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. -s
