Support unpackaged split DWARF.

Author: khuey

src/symbolize/gimli.rs

@@ -58,7 +58,7 @@ struct Mapping {
     // 'static lifetime is a lie to hack around lack of support for self-referential structs.
     cx: Context<'static>,
     _map: Mmap,
-    _stash: Stash,
+    stash: Stash,
 }
 
 enum Either<A, B> {
@@ -97,7 +97,7 @@ impl Mapping {
             // only borrow `map` and `stash` and we're preserving them below.
             cx: unsafe { core::mem::transmute::<Context<'_>, Context<'static>>(cx) },
             _map: data,
-            _stash: stash,
+            stash: stash,
         })
     }
 }
@@ -136,7 +136,10 @@ impl<'data> Context<'data> {
             package = Some(
                 gimli::DwarfPackage::load(
                     |id| -> Result<_, gimli::Error> {
-                        let data = dwp.section(stash, id.dwo_name().unwrap()).unwrap_or(&[]);
+                        let data = id
+                            .dwo_name()
+                            .and_then(|name| dwp.section(stash, name))
+                            .unwrap_or(&[]);
                         Ok(EndianSlice::new(data, Endian))
                     },
                     EndianSlice::new(&[], Endian),
@@ -154,10 +157,10 @@ impl<'data> Context<'data> {
 
     fn find_frames(
         &'_ self,
+        stash: &'data Stash,
         probe: u64,
     ) -> gimli::Result<addr2line::FrameIter<'_, EndianSlice<'data, Endian>>> {
         use addr2line::{LookupContinuation, LookupResult};
-        use alloc::sync::Arc;
 
         let mut l = self.dwarf.find_frames(probe);
         loop {
@@ -166,16 +169,7 @@ impl<'data> Context<'data> {
                 LookupResult::Load { load, continuation } => (load, continuation),
             };
 
-            let mut r: Option<Arc<gimli::Dwarf<_>>> = None;
-            if let Some(dwp) = self.package.as_ref() {
-                if let Ok(Some(cu)) = dwp.find_cu(load.dwo_id, &load.parent) {
-                    r = Some(Arc::new(cu));
-                }
-            }
-
-            // TODO: support unpacked split DWARF.
-
-            l = continuation.resume(r);
+            l = continuation.resume(handle_split_dwarf(self.package.as_ref(), stash, load));
         }
     }
 }
@@ -189,18 +183,18 @@ fn mmap(path: &Path) -> Option<Mmap> {
 cfg_if::cfg_if! {
     if #[cfg(windows)] {
         mod coff;
-        use self::coff::Object;
+        use self::coff::{handle_split_dwarf, Object};
     } else if #[cfg(any(
         target_os = "macos",
         target_os = "ios",
         target_os = "tvos",
         target_os = "watchos",
     ))] {
         mod macho;
-        use self::macho::Object;
+        use self::macho::{handle_split_dwarf, Object};
     } else {
         mod elf;
-        use self::elf::Object;
+        use self::elf::{handle_split_dwarf, Object};
     }
 }
 
@@ -349,7 +343,7 @@ impl Cache {
             .next()
     }
 
-    fn mapping_for_lib<'a>(&'a mut self, lib: usize) -> Option<&'a mut Context<'a>> {
+    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
@@ -375,10 +369,15 @@ impl Cache {
             self.mappings.insert(0, (lib, mapping));
         }
 
-        let cx: &'a mut Context<'static> = &mut self.mappings[0].1.cx;
+        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) })
+        Some((
+            unsafe { mem::transmute::<&'a mut Context<'static>, &'a mut Context<'a>>(cx) },
+            stash,
+        ))
     }
 }
 
@@ -400,12 +399,12 @@ pub unsafe fn resolve(what: ResolveWhat<'_>, cb: &mut dyn FnMut(&super::Symbol))
 
