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Use /proc/self/maps when available instead of std::env::current_exe #488
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alexcrichton
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rust-lang:master
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pnkfelix:use-proc-self-maps-when-avail-instead-of-current-exe
Oct 25, 2022
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3344386
standalone proc/self/maps parsing code to try instead of less reliabl…
pnkfelix 75d6b28
checkpoint regression test demonstrating failure of rust issue 101913.
pnkfelix 12f4fbc
fix code to work for cargo test --no-default-features .
pnkfelix 6a0b39d
fix test to ignore itself when it cannot invoke readelf.
pnkfelix b7bc9d0
Conditionalize 64-bit test. Add test that works for 32-bit targets.
pnkfelix b125d9c
placate cargo fmt.
pnkfelix cc0cdbb
switch to pure `Read` rather than `BufRead` based implementation, to …
pnkfelix 8dd32f0
Avoid using `str::split_once` method, since the MSRV is 1.42 but that…
pnkfelix 681ff30
placate cargo fmt.
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Original file line number | Diff line number | Diff line change |
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// Note: This file is only currently used on targets that call out to the code | ||
// in `mod libs_dl_iterate_phdr` (e.g. linux, freebsd, ...); it may be more | ||
// general purpose, but it hasn't been tested elsewhere. | ||
|
||
use super::mystd::fs::File; | ||
use super::mystd::io::Read; | ||
use super::mystd::str::FromStr; | ||
use super::{OsString, String, Vec}; | ||
|
||
#[derive(PartialEq, Eq, Debug)] | ||
pub(super) struct MapsEntry { | ||
/// start (inclusive) and limit (exclusive) of address range. | ||
address: (usize, usize), | ||
/// The perms field are the permissions for the entry | ||
/// | ||
/// r = read | ||
/// w = write | ||
/// x = execute | ||
/// s = shared | ||
/// p = private (copy on write) | ||
perms: [char; 4], | ||
/// Offset into the file (or "whatever"). | ||
offset: usize, | ||
/// device (major, minor) | ||
dev: (usize, usize), | ||
/// inode on the device. 0 indicates that no inode is associated with the memory region (e.g. uninitalized data aka BSS). | ||
inode: usize, | ||
/// Usually the file backing the mapping. | ||
/// | ||
/// Note: The man page for proc includes a note about "coordination" by | ||
/// using readelf to see the Offset field in ELF program headers. pnkfelix | ||
/// is not yet sure if that is intended to be a comment on pathname, or what | ||
/// form/purpose such coordination is meant to have. | ||
/// | ||
/// There are also some pseudo-paths: | ||
/// "[stack]": The initial process's (aka main thread's) stack. | ||
/// "[stack:<tid>]": a specific thread's stack. (This was only present for a limited range of Linux verisons; it was determined to be too expensive to provide.) | ||
/// "[vdso]": Virtual dynamically linked shared object | ||
/// "[heap]": The process's heap | ||
/// | ||
/// The pathname can be blank, which means it is an anonymous mapping | ||
/// obtained via mmap. | ||
/// | ||
/// Newlines in pathname are replaced with an octal escape sequence. | ||
/// | ||
/// The pathname may have "(deleted)" appended onto it if the file-backed | ||
/// path has been deleted. | ||
/// | ||
/// Note that modifications like the latter two indicated above imply that | ||
/// in general the pathname may be ambiguous. (I.e. you cannot tell if the | ||
/// denoted filename actually ended with the text "(deleted)", or if that | ||
/// was added by the maps rendering. | ||
pathname: OsString, | ||
} | ||
|
||
pub(super) fn parse_maps() -> Result<Vec<MapsEntry>, &'static str> { | ||
