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riscv, bpf: Sign extend struct ops return values properly #9651

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riscv, bpf: Sign extend struct ops return values properly #9651

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38 changes: 37 additions & 1 deletion arch/riscv/net/bpf_jit_comp64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -954,6 +954,35 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
return ret;
}

/*
* Sign-extend the register if necessary
*/
static int sign_extend(int rd, int rs, u8 size, u8 flags, struct rv_jit_context *ctx)
{
if (!(flags & BTF_FMODEL_SIGNED_ARG) && (size == 1 || size == 2))
return 0;

switch (size) {
case 1:
emit_sextb(rd, rs, ctx);
break;
case 2:
emit_sexth(rd, rs, ctx);
break;
case 4:
emit_sextw(rd, rs, ctx);
break;
case 8:
emit_mv(rd, rs, ctx);
break;
default:
pr_err("bpf-jit: invalid size %d for sign_extend\n", size);
return -EINVAL;
}

return 0;
}

static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
const struct btf_func_model *m,
struct bpf_tramp_links *tlinks,
Expand Down Expand Up @@ -1175,8 +1204,15 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
restore_args(min_t(int, nr_arg_slots, RV_MAX_REG_ARGS), args_off, ctx);

if (save_ret) {
emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx);
emit_ld(regmap[BPF_REG_0], -(retval_off - 8), RV_REG_FP, ctx);
if (is_struct_ops) {
ret = sign_extend(RV_REG_A0, regmap[BPF_REG_0],
m->ret_size, m->ret_flags, ctx);
if (ret)
goto out;
} else {
emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx);
}
}

emit_ld(RV_REG_S1, -sreg_off, RV_REG_FP, ctx);
Expand Down
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