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
use addr2line;
use findshlibs::{self, Segment, SharedLibrary};
use std::cell::RefCell;
use std::env;
use std::os::raw::c_void;
use std::path::{Path, PathBuf};
use std::u32;
use SymbolName;
const MAPPINGS_CACHE_SIZE: usize = 4;
thread_local! {
// A very small, very simple LRU cache for debug info mappings.
//
// The hit rate should be very high, since the typical stack doesn't cross
// between many shared libraries.
//
// The `addr2line::Mapping` structures are pretty expensive to create. Its
// cost is expected to be amortized by subsequent `locate` queries, which
// leverage the structures built when constructing `addr2line::Mapping`s to
// get nice speedups. If we didn't have this cache, that amortization would
// never happen, and symbolicating backtraces would be ssssllllooooowwww.
static MAPPINGS_CACHE: RefCell<Vec<(PathBuf, addr2line::Mapping)>>
= RefCell::new(Vec::with_capacity(MAPPINGS_CACHE_SIZE));
}
fn with_mapping_for_path<F>(path: PathBuf, mut f: F)
where
F: FnMut(&mut addr2line::Mapping)
{
MAPPINGS_CACHE.with(|cache| {
let mut cache = cache.borrow_mut();
let idx = cache.iter().position(|&(ref p, _)| p == &path);
// Invariant: after this conditional completes without early returning
// from an error, the cache entry for this path is at index 0.
if let Some(idx) = idx {
// When the mapping is already in the cache, move it to the front.
if idx != 0 {
let entry = cache.remove(idx);
cache.insert(0, entry);
}
} else {
// When the mapping is not in the cache, create a new mapping,
// insert it into the front of the cache, and evict the oldest cache
// entry if necessary.
let opts = addr2line::Options::default()
.with_functions();
let mapping = match opts.build(&path) {
Err(_) => return,
Ok(m) => m,
};
if cache.len() == MAPPINGS_CACHE_SIZE {
cache.pop();
}
cache.insert(0, (path, mapping));
}
f(&mut cache[0].1);
});
}
pub fn resolve(addr: *mut c_void, cb: &mut FnMut(&super::Symbol)) {
// First, find the file containing the segment that the given AVMA (after
// relocation) address falls within. Use the containing segment to compute
// the SVMA (before relocation) address.
//
// Note that the OS APIs that `SharedLibrary::each` is implemented with hold
// a lock for the duration of the `each` call, so we want to keep this
// section as short as possible to avoid contention with other threads
// capturing backtraces.
let addr = findshlibs::Avma(addr as *mut u8 as *const u8);
let mut so_info = None;
findshlibs::TargetSharedLibrary::each(|so| {
use findshlibs::IterationControl::*;
for segment in so.segments() {
if segment.contains_avma(so, addr) {
let addr = so.avma_to_svma(addr);
let path = so.name().to_string_lossy();
so_info = Some((addr, path.to_string()));
return Break;
}
}
Continue
});
let (addr, path) = match so_info {
None => return,
Some((a, p)) => (a, p),
};
// Second, fixup the path. Empty path means that this address falls within
// the main executable, not a shared library.
let path = if path.is_empty() {
match env::current_exe() {
Err(_) => return,
Ok(p) => p,
}
} else {
PathBuf::from(path)
};
// Finally, get a cached mapping or create a new mapping for this file, and
// evaluate the DWARF info to find the file/line/name for this address.
with_mapping_for_path(path, |mapping| {
let (file, line, func) = match mapping.locate(addr.0 as u64) {
Ok(None) | Err(_) => return,
Ok(Some((file, line, func))) => (file, line, func),
};
let sym = super::Symbol {
inner: Symbol::new(addr.0 as usize,
file,
line,
func.map(|f| f.to_string()))
};
cb(&sym);
});
}
pub struct Symbol {
addr: usize,
file: PathBuf,
line: Option<u64>,
name: Option<String>,
}
impl Symbol {
fn new(addr: usize,
file: PathBuf,
line: Option<u64>,
name: Option<String>)
-> Symbol {
Symbol {
addr,
file,
line,
name,
}
}
pub fn name(&self) -> Option<SymbolName> {
self.name.as_ref().map(|s| SymbolName::new(s.as_bytes()))
}
pub fn addr(&self) -> Option<*mut c_void> {
Some(self.addr as *mut c_void)
}
pub fn filename(&self) -> Option<&Path> {
Some(self.file.as_ref())
}
pub fn lineno(&self) -> Option<u32> {
self.line
.and_then(|l| if l > (u32::MAX as u64) {
None
} else {
Some(l as u32)
})
}
}