From 43e6e723418fdfc6876e64894a74cff33ac1a34e Mon Sep 17 00:00:00 2001 From: Hengqi Chen Date: Wed, 31 Dec 2025 15:19:20 +0800 Subject: [PATCH] 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 Signed-off-by: Huacai Chen Signed-off-by: maoxiaochuan --- arch/loongarch/net/bpf_jit.c | 16 ++++++++++++++++ arch/loongarch/net/bpf_jit.h | 26 ++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index f97dc9936..c67631303 100644 --- 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 5697158fd..75b633003 100644 --- 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;