Hi, > > Underlying problem is that x64 ProcessorBind.h sets visibility to > > hidden (anyone knows why?). > > Yes. Toolchains tend to assume that you are generating code for a > shared library once you enabled -fpic, and this results in lots of > pointless indirections via the GOT. (This has to do with the > copy-on-write footprint of shared library pages, as a GOT tends to > gather all relocated quantities in a small region of memory. It is > also related to ELF symbol preemption, which is another thing we don't > give a ^$& about). > > *However*, recent linkers do a better job getting rid of these GOT > references at link time, once you pass the --relax option. On X64 in > particular, there are special, relaxable GOTPCREL relocations now that > will not result in to symbol references via the GOT if the linker > notices that the symbol in question is never preempted and not > provided externally. > > So it is worth an experiment whether we still need this to begin with.
Seems to work fine on fedora 37, even without adding --relax, maybe this is enabled by default (there is a --no-relax switch after all). I'll go try older distros / compilers / binutils too. What would be the failure mode? Errors on ELF -> PE conversion because a GOT is present? Or will things break at runtime? > > Seems to be fine for freestanding binaries, > > but when linking host tools against shared libraries things break. For > > some reason on ubuntu only, fedora works fine (both gcc and clang). > > > > Automatically detecting freestanding vs. hosted would be even better, > > anyone knows whenever there is a define which can be used for this? At > > least the gcc man page doesn't mention any ... > > ard@gambale:~/linux-build-x86$ gcc -dM -E -o - -xc - <<< ""|grep HOSTED > #define __STDC_HOSTED__ 1 > ard@gambale:~/linux-build-x86$ gcc -ffreestanding -dM -E -o - -xc - > <<< ""|grep HOSTED > #define __STDC_HOSTED__ 0 Nice. So we have a plan b in case just dropping it doesn't work out. take care, Gerd -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#103160): https://edk2.groups.io/g/devel/message/103160 Mute This Topic: https://groups.io/mt/98257896/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
