Repository: luser/rust-minidump (rust)

Issue:
crash address being read as 64-bit for 32-bit platforms
socc-pair --crash-id=[082a152f-05b4-4de9-943b-c30550211210](https://crash-stats.mozilla.org/report/index/082a152f-05b4-4de9-943b-c30550211210)

```diff
 : {
   crash_info: {
-    did not match
+    address: 0xe5e5e5e5
-    address: 0xffffffffe5e5e5e5
     crashing_thread: 25
     type: EXCEPTION_ACCESS_VIOLATION_READ
   }
```

(+ is breakpad, - is rust-minidump)

This crash report is from x86, so it's almost certain that rust-minidump is wrong here.

Pull request:
Don't trust high bits of crash addresses
This is a minor breaking change, as get_crash_address now requires a Cpu.

Also adds some minimal Exception support to synth-minidump.

Fixes #360

Patch:
diff --git a/breakpad-symbols/src/sym_file/parser.rs b/breakpad-symbols/src/sym_file/parser.rs
index 31c1127..25eac34 100644
--- a/breakpad-symbols/src/sym_file/parser.rs
+++ b/breakpad-symbols/src/sym_file/parser.rs
@@ -62,7 +62,7 @@ named!(module_line<&[u8], ()>,
     || {}
 ));
 
-// Matches an INFO LINE record.
+// Matches an INFO URL record.
 named!(
     info_url<&[u8], Info>,
     chain!(
diff --git a/minidump-processor/src/processor.rs b/minidump-processor/src/processor.rs
index a202bbe..35f0b9b 100644
--- a/minidump-processor/src/processor.rs
+++ b/minidump-processor/src/processor.rs
@@ -197,7 +197,7 @@ where
     let (crash_reason, crash_address, crashing_thread_id) = if let Some(exception) = exception_ref {
         (
             Some(exception.get_crash_reason(system_info.os, system_info.cpu)),
-            Some(exception.get_crash_address(system_info.os)),
+            Some(exception.get_crash_address(system_info.os, system_info.cpu)),
             Some(exception.get_crashing_thread_id()),
         )
     } else {
diff --git a/minidump/README.md b/minidump/README.md
index e510484..03891fd 100644
--- a/minidump/README.md
+++ b/minidump/README.md
@@ -9,16 +9,16 @@ If you want richer analysis of the minidump (such as stackwalking and symbolicat
 
 # Usage
 
-The primary API for this library is the [`Minidump`][] struct, which can be
-instantiated by calling the [`Minidump::read`][] or [`Minidump::read_path`][] methods.
+The primary API for this library is the `Minidump` struct, which can be
+instantiated by calling the `Minidump::read` or `Minidump::read_path` methods.
 
 Succesfully parsing a Minidump struct means the minidump has a minimally valid
 header and stream directory. Individual streams are only parsed when they're
 requested.
 
 Although you may enumerate the streams in a minidump with methods like
-[`Minidump::all_streams`][], this is only really useful for debugging. Instead
-you should statically request streams with [`Minidump::get_stream`][].
+`Minidump::all_streams`, this is only really useful for debugging. Instead
+you should statically request streams with `Minidump::get_stream`.
 
 Depending on what analysis you're trying to perform, you may:
 
diff --git a/minidump/src/minidump.rs b/minidump/src/minidump.rs
index ad84f52..4dc328d 100644
--- a/minidump/src/minidump.rs
+++ b/minidump/src/minidump.rs
@@ -3732,6 +3732,16 @@ impl<'a> MinidumpStream<'a> for MinidumpException<'a> {
 }
 
 impl<'a> MinidumpException<'a> {
+    /// Get the cpu context of the crashing (or otherwise minidump-requesting) thread.
+    ///
+    /// CPU contexts are a platform-specific format, so SystemInfo is required
+    /// to reliably parse them. We used to use heuristics to avoid this requirement,
+    /// but this made us too brittle to otherwise-backwards-compatible additions
+    /// to the format.
+    ///
+    /// MiscInfo can contain additional details on the cpu context's format, but
+    /// is optional because those details can be safely ignored (at the cost of
+    /// being unable to parse some very obscure cpu state).
     pub fn context(
         &self,
         system_info: &MinidumpSystemInfo,
@@ -3742,9 +3752,18 @@ impl<'a> MinidumpException<'a> {
             .map(Cow::Owned)
     }
 
-    /// Get the crash address for an exception.
-    pub fn get_crash_address(&self, os: Os) -> u64 {
-        match (
+    /// Get the address that "caused" the crash.
+    ///
+    /// The meaning of this value depends on the kind of crash this was.
+    ///
+    /// By default, it's the instruction pointer at the time of the crash.
+    /// However, if the crash was caused by an illegal memory access, the
+    /// the address would be the memory address.
+    ///
+    /// So for instance, if you crashed from dereferencing a null pointer,
+    /// the crash_address will be 0 (or close to it, due to offsets).
+    pub fn get_crash_address(&self, os: Os, cpu: Cpu) -> u64 {
+        let addr = match (
             os,
             md::ExceptionCodeWindows::from_u32(self.raw.exception_record.exception_code),
         ) {
@@ -3755,14 +3774,33 @@ impl<'a> MinidumpException<'a> {
                 self.raw.exception_record.exception_information[1]
             }
             _ => self.raw.exception_record.exception_address,
+        };
+
+        // Sometimes on 32-bit these values can be incorrectly sign-extended,
+        // so mask and zero-extend them here.
+        match cpu.pointer_width() {
+            Some(4) => addr as u32 as u64,
+            _ => addr,
         }
     }
 
