From 0444056aa3ddd97e02478b7c41d130db74583d16 Mon Sep 17 00:00:00 2001 From: beetrees Date: Thu, 25 Jul 2024 22:15:47 +0100 Subject: [PATCH] Remove macOS 10.10 dynamic linker bug workaround --- compiler/rustc_codegen_llvm/src/consts.rs | 52 ------------------- library/std/src/fs.rs | 13 +++-- .../issues/issue-44056-macos-tls-align.rs | 27 ---------- 3 files changed, 6 insertions(+), 86 deletions(-) delete mode 100644 tests/codegen/issues/issue-44056-macos-tls-align.rs diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs index 80aa2018c81b5..0e50e32913c7b 100644 --- a/compiler/rustc_codegen_llvm/src/consts.rs +++ b/compiler/rustc_codegen_llvm/src/consts.rs @@ -440,58 +440,6 @@ impl<'ll> CodegenCx<'ll, '_> { if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) { llvm::set_thread_local_mode(g, self.tls_model); - - // Do not allow LLVM to change the alignment of a TLS on macOS. - // - // By default a global's alignment can be freely increased. - // This allows LLVM to generate more performant instructions - // e.g., using load-aligned into a SIMD register. - // - // However, on macOS 10.10 or below, the dynamic linker does not - // respect any alignment given on the TLS (radar 24221680). - // This will violate the alignment assumption, and causing segfault at runtime. - // - // This bug is very easy to trigger. In `println!` and `panic!`, - // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS, - // which the values would be `mem::replace`d on initialization. - // The implementation of `mem::replace` will use SIMD - // whenever the size is 32 bytes or higher. LLVM notices SIMD is used - // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary, - // which macOS's dyld disregarded and causing crashes - // (see issues #51794, #51758, #50867, #48866 and #44056). - // - // To workaround the bug, we trick LLVM into not increasing - // the global's alignment by explicitly assigning a section to it - // (equivalent to automatically generating a `#[link_section]` attribute). - // See the comment in the `GlobalValue::canIncreaseAlignment()` function - // of `lib/IR/Globals.cpp` for why this works. - // - // When the alignment is not increased, the optimized `mem::replace` - // will use load-unaligned instructions instead, and thus avoiding the crash. - // - // We could remove this hack whenever we decide to drop macOS 10.10 support. - if self.tcx.sess.target.is_like_osx { - // The `inspect` method is okay here because we checked for provenance, and - // because we are doing this access to inspect the final interpreter state - // (not as part of the interpreter execution). - // - // FIXME: This check requires that the (arbitrary) value of undefined bytes - // happens to be zero. Instead, we should only check the value of defined bytes - // and set all undefined bytes to zero if this allocation is headed for the - // BSS. - let all_bytes_are_zero = alloc.provenance().ptrs().is_empty() - && alloc - .inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()) - .iter() - .all(|&byte| byte == 0); - - let sect_name = if all_bytes_are_zero { - c"__DATA,__thread_bss" - } else { - c"__DATA,__thread_data" - }; - llvm::LLVMSetSection(g, sect_name.as_ptr()); - } } // Wasm statics with custom link sections get special treatment as they diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs index 536d0d1b356a9..25540410cc7eb 100644 --- a/library/std/src/fs.rs +++ b/library/std/src/fs.rs @@ -2471,16 +2471,15 @@ pub fn remove_dir>(path: P) -> io::Result<()> { /// # Platform-specific behavior /// /// This function currently corresponds to `openat`, `fdopendir`, `unlinkat` and `lstat` functions -/// on Unix (except for macOS before version 10.10 and REDOX) and the `CreateFileW`, -/// `GetFileInformationByHandleEx`, `SetFileInformationByHandle`, and `NtCreateFile` functions on -/// Windows. Note that, this [may change in the future][changes]. +/// on Unix (except for REDOX) and the `CreateFileW`, `GetFileInformationByHandleEx`, +/// `SetFileInformationByHandle`, and `NtCreateFile` functions on Windows. Note that, this +/// [may change in the future][changes]. /// /// [changes]: io#platform-specific-behavior /// -/// On macOS before version 10.10 and REDOX, as well as when running in Miri for any target, this -/// function is not protected against time-of-check to time-of-use (TOCTOU) race conditions, and -/// should not be used in security-sensitive code on those platforms. All other platforms are -/// protected. +/// On REDOX, as well as when running in Miri for any target, this function is not protected against +/// time-of-check to time-of-use (TOCTOU) race conditions, and should not be used in +/// security-sensitive code on those platforms. All other platforms are protected. /// /// # Errors /// diff --git a/tests/codegen/issues/issue-44056-macos-tls-align.rs b/tests/codegen/issues/issue-44056-macos-tls-align.rs deleted file mode 100644 index 972b8490d18f9..0000000000000 --- a/tests/codegen/issues/issue-44056-macos-tls-align.rs +++ /dev/null @@ -1,27 +0,0 @@ -// -//@ only-apple -//@ compile-flags: -O - -#![crate_type = "rlib"] -#![feature(thread_local)] - -// local_unnamed_addr does not appear when std is built with debug assertions. -// CHECK: @STATIC_VAR_1 = thread_local {{(local_unnamed_addr )?}}global <{ [32 x i8] }> zeroinitializer, section "__DATA,__thread_bss", align 4 -#[no_mangle] -#[thread_local] -static mut STATIC_VAR_1: [u32; 8] = [0; 8]; - -// CHECK: @STATIC_VAR_2 = thread_local {{(local_unnamed_addr )?}}global <{ [32 x i8] }> <{{[^>]*}}>, section "__DATA,__thread_data", align 4 -#[no_mangle] -#[thread_local] -static mut STATIC_VAR_2: [u32; 8] = [4; 8]; - -#[no_mangle] -pub unsafe fn f(x: &mut [u32; 8]) { - std::mem::swap(x, &mut STATIC_VAR_1) -} - -#[no_mangle] -pub unsafe fn g(x: &mut [u32; 8]) { - std::mem::swap(x, &mut STATIC_VAR_2) -}