         // 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 = match cache.mapping_for_lib(lib) {
-            Some(cx) => cx,
+        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(addr as u64) {
+        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 {
@@ -421,7 +420,7 @@ pub unsafe fn resolve(what: ResolveWhat<'_>, cb: &mut dyn FnMut(&super::Symbol))
         }
         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(object_addr) {
+                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 {

src/symbolize/gimli/coff.rs

@@ -106,3 +106,11 @@ impl<'a> Object<'a> {
         None
     }
 }
+
+pub(super) fn handle_split_dwarf<'data>(
+    package: Option<&gimli::DwarfPackage<EndianSlice<'data, Endian>>>,
+    stash: &'data Stash,
+    load: addr2line::SplitDwarfLoad<EndianSlice<'data, Endian>>,
+) -> Option<Arc<gimli::Dwarf<EndianSlice<'data, Endian>>>> {
+    None
+}

src/symbolize/gimli/elf.rs

@@ -3,7 +3,8 @@ use super::mystd::fs;
 use super::mystd::os::unix::ffi::{OsStrExt, OsStringExt};
 use super::mystd::path::{Path, PathBuf};
 use super::Either;
-use super::{Context, Mapping, Stash, Vec};
+use super::{gimli, Context, Endian, EndianSlice, Mapping, Stash, Vec};
+use alloc::sync::Arc;
 use core::convert::{TryFrom, TryInto};
 use core::str;
 use object::elf::{ELFCOMPRESS_ZLIB, ELF_NOTE_GNU, NT_GNU_BUILD_ID, SHF_COMPRESSED};
@@ -56,7 +57,7 @@ impl Mapping {
             let mut sup = None;
             if let Some((path_sup, build_id_sup)) = object.gnu_debugaltlink_path(&path) {
                 if let Some(map_sup) = super::mmap(&path_sup) {
-                    let map_sup = stash.set_mmap_aux(map_sup);
+                    let map_sup = stash.cache_mmap(map_sup);
                     if let Some(sup_) = Object::parse(map_sup) {
                         if sup_.build_id() == Some(build_id_sup) {
                             sup = Some(sup_);
@@ -84,7 +85,7 @@ impl Mapping {
             .unwrap_or_else(|| "dwp".into());
         path_dwp.set_extension(dwp_extension);
         if let Some(map_dwp) = super::mmap(&path_dwp) {
-            let map_dwp = stash.set_mmap_dwp(map_dwp);
+            let map_dwp = stash.cache_mmap(map_dwp);
             if let Some(dwp_) = Object::parse(map_dwp) {
                 return Some(dwp_);
             }
@@ -448,3 +449,53 @@ fn locate_debugaltlink(path: &Path, filename: &[u8], build_id: &[u8]) -> Option<
 
     locate_build_id(build_id)
 }
+
+fn convert_path<R: gimli::Reader>(r: &R) -> Result<PathBuf, gimli::Error> {
+    let bytes = r.to_slice()?;
+    Ok(PathBuf::from(OsStr::from_bytes(&bytes)))
+}
+
+pub(super) fn handle_split_dwarf<'data>(
+    package: Option<&gimli::DwarfPackage<EndianSlice<'data, Endian>>>,
+    stash: &'data Stash,
+    load: addr2line::SplitDwarfLoad<EndianSlice<'data, Endian>>,
+) -> Option<Arc<gimli::Dwarf<EndianSlice<'data, Endian>>>> {
+    if let Some(dwp) = package.as_ref() {
+        if let Ok(Some(cu)) = dwp.find_cu(load.dwo_id, &load.parent) {
+            return Some(Arc::new(cu));
+        }
+    }
+
+    let mut path = PathBuf::new();
+    if let Some(p) = load.comp_dir.as_ref() {
+        if let Ok(p) = convert_path(p) {
+            path.push(p);
+        }
+    }
+
+    if let Some(p) = load.path.as_ref() {
+        if let Ok(p) = convert_path(p) {
+            path.push(p);
+        }
+    }
+
+    if let Some(map_dwo) = super::mmap(&path) {
+        let map_dwo = stash.cache_mmap(map_dwo);
+        if let Some(dwo) = Object::parse(map_dwo) {
+            return gimli::Dwarf::load(|id| -> Result<_, ()> {
+                let data = id
+                    .dwo_name()
+                    .and_then(|name| dwo.section(stash, name))
+                    .unwrap_or(&[]);
+                Ok(EndianSlice::new(data, Endian))
+            })
+            .ok()
+            .map(|mut dwo_dwarf| {
+                dwo_dwarf.make_dwo(&load.parent);
+                Arc::new(dwo_dwarf)
+            });
+        }
+    }
+
+    None
+}

