hyperlight-host 0.17.0

A lightweight Virtual Machine Manager that can be hosted in an application to safely run untrusted or code within a VM partition with very low latency and overhead.
Documentation 
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// SPDX-License-Identifier: Apache-2.0
// Copyright 2025 The Hyperlight Authors.

use libc::c_int;

use crate::sandbox::SandboxConfiguration;

pub(crate) fn setup_signal_handlers(config: &SandboxConfiguration) -> crate::Result<()> {
    // This is unsafe because signal handlers only allow a very restrictive set of
    // functions (i.e., async-signal-safe functions) to be executed inside them.
    // Anything that performs memory allocations, locks, and others are non-async-signal-safe.
    // Hyperlight signal handlers are all designed to be async-signal-safe, so this function
    // should be safe to call.
    vmm_sys_util::signal::register_signal_handler(
        libc::SIGRTMIN() + config.get_interrupt_vcpu_sigrtmin_offset() as c_int,
        vm_kill_signal,
    )
    .map_err(crate::HyperlightError::VmmSysError)?;

    // Note: For libraries registering signal handlers, it's important to keep in mind that
    // the user of the library could have their own signal handlers that we don't want to
    // overwrite. The common practice there is to provide signal handling chaining, which
    // means that the signal is handled by all registered handlers from the last registered
    // to the first. **Hyperlight does not provide signal chaining**. For SIGSYS, this is because,
    // currently, Hyperlight handles SIGSYS signals by directly altering the instruction pointer at
    // the time the syscall occurred to call a function that will panic the host function execution.
    // For SIGRTMIN, this is because Hyperlight issues potentially 200 signals back-to-back and its
    // likely that the embedder will not want to handle this.

    Ok(())
}

extern "C" fn vm_kill_signal(_: libc::c_int, _: *mut libc::siginfo_t, _: *mut libc::c_void) {
    // Do nothing. SIGRTMIN is just used to issue a VM exit to the underlying VM.
}