     /// Get the crash reason for an exception.
+    ///
+    /// The returned value reflects our best attempt to recover a
+    /// "native" error for the crashing system based on the OS and
+    /// things like raw error codes.
+    ///
+    /// This is an imperfect process, because OSes may have overlapping
+    /// error types (e.g. WinError and NTSTATUS overlap, so we have to
+    /// pick one arbirarily).
+    ///
+    /// The raw error codes can be extracted from [MinidumpException::raw][].
     pub fn get_crash_reason(&self, os: Os, cpu: Cpu) -> CrashReason {
         CrashReason::from_exception(&self.raw, os, cpu)
     }
 
+    /// The id of the thread that caused the crash (or otherwise requested
+    /// the minidump, even if there wasn't actually a crash).
     pub fn get_crashing_thread_id(&self) -> u32 {
         self.thread_id
     }
@@ -4539,13 +4577,14 @@ fn stream_vendor(stream_type: u32) -> &'static str {
 mod test {
     use super::*;
     use md::GUID;
+    use minidump_common::format::ProcessorArchitecture;
     use std::mem;
     use synth_minidump::{
-        self, AnnotationValue, CrashpadInfo, DumpString, Memory, MemoryInfo as SynthMemoryInfo,
-        MiscFieldsBuildString, MiscFieldsPowerInfo, MiscFieldsProcessTimes, MiscFieldsTimeZone,
-        MiscInfo5Fields, MiscStream, Module as SynthModule, ModuleCrashpadInfo, SimpleStream,
-        SynthMinidump, SystemInfo, Thread, ThreadName, UnloadedModule as SynthUnloadedModule,
-        STOCK_VERSION_INFO,
+        self, AnnotationValue, CrashpadInfo, DumpString, Exception, Memory,
+        MemoryInfo as SynthMemoryInfo, MiscFieldsBuildString, MiscFieldsPowerInfo,
+        MiscFieldsProcessTimes, MiscFieldsTimeZone, MiscInfo5Fields, MiscStream,
+        Module as SynthModule, ModuleCrashpadInfo, SimpleStream, SynthMinidump, SystemInfo, Thread,
+        ThreadName, UnloadedModule as SynthUnloadedModule, STOCK_VERSION_INFO,
     };
     use test_assembler::*;
 
@@ -5757,4 +5796,55 @@ c70206ca83eb2852-de0206ca83eb2852  -w-s  10bac9000 fd:05 1196511 /usr/lib64/libt
             MinidumpAnnotation::Invalid
         );
     }
+
+    #[test]
+    fn test_exception_x86() {
+        // Defaults to x86
+        let system_info = SystemInfo::new(Endian::Little);
+
+        let mut exception = Exception::new(Endian::Little);
+
+        // Check that we clear the erroneous high bits for 32-bit
+        exception.exception_record.exception_address = 0xf0e1_d2c3_b4a5_9687;
+        // FIXME: test other fields too
+
+        let dump = SynthMinidump::with_endian(Endian::Little)
+            .add_system_info(system_info)
+            .add_exception(exception);
+
+        let dump = read_synth_dump(dump).unwrap();
+
+        let system_stream = dump.get_stream::<MinidumpSystemInfo>().unwrap();
+        let exception_stream = dump.get_stream::<MinidumpException>().unwrap();
+        assert_eq!(
+            exception_stream.get_crash_address(system_stream.os, system_stream.cpu),
+            0xb4a5_9687
+        );
+    }
+
+    #[test]
+    fn test_exception_x64() {
+        // Defaults to x86
+        let system_info = SystemInfo::new(Endian::Little)
+            .set_processor_architecture(ProcessorArchitecture::PROCESSOR_ARCHITECTURE_AMD64 as u16);
+
+        let mut exception = Exception::new(Endian::Little);
+
+        // Check that we don't truncate this on 64-bit
+        exception.exception_record.exception_address = 0xf0e1_d2c3_b4a5_9687;
+        // FIXME: test other fields too
+
+        let dump = SynthMinidump::with_endian(Endian::Little)
+            .add_system_info(system_info)
+            .add_exception(exception);
+
+        let dump = read_synth_dump(dump).unwrap();
+
+        let system_stream = dump.get_stream::<MinidumpSystemInfo>().unwrap();
+        let exception_stream = dump.get_stream::<MinidumpException>().unwrap();
+        assert_eq!(
+            exception_stream.get_crash_address(system_stream.os, system_stream.cpu),
+            0xf0e1_d2c3_b4a5_9687
+        );
+    }
 }
diff --git a/synth-minidump/src/lib.rs b/synth-minidump/src/lib.rs
index 1f7f9ca..042a052 100644
--- a/synth-minidump/src/lib.rs
+++ b/synth-minidump/src/lib.rs
@@ -29,6 +29,8 @@ pub struct SynthMinidump {
     stream_directory: Section,
     /// System info (cpu arch, os, etc.)
     system_info: Option<SystemInfo>,
+    /// High level crash info (error code, crash address, assertion, ...)
+    exception: Option<Exception>,
     /// List of modules in this minidump.
     module_list: Option<ListStream<Module>>,
     /// List of unloaded modules in this minidump.
@@ -170,6 +172,7 @@ impl SynthMinidump {
             stream_directory_rva,
             stream_directory: Section::with_endian(endian),
             system_info: None,
+            exception: None,
             module_list: Some(ListStream::new(
                 md::MINIDUMP_STREAM_TYPE::ModuleListStream,
                 endian,
@@ -287,11 +290,18 @@ impl SynthMinidump {
         self
     }
 
