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LoongArch: BPF: Sign extend kfunc call arguments

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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>
This commit is contained in:
Hengqi Chen 2025-12-31 15:19:20 +08:00 committed by Huacai Chen
parent 45cb47c628
commit 3f5a238f24
2 changed files with 42 additions and 0 deletions
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16
arch/loongarch/net/bpf_jit.c
View File

@ -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);

26
arch/loongarch/net/bpf_jit.h
View File

@ -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;