std: move `sys_common::backtrace` to `sys`

2 files changed, 228 insertions, 0 deletions

diff --git a/library/std/src/sys/backtrace.rs b/library/std/src/sys/backtrace.rs
new file mode 100644
index 00000000000..0b2338fd7de
--- /dev/null
+++ b/library/std/src/sys/backtrace.rs
@@ -0,0 +1,227 @@
+//! Common code for printing backtraces.
+
+use crate::backtrace_rs::{self, BacktraceFmt, BytesOrWideString, PrintFmt};
+use crate::borrow::Cow;
+use crate::env;
+use crate::fmt;
+use crate::io;
+use crate::io::prelude::*;
+use crate::path::{self, Path, PathBuf};
+use crate::sync::{Mutex, PoisonError};
+
+/// Max number of frames to print.
+const MAX_NB_FRAMES: usize = 100;
+
+pub fn lock() -> impl Drop {
+    static LOCK: Mutex<()> = Mutex::new(());
+    LOCK.lock().unwrap_or_else(PoisonError::into_inner)
+}
+
+/// Prints the current backtrace.
+pub fn print(w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
+    // There are issues currently linking libbacktrace into tests, and in
+    // general during std's own unit tests we're not testing this path. In
+    // test mode immediately return here to optimize away any references to the
+    // libbacktrace symbols
+    if cfg!(test) {
+        return Ok(());
+    }
+
+    // Use a lock to prevent mixed output in multithreading context.
+    // Some platforms also requires it, like `SymFromAddr` on Windows.
+    unsafe {
+        let _lock = lock();
+        _print(w, format)
+    }
+}
+
+unsafe fn _print(w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
+    struct DisplayBacktrace {
+        format: PrintFmt,
+    }
+    impl fmt::Display for DisplayBacktrace {
+        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+            unsafe { _print_fmt(fmt, self.format) }
+        }
+    }
+    write!(w, "{}", DisplayBacktrace { format })
+}
+
+unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::Result {
+    // Always 'fail' to get the cwd when running under Miri -
+    // this allows Miri to display backtraces in isolation mode
+    let cwd = if !cfg!(miri) { env::current_dir().ok() } else { None };
+
+    let mut print_path = move |fmt: &mut fmt::Formatter<'_>, bows: BytesOrWideString<'_>| {
+        output_filename(fmt, bows, print_fmt, cwd.as_ref())
+    };
+    writeln!(fmt, "stack backtrace:")?;
+    let mut bt_fmt = BacktraceFmt::new(fmt, print_fmt, &mut print_path);
+    bt_fmt.add_context()?;
+    let mut idx = 0;
+    let mut res = Ok(());
+    let mut omitted_count: usize = 0;
+    let mut first_omit = true;
+    // Start immediately if we're not using a short backtrace.
+    let mut start = print_fmt != PrintFmt::Short;
+    set_image_base();
+    backtrace_rs::trace_unsynchronized(|frame| {
+        if print_fmt == PrintFmt::Short && idx > MAX_NB_FRAMES {
+            return false;
+        }
+
+        let mut hit = false;
+        backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
+            hit = true;
+
+            // Any frames between `__rust_begin_short_backtrace` and `__rust_end_short_backtrace`
+            // are omitted from the backtrace in short mode, `__rust_end_short_backtrace` will be
+            // called before the panic hook, so we won't ignore any frames if there is no
+            // invoke of `__rust_begin_short_backtrace`.
+            if print_fmt == PrintFmt::Short {
+                if let Some(sym) = symbol.name().and_then(|s| s.as_str()) {
+                    if start && sym.contains("__rust_begin_short_backtrace") {
+                        start = false;
+                        return;
+                    }
+                    if sym.contains("__rust_end_short_backtrace") {
+                        start = true;
+                        return;
+                    }
+                    if !start {
+                        omitted_count += 1;
+                    }
+                }
+            }
+
+            if start {
+                if omitted_count > 0 {
+                    debug_assert!(print_fmt == PrintFmt::Short);
+                    // only print the message between the middle of frames
+                    if !first_omit {
+                        let _ = writeln!(
+                            bt_fmt.formatter(),
+                            "      [... omitted {} frame{} ...]",
