nemu_bind_host_fn
Register a JavaScript host function at a specific guest address, overriding any existing stub. The function receives guest registers (ctx.x(0)..x(7)), can read/write guest memory (ctx.read/ctx.write), and returns a BigInt value placed in x0. Use to mock custom shell imports at their resolved GOT ...
This record as markdown: /tools/io-github-vmoranv-jshookmcp/nemu-bind-host-fn.md
What nemu_bind_host_fn does on Jshookmcp
AI agents invoke nemu_bind_host_fn to trigger actions in Jshookmcp. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
Why nemu_bind_host_fn is rated High
Executes arbitrary JS with full guest memory read/write access, overriding existing stubs.
From the tool's definition Register a JavaScript host function, overriding any existing stub, read/write guest memory
Attacks that exploit this kind of access
The rule that runs nemu_bind_host_fn safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Jshookmcp, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For nemu_bind_host_fn, this is the rule to start with:
nemu_bind_host_fn stays usable, but rate-capped: a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Jshookmcp, apply this rule, and every nemu_bind_host_fn call is checked against it from then on.
Questions about nemu_bind_host_fn
Register a JavaScript host function at a specific guest address, overriding any existing stub. The function receives guest registers (ctx.x(0)..x(7)), can read/write guest memory (ctx.read/ctx.write), and returns a BigInt value placed in x0. Use to mock custom shell imports at their resolved GOT addresses. It is categorised as a Execute tool in the Jshookmcp MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Jshook MCP server in PolicyLayer and add a rule for nemu_bind_host_fn: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Jshookmcp. Nothing to install.
nemu_bind_host_fn is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the nemu_bind_host_fn rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for nemu_bind_host_fn. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
nemu_bind_host_fn is provided by the Jshook MCP server (@jshookmcp/jshook). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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