On 04/09/2018 04:47 PM, Stef O'Rear wrote: > On Mon, Apr 9, 2018 at 6:37 PM, Jeff Law <l...@redhat.com> wrote: >> On 04/09/2018 12:04 PM, Jim Wilson wrote: >>> On 04/08/2018 08:22 AM, Jeff Law wrote: >>>> On 03/31/2018 12:27 PM, Richard W.M. Jones wrote: >>>>> I'd like to talk about what changes we (may) need to GCC in >>>>> Fedora to get it working on 64-bit RISC-V, and also (more >>>>> importantly) to ask your advice on things we don't fully >>>>> understand yet. However, I don't know even what venue you'd >>>>> prefer to discuss this in. >>> >>> A discussion here is fine with me. I know of a few issues. >>> >>> I have a work-in-progress --with-multilib-list patch in PR 84797 but it >>> isn't quite right yet, and needs to work more like the patch in PR >>> 85142, which isn't OK to check in. >>> >>> There is a problem with atomics. We only have builtins for the ones >>> that can be implemented with a single instruction. Adding -latomic >>> unconditionally might fix it, but won't work for gcc builds and the gcc >>> testsuite unless we also add paths pointing into the libatomic build >>> dir. I'm also concerned that this might cause build problems, if we end >>> up trying to link with libatomic before we have built it. The simplest >>> solution might be to just add expanders for all of the missing atomics, >>> even if they require multiple instructions, just like how all of the >>> mainstream linux targets currently work. >>> >>> There is a problem with the linker not searching the right set of dirs >>> by default. That is more a binutils problem than a gcc problem, but the >>> linker might need some help from gcc to fix it, as the linker doesn't >>> normally take -march and -mabi options. >>> >>> There is a problem with libffi, which has RISC-V support upstream, but >>> not in the FSF GCC copy. This is needed for go language support. There >>> was also a dispute about go something naming, as to whether it should be >>> riscv64 or riscv, with one person doing a port choosing the former and >>> another person doing another port choosing the latter. >>> >>> Those are all of the Linux specific ones I can remember at the moment. I >>> might have missed some. >> Are you guys using qemu user mode emulation for testing purposes? When >> I've set up a suitable riscv64 rootfs and try to do anything nontrivial >> in it with qemu user mode emulation it immediately complains that my >> kernel is too old -- which is quite odd as I've got a dozen or so of >> these kinds of environments set up for testing which don't issue that >> complaint. >> >> I'd like to avoid full system emulation just from a cost standpoint.. > > That error is produced by glibc if uname() returns a kernel version > older than the oldest with arch support, which for riscv is 4.15.0. > qemu-user does not fake uname(), so qemu-user for riscv will only work > if the host is running 4.15.0 or newer. Hmm, makes sense since the hosts are running 4.10-ish
I'll hack around it somehow. I'd really like to add riscv64 to the tester and don't want to mess around with kernel updates. Thanks, jeff
