From: George Guo <dongtai.guo@linux.dev>
To: Huacai Chen <chenhuacai@kernel.org>,
Tiezhu Yang <yangtiezhu@loongson.cn>,
Hengqi Chen <hengqi.chen@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>, George Guo <guodongtai@kylinos.cn>,
bpf@vger.kernel.org, loongarch@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: [PATCH bpf-next v2 06/11] LoongArch: BPF: Support sign-extending loads from arena
Date: Thu, 2 Jul 2026 10:23:17 +0800 [thread overview]
Message-ID: <20260702022322.51033-7-dongtai.guo@linux.dev> (raw)
In-Reply-To: <20260702022322.51033-1-dongtai.guo@linux.dev>
From: George Guo <guodongtai@kylinos.cn>
A sign-extending load from an arena pointer is rewritten by the verifier
to BPF_PROBE_MEM32SX once the JIT advertises support for it through
bpf_jit_supports_insn(); the generic helper otherwise defaults to
rejecting arena instructions. Add the callback and implement the load:
route BPF_PROBE_MEM32SX through the existing BPF_PROBE_MEM32 path, which
adds the arena base held in REG_ARENA, while selecting the
sign-extending load variants (ld.b/ld.h/ld.w), and register an exception
table entry so a fault on the access is handled like the other arena
probes.
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
arch/loongarch/net/bpf_jit.c | 28 +++++++++++++++++++++++++---
1 file changed, 25 insertions(+), 3 deletions(-)
diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index f172ffc2c011..4a3b632c1fde 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -739,7 +739,8 @@ static int add_exception_handler(const struct bpf_insn *insn,
if (BPF_MODE(insn->code) != BPF_PROBE_MEM &&
BPF_MODE(insn->code) != BPF_PROBE_MEMSX &&
- BPF_MODE(insn->code) != BPF_PROBE_MEM32)
+ BPF_MODE(insn->code) != BPF_PROBE_MEM32 &&
+ BPF_MODE(insn->code) != BPF_PROBE_MEM32SX)
return 0;
if (WARN_ON_ONCE(ctx->num_exentries >= ctx->prog->aux->num_exentries))
@@ -1349,10 +1350,16 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
case BPF_LDX | BPF_PROBE_MEM32 | BPF_H:
case BPF_LDX | BPF_PROBE_MEM32 | BPF_W:
case BPF_LDX | BPF_PROBE_MEM32 | BPF_DW:
+ /* LDX | PROBE_MEM32SX: dst = *(signed size *)(src + REG_ARENA + off) */
+ case BPF_LDX | BPF_PROBE_MEM32SX | BPF_B:
+ case BPF_LDX | BPF_PROBE_MEM32SX | BPF_H:
+ case BPF_LDX | BPF_PROBE_MEM32SX | BPF_W:
sign_extend = BPF_MODE(code) == BPF_MEMSX ||
- BPF_MODE(code) == BPF_PROBE_MEMSX;
+ BPF_MODE(code) == BPF_PROBE_MEMSX ||
+ BPF_MODE(code) == BPF_PROBE_MEM32SX;
- if (BPF_MODE(code) == BPF_PROBE_MEM32) {
+ if (BPF_MODE(code) == BPF_PROBE_MEM32 ||
+ BPF_MODE(code) == BPF_PROBE_MEM32SX) {
emit_insn(ctx, addd, t2, src, REG_ARENA);
src = t2;
}
@@ -2548,6 +2555,21 @@ bool bpf_jit_supports_arena(void)
return true;
}
+bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena)
+{
+ if (!in_arena)
+ return true;
+
+ switch (insn->code) {
+ case BPF_STX | BPF_ATOMIC | BPF_W:
+ case BPF_STX | BPF_ATOMIC | BPF_DW:
+ /* Atomics on arena pointers are not implemented yet. */
+ return false;
+ }
+
+ return true;
+}
+
bool bpf_jit_supports_fsession(void)
{
return true;
--
2.25.1
next prev parent reply other threads:[~2026-07-02 2:24 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-02 2:23 [PATCH bpf-next v2 00/11] LoongArch: BPF: arena features, exceptions, private stack and may_goto George Guo
2026-07-02 2:23 ` [PATCH bpf-next v2 01/11] LoongArch: BPF: Fix tail call count pointer offset for arena programs George Guo
2026-07-02 2:35 ` sashiko-bot
2026-07-02 2:23 ` [PATCH bpf-next v2 02/11] LoongArch: BPF: Support internal-only MOV to resolve per-CPU addrs George Guo
2026-07-02 2:23 ` [PATCH bpf-next v2 03/11] LoongArch: BPF: Add timed may_goto support George Guo
2026-07-02 2:23 ` [PATCH bpf-next v2 04/11] LoongArch: BPF: Add private stack support George Guo
2026-07-02 2:23 ` [PATCH bpf-next v2 05/11] LoongArch: BPF: Add exceptions (bpf_throw) support George Guo
2026-07-02 2:39 ` sashiko-bot
2026-07-02 2:23 ` George Guo [this message]
2026-07-02 2:23 ` [PATCH bpf-next v2 07/11] LoongArch: BPF: Support atomics on arena pointers George Guo
2026-07-02 2:48 ` sashiko-bot
2026-07-02 2:23 ` [PATCH bpf-next v2 08/11] selftests/bpf: Enable struct_ops private stack test for LoongArch George Guo
2026-07-02 2:23 ` [PATCH bpf-next v2 09/11] selftests/bpf: Enable arena LDSX tests on LoongArch George Guo
2026-07-02 2:23 ` [PATCH bpf-next v2 10/11] selftests/bpf: Enable arena atomics " George Guo
2026-07-02 2:49 ` sashiko-bot
2026-07-02 2:23 ` [PATCH bpf-next v2 11/11] selftests/bpf: Add LoongArch deny list George Guo
2026-07-03 10:11 ` [PATCH bpf-next v2 00/11] LoongArch: BPF: arena features, exceptions, private stack and may_goto Huacai Chen
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