+    /// Set the SystemInfo stream.
     pub fn add_system_info(mut self, system_info: SystemInfo) -> Self {
         self.system_info = Some(system_info);
         self
     }
 
+    /// Set the Exception stream.
+    pub fn add_exception(mut self, exception: Exception) -> Self {
+        self.exception = Some(exception);
+        self
+    }
+
     /// Set the contents of the `LinuxMaps` stream.
     pub fn set_linux_maps(mut self, maps: &[u8]) -> SynthMinidump {
         self.linux_maps = Some(SimpleStream {
@@ -397,6 +407,9 @@ impl SynthMinidump {
         if let Some(stream) = self.system_info.take() {
             self = self.add_stream(stream);
         }
+        if let Some(stream) = self.exception.take() {
+            self = self.add_stream(stream);
+        }
         if let Some(stream) = self.linux_maps.take() {
             self = self.add_stream(stream);
         }
@@ -1650,6 +1663,7 @@ pub struct SystemInfo {
 }
 
 pub enum CpuInfo {
+    // Note, even if you're not on x86 this is a fine default.
     X86CpuInfo {
         vendor_id: [u32; 3],
         version_information: u32,
@@ -1732,6 +1746,76 @@ impl Stream for SystemInfo {
     }
 }
 
+pub struct Exception {
+    section: Section,
+    pub thread_id: u32,
+    // __align: u32,
+    pub exception_record: ExceptionRecord,
+    // TODO: implement this LOCATION_DESCRIPTOR properly
+    pub thread_context: (u32, u32),
+}
+
+pub struct ExceptionRecord {
+    pub exception_code: u32,
+    pub exception_flags: u32,
+    pub exception_record: u64,
+    pub exception_address: u64,
+    pub number_parameters: u32,
+    // __align: u32,
+    pub exception_information: [u64; 15],
+}
+
+impl Exception {
+    pub fn new(endian: Endian) -> Self {
+        Self {
+            section: Section::with_endian(endian),
+            thread_id: 0,
+            exception_record: ExceptionRecord {
+                exception_code: 0,
+                exception_flags: 0,
+                exception_record: 0,
+                exception_address: 0,
+                number_parameters: 0,
+                exception_information: [0; 15],
+            },
+            thread_context: (0, 0),
+        }
+    }
+}
+
+impl_dumpsection!(Exception);
+
+impl From<Exception> for Section {
+    fn from(info: Exception) -> Self {
+        let mut section = info
+            .section
+            .D32(info.thread_id)
+            .D32(0) // __align
+            .D32(info.exception_record.exception_code)
+            .D32(info.exception_record.exception_flags)
+            .D64(info.exception_record.exception_record)
+            .D64(info.exception_record.exception_address)
+            .D32(info.exception_record.number_parameters)
+            .D32(0); // __align
+
+        for &chunk in &info.exception_record.exception_information {
+            section = section.D64(chunk);
+        }
+
+        section = section
+            .D32(info.thread_context.0)
+            .D32(info.thread_context.1);
+
+        section
+    }
+}
+
+impl Stream for Exception {
+    fn stream_type(&self) -> u32 {
+        md::MINIDUMP_STREAM_TYPE::ExceptionStream.into()
+    }
+}
+
 #[test]
 fn test_dump_header() {
     let dump = SynthMinidump::with_endian(Endian::Little).flags(0x9f738b33685cc84c);


Test patch:
diff --git a/minidump-stackwalk/tests/test-minidump-stackwalk.rs b/minidump-stackwalk/tests/test-minidump-stackwalk.rs
index a847eda..5337ac3 100644
--- a/minidump-stackwalk/tests/test-minidump-stackwalk.rs
+++ b/minidump-stackwalk/tests/test-minidump-stackwalk.rs
@@ -657,7 +657,10 @@ fn test_unloaded_json() {
     assert_eq!(stderr, "");
 }
 
+// Temporarily disabled because it races with the _json version
+// on creating the minidump via `unloaded_minidump`.
 #[test]
+#[ignore]
 fn test_unloaded_human() {
     let synth_path = unloaded_minidump();