Unrolled build for rust-lang#130810

Rollup merge of rust-lang#130810 - kromych:master, r=workingjubilee

Don't trap into the debugger on panics under Linux

This breaks `rr`, see rust-lang#129019 (comment) for the discussion

CC `@khuey` `@workingjubilee`

library/std/src/sys/dbg.rs

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