//! Support for symbolication using the `gimli` crate on crates.io

//!

//! This is the default symbolication implementation for Rust.

use self::gimli::read::EndianSlice;

use self::gimli::NativeEndian as Endian;

use self::mmap::Mmap;

use self::stash::Stash;

use super::BytesOrWideString;

use super::ResolveWhat;

use super::SymbolName;

use addr2line::gimli;

use core::convert::TryInto;

use core::mem;

use core::u32;

use libc::c_void;

use mystd::ffi::OsString;

use mystd::fs::File;

use mystd::path::Path;

use mystd::prelude::v1::*;

#[cfg(backtrace_in_libstd)]

mod mystd {

    pub use crate::*;

}

#[cfg(not(backtrace_in_libstd))]

extern crate std as mystd;

cfg_if::cfg_if! {

    if #[cfg(windows)] {

        #[path = "gimli/mmap_windows.rs"]

        mod mmap;

    } else if #[cfg(target_vendor = "apple")] {

        #[path = "gimli/mmap_unix.rs"]

        mod mmap;

    } else if #[cfg(any(

        target_os = "android",

        target_os = "freebsd",

        target_os = "fuchsia",

        target_os = "haiku",

        target_os = "hurd",

        target_os = "linux",

        target_os = "openbsd",

        target_os = "solaris",

        target_os = "illumos",

        target_os = "aix",

    ))] {

        #[path = "gimli/mmap_unix.rs"]

        mod mmap;

    } else {

        #[path = "gimli/mmap_fake.rs"]

        mod mmap;

    }

}

mod stash;

const MAPPINGS_CACHE_SIZE: usize = 4;

struct Mapping {

    // 'static lifetime is a lie to hack around lack of support for self-referential structs.

    cx: Context<'static>,

    _map: Mmap,

    stash: Stash,

}

enum Either<A, B> {

    #[allow(dead_code)]

    A(A),

    B(B),

}

impl Mapping {

    /// Creates a `Mapping` by ensuring that the `data` specified is used to

    /// create a `Context` and it can only borrow from that or the `Stash` of

    /// decompressed sections or auxiliary data.

    fn mk<F>(data: Mmap, mk: F) -> Option<Mapping>

    where

        F: for<'a> FnOnce(&'a [u8], &'a Stash) -> Option<Context<'a>>,

    {

        Mapping::mk_or_other(data, move |data, stash| {

            let cx = mk(data, stash)?;

            Some(Either::B(cx))

        })

    }

    /// Creates a `Mapping` from `data`, or if the closure decides to, returns a

    /// different mapping.

    fn mk_or_other<F>(data: Mmap, mk: F) -> Option<Mapping>

    where

        F: for<'a> FnOnce(&'a [u8], &'a Stash) -> Option<Either<Mapping, Context<'a>>>,

    {

        let stash = Stash::new();

        let cx = match mk(&data, &stash)? {

            Either::A(mapping) => return Some(mapping),

            Either::B(cx) => cx,

        };

        Some(Mapping {

            // Convert to 'static lifetimes since the symbols should

            // only borrow `map` and `stash` and we're preserving them below.

            cx: unsafe { core::mem::transmute::<Context<'_>, Context<'static>>(cx) },

            _map: data,

            stash: stash,

        })

    }

Unexecuted instantiation: <backtrace::symbolize::gimli::Mapping>::mk_or_other::<<backtrace::symbolize::gimli::Mapping>::mk<<backtrace::symbolize::gimli::Mapping>::new_debug::{closure#0}>::{closure#0}>

Unexecuted instantiation: <backtrace::symbolize::gimli::Mapping>::mk_or_other::<<backtrace::symbolize::gimli::Mapping>::new::{closure#0}>

}

struct Context<'a> {

    dwarf: addr2line::Context<EndianSlice<'a, Endian>>,

    object: Object<'a>,

    package: Option<gimli::DwarfPackage<EndianSlice<'a, Endian>>>,

}

impl<'data> Context<'data> {

    fn new(

        stash: &'data Stash,

        object: Object<'data>,

        sup: Option<Object<'data>>,

        dwp: Option<Object<'data>>,

    ) -> Option<Context<'data>> {

        let mut sections = gimli::Dwarf::load(|id| -> Result<_, ()> {

            if cfg!(not(target_os = "aix")) {

                let data = object.section(stash, id.name()).unwrap_or(&[]);

                Ok(EndianSlice::new(data, Endian))

            } else {

                if let Some(name) = id.xcoff_name() {

                    let data = object.section(stash, name).unwrap_or(&[]);

                    Ok(EndianSlice::new(data, Endian))

                } else {

                    Ok(EndianSlice::new(&[], Endian))

                }

            }

        })

