libbacktrace.rs.html -- source
Description: Source to the Rust file `libstd/sys_common/gnu/libbacktrace.rs`.
Keywords: rust, rustlang, rust-lang

      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

    // 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 libc;

    use ffi::CStr;
    use io;
    use mem;
    use ptr;
    use sys::backtrace::BacktraceContext;
    use sys_common::backtrace::Frame;

    pub fn foreach_symbol_fileline<F>(frame: Frame,
                                      mut f: F,
                                      _: &BacktraceContext) -> io::Result<bool>
    where F: FnMut(&[u8], u32) -> io::Result<()>
    {
        // pcinfo may return an arbitrary number of file:line pairs,
        // in the order of stack trace (i.e. inlined calls first).
        // in order to avoid allocation, we stack-allocate a fixed size of entries.
        const FILELINE_SIZE: usize = 32;
        let mut fileline_buf = [(ptr::null(), !0); FILELINE_SIZE];
        let ret;
        let fileline_count = {
            let state = unsafe { init_state() };
            if state.is_null() {
                return Err(io::Error::new(
                    io::ErrorKind::Other,
                    "failed to allocate libbacktrace state")
                )
            }
            let mut fileline_win: &mut [FileLine] = &mut fileline_buf;
            let fileline_addr = &mut fileline_win as *mut &mut [FileLine];
            ret = unsafe {
                backtrace_pcinfo(state,
                                 frame.exact_position as libc::uintptr_t,
                                 pcinfo_cb,
                                 error_cb,
                                 fileline_addr as *mut libc::c_void)
            };
            FILELINE_SIZE - fileline_win.len()
        };
        if ret == 0 {
            for &(file, line) in &fileline_buf[..fileline_count] {
                if file.is_null() { continue; } // just to be sure
                let file = unsafe { CStr::from_ptr(file).to_bytes() };
                f(file, line)?;
            }
            Ok(fileline_count == FILELINE_SIZE)
        } else {
            Ok(false)
        }
    }

    /// Converts a pointer to symbol to its string value.
    pub fn resolve_symname<F>(frame: Frame,
                              callback: F,
                              _: &BacktraceContext) -> io::Result<()>
        where F: FnOnce(Option<&str>) -> io::Result<()>
    {
        let symname = {
            let state = unsafe { init_state() };
            if state.is_null() {
                return Err(io::Error::new(
                    io::ErrorKind::Other,
                    "failed to allocate libbacktrace state")
                )
            }
            let mut data: *const libc::c_char = ptr::null();
            let data_addr = &mut data as *mut *const libc::c_char;
            let ret = unsafe {
                backtrace_syminfo(state,
                                  frame.symbol_addr as libc::uintptr_t,
                                  syminfo_cb,
                                  error_cb,
                                  data_addr as *mut libc::c_void)
            };
            if ret == 0 || data.is_null() {
                None
            } else {
                unsafe {
                    CStr::from_ptr(data).to_str().ok()
                }
            }
        };
        callback(symname)
    }

    ////////////////////////////////////////////////////////////////////////
    // libbacktrace.h API
    ////////////////////////////////////////////////////////////////////////
    type backtrace_syminfo_callback =
    extern "C" fn(data: *mut libc::c_void,
                  pc: libc::uintptr_t,
                  symname: *const libc::c_char,
                  symval: libc::uintptr_t,
                  symsize: libc::uintptr_t);
    type backtrace_full_callback =
    extern "C" fn(data: *mut libc::c_void,
                  pc: libc::uintptr_t,
                  filename: *const libc::c_char,
                  lineno: libc::c_int,
                  function: *const libc::c_char) -> libc::c_int;
    type backtrace_error_callback =
    extern "C" fn(data: *mut libc::c_void,
                  msg: *const libc::c_char,
                  errnum: libc::c_int);
    enum backtrace_state {}

