can* link > a working PIE from -fPIE archives, if that is what you want, with > "-pie -Wl,-Bstatic", both before and after my patch.
I am working on compiling libc.a in glibc with -fPIE and building static PIE. This creates static executable with PIE: gcc -nostdlib -nostartfiles -static -o /export/build/gnu/glibc-static-pie/build-x86_64-linux/elf/sln -pie -Wl,--no-dynamic-linker /export/build/gnu/glibc-static-pie/build-x86_64-linux/csu/crt1.o /export/build/gnu/glibc-static-pie/build-x86_64-linux/csu/crti.o `gcc --print-file-name=crtbeginS.o` /export/build/gnu/glibc-static-pie/build-x86_64-linux/elf/sln.o /export/build/gnu/glibc-static-pie/build-x86_64-linux/elf/static-stubs.o -Wl,--start-group /export/build/gnu/glibc-static-pie/build-x86_64-linux/libc.a -lgcc -Wl,--end-group `gcc --print-file-name=crtendS.o` /export/build/gnu/glibc-static-pie/build-x86_64-linux/csu/crtn.o Currently, it only works with gcc configured with -disable-default-pie. With --enable-default-pie, I got [hjl@gnu-tools-1 build-x86_64-linux]$ /usr/gcc-7.1.1-x32-pie/bin/gcc -nostdlib -nostartfiles -static -o /tmp/sln -pie -Wl,--no-dynamic-linker /export/build/gnu/glibc-static-pie/build-x86_64-linux/csu/crt1.o /export/build/gnu/glibc-static-pie/build-x86_64-linux/csu/crti.o `gcc --print-file-name=crtbeginS.o` /export/build/gnu/glibc-static-pie/build-x86_64-linux/elf/sln.o /export/build/gnu/glibc-static-pie/build-x86_64-linux/elf/static-stubs.o -Wl,--start-group /export/build/gnu/glibc-static-pie/build-x86_64-linux/libc.a -lgcc -Wl,--end-group `gcc --print-file-name=crtendS.o` /export/build/gnu/glibc-static-pie/build-x86_64-linux/csu/crtn.o /export/build/gnu/glibc-static-pie/build-x86_64-linux/libc.a(dl-support.o): In function `elf_machine_load_address': /export/gnu/import/git/sources/glibc/elf/../sysdeps/x86_64/dl-machine.h:59: undefined reference to `_DYNAMIC' /export/build/gnu/glibc-static-pie/build-x86_64-linux/libc.a(dl-support.o): In function `elf_get_dynamic_info': /export/gnu/import/git/sources/glibc/elf/get-dynamic-info.h:48: undefined reference to `_DYNAMIC' collect2: error: ld returned 1 exit status [hjl@gnu-tools-1 build-x86_64-linux]$ Will your change fix it? -- H.J.
