diff options
Diffstat (limited to 'compiler/rustc_driver_impl/src')
| -rw-r--r-- | compiler/rustc_driver_impl/src/lib.rs | 83 | ||||
| -rw-r--r-- | compiler/rustc_driver_impl/src/signal_handler.rs | 142 |
2 files changed, 154 insertions, 71 deletions
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs index 841c626d0a3..1a16759d7f9 100644 --- a/compiler/rustc_driver_impl/src/lib.rs +++ b/compiler/rustc_driver_impl/src/lib.rs @@ -85,6 +85,15 @@ pub mod pretty; #[macro_use] mod print; mod session_diagnostics; +#[cfg(all(unix, any(target_env = "gnu", target_os = "macos")))] +mod signal_handler; + +#[cfg(not(all(unix, any(target_env = "gnu", target_os = "macos"))))] +mod signal_handler { + /// On platforms which don't support our signal handler's requirements, + /// simply use the default signal handler provided by std. + pub(super) fn install() {} +} use crate::session_diagnostics::{ RLinkEmptyVersionNumber, RLinkEncodingVersionMismatch, RLinkRustcVersionMismatch, @@ -852,11 +861,9 @@ fn print_crate_info( use rustc_target::spec::current_apple_deployment_target; if sess.target.is_like_osx { - println_info!( - "deployment_target={}", - current_apple_deployment_target(&sess.target) - .expect("unknown Apple target OS") - ) + let (major, minor) = current_apple_deployment_target(&sess.target) + .expect("unknown Apple target OS"); + println_info!("deployment_target={}", format!("{major}.{minor}")) } else { handler .early_error("only Apple targets currently support deployment version info") @@ -1442,72 +1449,6 @@ pub fn init_env_logger(handler: &EarlyErrorHandler, env: &str) { } } -#[cfg(all(unix, any(target_env = "gnu", target_os = "macos")))] -mod signal_handler { - extern "C" { - fn backtrace_symbols_fd( - buffer: *const *mut libc::c_void, - size: libc::c_int, - fd: libc::c_int, - ); - } - - extern "C" fn print_stack_trace(_: libc::c_int) { - const MAX_FRAMES: usize = 256; - static mut STACK_TRACE: [*mut libc::c_void; MAX_FRAMES] = - [std::ptr::null_mut(); MAX_FRAMES]; - unsafe { - let depth = libc::backtrace(STACK_TRACE.as_mut_ptr(), MAX_FRAMES as i32); - if depth == 0 { - return; - } - backtrace_symbols_fd(STACK_TRACE.as_ptr(), depth, 2); - } - } - - /// When an error signal (such as SIGABRT or SIGSEGV) is delivered to the - /// process, print a stack trace and then exit. - pub(super) fn install() { - use std::alloc::{alloc, Layout}; - - unsafe { - let alt_stack_size: usize = min_sigstack_size() + 64 * 1024; - let mut alt_stack: libc::stack_t = std::mem::zeroed(); - alt_stack.ss_sp = alloc(Layout::from_size_align(alt_stack_size, 1).unwrap()).cast(); - alt_stack.ss_size = alt_stack_size; - libc::sigaltstack(&alt_stack, std::ptr::null_mut()); - - let mut sa: libc::sigaction = std::mem::zeroed(); - sa.sa_sigaction = print_stack_trace as libc::sighandler_t; - sa.sa_flags = libc::SA_NODEFER | libc::SA_RESETHAND | libc::SA_ONSTACK; - libc::sigemptyset(&mut sa.sa_mask); - libc::sigaction(libc::SIGSEGV, &sa, std::ptr::null_mut()); - } - } - - /// Modern kernels on modern hardware can have dynamic signal stack sizes. - #[cfg(any(target_os = "linux", target_os = "android"))] - fn min_sigstack_size() -> usize { - const AT_MINSIGSTKSZ: core::ffi::c_ulong = 51; - let dynamic_sigstksz = unsafe { libc::getauxval(AT_MINSIGSTKSZ) }; - // If getauxval couldn't find the entry, it returns 0, - // so take the higher of the "constant" and auxval. - // This transparently supports older kernels which don't provide AT_MINSIGSTKSZ - libc::MINSIGSTKSZ.max(dynamic_sigstksz as _) - } - - /// Not all OS support hardware where this is needed. - #[cfg(not(any(target_os = "linux", target_os = "android")))] - fn min_sigstack_size() -> usize { - libc::MINSIGSTKSZ - } -} - -#[cfg(not(all(unix, any(target_env = "gnu", target_os = "macos"))))] -mod signal_handler { - pub(super) fn install() {} -} - pub fn main() -> ! { let start_time = Instant::now(); let start_rss = get_resident_set_size(); diff --git a/compiler/rustc_driver_impl/src/signal_handler.rs b/compiler/rustc_driver_impl/src/signal_handler.rs new file mode 100644 index 00000000000..deca1082221 --- /dev/null +++ b/compiler/rustc_driver_impl/src/signal_handler.rs @@ -0,0 +1,142 @@ +//! Signal handler for rustc +//! Primarily used to extract a backtrace from stack overflow + +use std::alloc::{alloc, Layout}; +use std::{fmt, mem, ptr}; + +extern "C" { + fn backtrace_symbols_fd(buffer: *const *mut libc::c_void, size: libc::c_int, fd: libc::c_int); +} + +fn backtrace_stderr(buffer: &[*mut libc::c_void]) { + let size = buffer.len().try_into().unwrap_or_default(); + unsafe { backtrace_symbols_fd(buffer.as_ptr(), size, libc::STDERR_FILENO) }; +} + +/// Unbuffered, unsynchronized writer to stderr. +/// +/// Only acceptable because everything will end soon anyways. +struct RawStderr(()); + +impl fmt::Write for RawStderr { + fn write_str(&mut self, s: &str) -> Result<(), fmt::Error> { + let ret = unsafe { libc::write(libc::STDERR_FILENO, s.as_ptr().cast(), s.len()) }; + if ret == -1 { Err(fmt::Error) } else { Ok(()) } + } +} + +/// We don't really care how many bytes we actually get out. SIGSEGV comes for our head. +/// Splash stderr with letters of our own blood to warn our friends about the monster. +macro raw_errln($tokens:tt) { + let _ = ::core::fmt::Write::write_fmt(&mut RawStderr(()), format_args!