src/symbolize/gimli/macho.rs

@@ -322,3 +322,11 @@ fn split_archive_path(path: &[u8]) -> Option<(&[u8], &[u8])> {
     let (archive, rest) = path.split_at(index);
     Some((archive, &rest[1..]))
 }
+
+pub(super) fn handle_split_dwarf<'data>(
+    package: Option<&gimli::DwarfPackage<EndianSlice<'data, Endian>>>,
+    stash: &'data Stash,
+    load: addr2line::SplitDwarfLoad<EndianSlice<'data, Endian>>,
+) -> Option<Arc<gimli::Dwarf<EndianSlice<'data, Endian>>>> {
+    None
+}

src/symbolize/gimli/stash.rs

@@ -9,16 +9,14 @@ use core::cell::UnsafeCell;
 /// A simple arena allocator for byte buffers.
 pub struct Stash {
     buffers: UnsafeCell<Vec<Vec<u8>>>,
-    mmap_aux: UnsafeCell<Option<Mmap>>,
-    mmap_dwp: UnsafeCell<Option<Mmap>>,
+    mmaps: UnsafeCell<Vec<Mmap>>,
 }
 
 impl Stash {
     pub fn new() -> Stash {
         Stash {
             buffers: UnsafeCell::new(Vec::new()),
-            mmap_aux: UnsafeCell::new(None),
-            mmap_dwp: UnsafeCell::new(None),
+            mmaps: UnsafeCell::new(Vec::new()),
         }
     }
 
@@ -37,35 +35,16 @@ impl Stash {
 
     /// Stores a `Mmap` for the lifetime of this `Stash`, returning a pointer
     /// which is scoped to just this lifetime.
-    pub fn set_mmap_aux(&self, map: Mmap) -> &[u8] {
+    pub fn cache_mmap(&self, map: Mmap) -> &[u8] {
         // SAFETY: this is the only location for a mutable pointer to
-        // `mmap_aux`, and this structure isn't threadsafe to shared across
-        // threads either. This also is careful to store at most one `mmap_aux`
-        // since overwriting a previous one would invalidate the previous
-        // pointer. Given that though we can safely return a pointer to our
-        // interior-owned contents.
+        // `mmaps`, and this structure isn't threadsafe to shared across
+        // threads either. We also never remove elements from `self.mmaps`,
+        // so a reference to the data inside the map will live as long as
+        // `self` does.
         unsafe {
-            let mmap_aux = &mut *self.mmap_aux.get();
-            assert!(mmap_aux.is_none());
-            *mmap_aux = Some(map);
-            mmap_aux.as_ref().unwrap()
-        }
-    }
-
-    /// Stores a `Mmap` for the lifetime of this `Stash`, returning a pointer
-    /// which is scoped to just this lifetime.
-    pub fn set_mmap_dwp(&self, map: Mmap) -> &[u8] {
-        // SAFETY: this is the only location for a mutable pointer to
-        // `mmap_dwp`, and this structure isn't threadsafe to shared across
-        // threads either. This also is careful to store at most one `mmap_dwp`
-        // since overwriting a previous one would invalidate the previous
-        // pointer. Given that though we can safely return a pointer to our
-        // interior-owned contents.
-        unsafe {
-            let mmap_dwp = &mut *self.mmap_dwp.get();
-            assert!(mmap_dwp.is_none());
-            *mmap_dwp = Some(map);
-            mmap_dwp.as_ref().unwrap()
+            let mmaps = &mut *self.mmaps.get();
+            mmaps.push(map);
+            mmaps.last().unwrap()
         }
     }
 }