        .ok()?;

        if let Some(sup) = sup {

            sections

                .load_sup(|id| -> Result<_, ()> {

                    let data = sup.section(stash, id.name()).unwrap_or(&[]);

                    Ok(EndianSlice::new(data, Endian))

                })

                .ok()?;

        }

        let dwarf = addr2line::Context::from_dwarf(sections).ok()?;

        let mut package = None;

        if let Some(dwp) = dwp {

            package = Some(

                gimli::DwarfPackage::load(

                    |id| -> Result<_, gimli::Error> {

                        let data = id

                            .dwo_name()

                            .and_then(|name| dwp.section(stash, name))

                            .unwrap_or(&[]);

                        Ok(EndianSlice::new(data, Endian))

                    },

                    EndianSlice::new(&[], Endian),

                )

                .ok()?,

            );

        }

        Some(Context {

            dwarf,

            object,

            package,

        })

    }

    fn find_frames(

        &'_ self,

        stash: &'data Stash,

        probe: u64,

    ) -> gimli::Result<addr2line::FrameIter<'_, EndianSlice<'data, Endian>>> {

        use addr2line::{LookupContinuation, LookupResult};

        let mut l = self.dwarf.find_frames(probe);

        loop {

            let (load, continuation) = match l {

                LookupResult::Output(output) => break output,

                LookupResult::Load { load, continuation } => (load, continuation),

            };

            l = continuation.resume(handle_split_dwarf(self.package.as_ref(), stash, load));

        }

    }

}

fn mmap(path: &Path) -> Option<Mmap> {

    let file = File::open(path).ok()?;

    let len = file.metadata().ok()?.len().try_into().ok()?;

    unsafe { Mmap::map(&file, len) }

}

cfg_if::cfg_if! {

    if #[cfg(windows)] {

        mod coff;

        use self::coff::{handle_split_dwarf, Object};

    } else if #[cfg(any(target_vendor = "apple"))] {

        mod macho;

        use self::macho::{handle_split_dwarf, Object};

    } else if #[cfg(target_os = "aix")] {

        mod xcoff;

        use self::xcoff::{handle_split_dwarf, Object};

    } else {

        mod elf;

        use self::elf::{handle_split_dwarf, Object};

    }

}

cfg_if::cfg_if! {

    if #[cfg(windows)] {

        mod libs_windows;

        use libs_windows::native_libraries;

    } else if #[cfg(target_vendor = "apple")] {

        mod libs_macos;

        use libs_macos::native_libraries;

    } else if #[cfg(target_os = "illumos")] {

        mod libs_illumos;

        use libs_illumos::native_libraries;

    } else if #[cfg(all(

        any(

            target_os = "linux",

            target_os = "fuchsia",

            target_os = "freebsd",

            target_os = "hurd",

            target_os = "openbsd",

            target_os = "netbsd",

            all(target_os = "android", feature = "dl_iterate_phdr"),

        ),

        not(target_env = "uclibc"),

    ))] {

        mod libs_dl_iterate_phdr;

        use libs_dl_iterate_phdr::native_libraries;

        #[path = "gimli/parse_running_mmaps_unix.rs"]

        mod parse_running_mmaps;

    } else if #[cfg(target_env = "libnx")] {

        mod libs_libnx;

        use libs_libnx::native_libraries;

    } else if #[cfg(target_os = "haiku")] {

        mod libs_haiku;

        use libs_haiku::native_libraries;

    } else if #[cfg(target_os = "aix")] {

        mod libs_aix;

        use libs_aix::native_libraries;

    } else {

        // Everything else should doesn't know how to load native libraries.

        fn native_libraries() -> Vec<Library> {

            Vec::new()

        }

    }

}

#[derive(Default)]

struct Cache {

    /// All known shared libraries that have been loaded.

    libraries: Vec<Library>,

    /// Mappings cache where we retain parsed dwarf information.

    ///

    /// This list has a fixed capacity for its entire lifetime which never

    /// increases. The `usize` element of each pair is an index into `libraries`

    /// above where `usize::max_value()` represents the current executable. The

    /// `Mapping` is corresponding parsed dwarf information.

    ///

    /// Note that this is basically an LRU cache and we'll be shifting things

    /// around in here as we symbolize addresses.

    mappings: Vec<(usize, Mapping)>,

}

struct Library {

    name: OsString,

    #[cfg(target_os = "aix")]

    /// On AIX, the library mmapped can be a member of a big-archive file.

    /// For example, with a big-archive named libfoo.a containing libbar.so,

    /// one can use `dlopen("libfoo.a(libbar.so)", RTLD_MEMBER | RTLD_LAZY)`

    /// to use the `libbar.so` library. In this case, only `libbar.so` is

    /// mmapped, not the whole `libfoo.a`.

    member_name: OsString,

    /// Segments of this library loaded into memory, and where they're loaded.

    segments: Vec<LibrarySegment>,

    /// The "bias" of this library, typically where it's loaded into memory.

