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: 5dc615520c ("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
a6f6a95f25