Rollup merge of #130810 - kromych:master, r=workingjubilee · qinheping/verify-rust-std@bcb9d23 (original) (raw)
`@@ -105,84 +105,7 @@ mod os {
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`}
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`}
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#[cfg(target_os = "linux")]
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mod os {
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use super::DebuggerPresence;
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``
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use crate::fs::File;
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use crate::io::Read;
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pub(super) fn is_debugger_present() -> Option {
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// This function is crafted with the following goals:
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// * Memory efficiency: It avoids crashing the panicking process due to
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// out-of-memory (OOM) conditions by not using large heap buffers or
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// allocating significant stack space, which could lead to stack overflow.
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// * Minimal binary size: The function uses a minimal set of facilities
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// from the standard library to avoid increasing the resulting binary size.
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//
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// To achieve these goals, the function does not use [std::io::BufReader]
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// and instead reads the file byte by byte using a sliding window approach.
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// It's important to note that the "/proc/self/status" pseudo-file is synthesized
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// by the Virtual File System (VFS), meaning it is not read from a slow or
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// non-volatile storage medium so buffering might not be as beneficial because
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// all data is read from memory, though this approach does incur a syscall for
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// each byte read.
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//
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// We cannot make assumptions about the file size or the position of the
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// target prefix ("TracerPid:"), so the function does not use
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// [std::fs::read_to_string] thus not employing UTF-8 to ASCII checking,
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// conversion, or parsing as we're looking for an ASCII prefix.
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//
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// These condiderations make the function deviate from the familiar concise pattern
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// of searching for a string in a text file.
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fn read_byte(file: &mut File) -> Option {
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let mut buffer = [0];
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file.read_exact(&mut buffer).ok()?;
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Some(buffer[0])
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}
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``
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// The ASCII prefix of the datum we're interested in.
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const TRACER_PID: &[u8] = b"TracerPid:\t";
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let mut file = File::open("/proc/self/status").ok()?;
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let mut matched = 0;
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// Look for the TRACER_PID prefix.
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while let Some(byte) = read_byte(&mut file) {
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if byte == TRACER_PID[matched] {
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matched += 1;
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if matched == TRACER_PID.len() {
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break;
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}
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} else {
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matched = 0;
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}
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}
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// Was the prefix found?
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if matched != TRACER_PID.len() {
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return None;
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}
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// It was; get the ASCII representation of the first digit
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// of the PID. That is enough to see if there is a debugger
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// attached as the kernel does not pad the PID on the left
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// with the leading zeroes.
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let byte = read_byte(&mut file)?;
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if byte.is_ascii_digit() && byte != b'0' {
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Some(DebuggerPresence::Detected)
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} else {
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Some(DebuggerPresence::NotDetected)
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}
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}
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}
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``
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#[cfg(not(any(
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target_os = "windows",
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target_vendor = "apple",
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target_os = "freebsd",
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target_os = "linux"
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)))]
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#[cfg(not(any(target_os = "windows", target_vendor = "apple", target_os = "freebsd")))]
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`mod os {
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`pub(super) fn is_debugger_present() -> Optionsuper::DebuggerPresence {
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`None
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