[SRU][N][PATCH v2 0/6] Fix FTBFS on jammy:linux-riscv-6.8

[Sarah Emery]

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 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.

Pu Lehui (6):
  riscv, bpf: Unify 32-bit sign-extension to emit_sextw
  riscv, bpf: Unify 32-bit zero-extension to emit_zextw
  riscv, bpf: Simplify sext and zext logics in branch instructions
  riscv, bpf: Add necessary Zbb instructions
  riscv, bpf: Optimize sign-extention mov insns with Zbb support
  riscv, bpf: Optimize bswap insns with Zbb support

 arch/riscv/net/bpf_jit.h        | 134 ++++++++++++++++++++
 arch/riscv/net/bpf_jit_comp64.c | 210 +++++++++++---------------------
 2 files changed, 205 insertions(+), 139 deletions(-)

-- 
2.51.0