From e5b76892cc5e6fbfb495bf6a7339962a287849a7 Mon Sep 17 00:00:00 2001 From: quininer Date: Mon, 13 Nov 2023 20:48:23 +0800 Subject: [PATCH] Add emulated TLS support Currently LLVM uses emutls by default for some targets (such as android, openbsd), but rust does not use it, because `has_thread_local` is false. This commit has some changes to allow users to enable emutls: 1. add `-Zhas-thread-local` flag to specify that std uses `#[thread_local]` instead of pthread key. 2. when using emutls, decorate symbol names to find thread local symbol correctly. 3. change `-Zforce-emulated-tls` to `-Ztls-model=emulated` to explicitly specify whether to generate emutls. --- compiler/rustc_codegen_gcc/src/context.rs | 1 + .../src/back/owned_target_machine.rs | 4 +-- compiler/rustc_codegen_llvm/src/back/write.rs | 6 ++-- compiler/rustc_codegen_llvm/src/context.rs | 1 + compiler/rustc_codegen_llvm/src/lib.rs | 4 ++- compiler/rustc_codegen_llvm/src/llvm/ffi.rs | 2 +- compiler/rustc_codegen_ssa/src/back/linker.rs | 4 ++- .../src/back/symbol_export.rs | 34 ++++++++++++++++++- .../rustc_llvm/llvm-wrapper/PassWrapper.cpp | 10 ++---- compiler/rustc_session/src/config.rs | 2 +- compiler/rustc_session/src/options.rs | 2 ++ .../rustc_target/src/spec/base/android.rs | 3 +- .../rustc_target/src/spec/base/linux_ohos.rs | 4 +-- .../rustc_target/src/spec/base/openbsd.rs | 3 +- compiler/rustc_target/src/spec/mod.rs | 9 ++--- library/std/src/sys/unix/thread_local_dtor.rs | 8 ++++- .../src/compiler-flags/tls-model.md | 2 ++ 17 files changed, 71 insertions(+), 28 deletions(-) diff --git a/compiler/rustc_codegen_gcc/src/context.rs b/compiler/rustc_codegen_gcc/src/context.rs index a043660ea632b..893cad0516182 100644 --- a/compiler/rustc_codegen_gcc/src/context.rs +++ b/compiler/rustc_codegen_gcc/src/context.rs @@ -569,5 +569,6 @@ fn to_gcc_tls_mode(tls_model: TlsModel) -> gccjit::TlsModel { TlsModel::LocalDynamic => gccjit::TlsModel::LocalDynamic, TlsModel::InitialExec => gccjit::TlsModel::InitialExec, TlsModel::LocalExec => gccjit::TlsModel::LocalExec, + TlsModel::Emulated => gccjit::TlsModel::GlobalDynamic, } } diff --git a/compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs b/compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs index 36484c3c3fc44..28a88dd2efea0 100644 --- a/compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs +++ b/compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs @@ -39,7 +39,7 @@ impl OwnedTargetMachine { split_dwarf_file: &CStr, output_obj_file: &CStr, debug_info_compression: &CStr, - force_emulated_tls: bool, + use_emulated_tls: bool, args_cstr_buff: &[u8], ) -> Result> { assert!(args_cstr_buff.len() > 0); @@ -71,7 +71,7 @@ impl OwnedTargetMachine { split_dwarf_file.as_ptr(), output_obj_file.as_ptr(), debug_info_compression.as_ptr(), - force_emulated_tls, + use_emulated_tls, args_cstr_buff.as_ptr() as *const c_char, args_cstr_buff.len(), ) diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs index 1a567c0fce816..bdabb9129a74f 100644 --- a/compiler/rustc_codegen_llvm/src/back/write.rs +++ b/compiler/rustc_codegen_llvm/src/back/write.rs @@ -33,7 +33,7 @@ use rustc_session::config::{self, Lto, OutputType, Passes, SplitDwarfKind, Switc use rustc_session::Session; use rustc_span::symbol::sym; use rustc_span::InnerSpan; -use rustc_target::spec::{CodeModel, RelocModel, SanitizerSet, SplitDebuginfo}; +use rustc_target::spec::{CodeModel, RelocModel, SanitizerSet, SplitDebuginfo, TlsModel}; use crate::llvm::diagnostic::OptimizationDiagnosticKind; use libc::{c_char, c_int, c_uint, c_void, size_t}; @@ -223,7 +223,7 @@ pub fn target_machine_factory( let path_mapping = sess.source_map().path_mapping().clone(); - let force_emulated_tls = sess.target.force_emulated_tls; + let use_emulated_tls = matches!