From: George Guo guodongtai@kylinos.cn
[ Upstream commit a6f6a95f25803500079513780d11a911ce551d76 ]
Just skip the opcode(BPF_ST | BPF_NOSPEC) in the BPF JIT instead of failing to JIT the entire program, given LoongArch currently has no couterpart of a speculation barrier instruction. To verify the issue, use the ltp testcase as shown below.
Also, Wang says:
I can confirm there's currently no speculation barrier equivalent on LonogArch. (Loongson says there are builtin mitigations for Spectre-V1 and V2 on their chips, and AFAIK efforts to port the exploits to mips/LoongArch have all failed a few years ago.)
Without this patch:
$ ./bpf_prog02 [...] bpf_common.c:123: TBROK: Failed verification: ??? (524) [...] Summary: passed 0 failed 0 broken 1 skipped 0 warnings 0
With this patch:
$ ./bpf_prog02 [...] Summary: passed 0 failed 0 broken 0 skipped 0 warnings 0
Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support") Signed-off-by: George Guo guodongtai@kylinos.cn Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: WANG Xuerui git@xen0n.name Cc: Tiezhu Yang yangtiezhu@loongson.cn Link: https://lore.kernel.org/bpf/20230328071335.2664966-1-guodongtai@kylinos.cn Signed-off-by: Sasha Levin sashal@kernel.org --- arch/loongarch/net/bpf_jit.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index 2467bfb8889a9..82b4402810da0 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -955,6 +955,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext emit_atomic(insn, ctx); break;
+ /* Speculation barrier */ + case BPF_ST | BPF_NOSPEC: + break; + default: pr_err("bpf_jit: unknown opcode %02x\n", code); return -EINVAL;