Cmnt: [SRU][N][PATCH 0/5] Fix FTBFS on jammy:linux-riscv-6.8

[Emil Renner Berthing]

Quoting Sarah Emery (2026-03-05 16:37:40)
> BugLink: https://bugs.launchpad.net/bugs/2142235
>
> SRU Justification:
>
> [ Impact ]
>
> Previously applied patches to the generic kernel are making
> jammy:linux-riscv-6.8 FTBFS because of missing declaration of
> some functions in arch/riscv/net/bpf_jit.h.
>
> Those previous patches were applied in bulk as part of upstream
> stable patchset 2026-01-26.
> See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2139072
>
> The following commit, fixing CVE-2025-40079, from kernel 6.12,
> uses functions that were not yet defined in 6.8:
>  riscv, bpf: Sign extend struct ops return values properly
> (fd2e08128944a7679e753f920e9eda72057e427c)
>
> Error log:
> /build/jammy/arch/riscv/net/bpf_jit_comp64.c:582:17:
> error: implicit declaration of function 'emit_sextb';
> did you mean 'emit_sub'? [-Werror=implicit-function-declaration]
>
> /build/jammy/arch/riscv/net/bpf_jit_comp64.c:585:17:
> error: implicit declaration of function 'emit_sexth';
> did you mean 'emit_zext_32'? [-Werror=implicit-function-declaration]
>
> /build/jammy/arch/riscv/net/bpf_jit_comp64.c:588:17:
> error: implicit declaration of function 'emit_sextw';
> did you mean 'emit_subw'? [-Werror=implicit-function-declaration]
> ... and more missing functions
>
> [ Fix ]
>
> Cherry picked 5 missing commits from upstream:
> - e33758f7493c9ad8cf6960bcf7c70f5761f3acfb
>         "riscv, bpf: Unify 32-bit sign-extension to emit_sextw"
> - 914c7a5ff18a225f7df254ae3433574f3d47b711
>         "riscv, bpf: Unify 32-bit zero-extension to emit_zextw"
> - 647b93f65daa128d9a0e4aac744a5fcf5f58b2d2
>         "riscv, bpf: Add necessary Zbb instructions"
> - 519fb722bea09ae2664ad21f8ef4360fb799eb2f
>         "riscv, bpf: Add rv_ext_enabled macro for runtime detection extentsion"
> - 06a33d024838414432b6c0f51f994e7f1695b74f
>         "riscv, bpf: Optimize bswap insns with Zbb support"

Hi Sarah,

Thanks for fixing this! If you follow the Link: to lore in the commit messages
you'll see that the original patchset had 6 commits, but you're skipping patch
3/6. The patch is probably not needed to fix this issue, but I worry some future
backport will be more complicated because of the omission.

/Emil