Reapply "LoongArch: BPF: Sign extend kfunc call arguments"

stable inclusion
from stable-v6.6.120
category: bugfix

With prev commit, it can build successfully now.

This reverts commit 1d1623f.

Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

Author: opsiff

arch/loongarch/net/bpf_jit.c

@@ -834,6 +834,22 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
 		if (ret < 0)
 			return ret;
 
+		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);
 

arch/loongarch/net/bpf_jit.h

@@ -87,6 +87,32 @@ 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;