    /// This value is added to each segment's stated address to get the actual

    /// virtual memory address that the segment is loaded into. Additionally

    /// this bias is subtracted from real virtual memory addresses to index into

    /// debuginfo and the symbol table.

    bias: usize,

}

struct LibrarySegment {

    /// The stated address of this segment in the object file. This is not

    /// actually where the segment is loaded, but rather this address plus the

    /// containing library's `bias` is where to find it.

    stated_virtual_memory_address: usize,

    /// The size of this segment in memory.

    len: usize,

}

#[cfg(target_os = "aix")]

fn create_mapping(lib: &Library) -> Option<Mapping> {

    let name = &lib.name;

    let member_name = &lib.member_name;

    Mapping::new(name.as_ref(), member_name)

}

#[cfg(not(target_os = "aix"))]

fn create_mapping(lib: &Library) -> Option<Mapping> {

    let name = &lib.name;

    Mapping::new(name.as_ref())

}

// unsafe because this is required to be externally synchronized

pub unsafe fn clear_symbol_cache() {

    Cache::with_global(|cache| cache.mappings.clear());

}

impl Cache {

    fn new() -> Cache {

        Cache {

            mappings: Vec::with_capacity(MAPPINGS_CACHE_SIZE),

            libraries: native_libraries(),

        }

    }

    // unsafe because this is required to be externally synchronized

    unsafe fn with_global(f: impl FnOnce(&mut Self)) {

        // A very small, very simple LRU cache for debug info mappings.

        //

        // The hit rate should be very high, since the typical stack doesn't cross

        // between many shared libraries.

        //

        // The `addr2line::Context` structures are pretty expensive to create. Its

        // cost is expected to be amortized by subsequent `locate` queries, which

        // leverage the structures built when constructing `addr2line::Context`s to

        // get nice speedups. If we didn't have this cache, that amortization would

        // never happen, and symbolicating backtraces would be ssssllllooooowwww.

        static mut MAPPINGS_CACHE: Option<Cache> = None;

        f(MAPPINGS_CACHE.get_or_insert_with(|| Cache::new()))

Unexecuted instantiation: <backtrace::symbolize::gimli::Cache>::with_global::<backtrace::symbolize::gimli::clear_symbol_cache::{closure#0}>::{closure#0}

Unexecuted instantiation: <backtrace::symbolize::gimli::Cache>::with_global::<backtrace::symbolize::gimli::resolve::{closure#1}>::{closure#0}

    }

Unexecuted instantiation: <backtrace::symbolize::gimli::Cache>::with_global::<backtrace::symbolize::gimli::clear_symbol_cache::{closure#0}>

Unexecuted instantiation: <backtrace::symbolize::gimli::Cache>::with_global::<backtrace::symbolize::gimli::resolve::{closure#1}>

    fn avma_to_svma(&self, addr: *const u8) -> Option<(usize, *const u8)> {

        self.libraries

            .iter()

            .enumerate()

            .filter_map(|(i, lib)| {

                // First up, test if this `lib` has any segment containing the

                // `addr` (handling relocation). If this check passes then we

                // can continue below and actually translate the address.

                //

                // Note that we're using `wrapping_add` here to avoid overflow

                // checks. It's been seen in the wild that the SVMA + bias

                // computation overflows. It seems a bit odd that would happen

                // but there's not a huge amount we can do about it other than

                // probably just ignore those segments since they're likely

                // pointing off into space. This originally came up in

                // rust-lang/backtrace-rs#329.

                if !lib.segments.iter().any(|s| {

                    let svma = s.stated_virtual_memory_address;

                    let start = svma.wrapping_add(lib.bias);

                    let end = start.wrapping_add(s.len);

                    let address = addr as usize;

                    start <= address && address < end

                }) {

                    return None;

                }

                // Now that we know `lib` contains `addr`, we can offset with

                // the bias to find the stated virtual memory address.

                let svma = (addr as usize).wrapping_sub(lib.bias);

                Some((i, svma as *const u8))

            })

            .next()

    }

    fn mapping_for_lib<'a>(&'a mut self, lib: usize) -> Option<(&'a mut Context<'a>, &'a Stash)> {

        let idx = self.mappings.iter().position(|(idx, _)| *idx == lib);

        // Invariant: after this conditional completes without early returning

        // from an error, the cache entry for this path is at index 0.

        if let Some(idx) = idx {

            // When the mapping is already in the cache, move it to the front.

            if idx != 0 {

                let entry = self.mappings.remove(idx);

                self.mappings.insert(0, entry);

            }

        } else {

            // When the mapping is not in the cache, create a new mapping,

            // insert it into the front of the cache, and evict the oldest cache

            // entry if necessary.

