Rust compiler crashes during compilation

[ethindp]

So, I have no idea exactly what I did. I'm writing an operating system and am working on implementing SATA disk IO in my kernel. My code is at https://github.com/ethindp/kernel.
In order to actively read from the disk and get all updates, I use read_volatile() all over the place in my disk IO functions. I have no idea what I did, but now my kernel doesn't build. When I run cargo xbuild, the following happens:

1. Cargo builds all dependencies and begins building the kernel.
2. Rustc sits there for over an hour, not producing any output, then crashes with (on windows) error code 0xc000000005 (access violation).

I am running the latest nightly version of rust, rustc 1.41.0-nightly (3e525e3 2019-11-18). The troublesome code is at https://github.com/ethindp/kernel/blob/master/src/drivers/storage/ahci.rs. (Note: the code is very messy right now.)

[hellow554]

@ethindp any specific commit one should use for the error to reproduce? What OS are you on?

Could you please elaborate the steps to reproduce this error a little bit further? e.g.

1. clone this repository (link please)
2. checkout commit 87cba879f78e
3. run cargo xbuild

something like that.

[hellow554]

So I did some RUSTC_LOG=debug and it seems, that the rust compiler runs into some kind of error. These are the last lines the debug output will give me:

Debug output

[INFO  rustc_codegen_ssa::base] codegen_instance(core::str::<impl str>::bytes)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::str::<impl str>::as_bytes)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::str::from_utf8_unchecked_mut)
[INFO  rustc_codegen_ssa::base] codegen_instance(<core::str::Bytes as core::iter::Iterator>::next)
[INFO  rustc_codegen_ssa::base] codegen_instance(init::{{closure}}#0)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::ptr::<impl *mut drivers::fs::vfs::Mountpoint>::is_null)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::ptr::<impl *const drivers::fs::vfs::Mountpoint>::is_null)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::ptr::null::<u8>)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::ptr::null_mut::<u8>)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::slice::<impl core::ops::IndexMut<core::ops::RangeFull> for [drivers::fs::vfs::Mountpoint]>::index_mut)
[INFO  rustc_codegen_ssa::base] codegen_instance(<i32 as core::ops::Add>::add)
[INFO  rustc_codegen_ssa::base] codegen_instance(<u64 as core::ops::Add>::add)
[INFO  rustc_codegen_ssa::base] codegen_instance(<usize as core::ops::Add>::add)
[INFO  rustc_codegen_ssa::base] codegen_instance(<usize as core::ops::AddAssign>::add_assign)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::iter::Iterator::find::check::<&ReErased bootloader::bootinfo::memory_map::MemoryRegion, &ReErased mut [closure@src/memory.rs:122:28: 122:83 closure_kind_ty=i16 closure_sig_ty=for<'r> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BrNamed(crate0:DefIndex(0), 'r)) &ReErased bootloader::bootinfo::memory_map::MemoryRegion,)) -> bool]>)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::iter::Iterator::find::check::<&ReErased bootloader::bootinfo::memory_map::MemoryRegion, &ReErased mut [closure@src/memory.rs:122:28: 122:83 closure_kind_ty=i16 closure_sig_ty=for<'r> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BrNamed(crate0:DefIndex(0), 'r)) &ReErased bootloader::bootinfo::memory_map::MemoryRegion,)) -> bool]>::{{closure}}#0)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::fmt::Arguments::new_v1_formatted)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::fmt::Arguments::new_v1)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::mem::size_of::<usize>)
[INFO  rustc_codegen_ssa::base] codegen_instance(pci::alloc::raw_vec::alloc_guard)
[INFO  rustc_codegen_ssa::base] codegen_instance(vga::volatile::Volatile::<vga::DrawableChar>::read)
[INFO  rustc_codegen_ssa::base] codegen_instance(vga::volatile::Volatile::<vga::DrawableChar>::write)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::arch::x86_64::_rdrand64_step)
[INFO  rustc_codegen_ssa::base] codegen_instance(<x86_64::structures::paging::page_table::PageTableFlags as core::ops::BitOr>::bitor)
[INFO  rustc_codegen_ssa::base] codegen_instance(<&ReErased mut x86_64::structures::idt::InterruptStackFrame as core::fmt::Debug>::fmt)
[INFO  rustc_codegen_ssa::base] codegen_instance(<x86_64::structures::paging::mapper::MapToError as core::convert::From<x86_64::structures::paging::mapper::MapToError>>::from)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::structures::paging::mapper::MapperFlush::<x86_64::structures::paging::page::Size4KiB>::flush)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::addr::VirtAddr::from_ptr::<[u8; Const { ty: usize, val: Value(Scalar(0x0000000000001000)) }]>)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::instructions::tlb::flush)
[INFO  rustc_codegen_ssa::base] codegen_instance(<core::marker::PhantomData<x86_64::structures::paging::page::Size4KiB> as core::clone::Clone>::clone)
[INFO  rustc_codegen_ssa::base] codegen_instance(<core::marker::PhantomData<x86_64::structures::paging::page::Size4KiB> as core::cmp::PartialOrd>::partial_cmp)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::clone::impls::<impl core::clone::Clone for i32>::clone)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::clone::impls::<impl core::clone::Clone for u32>::clone)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::clone::impls::<impl core::clone::Clone for u64>::clone)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::clone::impls::<impl core::clone::Clone for usize>::clone)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::instructions::tables::load_tss)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::char::from_u32_unchecked)
[INFO  rustc_codegen_ssa::base] codegen_instance(<u32 as core::default::Default>::default)
[INFO  rustc_codegen_ssa::base] codegen_instance(<bool as core::default::Default>::default)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::instructions::interrupts::enable)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::instructions::interrupts::disable)
[INFO  rustc_codegen_ssa::base] codegen_instance(<pci::alloc::collections::TryReserveError as core::convert::From<pci::alloc::collections::TryReserveError>>::from)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::structures::idt::PageFaultErrorCode::bits)
[INFO  rustc_codegen_ssa::base] codegen_instance(<&ReErased bootloader::bootinfo::memory_map::MemoryRegion as core::convert::From<&ReErased bootloader::bootinfo::memory_map::MemoryRegion>>::from)
[INFO  rustc_codegen_ssa::base] codegen_instance(x86_64::instructions::hlt)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::hint::unreachable_unchecked)
[INFO  rustc_codegen_ssa::base] codegen_instance(core::hint::spin_loop)

