bpf, mips: Add signed div/mod support - #8691
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Factor MIPS32 and MIPS64 division and modulo emission out of emit_alu_r() and emit_alu_r64(). This prepares the JITs to select signed or unsigned opcodes without duplicating the R6 and pre-R6 handling. No functional change intended. Suggested-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com> Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com>
Add uasm emitters for the signed DIV, MOD, DDIV, and DMOD instructions. Provide both pre-R6 and R6 division forms so users can select the instruction appropriate for the target ISA. Assisted-by: Codex:gpt-5.6-sol Link: https://lore.kernel.org/bpf/CAM1=_QS79dDBfaaNQXnWd61AqHd1M4o9aDMMiftnoJveNr=FZg@mail.gmail.com/ Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com>
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The MIPS JITs handle BPF_DIV and BPF_MOD without inspecting insn->off, which distinguishes BPF_SDIV and BPF_SMOD. Signed operations therefore use unsigned instructions, or unsigned helpers for ALU64 on 32-bit MIPS, and produce unsigned results for negative operands. Pass insn->off unchanged through immediate validation and register emission, and interpret it only in div/mod-specific paths. Use signed DIV/DDIV for pre-R6 and DIV/MOD/DDIV/DMOD for R6. On 32-bit MIPS, use div64_s64() and a signed remainder helper for ALU64. Keep the signed quotient signed while computing that remainder, and keep signed immediates out of the unsigned power-of-two shift/mask rewrite. check_alu_op() rejects immediate zero divisors. bpf_do_misc_fixups() rewrites signed immediate -1 and guards register divisors that are zero or, for signed operations, -1 before JIT compilation. The ALU32 paths continue to zero-extend their results. The remaining test_bpf failures are five MOVSX, eight BSWAP, three MEMSX, and one JMP32_JA. MOVSX and MEMSX will be addressed separately; Johan Almbladh is handling BSWAP and JMP32_JA. Found while auditing BPF JIT handling of signed div/mod. Assisted-by: Codex:gpt-5.6-sol Link: https://lore.kernel.org/bpf/CAM1=_QS79dDBfaaNQXnWd61AqHd1M4o9aDMMiftnoJveNr=FZg@mail.gmail.com/ Link: https://lore.kernel.org/bpf/CAM1=_QQ7XiJEozaetLt_+kVn91YAXWpJK_pyfT9=paXseW=wwA@mail.gmail.com/ Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com>
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Pull request for series with
subject: bpf, mips: Add signed div/mod support
version: 3
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1143650