Merge pull request #135 from afranchuk/buildid-fallback

Try to read the build id from the mapping file if reading from the process memory fails.

src/linux/errors.rs

@@ -254,6 +254,12 @@ pub enum WriterError {
 
 #[derive(Debug, Error)]
 pub enum ModuleReaderError {
+    #[error("failed to read module file ({path}): {error}")]
+    MapFile {
+        path: std::path::PathBuf,
+        #[source]
+        error: std::io::Error,
+    },
     #[error("failed to read module memory: {length} bytes at {offset}{}: {error}", .start_address.map(|addr| format!(" (start address: {addr})")).unwrap_or_default())]
     ReadModuleMemory {
         offset: u64,

src/linux/module_reader.rs

@@ -152,6 +152,17 @@ fn section_header_with_name<'sc>(
 /// Types which can be read from ProcessMemory.
 pub trait ReadFromModule: Sized {
     fn read_from_module(module_memory: ProcessMemory<'_>) -> Result<Self, Error>;
+
+    fn read_from_file(path: &std::path::Path) -> Result<Self, Error> {
+        let map = std::fs::File::open(path)
+            // Safety: the file is an executable binary (very likely read-only), and won't be changed.
+            .and_then(|file| unsafe { memmap2::Mmap::map(&file) })
+            .map_err(|error| Error::MapFile {
+                path: path.to_owned(),
+                error,
+            })?;
+        Self::read_from_module(ProcessMemory::Slice(&map))
+    }
 }
 
 /// The module build id.

src/linux/sections/mappings.rs

@@ -1,6 +1,6 @@
 use super::*;
 use crate::linux::maps_reader::MappingInfo;
-use crate::linux::module_reader::{BuildId, SoName};
+use crate::linux::module_reader::{BuildId, ReadFromModule, SoName};
 
 /// Write information about the mappings in effect. Because we are using the
 /// minidump format, the information about the mappings is pretty limited.
@@ -24,15 +24,40 @@ pub fn write(
         {
             continue;
         }
+        log::debug!("retrieving build id for {:?}", &dumper.mappings[map_idx]);
         let BuildId(identifier) = dumper
             .from_process_memory_for_index(map_idx)
-            .unwrap_or_else(|_| BuildId(Vec::new()));
+            .or_else(|e| {
+                // If the mapping has an associated name that is a file, try to read the build id
+                // from the file. If there is no note segment with the build id in
+                // the program headers, we can't get to the note section if the section header
+                // table isn't loaded.
+                if let Some(path) = &dumper.mappings[map_idx].name {
+                    let path = std::path::Path::new(&path);
+                    if path.exists() {
+                        log::debug!("failed to get build id from process memory ({e}), attempting to retrieve from {}", path.display());
+                        return BuildId::read_from_file(path)
+                            .map_err(errors::DumperError::ModuleReaderError);
+                    }
+                    log::debug!(
+                        "not attempting to get build id from {}: path does not exist",
+                        path.display()
+                    );
+                }
+                Err(e)
+            })
+            .unwrap_or_else(|e| {
+                log::warn!("failed to get build id for mapping: {e}");
+                BuildId(Vec::new())
+            });
 
         // If the identifier is all 0, its an uninteresting mapping (bmc#1676109)
         if identifier.is_empty() || identifier.iter().all(|&x| x == 0) {
             continue;
         }
 
+        // SONAME should always be accessible through program headers alone, so we don't really
+        // need to fall back to trying to read from the mapping file.
         let soname = dumper
             .from_process_memory_for_index(map_idx)
             .ok()