LoongArch: BPF: Sign extend kfunc call arguments

The kfunc calls are native calls so they should follow LoongArch calling
conventions. Sign extend its arguments properly to avoid kernel panic.
This is done by adding a new emit_abi_ext() helper. The emit_abi_ext()
helper performs extension in place meaning a value already store in the
target register (Note: this is different from the existing sign_extend()
helper and thus we can't reuse it).

Cc: stable@vger.kernel.org
Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 8dc58781b8eb7fb9d62815410fb57afb2f00d302..5352d0c30fb2863fb1ba5f7af8fb8ad33aaeb548 100644 (file)
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -950,6 +950,22 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
                        emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off);
                }
 
+               if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
+                       const struct btf_func_model *m;
+                       int i;
+
+                       m = bpf_jit_find_kfunc_model(ctx->prog, insn);
+                       if (!m)
+                               return -EINVAL;
+
+                       for (i = 0; i < m->nr_args; i++) {
+                               u8 reg = regmap[BPF_REG_1 + i];
+                               bool sign = m->arg_flags[i] & BTF_FMODEL_SIGNED_ARG;
+
+                               emit_abi_ext(ctx, reg, m->arg_size[i], sign);
+                       }
+               }
+
                move_addr(ctx, t1, func_addr);
                emit_insn(ctx, jirl, LOONGARCH_GPR_RA, t1, 0);
 

diff --git a/arch/loongarch/net/bpf_jit.h b/arch/loongarch/net/bpf_jit.h
index 5697158fd1645fdc3d83f598b00a9e20dfaa8f6d..75b6330030a9d11def05902e9a2f9a9e5132daa9 100644 (file)
--- a/arch/loongarch/net/bpf_jit.h
+++ b/arch/loongarch/net/bpf_jit.h
@@ -88,6 +88,32 @@ static inline void emit_sext_32(struct jit_ctx *ctx, enum loongarch_gpr reg, boo
        emit_insn(ctx, addiw, reg, reg, 0);
 }
 
+/* Emit proper extension according to ABI requirements.
+ * Note that it requires a value of size `size` already resides in register `reg`.
+ */
+static inline void emit_abi_ext(struct jit_ctx *ctx, int reg, u8 size, bool sign)
+{
+       /* ABI requires unsigned char/short to be zero-extended */
+       if (!sign && (size == 1 || size == 2))
+               return;
+
+       switch (size) {
+       case 1:
+               emit_insn(ctx, extwb, reg, reg);
+               break;
+       case 2:
+               emit_insn(ctx, extwh, reg, reg);
+               break;
+       case 4:
+               emit_insn(ctx, addiw, reg, reg, 0);
+               break;
+       case 8:
+               break;
+       default:
+               pr_warn("bpf_jit: invalid size %d for extension\n", size);
+       }
+}
+
 static inline void move_addr(struct jit_ctx *ctx, enum loongarch_gpr rd, u64 addr)
 {
        u64 imm_11_0, imm_31_12, imm_51_32, imm_63_52;