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/// Keeps track of mapped libraries in an address space. Stores a value
/// for each mapping, and allows efficient lookup of that value based on
/// an address.
#[derive(Debug, Clone)]
pub struct LibMappings<T> {
sorted_mappings: Vec<Mapping<T>>,
}
impl<T> Default for LibMappings<T> {
fn default() -> Self {
Self::new()
}
}
impl<T> LibMappings<T> {
/// Creates a new empty instance.
pub fn new() -> Self {
Self {
sorted_mappings: Vec::new(),
}
}
/// Add a mapping to this address space. Any existing mappings which overlap with the
/// new mapping are removed.
///
/// `start_avma` and `end_avma` describe the address range that this mapping
/// occupies.
///
/// AVMA = "actual virtual memory address"
///
/// `relative_address_at_start` is the "relative address" which corresponds
/// to `start_avma`, in the library that is mapped in this mapping. This is zero if
/// `start_avm` is the base address of the library.
///
/// A relative address is a `u32` value which is relative to the library base address.
/// So you will usually set `relative_address_at_start` to `start_avma - base_avma`.
///
/// For ELF binaries, the base address is the AVMA of the first segment, i.e. the
/// start_avma of the mapping created by the first ELF `LOAD` command.
///
/// For mach-O binaries, the base address is the vmaddr of the `__TEXT` segment.
///
/// For Windows binaries, the base address is the image load address.
pub fn add_mapping(
&mut self,
start_avma: u64,
end_avma: u64,
relative_address_at_start: u32,
value: T,
) {
let remove_range_begin = match self
.sorted_mappings
.binary_search_by_key(&start_avma, |r| r.start_avma)
{
Ok(i) => i,
Err(0) => 0,
Err(i) => {
// start_avma falls between the start_avmas of `i - 1` and `i`.
if start_avma < self.sorted_mappings[i - 1].end_avma {
i - 1
} else {
i
}
}
};
let mut remove_range_end = remove_range_begin;
for mapping in &self.sorted_mappings[remove_range_begin..] {
if mapping.start_avma < end_avma {
remove_range_end += 1;
} else {
break;
}
}
self.sorted_mappings.splice(
remove_range_begin..remove_range_end,
[Mapping {
start_avma,
end_avma,
relative_address_at_start,
value,
}],
);
}
/// Remove a mapping which starts at the given address. If found, this returns
/// the `relative_address_at_start` and the associated value of the mapping.
pub fn remove_mapping(&mut self, start_avma: u64) -> Option<(u32, T)> {
self.sorted_mappings
.binary_search_by_key(&start_avma, |m| m.start_avma)
.ok()
.map(|i| self.sorted_mappings.remove(i))
.map(|m| (m.relative_address_at_start, m.value))
}
/// Clear all mappings.
pub fn clear(&mut self) {
self.sorted_mappings.clear();
self.sorted_mappings.shrink_to_fit();
}
/// Look up the mapping which covers the given address.
fn lookup(&self, avma: u64) -> Option<&Mapping<T>> {
let mappings = &self.sorted_mappings[..];
let index = match mappings.binary_search_by_key(&avma, |r| r.start_avma) {
Err(0) => return None,
Ok(exact_match) => exact_match,
Err(insertion_index) => {
let mapping_index = insertion_index - 1;
if avma < mappings[mapping_index].end_avma {
mapping_index
} else {
return None;
}
}
};
Some(&mappings[index])
}
/// Converts an absolute address (AVMA, actual virtual memory address) into
/// a relative address and the mapping's associated value.
pub fn convert_address(&self, avma: u64) -> Option<(u32, &T)> {
let mapping = match self.lookup(avma) {
Some(mapping) => mapping,
None => return None,
};
let offset_from_mapping_start = (avma - mapping.start_avma) as u32;
let relative_address = mapping.relative_address_at_start + offset_from_mapping_start;
Some((relative_address, &mapping.value))
}
}
#[derive(Debug, Clone, PartialEq, PartialOrd, Ord, Eq)]
struct Mapping<T> {
start_avma: u64,
end_avma: u64,
relative_address_at_start: u32,
value: T,
}