Auto merge of #43635 - ids1024:backtrace-redox, r=alexcrichton

Make backtraces work on Redox, copying Unix implementation

The `backtrace/` directory here is the same as the Unix one, except for adding an implementation of `get_executable_filename`.

4 files changed, 159 insertions, 32 deletions

diff --git a/src/libstd/sys/redox/backtrace.rs b/src/libstd/sys/redox/backtrace.rs
deleted file mode 100644
index 6cafe3e69ba..00000000000
--- a/src/libstd/sys/redox/backtrace.rs
+++ /dev/null
@@ -1,32 +0,0 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-use io;
-use sys_common::backtrace::Frame;
-
-pub use sys_common::gnu::libbacktrace::{foreach_symbol_fileline, resolve_symname};
-pub struct BacktraceContext;
-
-#[inline(never)]
-pub fn unwind_backtrace(_frames: &mut [Frame])
-    -> io::Result<(usize, BacktraceContext)>
-{
-    Ok((0, BacktraceContext))
-}
-
-pub mod gnu {
-    use io;
-    use fs;
-    use libc::c_char;
-
-    pub fn get_executable_filename() -> io::Result<(Vec<c_char>, fs::File)> {
-        Err(io::Error::new(io::ErrorKind::Other, "Not implemented"))
-    }
-}
diff --git a/src/libstd/sys/redox/backtrace/mod.rs b/src/libstd/sys/redox/backtrace/mod.rs
new file mode 100644
index 00000000000..40b957d847b
--- /dev/null
+++ b/src/libstd/sys/redox/backtrace/mod.rs
@@ -0,0 +1,42 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// See sys/unix/backtrace/mod.rs for an explanation of the method used here.
+
+pub use self::tracing::unwind_backtrace;
+pub use self::printing::{foreach_symbol_fileline, resolve_symname};
+
+// tracing impls:
+mod tracing;
+// symbol resolvers:
+mod printing;
+
+pub mod gnu {
+    use io;
+    use fs;
+    use libc::c_char;
+    use vec::Vec;
+    use ffi::OsStr;
+    use os::unix::ffi::OsStrExt;
+    use io::Read;
+
+    pub fn get_executable_filename() -> io::Result<(Vec<c_char>, fs::File)> {
+        let mut exefile = fs::File::open("sys:exe")?;
+        let mut exename = Vec::new();
+        exefile.read_to_end(&mut exename)?;
+        if exename.last() == Some(&b'\n') {
+            exename.pop();
+        }
+        let file = fs::File::open(OsStr::from_bytes(&exename))?;
+        Ok((exename.into_iter().map(|c| c as c_char).collect(), file))
+    }
+}
+
+pub struct BacktraceContext;
diff --git a/src/libstd/sys/redox/backtrace/printing.rs b/src/libstd/sys/redox/backtrace/printing.rs
new file mode 100644
index 00000000000..3e937dbe623
--- /dev/null
+++ b/src/libstd/sys/redox/backtrace/printing.rs
@@ -0,0 +1,11 @@
+// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub use sys_common::gnu::libbacktrace::{foreach_symbol_fileline, resolve_symname};
diff --git a/src/libstd/sys/redox/backtrace/tracing.rs b/src/libstd/sys/redox/backtrace/tracing.rs
new file mode 100644
index 00000000000..cfeabaddda9
--- /dev/null
+++ b/src/libstd/sys/redox/backtrace/tracing.rs
@@ -0,0 +1,106 @@
+// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use error::Error;
+use io;
+use libc;
+use sys::backtrace::BacktraceContext;
+use sys_common::backtrace::Frame;
+
+use unwind as uw;
+
+struct Context<'a> {
+    idx: usize,
+    frames: &'a mut [Frame],
+}
+
+#[derive(Debug)]
+struct UnwindError(uw::_Unwind_Reason_Code);
+
+impl Error for UnwindError {
+    fn description(&self) -> &'static str {
+        "unexpected return value while unwinding"
+    }
+}
+
+impl ::fmt::Display for UnwindError {
+    fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result {
+        write!(f, "{}: {:?}", self.description(), self.0)
+    }
+}
+
+#[inline(never)] // if we know this is a function call, we can skip it when
+                 // tracing
+pub fn unwind_backtrace(frames: &mut [Frame])
+    -> io::Result<(usize, BacktraceContext)>
+{
+    let mut cx = Context {
+        idx: 0,
+        frames: frames,
+    };
+    let result_unwind = unsafe {
+        uw::_Unwind_Backtrace(trace_fn,
+                              &mut cx as *mut Context
+                              as *mut libc::c_void)
+    };
+    // See libunwind:src/unwind/Backtrace.c for the return values.
+    // No, there is no doc.
+    match result_unwind {
+        // These return codes seem to be benign and need to be ignored for backtraces
+        // to show up properly on all tested platforms.
+        uw::_URC_END_OF_STACK | uw::_URC_FATAL_PHASE1_ERROR | uw::_URC_FAILURE => {
+            Ok((cx.idx, BacktraceContext))
+        }
+        _ => {
+            Err(io::Error::new(io::ErrorKind::Other,
+                               UnwindError(result_unwind)))
+        }
+    }
+}
+
+extern fn trace_fn(ctx: *mut uw::_Unwind_Context,
+                   arg: *mut libc::c_void) -> uw::_Unwind_Reason_Code {
+    let cx = unsafe { &mut *(arg as *mut Context) };
+    let mut ip_before_insn = 0;
+    let mut ip = unsafe {
+        uw::_Unwind_GetIPInfo(ctx, &mut ip_before_insn) as *mut libc::c_void
+    };
+    if !ip.is_null() && ip_before_insn == 0 {
+        // this is a non-signaling frame, so `ip` refers to the address
+        // after the calling instruction. account for that.
+        ip = (ip as usize - 1) as *mut _;
+    }
+
+    // dladdr() on osx gets whiny when we use FindEnclosingFunction, and
+    // it appears to work fine without it, so we only use
+    // FindEnclosingFunction on non-osx platforms. In doing so, we get a
+    // slightly more accurate stack trace in the process.
+    //
+    // This is often because panic involves the last instruction of a
+    // function being "call std::rt::begin_unwind", with no ret
+    // instructions after it. This means that the return instruction
+    // pointer points *outside* of the calling function, and by
+    // unwinding it we go back to the original function.
+    let symaddr = if cfg!(target_os = "macos") || cfg!(target_os = "ios") {
+        ip
+    } else {
+        unsafe { uw::_Unwind_FindEnclosingFunction(ip) }
+    };
+
+    if cx.idx < cx.frames.len() {
+        cx.frames[cx.idx] = Frame {
+            symbol_addr: symaddr,
+            exact_position: ip,
+        };
+        cx.idx += 1;
+    }
+
+    uw::_URC_NO_REASON
+}