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. >> 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? Will static PIE be supported if libc is compiled with -fPIE by default? -- H.J.