+                            omitted_count,
+                            if omitted_count > 1 { "s" } else { "" }
+                        );
+                    }
+                    first_omit = false;
+                    omitted_count = 0;
+                }
+                res = bt_fmt.frame().symbol(frame, symbol);
+            }
+        });
+        #[cfg(target_os = "nto")]
+        if libc::__my_thread_exit as *mut libc::c_void == frame.ip() {
+            if !hit && start {
+                use crate::backtrace_rs::SymbolName;
+                res = bt_fmt.frame().print_raw(
+                    frame.ip(),
+                    Some(SymbolName::new("__my_thread_exit".as_bytes())),
+                    None,
+                    None,
+                );
+            }
+            return false;
+        }
+        if !hit && start {
+            res = bt_fmt.frame().print_raw(frame.ip(), None, None, None);
+        }
+
+        idx += 1;
+        res.is_ok()
+    });
+    res?;
+    bt_fmt.finish()?;
+    if print_fmt == PrintFmt::Short {
+        writeln!(
+            fmt,
+            "note: Some details are omitted, \
+             run with `RUST_BACKTRACE=full` for a verbose backtrace."
+        )?;
+    }
+    Ok(())
+}
+
+/// Fixed frame used to clean the backtrace with `RUST_BACKTRACE=1`. Note that
+/// this is only inline(never) when backtraces in std are enabled, otherwise
+/// it's fine to optimize away.
+#[cfg_attr(feature = "backtrace", inline(never))]
+pub fn __rust_begin_short_backtrace<F, T>(f: F) -> T
+where
+    F: FnOnce() -> T,
+{
+    let result = f();
+
+    // prevent this frame from being tail-call optimised away
+    crate::hint::black_box(());
+
+    result
+}
+
+/// Fixed frame used to clean the backtrace with `RUST_BACKTRACE=1`. Note that
+/// this is only inline(never) when backtraces in std are enabled, otherwise
+/// it's fine to optimize away.
+#[cfg_attr(feature = "backtrace", inline(never))]
+pub fn __rust_end_short_backtrace<F, T>(f: F) -> T
+where
+    F: FnOnce() -> T,
+{
+    let result = f();
+
+    // prevent this frame from being tail-call optimised away
+    crate::hint::black_box(());
+
+    result
+}
+
+/// Prints the filename of the backtrace frame.
+///
+/// See also `output`.
+pub fn output_filename(
+    fmt: &mut fmt::Formatter<'_>,
+    bows: BytesOrWideString<'_>,
+    print_fmt: PrintFmt,
+    cwd: Option<&PathBuf>,
+) -> fmt::Result {
+    let file: Cow<'_, Path> = match bows {
+        #[cfg(unix)]
+        BytesOrWideString::Bytes(bytes) => {
+            use crate::os::unix::prelude::*;
+            Path::new(crate::ffi::OsStr::from_bytes(bytes)).into()
+        }
+        #[cfg(not(unix))]
+        BytesOrWideString::Bytes(bytes) => {
+            Path::new(crate::str::from_utf8(bytes).unwrap_or("<unknown>")).into()
+        }
+        #[cfg(windows)]
+        BytesOrWideString::Wide(wide) => {
+            use crate::os::windows::prelude::*;
+            Cow::Owned(crate::ffi::OsString::from_wide(wide).into())
+        }
+        #[cfg(not(windows))]
+        BytesOrWideString::Wide(_wide) => Path::new("<unknown>").into(),
+    };
+    if print_fmt == PrintFmt::Short && file.is_absolute() {
+        if let Some(cwd) = cwd {
+            if let Ok(stripped) = file.strip_prefix(&cwd) {
+                if let Some(s) = stripped.to_str() {
+                    return write!(fmt, ".{}{s}", path::MAIN_SEPARATOR);
+                }
+            }
+        }
+    }
+    fmt::Display::fmt(&file.display(), fmt)
+}
+
+#[cfg(all(target_vendor = "fortanix", target_env = "sgx"))]
+pub fn set_image_base() {
+    let image_base = crate::os::fortanix_sgx::mem::image_base();
+    backtrace_rs::set_image_base(crate::ptr::without_provenance_mut(image_base as _));
+}
+
+#[cfg(not(all(target_vendor = "fortanix", target_env = "sgx")))]
+pub fn set_image_base() {
+    // nothing to do for platforms other than SGX
+}
diff --git a/library/std/src/sys/mod.rs b/library/std/src/sys/mod.rs
index 8f70cefc601..8aa35c40fe0 100644
--- a/library/std/src/sys/mod.rs
+++ b/library/std/src/sys/mod.rs
@@ -5,6 +5,7 @@ mod pal;
 
 mod personality;
 
+pub mod backtrace;
 pub mod cmath;
 pub mod os_str;
 pub mod path;