            let mapping = create_mapping(&self.libraries[lib])?;

            if self.mappings.len() == MAPPINGS_CACHE_SIZE {

                self.mappings.pop();

            }

            self.mappings.insert(0, (lib, mapping));

        }

        let mapping = &mut self.mappings[0].1;

        let cx: &'a mut Context<'static> = &mut mapping.cx;

        let stash: &'a Stash = &mapping.stash;

        // don't leak the `'static` lifetime, make sure it's scoped to just

        // ourselves

        Some((

            unsafe { mem::transmute::<&'a mut Context<'static>, &'a mut Context<'a>>(cx) },

            stash,

        ))

    }

}

pub unsafe fn resolve(what: ResolveWhat<'_>, cb: &mut dyn FnMut(&super::Symbol)) {

    let addr = what.address_or_ip();

    let mut call = |sym: Symbol<'_>| {

        // Extend the lifetime of `sym` to `'static` since we are unfortunately

        // required to here, but it's only ever going out as a reference so no

        // reference to it should be persisted beyond this frame anyway.

        let sym = mem::transmute::<Symbol<'_>, Symbol<'static>>(sym);

        (cb)(&super::Symbol { inner: sym });

    };

    Cache::with_global(|cache| {

        let (lib, addr) = match cache.avma_to_svma(addr.cast_const().cast::<u8>()) {

            Some(pair) => pair,

            None => return,

        };

        // Finally, get a cached mapping or create a new mapping for this file, and

        // evaluate the DWARF info to find the file/line/name for this address.

        let (cx, stash) = match cache.mapping_for_lib(lib) {

            Some((cx, stash)) => (cx, stash),

            None => return,

        };

        let mut any_frames = false;

        if let Ok(mut frames) = cx.find_frames(stash, addr as u64) {

            while let Ok(Some(frame)) = frames.next() {

                any_frames = true;

                let name = match frame.function {

                    Some(f) => Some(f.name.slice()),

                    None => cx.object.search_symtab(addr as u64),

                };

                call(Symbol::Frame {

                    addr: addr as *mut c_void,

                    location: frame.location,

                    name,

                });

            }

        }

        if !any_frames {

            if let Some((object_cx, object_addr)) = cx.object.search_object_map(addr as u64) {

                if let Ok(mut frames) = object_cx.find_frames(stash, object_addr) {

                    while let Ok(Some(frame)) = frames.next() {

                        any_frames = true;

                        call(Symbol::Frame {

                            addr: addr as *mut c_void,

                            location: frame.location,

                            name: frame.function.map(|f| f.name.slice()),

                        });

                    }

                }

            }

        }

        if !any_frames {

            if let Some(name) = cx.object.search_symtab(addr as u64) {

                call(Symbol::Symtab { name });

            }

        }

    });

}

pub enum Symbol<'a> {

    /// We were able to locate frame information for this symbol, and

    /// `addr2line`'s frame internally has all the nitty gritty details.

    Frame {

        addr: *mut c_void,

        location: Option<addr2line::Location<'a>>,

        name: Option<&'a [u8]>,

    },

    /// Couldn't find debug information, but we found it in the symbol table of

    /// the elf executable.

    Symtab { name: &'a [u8] },

}

impl Symbol<'_> {

    pub fn name(&self) -> Option<SymbolName<'_>> {

        match self {

            Symbol::Frame { name, .. } => {

                let name = name.as_ref()?;

                Some(SymbolName::new(name))

            }

            Symbol::Symtab { name, .. } => Some(SymbolName::new(name)),

        }

    }

    pub fn addr(&self) -> Option<*mut c_void> {

        match self {

            Symbol::Frame { addr, .. } => Some(*addr),

            Symbol::Symtab { .. } => None,

        }

    }

    pub fn filename_raw(&self) -> Option<BytesOrWideString<'_>> {

        match self {

            Symbol::Frame { location, .. } => {

                let file = location.as_ref()?.file?;

                Some(BytesOrWideString::Bytes(file.as_bytes()))

            }

            Symbol::Symtab { .. } => None,

        }

    }

    pub fn filename(&self) -> Option<&Path> {

        match self {

            Symbol::Frame { location, .. } => {

                let file = location.as_ref()?.file?;

                Some(Path::new(file))

            }

            Symbol::Symtab { .. } => None,

        }

    }

    pub fn lineno(&self) -> Option<u32> {

        match self {

            Symbol::Frame { location, .. } => location.as_ref()?.line,

            Symbol::Symtab { .. } => None,

        }

    }

    pub fn colno(&self) -> Option<u32> {

        match self {

            Symbol::Frame { location, .. } => location.as_ref()?.column,

            Symbol::Symtab { .. } => None,

        }

    }

}