($tokens)); + let _ = ::core::fmt::Write::write_char(&mut RawStderr(()), '\n'); +} + +/// Signal handler installed for SIGSEGV +extern "C" fn print_stack_trace(_: libc::c_int) { + const MAX_FRAMES: usize = 256; + // Reserve data segment so we don't have to malloc in a signal handler, which might fail + // in incredibly undesirable and unexpected ways due to e.g. the allocator deadlocking + static mut STACK_TRACE: [*mut libc::c_void; MAX_FRAMES] = [ptr::null_mut(); MAX_FRAMES]; + let stack = unsafe { + // Collect return addresses + let depth = libc::backtrace(STACK_TRACE.as_mut_ptr(), MAX_FRAMES as i32); + if depth == 0 { + return; + } + &STACK_TRACE.as_slice()[0..(depth as _)] + }; + + // Just a stack trace is cryptic. Explain what we're doing. + raw_errln!("error: rustc interrupted by SIGSEGV, printing backtrace\n"); + let mut written = 1; + let mut consumed = 0; + // Begin elaborating return addrs into symbols and writing them directly to stderr + // Most backtraces are stack overflow, most stack overflows are from recursion + // Check for cycles before writing 250 lines of the same ~5 symbols + let cycled = |(runner, walker)| runner == walker; + let mut cyclic = false; + if let Some(period) = stack.iter().skip(1).step_by(2).zip(stack).position(cycled) { + let period = period.saturating_add(1); // avoid "what if wrapped?" branches + let Some(offset) = stack.iter().skip(period).zip(stack).position(cycled) else { + // impossible. + return; + }; + + // Count matching trace slices, else we could miscount "biphasic cycles" + // with the same period + loop entry but a different inner loop + let next_cycle = stack[offset..].chunks_exact(period).skip(1); + let cycles = 1 + next_cycle + .zip(stack[offset..].chunks_exact(period)) + .filter(|(next, prev)| next == prev) + .count(); + backtrace_stderr(&stack[..offset]); + written += offset; + consumed += offset; + if cycles > 1 { + raw_errln!("\n### cycle encountered after {offset} frames with period {period}"); + backtrace_stderr(&stack[consumed..consumed + period]); + raw_errln!("### recursed {cycles} times\n"); + written += period + 4; + consumed += period * cycles; + cyclic = true; + }; + } + let rem = &stack[consumed..]; + backtrace_stderr(rem); + raw_errln!(""); + written += rem.len() + 1; + + let random_depth = || 8 * 16; // chosen by random diceroll (2d20) + if cyclic || stack.len() > random_depth() { + // technically speculation, but assert it with confidence anyway. + // rustc only arrived in this signal handler because bad things happened + // and this message is for explaining it's not the programmer's fault + raw_errln!("note: rustc unexpectedly overflowed its stack! this is a bug"); + written += 1; + } + if stack.len() == MAX_FRAMES { + raw_errln!("note: maximum backtrace depth reached, frames may have been lost"); + written += 1; + } + raw_errln!("note: we would appreciate a report at https://github.com/rust-lang/rust"); + written += 1; + if written > 24 { + // We probably just scrolled the earlier "we got SIGSEGV" message off the terminal + raw_errln!("note: backtrace dumped due to SIGSEGV! resuming signal"); + }; +} + +/// When SIGSEGV is delivered to the process, print a stack trace and then exit. +pub(super) fn install() { + unsafe { + let alt_stack_size: usize = min_sigstack_size() + 64 * 1024; + let mut alt_stack: libc::stack_t = mem::zeroed(); + alt_stack.ss_sp = alloc(Layout::from_size_align(alt_stack_size, 1).unwrap()).cast(); + alt_stack.ss_size = alt_stack_size; + libc::sigaltstack(&alt_stack, ptr::null_mut()); + + let mut sa: libc::sigaction = mem::zeroed(); + sa.sa_sigaction = print_stack_trace as libc::sighandler_t; + sa.sa_flags = libc::SA_NODEFER | libc::SA_RESETHAND | libc::SA_ONSTACK; + libc::sigemptyset(&mut sa.sa_mask); + libc::sigaction(libc::SIGSEGV, &sa, ptr::null_mut()); + } +} + +/// Modern kernels on modern hardware can have dynamic signal stack sizes. +#[cfg(any(target_os = "linux", target_os = "android"))] +fn min_sigstack_size() -> usize { + const AT_MINSIGSTKSZ: core::ffi::c_ulong = 51; + let dynamic_sigstksz = unsafe { libc::getauxval(AT_MINSIGSTKSZ) }; + // If getauxval couldn't find the entry, it returns 0, + // so take the higher of the "constant" and auxval. + // This transparently supports older kernels which don't provide AT_MINSIGSTKSZ + libc::MINSIGSTKSZ.max(dynamic_sigstksz as _) +} + +/// Not all OS support hardware where this is needed. +#[cfg(not(any(target_os = "linux", target_os = "android")))] +fn min_sigstack_size() -> usize { + libc::MINSIGSTKSZ +} |