(sess.tls_model(), TlsModel::Emulated); // copy the exe path, followed by path all into one buffer // null terminating them so we can use them as null terminated strings @@ -297,7 +297,7 @@ pub fn target_machine_factory( &split_dwarf_file, &output_obj_file, &debuginfo_compression, - force_emulated_tls, + use_emulated_tls, &args_cstr_buff, ) }) diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs index 92a8c00510b94..ed0d5e68cbf9a 100644 --- a/compiler/rustc_codegen_llvm/src/context.rs +++ b/compiler/rustc_codegen_llvm/src/context.rs @@ -120,6 +120,7 @@ fn to_llvm_tls_model(tls_model: TlsModel) -> llvm::ThreadLocalMode { TlsModel::LocalDynamic => llvm::ThreadLocalMode::LocalDynamic, TlsModel::InitialExec => llvm::ThreadLocalMode::InitialExec, TlsModel::LocalExec => llvm::ThreadLocalMode::LocalExec, + TlsModel::Emulated => llvm::ThreadLocalMode::GeneralDynamic, } } diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs index 915cf31de08fb..33b19ab362af2 100644 --- a/compiler/rustc_codegen_llvm/src/lib.rs +++ b/compiler/rustc_codegen_llvm/src/lib.rs @@ -306,7 +306,9 @@ impl CodegenBackend for LlvmCodegenBackend { } PrintKind::TlsModels => { writeln!(out, "Available TLS models:"); - for name in &["global-dynamic", "local-dynamic", "initial-exec", "local-exec"] { + for name in + &["global-dynamic", "local-dynamic", "initial-exec", "local-exec", "emulated"] + { writeln!(out, " {name}"); } writeln!(out); diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs index 6c3ccc9cf0dee..432cfe203c80a 100644 --- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs +++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs @@ -2159,7 +2159,7 @@ extern "C" { SplitDwarfFile: *const c_char, OutputObjFile: *const c_char, DebugInfoCompression: *const c_char, - ForceEmulatedTls: bool, + UseEmulatedTls: bool, ArgsCstrBuff: *const c_char, ArgsCstrBuffLen: usize, ) -> *mut TargetMachine; diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs index bb5f6e27e4d45..eeb57d4d0f4d8 100644 --- a/compiler/rustc_codegen_ssa/src/back/linker.rs +++ b/compiler/rustc_codegen_ssa/src/back/linker.rs @@ -1748,7 +1748,9 @@ fn exported_symbols_for_non_proc_macro(tcx: TyCtxt<'_>, crate_type: CrateType) - let export_threshold = symbol_export::crates_export_threshold(&[crate_type]); for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| { if info.level.is_below_threshold(export_threshold) { - symbols.push(symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, cnum)); + symbols.push(symbol_export::exporting_symbol_name_for_instance_in_crate( + tcx, symbol, cnum, + )); } }); diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs index 5f2fad0536b70..c092ce0fddf91 100644 --- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs +++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs @@ -16,7 +16,7 @@ use rustc_middle::ty::{self, SymbolName, TyCtxt}; use rustc_middle::ty::{GenericArgKind, GenericArgsRef}; use rustc_middle::util::Providers; use rustc_session::config::{CrateType, OomStrategy}; -use rustc_target::spec::SanitizerSet; +use rustc_target::spec::{SanitizerSet, TlsModel}; pub fn threshold(tcx: TyCtxt<'_>) -> SymbolExportLevel { crates_export_threshold(tcx.crate_types()) @@ -552,6 +552,12 @@ pub fn linking_symbol_name_for_instance_in_crate<'tcx>( let mut undecorated = symbol_name_for_instance_in_crate(tcx, symbol, instantiating_crate); + // thread local will not be a function call, + // so it is safe to return before windows symbol decoration check. + if let Some(name) = maybe_emutls_symbol_name(tcx, symbol, &undecorated) { + return name; + } + let target = &tcx.sess.target; if !target.is_like_windows { // Mach-O has a global "_" suffix and `object` crate will handle it. @@ -612,6 +618,32 @@ pub fn linking_symbol_name_for_instance_in_crate<'tcx>( format!("{prefix}{undecorated}{suffix}{args_in_bytes}") } +pub fn exporting_symbol_name_for_instance_in_crate<'tcx>( + tcx: TyCtxt<'tcx>, + symbol: ExportedSymbol<'tcx>, + cnum: CrateNum, +) -> String { + let undecorated = symbol_name_for_instance_in_crate(tcx, symbol, cnum); + maybe_emutls_symbol_name(tcx, symbol, &undecorated).unwrap_or(undecorated) +} + +fn maybe_emutls_symbol_name<'tcx>( + tcx: TyCtxt<'tcx>, + symbol: ExportedSymbol<'tcx>, + undecorated: &str, +) -> Option { + if matches!(tcx.sess.tls_model(), TlsModel::Emulated) + && let ExportedSymbol::NonGeneric(def_id) = symbol + && tcx.is_thread_local_static(def_id) + { + // When using emutls, LLVM will add the `__emutls_v.