and then it just halts... Actually busy waiting (100% CPU load on one core).

gdb output:

(gdb) info threads 
  Id   Target Id                                 Frame 
* 1    Thread 0x7fd470219400 (LWP 20211) "rustc" __GI___pthread_timedjoin_ex (
    threadid=140550382548736, thread_return=0x0, abstime=<optimized out>, block=<optimized out>)
    at pthread_join_common.c:142
  2    Thread 0x7fd46f9ff700 (LWP 20212) "rustc" futex_wait_cancelable (private=<optimized out>, 
    expected=0, futex_word=0x7fd46fe1123c) at ../sysdeps/unix/sysv/linux/futex-internal.h:80
  3    Thread 0x7fd468a0b700 (LWP 20249) "rustc" futex_wait_cancelable (private=<optimized out>, 
    expected=0, futex_word=0x7fd4627f123c) at ../sysdeps/unix/sysv/linux/futex-internal.h:80
  4    Thread 0x7fd45cce3700 (LWP 20250) "rustc" futex_wait_cancelable (private=<optimized out>, 
    expected=0, futex_word=0x7fd4627f1598) at ../sysdeps/unix/sysv/linux/futex-internal.h:80
  5    Thread 0x7fd45b17f700 (LWP 20268) "rustc" 0x00007fd46aa5ffd2 in (anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
(gdb) thread 5
[Switching to thread 5 (Thread 0x7fd45b17f700 (LWP 20268))]
#0  0x00007fd46aa5ffd2 in (anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
(gdb) bt
#0  0x00007fd46aa5ffd2 in (anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#1  0x00007fd46aa0611c in (anonymous namespace)::DAGCombiner::visit(llvm::SDNode*) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#2  0x00007fd46aa02a4c in (anonymous namespace)::DAGCombiner::combine(llvm::SDNode*) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#3  0x00007fd46aa011e3 in llvm::SelectionDAG::Combine(llvm::CombineLevel, llvm::AAResults*, llvm::CodeGenOpt::Level) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#4  0x00007fd46ac382f0 in llvm::SelectionDAGISel::CodeGenAndEmitDAG() ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#5  0x00007fd46ac37b48 in llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#6  0x00007fd46ac34176 in llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#7  0x00007fd46c70591d in (anonymous namespace)::X86DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#8  0x00007fd46a7fcd9e in llvm::MachineFunctionPass::runOnFunction(llvm::Function&) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#9  0x00007fd46a60542f in llvm::FPPassManager::runOnFunction(llvm::Function&) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#10 0x00007fd46a605893 in llvm::FPPassManager::runOnModule(llvm::Module&) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#11 0x00007fd46a606030 in llvm::legacy::PassManagerImpl::run(llvm::Module&) ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/../lib/libLLVM-9-rust-1.41.0-nightly.so
#12 0x00007fd46d07a4ef in LLVMRustWriteOutputFile () from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#13 0x00007fd46d027a9c in rustc_codegen_llvm::back::write::write_output_file ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#14 0x00007fd46cf17b96 in rustc_codegen_llvm::back::write::codegen::{{closure}} ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#15 0x00007fd46cf15ff1 in rustc::util::common::time_ext () from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#16 0x00007fd46d0366c1 in <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::write::WriteBackendMethods>::codegen ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#17 0x00007fd46cf477c4 in std::sys_common::backtrace::__rust_begin_short_backtrace ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#18 0x00007fd46cf4c5d6 in std::panicking::try::do_call () from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#19 0x00007fd4708cef5a in __rust_maybe_catch_panic () at src/libpanic_unwind/lib.rs:86
#20 0x00007fd46cf4ce16 in core::ops::function::FnOnce::call_once{{vtable-shim}} ()
   from /home/op/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends/librustc_codegen_llvm-llvm.so
#21 0x00007fd47089fcbf in <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once () at /rustc/5c5b8afd80e6fa1d24632153cb2257c686041d41/src/liballoc/boxed.rs:942
#22 0x00007fd4708cd980 in <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once () at /rustc/5c5b8afd80e6fa1d24632153cb2257c686041d41/src/liballoc/boxed.rs:942
#23 std::sys_common::thread::start_thread () at src/libstd/sys_common/thread.rs:13
#24 std::sys::unix::thread::Thread::new::thread_start () at src/libstd/sys/unix/thread.rs:79
#25 0x00007fd47080d669 in start_thread (arg=<optimized out>) at pthread_create.c:479
#26 0x00007fd470722323 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Looking at the assembly, there's are these 4 lines

