1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
use crate::BytesOrWideString;
use core::ffi::c_void;
use core::fmt;

const HEX_WIDTH: usize = 2 + 2 * core::mem::size_of::<usize>();

#[cfg(target_os = "fuchsia")]
mod fuchsia;

/// A formatter for backtraces.
///
/// This type can be used to print a backtrace regardless of where the backtrace
/// itself comes from. If you have a `Backtrace` type then its `Debug`
/// implementation already uses this printing format.
pub struct BacktraceFmt<'a, 'b> {
    fmt: &'a mut fmt::Formatter<'b>,
    frame_index: usize,
    format: PrintFmt,
    print_path: &'a mut (FnMut(&mut fmt::Formatter, BytesOrWideString) -> fmt::Result + 'b),
}

/// The styles of printing that we can print
#[derive(Copy, Clone, Eq, PartialEq)]
pub enum PrintFmt {
    /// Prints a terser backtrace which ideally only contains relevant information
    Short,
    /// Prints a backtrace that contains all possible information
    Full,
    #[doc(hidden)]
    __Nonexhaustive,
}

impl<'a, 'b> BacktraceFmt<'a, 'b> {
    /// Create a new `BacktraceFmt` which will write output to the provided
    /// `fmt`.
    ///
    /// The `format` argument will control the style in which the backtrace is
    /// printed, and the `print_path` argument will be used to print the
    /// `BytesOrWideString` instances of filenames. This type itself doesn't do
    /// any printing of filenames, but this callback is required to do so.
    pub fn new(
        fmt: &'a mut fmt::Formatter<'b>,
        format: PrintFmt,
        print_path: &'a mut (FnMut(&mut fmt::Formatter, BytesOrWideString) -> fmt::Result + 'b),
    ) -> Self {
        BacktraceFmt {
            fmt,
            frame_index: 0,
            format,
            print_path,
        }
    }

    /// Prints a preamble for the backtrace about to be printed.
    ///
    /// This is required on some platforms for backtraces to be fully
    /// sumbolicated later, and otherwise this should just be the first method
    /// you call after creating a `BacktraceFmt`.
    pub fn add_context(&mut self) -> fmt::Result {
        self.fmt.write_str("stack backtrace:\n")?;
        #[cfg(target_os = "fuchsia")]
        fuchsia::print_dso_context(self.fmt)?;
        Ok(())
    }

    /// Adds a frame to the backtrace output.
    ///
    /// This commit returns an RAII instance of a `BacktraceFrameFmt` which can be used
    /// to actually print a frame, and on destruction it will increment the
    /// frame counter.
    pub fn frame(&mut self) -> BacktraceFrameFmt<'_, 'a, 'b> {
        BacktraceFrameFmt {
            fmt: self,
            symbol_index: 0,
        }
    }

    /// Completes the backtrace output.
    ///
    /// This is currently a no-op but is added for future compatibility with
    /// backtrace formats.
    pub fn finish(&mut self) -> fmt::Result {
        // Currently a no-op-- including this hook to allow for future additions.
        Ok(())
    }
}

/// A formatter for just one frame of a backtrace.
///
/// This type is created by the `BacktraceFmt::frame` function.
pub struct BacktraceFrameFmt<'fmt, 'a, 'b> {
    fmt: &'fmt mut BacktraceFmt<'a, 'b>,
    symbol_index: usize,
}

impl BacktraceFrameFmt<'_, '_, '_> {
    /// Prints a `BacktraceFrame` with this frame formatter.
    ///
    /// This will recusrively print all `BacktraceSymbol` instances within the
    /// `BacktraceFrame`.
    ///
    /// # Required features
    ///
    /// This function requires the `std` feature of the `backtrace` crate to be
    /// enabled, and the `std` feature is enabled by default.
    #[cfg(feature = "std")]
    pub fn backtrace_frame(&mut self, frame: &crate::BacktraceFrame) -> fmt::Result {
        let symbols = frame.symbols();
        for symbol in symbols {
            self.backtrace_symbol(frame, symbol)?;
        }
        if symbols.is_empty() {
            self.print_raw(frame.ip(), None, None, None)?;
        }
        Ok(())
    }

    /// Prints a `BacktraceSymbol` within a `BacktraceFrame`.
    ///
    /// # Required features
    ///
    /// This function requires the `std` feature of the `backtrace` crate to be
    /// enabled, and the `std` feature is enabled by default.
    #[cfg(feature = "std")]
    pub fn backtrace_symbol(
        &mut self,
        frame: &crate::BacktraceFrame,
        symbol: &crate::BacktraceSymbol,
    ) -> fmt::Result {
        self.print_raw(
            frame.ip(),
            symbol.name(),
            // TODO: this isn't great that we don't end up printing anything
            // with non-utf8 filenames. Thankfully almost everything is utf8 so
            // this shouldn't be too too bad.
            symbol
                .filename()
                .and_then(|p| Some(BytesOrWideString::Bytes(p.to_str()?.as_bytes()))),
            symbol.lineno(),
        )?;
        Ok(())
    }

