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Auto merge of rust-lang#76448 - haraldh:default_alloc_error_handler_r…
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…educed, r=Amanieu

Implement Make `handle_alloc_error` default to panic (for no_std + liballoc)

Related: rust-lang#66741

Guarded with `#![feature(default_alloc_error_handler)]` a default
`alloc_error_handler` is called, if a custom allocator is used and no
other custom `#[alloc_error_handler]` is defined.
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bors committed Oct 4, 2020
2 parents 32cbc65 + cadd12b commit 0d37dca
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Showing 12 changed files with 292 additions and 7 deletions.
45 changes: 44 additions & 1 deletion compiler/rustc_codegen_llvm/src/allocator.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,11 +3,17 @@ use libc::c_uint;
use rustc_ast::expand::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS};
use rustc_middle::bug;
use rustc_middle::ty::TyCtxt;
use rustc_span::symbol::sym;

use crate::llvm::{self, False, True};
use crate::ModuleLlvm;

pub(crate) unsafe fn codegen(tcx: TyCtxt<'_>, mods: &mut ModuleLlvm, kind: AllocatorKind) {
pub(crate) unsafe fn codegen(
tcx: TyCtxt<'_>,
mods: &mut ModuleLlvm,
kind: AllocatorKind,
has_alloc_error_handler: bool,
) {
let llcx = &*mods.llcx;
let llmod = mods.llmod();
let usize = match &tcx.sess.target.target.target_pointer_width[..] {
Expand Down Expand Up @@ -82,4 +88,41 @@ pub(crate) unsafe fn codegen(tcx: TyCtxt<'_>, mods: &mut ModuleLlvm, kind: Alloc
}
llvm::LLVMDisposeBuilder(llbuilder);
}

// rust alloc error handler
let args = [usize, usize]; // size, align

let ty = llvm::LLVMFunctionType(void, args.as_ptr(), args.len() as c_uint, False);
let name = format!("__rust_alloc_error_handler");
let llfn = llvm::LLVMRustGetOrInsertFunction(llmod, name.as_ptr().cast(), name.len(), ty);
// -> ! DIFlagNoReturn
llvm::Attribute::NoReturn.apply_llfn(llvm::AttributePlace::Function, llfn);

if tcx.sess.target.target.options.default_hidden_visibility {
llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
}
if tcx.sess.must_emit_unwind_tables() {
attributes::emit_uwtable(llfn, true);
}

let kind = if has_alloc_error_handler { AllocatorKind::Global } else { AllocatorKind::Default };
let callee = kind.fn_name(sym::oom);
let callee = llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
// -> ! DIFlagNoReturn
llvm::Attribute::NoReturn.apply_llfn(llvm::AttributePlace::Function, callee);
llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);

let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());

let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
let args = args
.iter()
.enumerate()
.map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
.collect::<Vec<_>>();
let ret = llvm::LLVMRustBuildCall(llbuilder, callee, args.as_ptr(), args.len() as c_uint, None);
llvm::LLVMSetTailCall(ret, True);
llvm::LLVMBuildRetVoid(llbuilder);
llvm::LLVMDisposeBuilder(llbuilder);
}
3 changes: 2 additions & 1 deletion compiler/rustc_codegen_llvm/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -95,8 +95,9 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
tcx: TyCtxt<'tcx>,
mods: &mut ModuleLlvm,
kind: AllocatorKind,
has_alloc_error_handler: bool,
) {
unsafe { allocator::codegen(tcx, mods, kind) }
unsafe { allocator::codegen(tcx, mods, kind, has_alloc_error_handler) }
}
fn compile_codegen_unit(
&self,
Expand Down
5 changes: 3 additions & 2 deletions compiler/rustc_codegen_ssa/src/base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -538,8 +538,9 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
let llmod_id =
cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("allocator")).to_string();
let mut modules = backend.new_metadata(tcx, &llmod_id);
tcx.sess
.time("write_allocator_module", || backend.codegen_allocator(tcx, &mut modules, kind));
tcx.sess.time("write_allocator_module", || {
backend.codegen_allocator(tcx, &mut modules, kind, tcx.lang_items().oom().is_some())
});

Some(ModuleCodegen { name: llmod_id, module_llvm: modules, kind: ModuleKind::Allocator })
} else {
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_codegen_ssa/src/traits/backend.rs
Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,7 @@ pub trait ExtraBackendMethods: CodegenBackend + WriteBackendMethods + Sized + Se
tcx: TyCtxt<'tcx>,
mods: &mut Self::Module,
kind: AllocatorKind,
has_alloc_error_handler: bool,
);
/// This generates the codegen unit and returns it along with
/// a `u64` giving an estimate of the unit's processing cost.
Expand Down
3 changes: 3 additions & 0 deletions compiler/rustc_feature/src/active.rs
Original file line number Diff line number Diff line change
Expand Up @@ -593,6 +593,9 @@ declare_features! (
/// Allows to use the `#[cmse_nonsecure_entry]` attribute.
(active, cmse_nonsecure_entry, "1.48.0", Some(75835), None),