>0x7fd46aa5ffd2 <(anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*)+26418>    mov    0x20(%rcx),%rcx
 0x7fd46aa5ffd6 <(anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*)+26422>    test   %rcx,%rcx
 0x7fd46aa5ffd9 <(anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*)+26425>    je     0x7fd46aa5fff0 <(anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*)+26448>
 0x7fd46aa5ffdb <(anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*)+26427>    cmp    %eax,0x8(%rcx)
 0x7fd46aa5ffde <(anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*)+26430>    jne    0x7fd46aa5ffd2 <(anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*)+26418>

and this loops "forever". Not quiet sure what it's trying to find there.

So this is a LLVM bug?

[hellow554]

struct HbaCmdTbl {
    _prdt_entry: [HbaPrdtEntry; 65535],
}

struct HbaPrdtEntry {
    _non_empty: u32 
}

fn main() {
    let cmdtbl_ptr = std::ptr::null_mut::<HbaCmdTbl>();
    let _cmdtbl = unsafe { cmdtbl_ptr.read_volatile() };
}

the 65535 is taken from the sourcecode, I'm not sure if it can be lowered any further. but this code triggers the long build time for me.

@rustbot modify labels: -E-needs-mcve

edit: In fact I optimized too much I'm afraid. The build succeeds after roughly 6m. I'm not sure if I optimized something away. Should I dig further?

[ethindp]

Yeah, I can see how that might take a while, but before I made the read_volatile changes that didn't take as long as it does now. Now it taks over an horu and then bails out, which never happened before, even with the 65535 in there. OS is windows, latest commit.

…

On 11/21/19, Marcel Hellwig ***@***.***> wrote: ```rust struct HbaCmdTbl { _prdt_entry: [HbaPrdtEntry; 65535], } struct HbaPrdtEntry { _non_empty: u32 } fn main() { let cmdtbl_ptr = std::ptr::null_mut::<HbaCmdTbl>(); let _cmdtbl = unsafe { cmdtbl_ptr.read_volatile() }; } ``` the `65535` is taken from the sourcecode, I'm not sure if it can be lowered any further. but this code triggers the long build time for me. -- You are receiving this because you were mentioned. Reply to this email directly or view it on GitHub: #66595 (comment)

-- Signed, Ethin D. Probst

[Aaron1011]

It looks like LLVM is getting stuck in this loop forever

[ethindp]

Any progress on this?