WebAssembly in Action

E.2. Function pointers

WebAssembly modules have an optional Table known section, which is a typed array of references, like functions, that can’t be stored in memory as raw bytes for security reasons. If the addresses were stored in the module’s memory, there would be a chance that a malicious module would try to modify an address to access data that it shouldn’t have access to.

When a module’s code wants to access the data referenced in the Table section, it asks for the WebAssembly framework to operate on the item at a specific index in the table. The WebAssembly framework then reads the address stored at that index and performs the action.

The Table section is defined with an s-expression that starts with a label using the word table, followed ...