    extern {
        fn backtrace_create_state(filename: *const libc::c_char,
                                  threaded: libc::c_int,
                                  error: backtrace_error_callback,
                                  data: *mut libc::c_void)
            -> *mut backtrace_state;
        fn backtrace_syminfo(state: *mut backtrace_state,
                             addr: libc::uintptr_t,
                             cb: backtrace_syminfo_callback,
                             error: backtrace_error_callback,
                             data: *mut libc::c_void) -> libc::c_int;
        fn backtrace_pcinfo(state: *mut backtrace_state,
                            addr: libc::uintptr_t,
                            cb: backtrace_full_callback,
                            error: backtrace_error_callback,
                            data: *mut libc::c_void) -> libc::c_int;
    }

    ////////////////////////////////////////////////////////////////////////
    // helper callbacks
    ////////////////////////////////////////////////////////////////////////

    type FileLine = (*const libc::c_char, u32);

    extern fn error_cb(_data: *mut libc::c_void, _msg: *const libc::c_char,
                       _errnum: libc::c_int) {
        // do nothing for now
    }
    extern fn syminfo_cb(data: *mut libc::c_void,
                         _pc: libc::uintptr_t,
                         symname: *const libc::c_char,
                         _symval: libc::uintptr_t,
                         _symsize: libc::uintptr_t) {
        let slot = data as *mut *const libc::c_char;
        unsafe { *slot = symname; }
    }
    extern fn pcinfo_cb(data: *mut libc::c_void,
                        _pc: libc::uintptr_t,
                        filename: *const libc::c_char,
                        lineno: libc::c_int,
                        _function: *const libc::c_char) -> libc::c_int {
        if !filename.is_null() {
            let slot = data as *mut &mut [FileLine];
            let buffer = unsafe {ptr::read(slot)};

            // if the buffer is not full, add file:line to the buffer
            // and adjust the buffer for next possible calls to pcinfo_cb.
            if !buffer.is_empty() {
                buffer[0] = (filename, lineno as u32);
                unsafe { ptr::write(slot, &mut buffer[1..]); }
            }
        }

        0
    }

    // The libbacktrace API supports creating a state, but it does not
    // support destroying a state. I personally take this to mean that a
    // state is meant to be created and then live forever.
    //
    // I would love to register an at_exit() handler which cleans up this
    // state, but libbacktrace provides no way to do so.
    //
    // With these constraints, this function has a statically cached state
    // that is calculated the first time this is requested. Remember that
    // backtracing all happens serially (one global lock).
    //
    // Things don't work so well on not-Linux since libbacktrace can't track
    // down that executable this is. We at one point used env::current_exe but
    // it turns out that there are some serious security issues with that
    // approach.
    //
    // Specifically, on certain platforms like BSDs, a malicious actor can cause
    // an arbitrary file to be placed at the path returned by current_exe.
    // libbacktrace does not behave defensively in the presence of ill-formed
    // DWARF information, and has been demonstrated to segfault in at least one
    // case. There is no evidence at the moment to suggest that a more carefully
    // constructed file can't cause arbitrary code execution. As a result of all
    // of this, we don't hint libbacktrace with the path to the current process.
    unsafe fn init_state() -> *mut backtrace_state {
        static mut STATE: *mut backtrace_state = ptr::null_mut();
        if !STATE.is_null() { return STATE  }

        let filename = match ::sys::backtrace::gnu::get_executable_filename() {
            Ok((filename, file)) => {
                // filename is purposely leaked here since libbacktrace requires
                // it to stay allocated permanently, file is also leaked so that
                // the file stays locked
                let filename_ptr = filename.as_ptr();
                mem::forget(filename);
                mem::forget(file);
                filename_ptr
            },
            Err(_) => ptr::null(),
        };

        STATE = backtrace_create_state(filename, 0, error_cb,
                                       ptr::null_mut());
        STATE
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g. `str,u8` or `String,struct:Vec,test`)