acpi-rs/aml_parser/src/lib.rs

//! `aml_parser` is a pure-Rust AML (ACPI Machine Language) parser, used for parsing the DSDT and
//! SSDT tables from ACPI. This crate can be used by kernels to gather information about the
//! hardware, and invoke control methods (this is not yet supported) to query and change the state
//! of devices in a hardware-independent way.
//!
//! ### Using the library
//! To use the library, you will mostly interact with the `AmlContext` type. You should create an
//! instance of this type using `AmlContext::new()`, and then pass it tables containing AML
//! (probably from the `acpi` crate), which you've mapped into the virtual address space. This will
//! parse the table, populating the namespace with objects encoded by the AML. After this, you may
//! unmap the memory the table was mapped into - all the information needed will be extracted and
//! allocated on the heap.
//!
//! You can then access specific objects by name like so: e.g.
//! ```ignore
//! let my_aml_value = aml_context.lookup(&AmlName::from_str("\\_SB.PCI0.S08._ADR").unwrap());
//! ```
//!
//! ### About the parser
//! The parser is written using a set of custom parser combinators - the code can be confusing on
//! first reading, but provides an extensible and type-safe way to write parsers. For an easy
//! introduction to parser combinators and the foundations used for this library, I suggest reading
//! [Bodil's fantastic blog post](https://bodil.lol/parser-combinators/).
//!
//! The actual combinators can be found in `parser.rs`. Various tricks are used to provide a nice
//! API and work around limitations in the type system, such as the concrete types like
//! `MapWithContext`, and the `make_parser_concrete` hack macro.
//!
//! The actual parsers are then grouped into categories based loosely on the AML grammar sections in
//! the ACPI spec. Most are written in terms of combinators, but some have to be written in a more
//! imperitive style, either because they're clearer, or because we haven't yet found good
//! combinator patterns to express the parse.

#![no_std]
#![feature(decl_macro, type_ascription, box_syntax)]

extern crate alloc;

#[cfg(test)]
extern crate std;

#[cfg(test)]
mod test_utils;

pub(crate) mod misc;
pub(crate) mod name_object;
pub(crate) mod namespace;
pub(crate) mod opcode;
pub(crate) mod parser;
pub(crate) mod pkg_length;
pub(crate) mod term_object;
pub(crate) mod type1;
pub(crate) mod type2;
pub mod value;

pub use crate::{
    namespace::{AmlHandle, AmlName, Namespace},
    value::AmlValue,
};

use alloc::string::String;
use log::error;
use misc::{ArgNum, LocalNum};
use parser::Parser;
use pkg_length::PkgLength;
use value::Args;

/// AML has a `RevisionOp` operator that returns the "AML interpreter revision". It's not clear
/// what this is actually used for, but this is ours.
pub const AML_INTERPRETER_REVISION: u64 = 0;

#[derive(Debug)]
pub struct AmlContext {
    pub namespace: Namespace,
    current_scope: AmlName,

    /*
     * AML local variables. These are used when we invoke a control method. A `None` value
     * represents a null AML object.
     */
    local_0: Option<AmlValue>,
    local_1: Option<AmlValue>,
    local_2: Option<AmlValue>,
    local_3: Option<AmlValue>,
    local_4: Option<AmlValue>,
    local_5: Option<AmlValue>,
    local_6: Option<AmlValue>,
    local_7: Option<AmlValue>,

    /// If we're currently invoking a control method, this stores the arguments that were passed to
    /// it. It's `None` if we aren't invoking a method.
    current_args: Option<Args>,
}

impl AmlContext {
    pub fn new() -> AmlContext {
        AmlContext {
            namespace: Namespace::new(),
            current_scope: AmlName::root(),
            local_0: None,
            local_1: None,
            local_2: None,
            local_3: None,
            local_4: None,
            local_5: None,
            local_6: None,
            local_7: None,
            current_args: None,
        }
    }

    pub fn parse_table(&mut self, stream: &[u8]) -> Result<(), AmlError> {
        if stream.len() == 0 {
            return Err(AmlError::UnexpectedEndOfStream);
        }

        let table_length = PkgLength::from_raw_length(stream, stream.len() as u32) as PkgLength;
        match term_object::term_list(table_length).parse(stream, self) {
            Ok(_) => Ok(()),
            Err((remaining, _context, err)) => {
                error!("Failed to parse AML stream. Err = {:?}", err);
                Err(err)
            }
        }
    }

    /// Invoke a method referred to by its path in the namespace, with the given arguments.
    pub fn invoke_method(&mut self, path: &AmlName, args: Args) -> Result<AmlValue, AmlError> {
        self.namespace.get_by_path(path)?.clone().invoke(self, args, path.clone())
    }

    pub(crate) fn current_arg(&self, arg: ArgNum) -> Result<&AmlValue, AmlError> {
        self.current_args.as_ref().ok_or(AmlError::InvalidArgumentAccess(0xff))?.arg(arg)
    }

    /// Get the current value of a local by its local number.
    ///
    /// ### Panics
    /// Panics if an invalid local number is passed (valid local numbers are `0..=7`)
    pub(crate) fn local(&self, local: LocalNum) -> Result<&AmlValue, AmlError> {
        match local {
            0 => self.local_0.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            1 => self.local_1.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            2 => self.local_2.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            3 => self.local_3.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            4 => self.local_4.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            5 => self.local_5.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            6 => self.local_6.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            7 => self.local_7.as_ref().ok_or(AmlError::InvalidLocalAccess(local)),
            _ => panic!("Invalid local number: {}", local),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum AmlError {
    /*
     * Errors produced parsing the AML stream.
     */
    UnexpectedEndOfStream,
    UnexpectedByte(u8),
    InvalidNameSeg([u8; 4]),
    InvalidFieldFlags,
    IncompatibleValueConversion,
    UnterminatedStringConstant,
    InvalidStringConstant,
    InvalidRegionSpace(u8),
    /// Emitted by a parser when it's clear that the stream doesn't encode the object parsed by
    /// that parser (e.g. the wrong opcode starts the stream). This is handled specially by some
    /// parsers such as `or` and `choice!`.
    WrongParser,

    /*
     * Errors produced manipulating AML names.
     */
    /// Produced when trying to normalize a path that does not point to a valid level of the
    /// namespace. E.g. `\_SB.^^PCI0` goes above the root of the namespace.
    InvalidNormalizedName(String),
    RootHasNoParent,

    /*
     * Errors produced working with the namespace.
     */
    /// Produced when a path is given that does not point to an object in the AML namespace.
    ObjectDoesNotExist(String),
    HandleDoesNotExist(AmlHandle),
    /// Produced when two values with the same name are added to the namespace.
    NameCollision(AmlName),

    /*
     * Errors produced executing control methods.
     */
    /// Produced when a method accesses an argument it does not have (e.g. a method that takes 2
    /// arguments accesses `Arg4`). The inner value is the number of the argument accessed. If any
    /// arguments are accessed when a method is not being executed, this error is produced with an
    /// argument number of `0xff`.
    InvalidArgumentAccess(ArgNum),
    InvalidLocalAccess(LocalNum),
    /// This is not a real error, but is used to propagate return values from within the deep
    /// parsing call-stack. It should only be emitted when parsing a `DefReturn`. We use the
    /// error system here because the way errors are propagated matches how we want to handle
    /// return values.
    Return(AmlValue),
}