hyperlight_guest/
host_function_call.rs

1/*
2Copyright 2024 The Hyperlight Authors.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8    http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16
17use alloc::format;
18use alloc::string::ToString;
19use alloc::vec::Vec;
20use core::arch::global_asm;
21
22use hyperlight_common::flatbuffer_wrappers::function_call::{FunctionCall, FunctionCallType};
23use hyperlight_common::flatbuffer_wrappers::function_types::{
24    ParameterValue, ReturnType, ReturnValue,
25};
26use hyperlight_common::flatbuffer_wrappers::guest_error::ErrorCode;
27use hyperlight_common::flatbuffer_wrappers::util::get_flatbuffer_result;
28use hyperlight_common::mem::RunMode;
29
30use crate::error::{HyperlightGuestError, Result};
31use crate::host_error::check_for_host_error;
32use crate::host_functions::validate_host_function_call;
33use crate::shared_input_data::try_pop_shared_input_data_into;
34use crate::shared_output_data::push_shared_output_data;
35use crate::{OUTB_PTR, OUTB_PTR_WITH_CONTEXT, P_PEB, RUNNING_MODE};
36
37pub enum OutBAction {
38    Log = 99,
39    CallFunction = 101,
40    Abort = 102,
41}
42
43/// Get a return value from a host function call.
44/// This usually requires a host function to be called first using `call_host_function`.
45pub fn get_host_return_value<T: TryFrom<ReturnValue>>() -> Result<T> {
46    let return_value = try_pop_shared_input_data_into::<ReturnValue>()
47        .expect("Unable to deserialize a return value from host");
48    T::try_from(return_value).map_err(|_| {
49        HyperlightGuestError::new(
50            ErrorCode::GuestError,
51            format!(
52                "Host return value was not a {} as expected",
53                core::any::type_name::<T>()
54            ),
55        )
56    })
57}
58
59// TODO: Make this generic, return a Result<T, ErrorCode> this should allow callers to call this function and get the result type they expect
60// without having to do the conversion themselves
61
62pub fn call_host_function(
63    function_name: &str,
64    parameters: Option<Vec<ParameterValue>>,
65    return_type: ReturnType,
66) -> Result<()> {
67    let host_function_call = FunctionCall::new(
68        function_name.to_string(),
69        parameters,
70        FunctionCallType::Host,
71        return_type,
72    );
73
74    validate_host_function_call(&host_function_call)?;
75
76    let host_function_call_buffer: Vec<u8> = host_function_call
77        .try_into()
78        .expect("Unable to serialize host function call");
79
80    push_shared_output_data(host_function_call_buffer)?;
81
82    outb(OutBAction::CallFunction as u16, 0);
83
84    Ok(())
85}
86
87pub fn outb(port: u16, value: u8) {
88    unsafe {
89        match RUNNING_MODE {
90            RunMode::Hypervisor => {
91                hloutb(port, value);
92            }
93            RunMode::InProcessLinux | RunMode::InProcessWindows => {
94                if let Some(outb_func) = OUTB_PTR_WITH_CONTEXT {
95                    if let Some(peb_ptr) = P_PEB {
96                        outb_func((*peb_ptr).pOutbContext, port, value);
97                    }
98                } else if let Some(outb_func) = OUTB_PTR {
99                    outb_func(port, value);
100                } else {
101                    panic!("Tried to call outb without hypervisor and without outb function ptrs");
102                }
103            }
104            _ => {
105                panic!("Tried to call outb in invalid runmode");
106            }
107        }
108
109        check_for_host_error();
110    }
111}
112
113extern "win64" {
114    fn hloutb(port: u16, value: u8);
115}
116
117pub fn print_output_as_guest_function(function_call: &FunctionCall) -> Result<Vec<u8>> {
118    if let ParameterValue::String(message) = function_call.parameters.clone().unwrap()[0].clone() {
119        call_host_function(
120            "HostPrint",
121            Some(Vec::from(&[ParameterValue::String(message.to_string())])),
122            ReturnType::Int,
123        )?;
124        let res_i = get_host_return_value::<i32>()?;
125        Ok(get_flatbuffer_result(res_i))
126    } else {
127        Err(HyperlightGuestError::new(
128            ErrorCode::GuestError,
129            "Wrong Parameters passed to print_output_as_guest_function".to_string(),
130        ))
131    }
132}
133
134// port: RCX(cx), value: RDX(dl)
135global_asm!(
136    ".global hloutb
137        hloutb:
138            xor rax, rax
139            mov al, dl
140            mov dx, cx
141            out dx, al
142            ret"
143);
hyperlight_guest/host_function_call.rs

hyperlight_guest/
host_function_call.rs
