Fix bug decode DWARF backtraces on Linux without --decode

markbenvenuto · Apr 10, 2020 · 97367ce · 97367ce
1 parent 1fbb212
commit 97367ce
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Showing 3 changed files with 40 additions and 8 deletions.
diff --git a/Cargo.toml b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "mrlog"
-version = "0.2.0"
+version = "0.2.1"
 authors = ["Mark Benvenuto <[email protected]>"]
 edition = "2018"
 

diff --git a/README.md b/README.md
@@ -2,6 +2,13 @@
 
 Converts MongoDB 4.4 log format to MongoDB 4.2 and prior style text logs
 
+## Features
+* Converts JSON to text
+* Optional output coloring
+* Subprocess execution
+* Demangles C++ names automatically
+* Optional decoding of stacktraces using DWARF to give line numbers (Linux only)
+
 ## Run
 
 To read from standard in:
@@ -14,12 +21,19 @@ To convert a file:
 
 File is printed to standard out
 
+**Advanced Features:**
+
 To run a command and colorize its output:
 
 ```mrlog -c -e python -- buildscripts/resmoke.py ...```
 
 Separate the command executable from its arguments with `--`.
 
+To decode stacktraces using DWARF fromm mongod (Linux only).
+
+```mrlog --decode=mongod <optional file>```
+
+
 ## Options
 
 ```
@@ -45,7 +59,11 @@ ARGS:
 ```
 
 ## Build
-```cargo build```
+Get Rust from https://rustup.rs/.
+
+```cargo build --release```
+
+**Note**: Release builds are needed for good performance for decoding DWARF.
 
 ## License
 

diff --git a/src/main.rs b/src/main.rs
@@ -342,12 +342,21 @@ impl LogFormatter {
         let ret = self.objs.contains_key(path);
 
         if !ret {
-            let file = File::open(path).with_context(|| format!("Failed to open file '{}' for dwarf and symbols", path) )?;
-
-            let m1 = unsafe { memmap2::Mmap::map(&file).with_context(|| format!("Failed to mmap file '{}' for dwarf and symbols", path))? };
+            let file = File::open(path)
+                .with_context(|| format!("Failed to open file '{}' for dwarf and symbols", path))?;
+
+            let m1 = unsafe {
+                memmap2::Mmap::map(&file).with_context(|| {
+                    format!("Failed to mmap file '{}' for dwarf and symbols", path)
+                })?
+            };
             let r1 = rent_object::RentObject::new(
                 Rc::new(m1),
-                |m3| Rc::new(object::File::parse(m3).expect(&format!("Failed to parse file '{}'", path))) ,
+                |m3| {
+                    Rc::new(
+                        object::File::parse(m3).expect(&format!("Failed to parse file '{}'", path)),
+                    )
+                },
                 |a1, _| Rc::new(a1.symbol_map()),
             );
 
@@ -590,8 +599,13 @@ impl LogFormatter {
                 // Only mac and linux have processInfo
                 // Note: decoding only works on Linux for now since gimli::Object does not support multi-arch binaries on Mac
                 // TODO - use goblin instead
-                if cfg!(target_os = "linux") && msg.starts_with("BACKTRACE") && attr["bt"].has_key("processInfo")
-                && attr["bt"]["processInfo"]["somap"][0].has_key("elfType") {
+                // See https://github.com/rust-lang/backtrace-rs/blob/ac175e25d15e7bd2c870cd4d06e141bc62bbf59e/src/symbolize/gimli.rs#L38-L61
+                if cfg!(target_os = "linux")
+                    && self.decode.is_some()
+                    && msg.starts_with("BACKTRACE")
+                    && attr["bt"].has_key("processInfo")
+                    && attr["bt"]["processInfo"]["somap"][0].has_key("elfType")
+                {
                     return self.demangle_backtrace(
                         &attr["bt"],
                         s,