let mut v = Vec::new(); | ||
let mut proc_self_maps = | ||
File::open("/proc/self/maps").map_err(|_| "Couldn't open /proc/self/maps")?; | ||
let mut buf = String::new(); | ||
let _bytes_read = proc_self_maps | ||
.read_to_string(&mut buf) | ||
.map_err(|_| "Couldn't read /proc/self/maps")?; | ||
for line in buf.lines() { | ||
v.push(line.parse()?); | ||
} | ||
|
||
Ok(v) | ||
} | ||
|
||
impl MapsEntry { | ||
pub(super) fn pathname(&self) -> &OsString { | ||
&self.pathname | ||
} | ||
|
||
pub(super) fn ip_matches(&self, ip: usize) -> bool { | ||
self.address.0 <= ip && ip < self.address.1 | ||
} | ||
} | ||
|
||
impl FromStr for MapsEntry { | ||
type Err = &'static str; | ||
|
||
// Format: address perms offset dev inode pathname | ||
// e.g.: "ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]" | ||
// e.g.: "7f5985f46000-7f5985f48000 rw-p 00039000 103:06 76021795 /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2" | ||
// e.g.: "35b1a21000-35b1a22000 rw-p 00000000 00:00 0" | ||
fn from_str(s: &str) -> Result<Self, Self::Err> { | ||
let mut parts = s | ||
.split(' ') // space-separated fields | ||
.filter(|s| s.len() > 0); // multiple spaces implies empty strings that need to be skipped. | ||
let range_str = parts.next().ok_or("Couldn't find address")?; | ||
let perms_str = parts.next().ok_or("Couldn't find permissions")?; | ||
let offset_str = parts.next().ok_or("Couldn't find offset")?; | ||
let dev_str = parts.next().ok_or("Couldn't find dev")?; | ||
let inode_str = parts.next().ok_or("Couldn't find inode")?; | ||
let pathname_str = parts.next().unwrap_or(""); // pathname may be omitted. | ||
|
||
let hex = |s| usize::from_str_radix(s, 16).map_err(|_| "Couldn't parse hex number"); | ||
let address = { | ||
// This could use `range_str.split_once('-')` once the MSRV passes 1.52. | ||
if let Some(idx) = range_str.find('-') { | ||
let (start, rest) = range_str.split_at(idx); | ||
let (_div, limit) = rest.split_at(1); | ||
(hex(start)?, hex(limit)?) | ||
} else { | ||
return Err("Couldn't parse address range"); | ||
} | ||
}; | ||
let perms: [char; 4] = { | ||
let mut chars = perms_str.chars(); | ||
let mut c = || chars.next().ok_or("insufficient perms"); | ||
let perms = [c()?, c()?, c()?, c()?]; | ||
if chars.next().is_some() { | ||
return Err("too many perms"); | ||
} | ||
perms | ||
}; | ||
let offset = hex(offset_str)?; | ||
let dev = { | ||
// This could use `dev_str.split_once(':')` once the MSRV passes 1.52. | ||
if let Some(idx) = dev_str.find(':') { | ||
let (major, rest) = dev_str.split_at(idx); | ||
let (_div, minor) = rest.split_at(1); | ||
(hex(major)?, hex(minor)?) | ||
} else { | ||
return Err("Couldn't parse dev")?; | ||
} | ||
}; | ||
let inode = hex(inode_str)?; | ||
let pathname = pathname_str.into(); | ||
|
||
Ok(MapsEntry { | ||
address, | ||
perms, | ||
offset, | ||
dev, | ||
inode, | ||
pathname, | ||
}) | ||
} | ||
} | ||
|
||
// Make sure we can parse 64-bit sample output if we're on a 64-bit target. | ||
#[cfg(target_pointer_width = "64")] | ||
#[test] | ||
fn check_maps_entry_parsing_64bit() { | ||
assert_eq!( | ||
"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 \ | ||
[vsyscall]" | ||
.parse::<MapsEntry>() | ||
.unwrap(), | ||
MapsEntry { | ||
address: (0xffffffffff600000, 0xffffffffff601000), | ||
perms: ['-', '-', 'x', 'p'], | ||
offset: 0x00000000, | ||
dev: (0x00, 0x00), | ||
inode: 0x0, | ||
pathname: "[vsyscall]".into(), | ||
} | ||
); | ||
|
||
assert_eq!( | ||
"7f5985f46000-7f5985f48000 rw-p 00039000 103:06 76021795 \ | ||
/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2" | ||
.parse::<MapsEntry>() | ||
.unwrap(), | ||
MapsEntry { | ||
address: (0x7f5985f46000, 0x7f5985f48000), | ||
perms: ['r', 'w', '-', 'p'], | ||
