[Bug 2142235] Re: linux-riscv-6.8 is FTBFS because of missing patches

This bug is awaiting verification that the linux/6.8.0-110.110 kernel in
-proposed solves the problem. Please test the kernel and update this bug
with the results. If the problem is solved, change the tag
'verification-needed-noble-linux' to 'verification-done-noble-linux'. If
the problem still exists, change the tag 'verification-needed-noble-
linux' to 'verification-failed-noble-linux'.


If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.


See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
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** Tags added: kernel-spammed-noble-linux-v2 verification-needed-noble-linux

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https://bugs.launchpad.net/bugs/2142235

Title:
linux-riscv-6.8 is FTBFS because of missing patches

Status in linux package in Ubuntu:
Invalid
Status in linux-riscv-6.8 package in Ubuntu:
Fix Committed
Status in linux source package in Jammy:
Invalid
Status in linux-riscv-6.8 source package in Jammy:
Fix Released
Status in linux source package in Noble:
Fix Committed
Status in linux-riscv-6.8 source package in Noble:
Invalid

Bug description:
[ 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 6 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"
- - 361db44c3c59cde05e9926647f16255e274a37f4 "riscv, bpf: Simplify sext and zext logics in branch instructions"
- 647b93f65daa128d9a0e4aac744a5fcf5f58b2d2 "riscv, bpf: Add necessary Zbb instructions"
- 519fb722bea09ae2664ad21f8ef4360fb799eb2f "riscv, bpf: Optimize sign-extention mov insns with Zbb support"
- 06a33d024838414432b6c0f51f994e7f1695b74f "riscv, bpf: Optimize bswap insns with Zbb support"

Those commits add definitions for the missing functions emit_sextX and
others.

[ Test Case ]

Kernel build succeeded.

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