qemu: Add termios2 patches for glibc 2.42 compat

[dramforever]

QEMU doesn't yet implement termios 2 (TCGETS2 etc), but glibc 2.42+ require on archs that have it for various terminal operations like isatty(). This causes, for example, programs like bash to mistakenly run in non-interactive mode.

Apply patch series for this from the mailing list.

Patch series was tested by @Icenowy (thank you), including various cursed combinations like ppc64le host + riscv64 guest.

Known issue: Setting non-standard baud rates on ppc guest and non-ppc host doesn't work. It didn't work before anyway and it's a rather minor problem compared to isatty() being broken.

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[alyssais]

I am nervous about applying patches before they have been accepted upstream, because that can mean we never get rid of them. Do we know why these have not progressed further?

[dramforever]

Marking back as draft as it's not really that urgent. We'll see.

[dramforever]

Someone from Gentoo actually bothered to send the entire series to the mailing list, properly, so we now have nice links to fetch patches from. Nice.

For patches with hash changes I've manually confirmed that there are only line number changes. fetchpatch my beloved.

[Ma27]

I am nervous about applying patches before they have been accepted upstream, because that can mean we never get rid of them. Do we know why these have not progressed further?

Hmm, does this apply here though?
This is merely a compat fix that will have to happen upstream sooner or later as well given the rollout of glibc 2.42.

[fabianhjr]

Seems like upstream does have a tracking isssue were @dramforever already bumped/asked about upstreaming: https://gitlab.com/qemu-project/qemu/-/issues/3065

Patchset has already been sent via the indicated channel: https://mail.gnu.org/archive/html/qemu-devel/2026-01/msg00129.html

[alyssais]

This is merely a compat fix that will have to happen upstream sooner or later as well given the rollout of glibc 2.42.

One would hope so, but without somebody actively driving that to happen upstream (which seemed to be the case here), there's no guarantee of that.

With it having now been submitted upstream properly it's probably reached the usual standards though.