From: George Guo <guodongtai@xxxxxxxxxx>
[ 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@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: WANG Xuerui <git@xxxxxxxxxx>
Cc: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20230328071335.2664966-1-guodongtai@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 288003a9f0cae..d586df48ecc64 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1022,6 +1022,10 @@ 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;
--
2.39.2