` prefix to thread local symbols, + // and exported symbol name need to match this. + Some(format!("__emutls_v.{undecorated}")) + } else { + None + } +} + fn wasm_import_module_map(tcx: TyCtxt<'_>, cnum: CrateNum) -> FxHashMap { // Build up a map from DefId to a `NativeLib` structure, where // `NativeLib` internally contains information about diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp index 0edcac93b6224..55e1c84c8a208 100644 --- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp +++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp @@ -410,7 +410,7 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine( const char *SplitDwarfFile, const char *OutputObjFile, const char *DebugInfoCompression, - bool ForceEmulatedTls, + bool UseEmulatedTls, const char *ArgsCstrBuff, size_t ArgsCstrBuffLen) { auto OptLevel = fromRust(RustOptLevel); @@ -456,13 +456,9 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine( Options.UseInitArray = UseInitArray; #if LLVM_VERSION_LT(17, 0) - if (ForceEmulatedTls) { - Options.ExplicitEmulatedTLS = true; - Options.EmulatedTLS = true; - } -#else - Options.EmulatedTLS = ForceEmulatedTls || Trip.hasDefaultEmulatedTLS(); + Options.ExplicitEmulatedTLS = true; #endif + Options.EmulatedTLS = UseEmulatedTls; if (TrapUnreachable) { // Tell LLVM to codegen `unreachable` into an explicit trap instruction. diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs index e694e150b314b..edf12023af1ed 100644 --- a/compiler/rustc_session/src/config.rs +++ b/compiler/rustc_session/src/config.rs @@ -1283,7 +1283,7 @@ fn default_configuration(sess: &Session) -> Cfg { ret.insert((sym::relocation_model, Some(relocation_model))); } ret.insert((sym::target_vendor, Some(Symbol::intern(vendor)))); - if sess.target.has_thread_local { + if sess.opts.unstable_opts.has_thread_local.unwrap_or(sess.target.has_thread_local) { ret.insert((sym::target_thread_local, None)); } let mut has_atomic = false; diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs index 7a6108bfbe24c..b1cf43f471a65 100644 --- a/compiler/rustc_session/src/options.rs +++ b/compiler/rustc_session/src/options.rs @@ -1624,6 +1624,8 @@ options! { graphviz_font: String = ("Courier, monospace".to_string(), parse_string, [UNTRACKED], "use the given `fontname` in graphviz output; can be overridden by setting \ environment variable `RUSTC_GRAPHVIZ_FONT` (default: `Courier, monospace`)"), + has_thread_local: Option = (None, parse_opt_bool, [TRACKED], + "explicitly enable the `cfg(target_thread_local)` directive"), hir_stats: bool = (false, parse_bool, [UNTRACKED], "print some statistics about AST and HIR (default: no)"), human_readable_cgu_names: bool = (false, parse_bool, [TRACKED], diff --git a/compiler/rustc_target/src/spec/base/android.rs b/compiler/rustc_target/src/spec/base/android.rs index af15c16a5a9a8..5320f1b4bbbea 100644 --- a/compiler/rustc_target/src/spec/base/android.rs +++ b/compiler/rustc_target/src/spec/base/android.rs @@ -1,10 +1,11 @@ -use crate::spec::{base, SanitizerSet, TargetOptions}; +use crate::spec::{base, SanitizerSet, TargetOptions, TlsModel}; pub fn opts() -> TargetOptions { let mut base = base::linux::opts(); base.os = "android".into(); base.is_like_android = true; base.default_dwarf_version = 2; + base.tls_model = TlsModel::Emulated; base.has_thread_local = false; base.supported_sanitizers = SanitizerSet::ADDRESS; // This is for backward compatibility, see https://github.com/rust-lang/rust/issues/49867 diff --git a/compiler/rustc_target/src/spec/base/linux_ohos.rs b/compiler/rustc_target/src/spec/base/linux_ohos.rs index 273e6a98dd4d2..8272cda05e791 100644 --- a/compiler/rustc_target/src/spec/base/linux_ohos.rs +++ b/compiler/rustc_target/src/spec/base/linux_ohos.rs @@ -1,11 +1,11 @@ -use crate::spec::{base, TargetOptions}; +use crate::spec::{base, TargetOptions, TlsModel}; pub fn opts() -> TargetOptions { let mut base = base::linux::opts(); base.env = "ohos".into(); base.crt_static_default = false; - base.force_emulated_tls = true; + base.tls_model = TlsModel::Emulated; base.has_thread_local = false; base diff --git a/compiler/rustc_target/src/spec/base/openbsd.rs b/compiler/rustc_target/src/spec/base/openbsd.rs index e7db14e05a4ec..bc3aecb5c1e83 100644 --- a/compiler/rustc_target/src/spec/base/openbsd.rs +++ b/compiler/rustc_target/src/spec/base/openbsd.rs @@ -1,4 +1,4 @@ -use crate::spec::{cvs, FramePointer, RelroLevel, TargetOptions}; +use crate::spec::{cvs, FramePointer, RelroLevel, TargetOptions, TlsModel}; pub fn opts() -> TargetOptions { TargetOptions { @@ -11,6 +11,7 @@ pub fn opts() -> TargetOptions { frame_pointer: FramePointer::Always, // FIXME 43575: should be MayOmit... relro_level: RelroLevel::Full, default_dwarf_version: 2, + tls_model: TlsModel::Emulated, ..Default::default() } } diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs index dbce2f30f9397..def74d37df7f1 100644 --- a/compiler/rustc_target/src/spec/mod.rs +++ b/compiler/rustc_target/src/spec/mod.rs @@ -929,6 +929,7 @@ pub enum TlsModel { LocalDynamic, InitialExec, LocalExec, + Emulated, } impl FromStr for TlsModel { @@ -942,6 +943,7 @@ impl FromStr for TlsModel { "local-dynamic" => TlsModel::LocalDynamic, "initial-exec" => TlsModel::InitialExec, "local-exec" => TlsModel::LocalExec, + "emulated" => TlsModel::Emulated, _ => return Err(()), }) } @@ -954,6 +956,7 @@ impl ToJson for TlsModel { TlsModel::LocalDynamic => "local-dynamic", TlsModel::InitialExec => "initial-exec", TlsModel::LocalExec => "local-exec", + TlsModel::Emulated => "emulated", } .to_json() } @@ -2190,9 +2193,6 @@ pub struct TargetOptions { /// Whether the target supports XRay instrumentation. pub supports_xray: bool, - - /// Forces the use of emulated TLS (__emutls_get_address) - pub force_emulated_tls: bool, } /// Add arguments for the given flavor and also for its "twin" flavors @@ -2408,7 +2408,6 @@ impl Default for TargetOptions { entry_name: "main".into(), entry_abi: Conv::C, supports_xray: false, - force_emulated_tls: false, } } } @@ -3112,7 +3111,6 @@ impl Target { key!(entry_name); key!(entry_abi, Conv)?; key!(supports_xray, bool); - key!(force_emulated_tls, bool); if base.is_builtin { // This can cause unfortunate ICEs later down the line. @@ -3368,7 +3366,6 @@ impl ToJson for Target { target_option_val!(entry_name); target_option_val!(entry_abi); target_option_val!(supports_xray); - target_option_val!(force_emulated_tls); if let Some(abi) = self.default_adjusted_cabi { d.insert("default-adjusted-cabi".into(), Abi::name(abi).to_json()); diff --git a/library/std/src/sys/unix/thread_local_dtor.rs b/library/std/src/sys/unix/thread_local_dtor.rs index 667fd51696249..ac85531c372ea 100644 --- a/library/std/src/sys/unix/thread_local_dtor.rs +++ b/library/std/src/sys/unix/thread_local_dtor.rs @@ -12,7 +12,13 @@ // compiling from a newer linux to an older linux, so we also have a // fallback implementation to use as well. #[allow(unexpected_cfgs)] -#[cfg(any(target_os = "linux", target_os = "fuchsia", target_os = "redox", target_os = "hurd"))] +#[cfg(any( + target_os = "linux", + target_os = "android", + target_os = "fuchsia", + target_os = "redox", + target_os = "hurd" +))] // FIXME: The Rust compiler currently omits weakly function definitions (i.e., // __cxa_thread_atexit_impl) and its metadata from LLVM IR. #[no_sanitize(cfi, kcfi)] diff --git a/src/doc/unstable-book/src/compiler-flags/tls-model.md b/src/doc/unstable-book/src/compiler-flags/tls-model.md index 8b19e785c6a5b..b7024ba88dec0 100644 --- a/src/doc/unstable-book/src/compiler-flags/tls-model.md +++ b/src/doc/unstable-book/src/compiler-flags/tls-model.md @@ -20,6 +20,8 @@ loaded at program startup. The TLS data must not be in a library loaded after startup (via `dlopen`). - `local-exec` - model usable only if the TLS data is defined directly in the executable, but not in a shared library, and is accessed only from that executable. +- `emulated` - Uses thread-specific data keys to implement emulated TLS. +It is like using a general-dynamic TLS model for all modes. `rustc` and LLVM may use a more optimized model than specified if they know that we are producing an executable rather than a library, or that the `static` item is private enough.