    /// Prints a raw traced `Frame` and `Symbol`, typically from within the raw
    /// callbacks of this crate.
    pub fn symbol(&mut self, frame: &crate::Frame, symbol: &crate::Symbol) -> fmt::Result {
        self.print_raw(
            frame.ip(),
            symbol.name(),
            symbol.filename_raw(),
            symbol.lineno(),
        )?;
        Ok(())
    }

    /// Adds a raw frame to the backtrace output.
    ///
    /// This method, unlike the previous, takes the raw arguments in case
    /// they're being source from different locations. Note that this may be
    /// called multiple times for one frame.
    pub fn print_raw(
        &mut self,
        frame_ip: *mut c_void,
        symbol_name: Option<crate::SymbolName>,
        filename: Option<BytesOrWideString>,
        lineno: Option<u32>,
    ) -> fmt::Result {
        // Fuchsia is unable to symbolize within a process so it has a special
        // format which can be used to symbolize later. Print that instead of
        // printing addresses in our own format here.
        if cfg!(target_os = "fuchsia") {
            self.print_raw_fuchsia(frame_ip)?;
        } else {
            self.print_raw_generic(frame_ip, symbol_name, filename, lineno)?;
        }
        self.symbol_index += 1;
        Ok(())
    }

    #[allow(unused_mut)]
    fn print_raw_generic(
        &mut self,
        mut frame_ip: *mut c_void,
        symbol_name: Option<crate::SymbolName>,
        filename: Option<BytesOrWideString>,
        lineno: Option<u32>,
    ) -> fmt::Result {
        // No need to print "null" frames, it basically just means that the
        // system backtrace was a bit eager to trace back super far.
        if let PrintFmt::Short = self.fmt.format {
            if frame_ip.is_null() {
                return Ok(());
            }
        }

        // To reduce TCB size in Sgx enclave, we do not want to implement symbol
        // resolution functionality.  Rather, we can print the offset of the
        // address here, which could be later mapped to correct function.
        #[cfg(all(feature = "std", target_env = "sgx"))]
        {
            frame_ip =
                usize::wrapping_sub(frame_ip, std::os::fortanix_sgx::mem::image_base() as _) as _;
        }

        // Print the index of the frame as well as the optional instruction
        // pointer of the frame. If we're beyond the first symbol of this frame
        // though we just print appropriate whitespace.
        if self.symbol_index == 0 {
            write!(self.fmt.fmt, "{:4}: ", self.fmt.frame_index)?;
            if let PrintFmt::Full = self.fmt.format {
                write!(self.fmt.fmt, "{:1$?} - ", frame_ip, HEX_WIDTH)?;
            }
        } else {
            write!(self.fmt.fmt, "      ")?;
            if let PrintFmt::Full = self.fmt.format {
                write!(self.fmt.fmt, "{:1$}", "", HEX_WIDTH + 3)?;
            }
        }

        // Next up write out the symbol name, using the alternate formatting for
        // more information if we're a full backtrace. Here we also handle
        // symbols which don't have a name,
        match (symbol_name, &self.fmt.format) {
            (Some(name), PrintFmt::Short) => write!(self.fmt.fmt, "{:#}", name)?,
            (Some(name), PrintFmt::Full) => write!(self.fmt.fmt, "{}", name)?,
            (None, _) | (_, PrintFmt::__Nonexhaustive) => write!(self.fmt.fmt, "<unknown>")?,
        }
        self.fmt.fmt.write_str("\n")?;

        // And last up, print out the filename/line number if they're available.
        if let (Some(file), Some(line)) = (filename, lineno) {
            self.print_fileline(file, line)?;
        }

        Ok(())
    }

    fn print_fileline(&mut self, file: BytesOrWideString, line: u32) -> fmt::Result {
        // Filename/line are printed on lines under the symbol name, so print
        // some appropriate whitespace to sort of right-align ourselves.
        if let PrintFmt::Full = self.fmt.format {
            write!(self.fmt.fmt, "{:1$}", "", HEX_WIDTH)?;
        }
        write!(self.fmt.fmt, "             at ")?;

        // Delegate to our internal callback to print the filename and then
        // print out the line number.
        (self.fmt.print_path)(self.fmt.fmt, file)?;
        write!(self.fmt.fmt, ":{}\n", line)?;
        Ok(())
    }

    fn print_raw_fuchsia(&mut self, frame_ip: *mut c_void) -> fmt::Result {
        // We only care about the first symbol of a frame
        if self.symbol_index == 0 {
            self.fmt.fmt.write_str("{{{bt:")?;
            write!(self.fmt.fmt, "{}:{:?}", self.fmt.frame_index, frame_ip)?;
            self.fmt.fmt.write_str("}}}\n")?;
        }
        Ok(())
    }
}

impl Drop for BacktraceFrameFmt<'_, '_, '_> {
    fn drop(&mut self) {
        self.fmt.frame_index += 1;
    }
}