On Sun, Feb 16, 2020 at 04:27:11PM +0000, Ben Hutchings wrote: > This was discussed on IRC with Julien Cristau, but unfortunately I > didn't save a log. The main points that came up were: > > * Executables built for the O32 FP64 ABI require this kernel config > change and older kernel versions will refuse to load them. So the > kernel needs to be upgraded before installing any binaries built > for the new FP ABI. > > * Normally the support for an additional ABI would be included in > release N.0 and used in N+1. Since this was not present in 10.0, it > would be possible for users to start upgrading to bullseye while > still running a kernel that does not support O32 FP64. We need to > prevent them getting a broken system. > > * Julien proposed that libc6 would have a preinst check on the kernel > when it is changed to use the new FP ABI. Presumably all binaries > built for the new FP ABI should also have a versioned dependency on > at least this version of libc6. > > So I don't see any reason not to update the kernel configuration > already, as it will remain compatible with the O32 FPXX binaries in > buster. Only the user-space changes in unstable (libc6 and toolchain) > need to be carefully coordinated. > Here's the irc log for the record:
< bwh> jcristau: While you are here, could you have a quick look at #949259? < jcristau> that's kind of awkward < jcristau> maybe it's ok because it's only mips, but... < bwh> but what? < jcristau> well i'd normally expect bullseye to run on buster r0 < jcristau> what's the failure mode if the kernel doesn't support O32_FP64? < bwh> syq_: Can you answer? < bwh> jcristau: It looks to me like exec will fail for programs built for the new FP ABI < jcristau> so they'll need to get a dependency on a new libc with a preinst check? < bwh> jcristau: That seems like a reasonable approach < bwh> that + prominent notice in the release notes < syq_> jcristau: it will complain that not support such binary < syq_> jcristau: if kernel doesn't enable FP64 I think you can go ahead provided that: - enabling this support in the kernel doesn't break previously-supported userspace - Aurélien as glibc maintainer is OK with this plan Thanks, Julien