offset: 0x00039000, | ||
dev: (0x103, 0x06), | ||
inode: 0x76021795, | ||
pathname: "/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2".into(), | ||
} | ||
); | ||
assert_eq!( | ||
"35b1a21000-35b1a22000 rw-p 00000000 00:00 0" | ||
.parse::<MapsEntry>() | ||
.unwrap(), | ||
MapsEntry { | ||
address: (0x35b1a21000, 0x35b1a22000), | ||
perms: ['r', 'w', '-', 'p'], | ||
offset: 0x00000000, | ||
dev: (0x00, 0x00), | ||
inode: 0x0, | ||
pathname: Default::default(), | ||
} | ||
); | ||
} | ||
|
||
// (This output was taken from a 32-bit machine, but will work on any target) | ||
#[test] | ||
fn check_maps_entry_parsing_32bit() { | ||
/* Example snippet of output: | ||
08056000-08077000 rw-p 00000000 00:00 0 [heap] | ||
b7c79000-b7e02000 r--p 00000000 08:01 60662705 /usr/lib/locale/locale-archive | ||
b7e02000-b7e03000 rw-p 00000000 00:00 0 | ||
*/ | ||
assert_eq!( | ||
"08056000-08077000 rw-p 00000000 00:00 0 \ | ||
[heap]" | ||
.parse::<MapsEntry>() | ||
.unwrap(), | ||
MapsEntry { | ||
address: (0x08056000, 0x08077000), | ||
perms: ['r', 'w', '-', 'p'], | ||
offset: 0x00000000, | ||
dev: (0x00, 0x00), | ||
inode: 0x0, | ||
pathname: "[heap]".into(), | ||
} | ||
); | ||
|
||
assert_eq!( | ||
"b7c79000-b7e02000 r--p 00000000 08:01 60662705 \ | ||
/usr/lib/locale/locale-archive" | ||
.parse::<MapsEntry>() | ||
.unwrap(), | ||
MapsEntry { | ||
address: (0xb7c79000, 0xb7e02000), | ||
perms: ['r', '-', '-', 'p'], | ||
offset: 0x00000000, | ||
dev: (0x08, 0x01), | ||
inode: 0x60662705, | ||
pathname: "/usr/lib/locale/locale-archive".into(), | ||
} | ||
); | ||
assert_eq!( | ||
"b7e02000-b7e03000 rw-p 00000000 00:00 0" | ||
.parse::<MapsEntry>() | ||
.unwrap(), | ||
MapsEntry { | ||
address: (0xb7e02000, 0xb7e03000), | ||
perms: ['r', 'w', '-', 'p'], | ||
offset: 0x00000000, | ||
dev: (0x00, 0x00), | ||
inode: 0x0, | ||
pathname: Default::default(), | ||
} | ||
); | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,14 @@ | ||
/// Some tests only make sense in contexts where they can re-exec the test | ||
/// itself. Not all contexts support this, so you can call this method to find | ||
/// out which case you are in. | ||
pub fn cannot_reexec_the_test() -> bool { | ||
// These run in docker containers on CI where they can't re-exec the test, | ||
// so just skip these for CI. No other reason this can't run on those | ||
// platforms though. | ||
// Miri does not have support for re-execing a file | ||
cfg!(unix) | ||
&& (cfg!(target_arch = "arm") | ||
|| cfg!(target_arch = "aarch64") | ||
|| cfg!(target_arch = "s390x")) | ||
|| cfg!(miri) | ||
} |
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This logic only applies to linux I think. Netbsd has
/proc/curproc/
. macOS doesn't have/proc
at all. As for other unixes I'm not quite sure.There was a problem hiding this comment.
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I'm happy to revise this so that only Linux pulls in the "interesting"
parse_maps
file, and every other target just goes to the no-op variant.(I was hoping that I had gotten the logic right such that targets that didn't have the
/proc/self/maps
pseudo-file, or if it failed to parse said file, it would silently just fall back onstd::env::current_exe
, but I haven't confirmed that yet.)There was a problem hiding this comment.
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I looked again, and realized that the sole calling module is solely defined here:
backtrace-rs/src/symbolize/gimli.rs
Lines 175 to 185 in 8b83ba1
That makes this a lot easier to limit to just these small subset of targets.
I force-pushed an update that fixes that (and backtraces my API to a simpler one now enabled by removing the
parse_running_mmaps_noop.rs
code).