/// Allows rustc to inject a default alloc_error_handler
(active, default_alloc_error_handler, "1.48.0", Some(66741), None),

// -------------------------------------------------------------------------
// feature-group-end: actual feature gates
// -------------------------------------------------------------------------
Expand Down
5 changes: 4 additions & 1 deletion compiler/rustc_passes/src/weak_lang_items.rs
Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,10 @@ fn verify<'tcx>(tcx: TyCtxt<'tcx>, items: &lang_items::LanguageItems) {
if item == LangItem::PanicImpl {
tcx.sess.err("`#[panic_handler]` function required, but not found");
} else if item == LangItem::Oom {
tcx.sess.err("`#[alloc_error_handler]` function required, but not found");
if !tcx.features().default_alloc_error_handler {
tcx.sess.err("`#[alloc_error_handler]` function required, but not found.");
tcx.sess.note_without_error("Use `#![feature(default_alloc_error_handler)]` for a default error handler.");
}
} else {
tcx.sess.err(&format!("language item required, but not found: `{}`", name));
}
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -415,6 +415,7 @@ symbols! {
decl_macro,
declare_lint_pass,
decode,
default_alloc_error_handler,
default_lib_allocator,
default_type_parameter_fallback,
default_type_params,
Expand Down
47 changes: 47 additions & 0 deletions library/alloc/src/alloc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,8 @@ extern "Rust" {
fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
#[rustc_allocator_nounwind]
fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
#[rustc_allocator_nounwind]
fn __rust_alloc_error_handler(size: usize, align: usize) -> !;
}

/// The global memory allocator.
Expand Down Expand Up @@ -334,6 +336,24 @@ pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html
/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html
#[stable(feature = "global_alloc", since = "1.28.0")]
#[cfg(not(any(test, bootstrap)))]
#[rustc_allocator_nounwind]
pub fn handle_alloc_error(layout: Layout) -> ! {
unsafe {
__rust_alloc_error_handler(layout.size(), layout.align());
}
}

// For alloc test `std::alloc::handle_alloc_error` can be used directly.
#[cfg(test)]
pub use std::alloc::handle_alloc_error;

// In stage0 (bootstrap) `__rust_alloc_error_handler`,
// might not be generated yet, because an old compiler is used,
// so use the old direct call.
#[cfg(all(bootstrap, not(test)))]
#[stable(feature = "global_alloc", since = "1.28.0")]
#[doc(hidden)]
#[rustc_allocator_nounwind]
pub fn handle_alloc_error(layout: Layout) -> ! {
extern "Rust" {
Expand All @@ -342,3 +362,30 @@ pub fn handle_alloc_error(layout: Layout) -> ! {
}
unsafe { oom_impl(layout) }
}

#[cfg(not(any(test, bootstrap)))]
#[doc(hidden)]
#[allow(unused_attributes)]
#[unstable(feature = "alloc_internals", issue = "none")]
pub mod __default_lib_allocator {
use crate::alloc::Layout;

// called via generated `__rust_alloc_error_handler`

// if there is no `#[alloc_error_handler]`
#[rustc_std_internal_symbol]
pub unsafe extern "C" fn __rdl_oom(size: usize, _align: usize) -> ! {
panic!("memory allocation of {} bytes failed", size)
}

// if there is a `#[alloc_error_handler]`
#[rustc_std_internal_symbol]
pub unsafe extern "C" fn __rg_oom(size: usize, align: usize) -> ! {
let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
extern "Rust" {
#[lang = "oom"]
fn oom_impl(layout: Layout) -> !;
}
unsafe { oom_impl(layout) }
}
}
4 changes: 3 additions & 1 deletion src/test/ui/allocator/auxiliary/helper.rs
Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
// no-prefer-dynamic

#![crate_type = "rlib"]
#![no_std]

use std::fmt;
extern crate alloc;
use alloc::fmt;

pub fn work_with(p: &fmt::Debug) {
drop(p);
Expand Down
97 changes: 97 additions & 0 deletions src/test/ui/allocator/no_std-alloc-error-handler-custom.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,97 @@
// run-pass
// ignore-android no libc
// ignore-cloudabi no libc
// ignore-emscripten no libc
// ignore-sgx no libc
// ignore-wasm32 no libc
// only-linux
// compile-flags:-C panic=abort
// aux-build:helper.rs

#![feature(start, rustc_private, new_uninit, panic_info_message)]
#![feature(alloc_error_handler)]
#![no_std]

extern crate alloc;
extern crate libc;

// ARM targets need these symbols
#[no_mangle]
pub fn __aeabi_unwind_cpp_pr0() {}

#[no_mangle]
pub fn __aeabi_unwind_cpp_pr1() {}

use core::ptr::null_mut;
use core::alloc::{GlobalAlloc, Layout};
use alloc::boxed::Box;

extern crate helper;

struct MyAllocator;

#[alloc_error_handler]
fn my_oom(layout: Layout) -> !
{
use alloc::fmt::write;
unsafe {
let size = layout.size();
let mut s = alloc::string::String::new();
write(&mut s, format_args!("My OOM: failed to allocate {} bytes!\n", size)).unwrap();
let s = s.as_str();
libc::write(libc::STDERR_FILENO, s as *const _ as _, s.len());
libc::exit(0)
}
}

unsafe impl GlobalAlloc for MyAllocator {
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
if layout.size() < 4096 {
libc::malloc(layout.size()) as _
} else {
null_mut()
}
}
unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {}
}

#[global_allocator]
static A: MyAllocator = MyAllocator;

#[panic_handler]
fn panic(panic_info: &core::panic::PanicInfo) -> ! {
unsafe {
if let Some(s) = panic_info.payload().downcast_ref::<&str>() {
const PSTR: &str = "panic occurred: ";
const CR: &str = "\n";
libc::write(libc::STDERR_FILENO, PSTR as *const _ as _, PSTR.len());
libc::write(libc::STDERR_FILENO, s as *const _ as _, s.len());
libc::write(libc::STDERR_FILENO, CR as *const _ as _, CR.len());
}
if let Some(args) = panic_info.message() {
let mut s = alloc::string::String::new();
alloc::fmt::write(&mut s, *args).unwrap();
let s = s.as_str();
const PSTR: &str = "panic occurred: ";
const CR: &str = "\n";
libc::write(libc::STDERR_FILENO, PSTR as *const _ as _, PSTR.len());
libc::write(libc::STDERR_FILENO, s as *const _ as _, s.len());
libc::write(libc::STDERR_FILENO, CR as *const _ as _, CR.len());
} else {
const PSTR: &str = "panic occurred\n";
libc::write(libc::STDERR_FILENO, PSTR as *const _ as _, PSTR.len());
}
libc::exit(1)
}
}

#[derive(Debug)]
struct Page([[u64; 32]; 16]);

#[start]
pub fn main(_argc: isize, _argv: *const *const u8) -> isize {
let zero = Box::<Page>::new_zeroed();
let zero = unsafe { zero.assume_init() };
helper::work_with(&zero);
1
}
84 changes: 84 additions & 0 deletions src/test/ui/allocator/no_std-alloc-error-handler-default.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,84 @@
// run-pass
// ignore-android no libc
// ignore-cloudabi no libc
// ignore-emscripten no libc
// ignore-sgx no libc
// ignore-wasm32 no libc
// only-linux
// compile-flags:-C panic=abort
// aux-build:helper.rs
// gate-test-default_alloc_error_handler

#![feature(start, rustc_private, new_uninit, panic_info_message)]
#![feature(default_alloc_error_handler)]
#![no_std]

extern crate alloc;
extern crate libc;

// ARM targets need these symbols
#[no_mangle]
pub fn __aeabi_unwind_cpp_pr0() {}

#[no_mangle]
pub fn __aeabi_unwind_cpp_pr1() {}

use alloc::boxed::Box;
use core::alloc::{GlobalAlloc, Layout};
use core::ptr::null_mut;

extern crate helper;

struct MyAllocator;

unsafe impl GlobalAlloc for MyAllocator {
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
if layout.size() < 4096 {
libc::malloc(layout.size()) as _
} else {
null_mut()
}
}
unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {}
}

#[global_allocator]
static A: MyAllocator = MyAllocator;

#[panic_handler]
fn panic(panic_info: &core::panic::PanicInfo) -> ! {
unsafe {
if let Some(s) = panic_info.payload().downcast_ref::<&str>() {
const PSTR: &str = "panic occurred: ";
const CR: &str = "\n";
libc::write(libc::STDERR_FILENO, PSTR as *const _ as _, PSTR.len());
libc::write(libc::STDERR_FILENO, s as *const _ as _, s.len());
libc::write(libc::STDERR_FILENO, CR as *const _ as _, CR.len());
}
if let Some(args) = panic_info.message() {
let mut s = alloc::string::String::new();
alloc::fmt::write(&mut s, *args).unwrap();
let s = s.as_str();
const PSTR: &str = "panic occurred: ";
const CR: &str = "\n";
libc::write(libc::STDERR_FILENO, PSTR as *const _ as _, PSTR.len());
libc::write(libc::STDERR_FILENO, s as *const _ as _, s.len());
libc::write(libc::STDERR_FILENO, CR as *const _ as _, CR.len());
} else {
const PSTR: &str = "panic occurred\n";
libc::write(libc::STDERR_FILENO, PSTR as *const _ as _, PSTR.len());
}
libc::exit(0)
}
}

#[derive(Debug)]
struct Page([[u64; 32]; 16]);

#[start]
pub fn main(_argc: isize, _argv: *const *const u8) -> isize {
let zero = Box::<Page>::new_zeroed();
let zero = unsafe { zero.assume_init() };
helper::work_with(&zero);
1
}
4 changes: 3 additions & 1 deletion src/test/ui/missing/missing-alloc_error_handler.stderr
Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
error: `#[alloc_error_handler]` function required, but not found
error: `#[alloc_error_handler]` function required, but not found.

note: Use `#![feature(default_alloc_error_handler)]` for a default error handler.

error: aborting due to previous error

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